JDBC
JDBC
一、JDBC快速入门
1.jdbc的概念
- JDBC（Java DataBase Connectivity,java数据库连接）是一种用于执行SQL语句的Java API，可以为多种关系型数据库提供统一访问，它是由一组用Java语言编写的类和接口组成的。
2.jdbc的本质
- 其实就是java官方提供的一套规范(接口)。用于帮助开发人员快速实现不同关系型数据库的连接！
3.jdbc的快速入门程序
导入jar包
注册驱动
Class.forName("com.mysql.jdbc.Driver");获取连接
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/db2", "root", "root");获取执行者对象
Statement stat = con.createStatement();执行sql语句，并接收返回结果
String sql = "SELECT * FROM user"; ResultSet rs = stat.executeQuery(sql);处理结果
while(rs.next()) { System.out.println(rs.getInt("id") + "\t" + rs.getString("name")); }释放资源
con.close(); stat.close(); rs.close();
二、JDBC各个功能类详解
1.DriverManager
DriverManager：驱动管理对象
注册驱动(告诉程序该使用哪一个数据库驱动)
- static void registerDriver(Driver driver)：注册与给定的驱动程序 DriverManager
- 写代码使用：Class.forName(“com.mysql.jdbc.Driver”);
- 通过查看源码发现：在com.mysql.jdbc.Driver类中存在静态代码块
static { try { java.sql.DriverManager.registerDriver(new Driver()); } catch (SQLException E) { throw new RuntimeException("Can't register driver!"); } }- 注意：mysql5之后的驱动jar包可以省略注册驱动的步骤。在jar包中，存在一个java.sql.Driver配置文件，文件中指定了com.mysql.jdbc.Driver
获取数据库连接(获取到数据库的连接并返回连接对象)
- static Connection getConnection(String url, String user, String password);
- 返回值：Connection数据库连接对象
- 参数
- url：指定连接的路径。语法：jdbc:mysql://ip地址(域名):端口号/数据库名称
- user：用户名
- password：密码
- static Connection getConnection(String url, String user, String password);
2.Connection
- Connection：数据库连接对象
- 获取执行者对象
- 获取普通执行者对象：Statement createStatement();
- 获取预编译执行者对象：PreparedStatement prepareStatement(String sql);
- 管理事务
- 开启事务：setAutoCommit(boolean autoCommit); 参数为false，则开启事务。
- 提交事务：commit();
- 回滚事务：rollback();
- 释放资源
- 立即将数据库连接对象释放：void close();
- 获取执行者对象
3.Statement
- Statement：执行sql语句的对象
- 执行DML语句：int executeUpdate(String sql);
- 返回值int：返回影响的行数。
- 参数sql：可以执行insert、update、delete语句。
- 执行DQL语句：ResultSet executeQuery(String sql);
- 返回值ResultSet：封装查询的结果。
- 参数sql：可以执行select语句。
- 释放资源
- 立即将执行者对象释放：void close();
- 执行DML语句：int executeUpdate(String sql);
4.ResultSet
- ResultSet：结果集对象
- 判断结果集中是否还有数据：boolean next();
- 有数据返回true，并将索引向下移动一行
- 没有数据返回false
- 获取结果集中的数据：XXX getXxx(“列名”);
- XXX代表数据类型(要获取某列数据，这一列的数据类型)
- 例如：String getString(“name”); int getInt(“age”);
- 释放资源
- 立即将结果集对象释放：void close();
- 判断结果集中是否还有数据：boolean next();
三、JDBC案例student学生表的CRUD
1.数据准备
- 数据库和数据表
-- 创建db14数据库
CREATE DATABASE db14;
-- 使用db14数据库
USE db14;
-- 创建student表
CREATE TABLE student(
sid INT PRIMARY KEY AUTO_INCREMENT, -- 学生id
NAME VARCHAR(20), -- 学生姓名
age INT, -- 学生年龄
birthday DATE -- 学生生日
);
-- 添加数据
INSERT INTO student VALUES (NULL,'张三',23,'1999-09-23'),(NULL,'李四',24,'1998-08-10'),(NULL,'王五',25,'1996-06-06'),(NULL,'赵六',26,'1994-10-20');- 实体类
- Student类，成员变量对应表中的列
- 注意：所有的基本数据类型需要使用包装类，以防null值无法赋值
package com.itheima02.domain;
import java.util.Date;
public class Student {
private Integer sid;
private String name;
private Integer age;
private Date birthday;
public Student() {
}
public Student(Integer sid, String name, Integer age, Date birthday) {
this.sid = sid;
this.name = name;
this.age = age;
this.birthday = birthday;
}
public Integer getSid() {
return sid;
}
public void setSid(Integer sid) {
this.sid = sid;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
@Override
public String toString() {
return "Student{" +
"sid=" + sid +
", name='" + name + '\'' +
", age=" + age +
", birthday=" + birthday +
'}';
}
}2.需求一：查询全部
- 持久层
/*
查询所有学生信息
*/
@Override
public ArrayList<Student> findAll() {
ArrayList<Student> list = new ArrayList<>();
Connection con = null;
Statement stat = null;
ResultSet rs = null;
try{
//1.注册驱动
Class.forName("com.mysql.jdbc.Driver");
//2.获取数据库连接
con = DriverManager.getConnection("jdbc:mysql://192.168.59.129:3306/db14", "root", "itheima");
//3.获取执行者对象
stat = con.createStatement();
//4.执行sql语句，并且接收返回的结果集
String sql = "SELECT * FROM student";
rs = stat.executeQuery(sql);
//5.处理结果集
while(rs.next()) {
Integer sid = rs.getInt("sid");
String name = rs.getString("name");
Integer age = rs.getInt("age");
Date birthday = rs.getDate("birthday");
//封装Student对象
Student stu = new Student(sid,name,age,birthday);
//将student对象保存到集合中
list.add(stu);
}
} catch(Exception e) {
e.printStackTrace();
} finally {
//6.释放资源
if(con != null) {
try {
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(stat != null) {
try {
stat.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
//将集合对象返回
return list;
}- 业务层
/*
查询所有学生信息
*/
@Override
public ArrayList<Student> findAll() {
return dao.findAll();
}- 控制层
/*
查询所有学生信息
*/
@Test
public void findAll() {
ArrayList<Student> list = service.findAll();
for(Student stu : list) {
System.out.println(stu);
}
}3.需求二：条件查询
- 持久层
/*
条件查询，根据id查询学生信息
*/
@Override
public Student findById(Integer id) {
Student stu = new Student();
Connection con = null;
Statement stat = null;
ResultSet rs = null;
try{
//1.注册驱动
Class.forName("com.mysql.jdbc.Driver");
//2.获取数据库连接
con = DriverManager.getConnection("jdbc:mysql://192.168.59.129:3306/db14", "root", "itheima");
//3.获取执行者对象
stat = con.createStatement();
//4.执行sql语句，并且接收返回的结果集
String sql = "SELECT * FROM student WHERE sid='"+id+"'";
rs = stat.executeQuery(sql);
//5.处理结果集
while(rs.next()) {
Integer sid = rs.getInt("sid");
String name = rs.getString("name");
Integer age = rs.getInt("age");
Date birthday = rs.getDate("birthday");
//封装Student对象
stu.setSid(sid);
stu.setName(name);
stu.setAge(age);
stu.setBirthday(birthday);
}
} catch(Exception e) {
e.printStackTrace();
} finally {
//6.释放资源
if(con != null) {
try {
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(stat != null) {
try {
stat.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
//将对象返回
return stu;
}- 业务层
/*
条件查询，根据id查询学生信息
*/
@Override
public Student findById(Integer id) {
return dao.findById(id);
}- 控制层
/*
条件查询，根据id查询学生信息
*/
@Test
public void findById() {
Student stu = service.findById(3);
System.out.println(stu);
}4.需求三：新增数据
- 持久层
/*
添加学生信息
*/
@Override
public int insert(Student stu) {
Connection con = null;
Statement stat = null;
int result = 0;
try{
//1.注册驱动
Class.forName("com.mysql.jdbc.Driver");
//2.获取数据库连接
con = DriverManager.getConnection("jdbc:mysql://192.168.59.129:3306/db14", "root", "itheima");
//3.获取执行者对象
stat = con.createStatement();
//4.执行sql语句，并且接收返回的结果集
Date d = stu.getBirthday();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
String birthday = sdf.format(d);
String sql = "INSERT INTO student VALUES ('"+stu.getSid()+"','"+stu.getName()+"','"+stu.getAge()+"','"+birthday+"')";
result = stat.executeUpdate(sql);
} catch(Exception e) {
e.printStackTrace();
} finally {
//6.释放资源
if(con != null) {
try {
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(stat != null) {
try {
stat.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
//将结果返回
return result;
}- 业务层
/*
新增学生信息
*/
@Override
public int insert(Student stu) {
return dao.insert(stu);
}- 控制层
/*
新增学生信息
*/
@Test
public void insert() {
Student stu = new Student(5,"周七",27,new Date());
int result = service.insert(stu);
if(result != 0) {
System.out.println("新增成功");
}else {
System.out.println("新增失败");
}
}5.需求四：修改数据
- 持久层
/*
修改学生信息
*/
@Override
public int update(Student stu) {
Connection con = null;
Statement stat = null;
int result = 0;
try{
//1.注册驱动
Class.forName("com.mysql.jdbc.Driver");
//2.获取数据库连接
con = DriverManager.getConnection("jdbc:mysql://192.168.59.129:3306/db14", "root", "itheima");
//3.获取执行者对象
stat = con.createStatement();
//4.执行sql语句，并且接收返回的结果集
Date d = stu.getBirthday();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
String birthday = sdf.format(d);
String sql = "UPDATE student SET sid='"+stu.getSid()+"',name='"+stu.getName()+"',age='"+stu.getAge()+"',birthday='"+birthday+"' WHERE sid='"+stu.getSid()+"'";
result = stat.executeUpdate(sql);
} catch(Exception e) {
e.printStackTrace();
} finally {
//6.释放资源
if(con != null) {
try {
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(stat != null) {
try {
stat.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
//将结果返回
return result;
}- 业务层
/*
修改学生信息
*/
@Override
public int update(Student stu) {
return dao.update(stu);
}- 控制层
/*
修改学生信息
*/
@Test
public void update() {
Student stu = service.findById(5);
stu.setName("周七七");
int result = service.update(stu);
if(result != 0) {
System.out.println("修改成功");
}else {
System.out.println("修改失败");
}
}6.需求五：删除数据
- 持久层
/*
删除学生信息
*/
@Override
public int delete(Integer id) {
Connection con = null;
Statement stat = null;
int result = 0;
try{
//1.注册驱动
Class.forName("com.mysql.jdbc.Driver");
//2.获取数据库连接
con = DriverManager.getConnection("jdbc:mysql://192.168.59.129:3306/db14", "root", "itheima");
//3.获取执行者对象
stat = con.createStatement();
//4.执行sql语句，并且接收返回的结果集
String sql = "DELETE FROM student WHERE sid='"+id+"'";
result = stat.executeUpdate(sql);
} catch(Exception e) {
e.printStackTrace();
} finally {
//6.释放资源
if(con != null) {
try {
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(stat != null) {
try {
stat.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
//将结果返回
return result;
}- 业务层
/*
删除学生信息
*/
@Override
public int delete(Integer id) {
return dao.delete(id);
}- 控制层
/*
删除学生信息
*/
@Test
public void delete() {
int result = service.delete(5);
if(result != 0) {
System.out.println("删除成功");
}else {
System.out.println("删除失败");
}
}四、JDBC工具类
1.工具类的抽取
- 配置文件(在src下创建config.properties)
driverClass=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/db14
username=root
password=itheima- 工具类
/*
JDBC工具类
*/
public class JDBCUtils {
//1.私有构造方法
private JDBCUtils(){};
//2.声明配置信息变量
private static String driverClass;
private static String url;
private static String username;
private static String password;
private static Connection con;
//3.静态代码块中实现加载配置文件和注册驱动
static{
try{
//通过类加载器返回配置文件的字节流
InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("config.properties");
//创建Properties集合，加载流对象的信息
Properties prop = new Properties();
prop.load(is);
//获取信息为变量赋值
driverClass = prop.getProperty("driverClass");
url = prop.getProperty("url");
username = prop.getProperty("username");
password = prop.getProperty("password");
//注册驱动
Class.forName(driverClass);
} catch (Exception e) {
e.printStackTrace();
}
}
//4.获取数据库连接的方法
public static Connection getConnection() {
try {
con = DriverManager.getConnection(url,username,password);
} catch (SQLException e) {
e.printStackTrace();
}
return con;
}
//5.释放资源的方法
public static void close(Connection con, Statement stat, ResultSet rs) {
if(con != null) {
try {
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(stat != null) {
try {
stat.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
public static void close(Connection con, Statement stat) {
close(con,stat,null);
}
}2.使用工具类优化student表的CRUD
- 查询全部
/*
查询所有学生信息
*/
@Override
public ArrayList<Student> findAll() {
ArrayList<Student> list = new ArrayList<>();
Connection con = null;
Statement stat = null;
ResultSet rs = null;
try{
con = JDBCUtils.getConnection();
//3.获取执行者对象
stat = con.createStatement();
//4.执行sql语句，并且接收返回的结果集
String sql = "SELECT * FROM student";
rs = stat.executeQuery(sql);
//5.处理结果集
while(rs.next()) {
Integer sid = rs.getInt("sid");
String name = rs.getString("name");
Integer age = rs.getInt("age");
Date birthday = rs.getDate("birthday");
//封装Student对象
Student stu = new Student(sid,name,age,birthday);
//将student对象保存到集合中
list.add(stu);
}
} catch(Exception e) {
e.printStackTrace();
} finally {
//6.释放资源
JDBCUtils.close(con,stat,rs);
}
//将集合对象返回
return list;
}- 条件查询
/*
条件查询，根据id查询学生信息
*/
@Override
public Student findById(Integer id) {
Student stu = new Student();
Connection con = null;
Statement stat = null;
ResultSet rs = null;
try{
con = JDBCUtils.getConnection();
//3.获取执行者对象
stat = con.createStatement();
//4.执行sql语句，并且接收返回的结果集
String sql = "SELECT * FROM student WHERE sid='"+id+"'";
rs = stat.executeQuery(sql);
//5.处理结果集
while(rs.next()) {
Integer sid = rs.getInt("sid");
String name = rs.getString("name");
Integer age = rs.getInt("age");
Date birthday = rs.getDate("birthday");
//封装Student对象
stu.setSid(sid);
stu.setName(name);
stu.setAge(age);
stu.setBirthday(birthday);
}
} catch(Exception e) {
e.printStackTrace();
} finally {
//6.释放资源
JDBCUtils.close(con,stat,rs);
}
//将对象返回
return stu;
}- 新增数据
/*
添加学生信息
*/
@Override
public int insert(Student stu) {
Connection con = null;
Statement stat = null;
int result = 0;
try{
con = JDBCUtils.getConnection();
//3.获取执行者对象
stat = con.createStatement();
//4.执行sql语句，并且接收返回的结果集
Date d = stu.getBirthday();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
String birthday = sdf.format(d);
String sql = "INSERT INTO student VALUES ('"+stu.getSid()+"','"+stu.getName()+"','"+stu.getAge()+"','"+birthday+"')";
result = stat.executeUpdate(sql);
} catch(Exception e) {
e.printStackTrace();
} finally {
//6.释放资源
JDBCUtils.close(con,stat);
}
//将结果返回
return result;
}- 修改数据
/*
修改学生信息
*/
@Override
public int update(Student stu) {
Connection con = null;
Statement stat = null;
int result = 0;
try{
con = JDBCUtils.getConnection();
//3.获取执行者对象
stat = con.createStatement();
//4.执行sql语句，并且接收返回的结果集
Date d = stu.getBirthday();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
String birthday = sdf.format(d);
String sql = "UPDATE student SET sid='"+stu.getSid()+"',name='"+stu.getName()+"',age='"+stu.getAge()+"',birthday='"+birthday+"' WHERE sid='"+stu.getSid()+"'";
result = stat.executeUpdate(sql);
} catch(Exception e) {
e.printStackTrace();
} finally {
//6.释放资源
JDBCUtils.close(con,stat);
}
//将结果返回
return result;
}- 删除数据
/*
删除学生信息
*/
@Override
public int delete(Integer id) {
Connection con = null;
Statement stat = null;
int result = 0;
try{
con = JDBCUtils.getConnection();
//3.获取执行者对象
stat = con.createStatement();
//4.执行sql语句，并且接收返回的结果集
String sql = "DELETE FROM student WHERE sid='"+id+"'";
result = stat.executeUpdate(sql);
} catch(Exception e) {
e.printStackTrace();
} finally {
//6.释放资源
JDBCUtils.close(con,stat);
}
//将结果返回
return result;
}3.student表的CRUD整合页面
- 用户表的数据准备
-- 创建用户表
CREATE TABLE USER(
uid VARCHAR(50) PRIMARY KEY, -- 用户id
ucode VARCHAR(50), -- 用户标识
loginname VARCHAR(100), -- 登录用户名
PASSWORD VARCHAR(100), -- 登录密码
username VARCHAR(100), -- 用户名
gender VARCHAR(10), -- 用户性别
birthday DATE, -- 出生日期
dutydate DATE -- 入职日期
);
-- 添加一条测试数据
INSERT INTO `user` VALUES ('11111111', 'zhangsan001', 'zhangsan', '1234', '张三', '男', '2008-10-28', '2018-10-28');- 将student表的dao层操作复制到项目中的dao层即可
public class StudentDaoImpl implements StudentDao {
/*
查询所有学生信息
*/
@Override
public ArrayList<Student> findAll() {
Connection con = null;
Statement stat = null;
ResultSet rs = null;
ArrayList<Student> list = new ArrayList<>();
try {
//1.获取连接
con = JDBCUtils.getConnection();
//2.获取执行者对象
stat = con.createStatement();
//3.执行sql语句，并接收结果
String sql = "SELECT * FROM student";
rs = stat.executeQuery(sql);
//4.处理结果，将每条记录封装成一个Student对象。将多个Student对象保存到集合中
while(rs.next()) {
Integer sid = rs.getInt("sid");
String name = rs.getString("name");
Integer age = rs.getInt("age");
Date birthday = rs.getDate("birthday");
Student stu = new Student(sid,name,age,birthday);
list.add(stu);
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
//5.释放资源
JDBCUtils.close(con,stat,rs);
}
return list;
}
/*
条件查询，根据id查询学生信息
*/
@Override
public Student findById(Integer id) {
Connection con = null;
Statement stat = null;
ResultSet rs = null;
Student stu = new Student();
try {
//1.获取连接
con = JDBCUtils.getConnection();
//2.获取执行者对象
stat = con.createStatement();
//3.执行sql语句，并接收结果
String sql = "SELECT * FROM student WHERE sid='"+id+"'";
rs = stat.executeQuery(sql);
//4.处理结果，将记录封装成一个Student对象。
if(rs.next()) {
Integer sid = rs.getInt("sid");
String name = rs.getString("name");
Integer age = rs.getInt("age");
Date birthday = rs.getDate("birthday");
stu.setSid(sid);
stu.setName(name);
stu.setAge(age);
stu.setBirthday(birthday);
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
//5.释放资源
JDBCUtils.close(con,stat,rs);
}
return stu;
}
/*
新增学生信息
*/
@Override
public int insert(Student stu) {
Connection con = null;
Statement stat = null;
int result = 0;
try{
//1.获取连接
con = JDBCUtils.getConnection();
//2.获取执行者对象
stat = con.createStatement();
//3.执行sql语句，并接收结果
Date date = stu.getBirthday();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
String birthday = sdf.format(date);
String sql = "INSERT INTO student VALUES (null,'"+stu.getName()+"','"+stu.getAge()+"','"+birthday+"')";
result = stat.executeUpdate(sql);
} catch (SQLException e) {
e.printStackTrace();
} finally {
//4.释放资源
JDBCUtils.close(con,stat);
}
return result;
}
/*
修改学生信息
*/
@Override
public int update(Student stu) {
Connection con = null;
Statement stat = null;
int result = 0;
try{
//1.获取连接
con = JDBCUtils.getConnection();
//2.获取执行者对象
stat = con.createStatement();
//3.执行sql语句，并接收结果
Date date = stu.getBirthday();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
String birthday = sdf.format(date);
String sql = "UPDATE student SET sid='"+stu.getSid()+"',name='"+stu.getName()+"',age='"+stu.getAge()+"',birthday='"+birthday+"' WHERE sid='"+stu.getSid()+"'";
result = stat.executeUpdate(sql);
} catch (SQLException e) {
e.printStackTrace();
} finally {
//4.释放资源
JDBCUtils.close(con,stat);
}
return result;
}
/*
删除学生信息
*/
@Override
public int delete(Integer id) {
Connection con = null;
Statement stat = null;
int result = 0;
try{
//1.获取连接
con = JDBCUtils.getConnection();
//2.获取执行者对象
stat = con.createStatement();
//3.执行sql语句，并接收结果
String sql = "DELETE FROM student WHERE sid='"+id+"'";
result = stat.executeUpdate(sql);
} catch (SQLException e) {
e.printStackTrace();
} finally {
//4.释放资源
JDBCUtils.close(con,stat);
}
return result;
}
}五、SQL注入攻击
1.sql注入攻击的演示
- 在登录界面，输入一个错误的用户名或密码，也可以登录成功
2.sql注入攻击的原理
- 按照正常道理来说，我们在密码处输入的所有内容，都应该认为是密码的组成
- 但是现在Statement对象在执行sql语句时，将一部分内容当做查询条件来执行了
3.PreparedStatement的介绍
- 预编译sql语句的执行者对象。在执行sql语句之前，将sql语句进行提前编译。明确sql语句的格式后，就不会改变了。剩余的内容都会认为是参数！参数使用?作为占位符
- 为参数赋值的方法：setXxx(参数1,参数2);
- 参数1：?的位置编号(编号从1开始)
- 参数2：?的实际参数
- 执行sql语句的方法
- 执行insert、update、delete语句：int executeUpdate();
- 执行select语句：ResultSet executeQuery();
4.PreparedStatement的使用
/*
使用PreparedStatement的登录方法，解决注入攻击
*/
@Override
public User findByLoginNameAndPassword(String loginName, String password) {
//定义必要信息
Connection conn = null;
PreparedStatement pstm = null;
ResultSet rs = null;
User user = null;
try {
//1.获取连接
conn = JDBCUtils.getConnection();
//2.创建操作SQL对象
String sql = "SELECT * FROM user WHERE loginname=? AND password=?";
pstm = conn.prepareStatement(sql);
//3.设置参数
pstm.setString(1,loginName);
pstm.setString(2,password);
System.out.println(sql);
//4.执行sql语句，获取结果集
rs = pstm.executeQuery();
//5.获取结果集
if (rs.next()) {
//6.封装
user = new User();
user.setUid(rs.getString("uid"));
user.setUcode(rs.getString("ucode"));
user.setUsername(rs.getString("username"));
user.setPassword(rs.getString("password"));
user.setGender(rs.getString("gender"));
user.setDutydate(rs.getDate("dutydate"));
user.setBirthday(rs.getDate("birthday"));
user.setLoginname(rs.getString("loginname"));
}
//7.返回
return user;
}catch (Exception e){
throw new RuntimeException(e);
}finally {
JDBCUtils.close(conn,pstm,rs);
}
}5.使用PreparedStatement优化student表的CRUD（作业）
public class StudentDaoImpl implements StudentDao {
@Override
public ArrayList<Student> findAll() {
//定义必要信息
Connection conn = null;
PreparedStatement pstm = null;
ResultSet rs = null;
ArrayList<Student> students = null;
try {
//1.获取连接
conn = JDBCUtils.getConnection();
//2.获取操作对象
pstm = conn.prepareStatement("select * from student");
//3.执行sql语句，获取结果集
rs = pstm.executeQuery();
//4.遍历结果集
students = new ArrayList<Student>();
while (rs.next()) {
//5.封装
Student student = new Student();
student.setSid(rs.getInt("sid"));
student.setName(rs.getString("name"));
student.setAge(rs.getInt("age"));
student.setBirthday(rs.getDate("birthday"));
//加入到集合中
students.add(student);
}
//6.返回
return students;
}catch (Exception e){
throw new RuntimeException(e);
}finally {
JDBCUtils.close(conn,pstm,rs);
}
}
@Override
public Student findById(Integer sid) {
//定义必要信息
Connection conn = null;
PreparedStatement pstm = null;
ResultSet rs = null;
Student student = null;
try {
//1.获取连接
conn = JDBCUtils.getConnection();
//2.获取操作对象
pstm = conn.prepareStatement("select * from student where sid = ? ");
pstm.setInt(1,sid);
//3.执行sql语句，获取结果集
rs = pstm.executeQuery();
//4.遍历结果集
if (rs.next()) {
//5.封装
student = new Student();
student.setSid(rs.getInt("sid"));
student.setName(rs.getString("name"));
student.setAge(rs.getInt("age"));
student.setBirthday(rs.getDate("birthday"));
}
//6.返回
return student;
}catch (Exception e){
throw new RuntimeException(e);
}finally {
JDBCUtils.close(conn,pstm,rs);
}
}
@Override
public int insert(Student student) {
//定义必要信息
Connection conn = null;
PreparedStatement pstm = null;
int result = 0;
try {
//1.获取连接
conn = JDBCUtils.getConnection();
//2.获取操作对象
pstm = conn.prepareStatement("insert into student(sid,name,age,birthday)values(null,?,?,?)");
//3.设置参数
//pstm.setInt(1,null);
pstm.setString(1,student.getName());
pstm.setInt(2,student.getAge());
pstm.setDate(3,new Date(student.getBirthday().getTime()));
//4.执行sql语句
result = pstm.executeUpdate();
}catch (Exception e){
throw new RuntimeException(e);
}finally {
JDBCUtils.close(conn,pstm);
}
return result;
}
@Override
public int update(Student student) {
//定义必要信息
Connection conn = null;
PreparedStatement pstm = null;
int result = 0;
try {
//1.获取连接
conn = JDBCUtils.getConnection();
//2.获取操作对象
pstm = conn.prepareStatement("update student set name=?,age=?,birthday=? where sid=? ");
//3.设置参数
pstm.setString(1,student.getName());
pstm.setInt(2,student.getAge());
pstm.setDate(3,new Date(student.getBirthday().getTime()));
pstm.setInt(4,student.getSid());
//4.执行sql语句
result = pstm.executeUpdate();
}catch (Exception e){
throw new RuntimeException(e);
}finally {
JDBCUtils.close(conn,pstm);
}
return result;
}
@Override
public int delete(Integer sid) {
//定义必要信息
Connection conn = null;
PreparedStatement pstm = null;
int result = 0;
try {
//1.获取连接
conn = JDBCUtils.getConnection();
//2.获取操作对象
pstm = conn.prepareStatement("delete from student where sid=? ");
//3.设置参数
pstm.setInt(1,sid);
//4.执行sql语句
result = pstm.executeUpdate();
}catch (Exception e){
throw new RuntimeException(e);
}finally {
JDBCUtils.close(conn,pstm);
}
return result;
}
}六、综合案例-课程表批量新增加事务管理
1.service层
- 接口
/*
批量添加
*/
void batchAdd(List<User> users);- 实现类
/*
事务要控制在此处
*/
@Override
public void batchAdd(List<User> users) {
//获取数据库连接
Connection connection = JDBCUtils.getConnection();
try {
//开启事务
connection.setAutoCommit(false);
for (User user : users) {
//1.创建ID,并把UUID中的-替换
String uid = UUID.randomUUID().toString().replace("-", "").toUpperCase();
//2.给user的uid赋值
user.setUid(uid);
//3.生成员工编号
user.setUcode(uid);
//模拟异常
//int n = 1 / 0;
//4.保存
userDao.save(connection,user);
}
//提交事务
connection.commit();
}catch (Exception e){
try {
//回滚事务
connection.rollback();
}catch (Exception ex){
ex.printStackTrace();
}
e.printStackTrace();
}finally {
JDBCUtils.close(connection,null,null);
}
}2.dao层
- 接口
/**
支持事务的添加
*/
void save(Connection connection,User user);- 实现类
/*
支持事务的添加
*/
@Override
public void save(Connection connection, User user) {
//定义必要信息
PreparedStatement pstm = null;
try {
//1.获取连接
connection = JDBCUtils.getConnection();
//2.获取操作对象
pstm = connection.prepareStatement("insert into user(uid,ucode,loginname,password,username,gender,birthday,dutydate)values(?,?,?,?,?,?,?,?)");
//3.设置参数
pstm.setString(1,user.getUid());
pstm.setString(2,user.getUcode());
pstm.setString(3,user.getLoginname());
pstm.setString(4,user.getPassword());
pstm.setString(5,user.getUsername());
pstm.setString(6,user.getGender());
pstm.setDate(7,new Date(user.getBirthday().getTime()));
pstm.setDate(8,new Date(user.getDutydate().getTime()));
//4.执行sql语句，获取结果集
pstm.executeUpdate();
}catch (Exception e){
throw new RuntimeException(e);
}finally {
JDBCUtils.close(null,pstm,null);
}
}七、数据库连接池
1.数据库连接池的概念
- 数据库连接背景
- 数据库连接是一种关键的、有限的、昂贵的资源，这一点在多用户的网页应用程序中体现得尤为突出。对数据库连接的管理能显著影响到整个应用程序的伸缩性和健壮性，影响到程序的性能指标。数据库连接池正是针对这个问题提出来的。
- 数据库连接池
- 数据库连接池负责分配、管理和释放数据库连接，它允许应用程序重复使用一个现有的数据库连接，而不是再重新建立一个。这项技术能明显提高对数据库操作的性能。
- 数据库连接池原理
2.自定义连接池
- java.sql.DataSource接口：数据源(数据库连接池)。java官方提供的数据库连接池规范(接口)
- 获取数据库连接对象：Connection getConnection();
- 自定义连接池
/*
自定义连接池类
*/
public class MyDataSource implements DataSource{
//定义集合容器，用于保存多个数据库连接对象
private static List<Connection> pool = Collections.synchronizedList(new ArrayList<Connection>());
//静态代码块，生成10个数据库连接保存到集合中
static {
for (int i = 0; i < 10; i++) {
Connection con = JDBCUtils.getConnection();
pool.add(con);
}
}
//返回连接池的大小
public int getSize() {
return pool.size();
}
//从池中返回一个数据库连接
@Override
public Connection getConnection() {
if(pool.size() > 0) {
//从池中获取数据库连接
return pool.remove(0);
}else {
throw new RuntimeException("连接数量已用尽");
}
}
@Override
public Connection getConnection(String username, String password) throws SQLException {
return null;
}
@Override
public <T> T unwrap(Class<T> iface) throws SQLException {
return null;
}
@Override
public boolean isWrapperFor(Class<?> iface) throws SQLException {
return false;
}
@Override
public PrintWriter getLogWriter() throws SQLException {
return null;
}
@Override
public void setLogWriter(PrintWriter out) throws SQLException {
}
@Override
public void setLoginTimeout(int seconds) throws SQLException {
}
@Override
public int getLoginTimeout() throws SQLException {
return 0;
}
@Override
public Logger getParentLogger() throws SQLFeatureNotSupportedException {
return null;
}
}3.自定义连接池测试
public class MyDataSourceTest {
public static void main(String[] args) throws Exception{
//创建数据库连接池对象
MyDataSource dataSource = new MyDataSource();
System.out.println("使用之前连接池数量：" + dataSource.getSize());
//获取数据库连接对象
Connection con = dataSource.getConnection();
System.out.println(con.getClass());// JDBC4Connection
//查询学生表全部信息
String sql = "SELECT * FROM student";
PreparedStatement pst = con.prepareStatement(sql);
ResultSet rs = pst.executeQuery();
while(rs.next()) {
System.out.println(rs.getInt("sid") + "\t" + rs.getString("name") + "\t" + rs.getInt("age") + "\t" + rs.getDate("birthday"));
}
//释放资源
rs.close();
pst.close();
//目前的连接对象close方法，是直接关闭连接，而不是将连接归还池中
con.close();
System.out.println("使用之后连接池数量：" + dataSource.getSize());
}
}4.归还连接
继承(无法解决)
- 通过打印连接对象，发现DriverManager获取的连接实现类是JDBC4Connection。
- 自定义一个类，继承JDBC4Connection这个类，重写close()方法。
/* 自定义Connection类 */ public class MyConnection1 extends JDBC4Connection { //声明连接对象和连接池集合对象 private Connection con; private List<Connection> pool; //通过构造方法给成员变量赋值 public MyConnection1(String hostToConnectTo, int portToConnectTo, Properties info, String databaseToConnectTo, String url,Connection con,List<Connection> pool) throws SQLException { super(hostToConnectTo, portToConnectTo, info, databaseToConnectTo, url); this.con = con; this.pool = pool; } //重写close()方法，将连接归还给池中 @Override public void close() throws SQLException { pool.add(con); } }- 但是这种方式行不通，通过查看JDBC工具类获取连接的方法我们发现：我们虽然自定义了一个子类，完成了归还连接的操作。但是DriverManager获取的还是JDBC4Connection这个对象，并不是我们的子类对象。而我们又不能整体去修改驱动包中类的功能！
//将之前的连接对象换成自定义的子类对象 private static MyConnection1 con; //4.获取数据库连接的方法 public static Connection getConnection() { try { //等效于：MyConnection1 con = new JDBC4Connection(); 语法错误！ con = DriverManager.getConnection(url,username,password); } catch (SQLException e) { e.printStackTrace(); } return con; }装饰设计模式
- 自定义连接类
/* 自定义Connection类。通过装饰设计模式，实现和mysql驱动包中的Connection实现类相同的功能！ 实现步骤： 1.定义一个类，实现Connection接口 2.定义Connection连接对象和连接池容器对象的变量 3.提供有参构造方法，接收连接对象和连接池对象，对变量赋值 4.在close()方法中，完成连接的归还 5.剩余方法，只需要调用mysql驱动包的连接对象完成即可 */ public class MyConnection2 implements Connection { //2.定义Connection连接对象和连接池容器对象的变量 private Connection con; private List<Connection> pool; //3.提供有参构造方法，接收连接对象和连接池对象，对变量赋值 public MyConnection2(Connection con,List<Connection> pool) { this.con = con; this.pool = pool; } //4.在close()方法中，完成连接的归还 @Override public void close() throws SQLException { pool.add(con); } @Override public Statement createStatement() throws SQLException { return con.createStatement(); } @Override public PreparedStatement prepareStatement(String sql) throws SQLException { return con.prepareStatement(sql); } @Override public CallableStatement prepareCall(String sql) throws SQLException { return con.prepareCall(sql); } @Override public String nativeSQL(String sql) throws SQLException { return con.nativeSQL(sql); } @Override public void setAutoCommit(boolean autoCommit) throws SQLException { con.setAutoCommit(autoCommit); } @Override public boolean getAutoCommit() throws SQLException { return con.getAutoCommit(); } @Override public void commit() throws SQLException { con.commit(); } @Override public void rollback() throws SQLException { con.rollback(); } @Override public boolean isClosed() throws SQLException { return con.isClosed(); } @Override public DatabaseMetaData getMetaData() throws SQLException { return con.getMetaData(); } @Override public void setReadOnly(boolean readOnly) throws SQLException { con.setReadOnly(readOnly); } @Override public boolean isReadOnly() throws SQLException { return con.isReadOnly(); } @Override public void setCatalog(String catalog) throws SQLException { con.setCatalog(catalog); } @Override public String getCatalog() throws SQLException { return con.getCatalog(); } @Override public void setTransactionIsolation(int level) throws SQLException { con.setTransactionIsolation(level); } @Override public int getTransactionIsolation() throws SQLException { return con.getTransactionIsolation(); } @Override public SQLWarning getWarnings() throws SQLException { return con.getWarnings(); } @Override public void clearWarnings() throws SQLException { con.clearWarnings(); } @Override public Statement createStatement(int resultSetType, int resultSetConcurrency) throws SQLException { return con.createStatement(resultSetType,resultSetConcurrency); } @Override public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency) throws SQLException { return con.prepareStatement(sql,resultSetType,resultSetConcurrency); } @Override public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency) throws SQLException { return con.prepareCall(sql,resultSetType,resultSetConcurrency); } @Override public Map<String, Class<?>> getTypeMap() throws SQLException { return con.getTypeMap(); } @Override public void setTypeMap(Map<String, Class<?>> map) throws SQLException { con.setTypeMap(map); } @Override public void setHoldability(int holdability) throws SQLException { con.setHoldability(holdability); } @Override public int getHoldability() throws SQLException { return con.getHoldability(); } @Override public Savepoint setSavepoint() throws SQLException { return con.setSavepoint(); } @Override public Savepoint setSavepoint(String name) throws SQLException { return con.setSavepoint(name); } @Override public void rollback(Savepoint savepoint) throws SQLException { con.rollback(savepoint); } @Override public void releaseSavepoint(Savepoint savepoint) throws SQLException { con.releaseSavepoint(savepoint); } @Override public Statement createStatement(int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException { return con.createStatement(resultSetType,resultSetConcurrency,resultSetHoldability); } @Override public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException { return con.prepareStatement(sql,resultSetType,resultSetConcurrency,resultSetHoldability); } @Override public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException { return con.prepareCall(sql,resultSetType,resultSetConcurrency,resultSetHoldability); } @Override public PreparedStatement prepareStatement(String sql, int autoGeneratedKeys) throws SQLException { return con.prepareStatement(sql,autoGeneratedKeys); } @Override public PreparedStatement prepareStatement(String sql, int[] columnIndexes) throws SQLException { return con.prepareStatement(sql,columnIndexes); } @Override public PreparedStatement prepareStatement(String sql, String[] columnNames) throws SQLException { return con.prepareStatement(sql,columnNames); } @Override public Clob createClob() throws SQLException { return con.createClob(); } @Override public Blob createBlob() throws SQLException { return con.createBlob(); } @Override public NClob createNClob() throws SQLException { return con.createNClob(); } @Override public SQLXML createSQLXML() throws SQLException { return con.createSQLXML(); } @Override public boolean isValid(int timeout) throws SQLException { return con.isValid(timeout); } @Override public void setClientInfo(String name, String value) throws SQLClientInfoException { con.setClientInfo(name,value); } @Override public void setClientInfo(Properties properties) throws SQLClientInfoException { con.setClientInfo(properties); } @Override public String getClientInfo(String name) throws SQLException { return con.getClientInfo(name); } @Override public Properties getClientInfo() throws SQLException { return con.getClientInfo(); } @Override public Array createArrayOf(String typeName, Object[] elements) throws SQLException { return con.createArrayOf(typeName,elements); } @Override public Struct createStruct(String typeName, Object[] attributes) throws SQLException { return con.createStruct(typeName,attributes); } @Override public void setSchema(String schema) throws SQLException { con.setSchema(schema); } @Override public String getSchema() throws SQLException { return con.getSchema(); } @Override public void abort(Executor executor) throws SQLException { con.abort(executor); } @Override public void setNetworkTimeout(Executor executor, int milliseconds) throws SQLException { con.setNetworkTimeout(executor,milliseconds); } @Override public int getNetworkTimeout() throws SQLException { return con.getNetworkTimeout(); } @Override public <T> T unwrap(Class<T> iface) throws SQLException { return con.unwrap(iface); } @Override public boolean isWrapperFor(Class<?> iface) throws SQLException { return con.isWrapperFor(iface); } }- 自定义连接池类
public class MyDataSource implements DataSource{ //定义集合容器，用于保存多个数据库连接对象 private static List<Connection> pool = Collections.synchronizedList(new ArrayList<Connection>()); //静态代码块，生成10个数据库连接保存到集合中 static { for (int i = 0; i < 10; i++) { Connection con = JDBCUtils.getConnection(); pool.add(con); } } //返回连接池的大小 public int getSize() { return pool.size(); } //从池中返回一个数据库连接 @Override public Connection getConnection() { if(pool.size() > 0) { //从池中获取数据库连接 Connection con = pool.remove(0); //通过自定义连接对象进行包装 MyConnection2 mycon = new MyConnection2(con,pool); //返回包装后的连接对象 return mycon; }else { throw new RuntimeException("连接数量已用尽"); } } }适配器设计模式
- 通过之前MyConnection2连接类我们发现，有很多个需要实现的方法。这个时候我们就可以使用适配器设计模式了。提供一个适配器类，实现Connection接口，将所有功能进行实现(除了close方法)。自定义连接类只需要继承这个适配器类，重写需要改进的close()方法即可！
- 适配器类
/* 适配器抽象类。实现Connection接口。 实现所有的方法，调用mysql驱动包中Connection连接对象的方法 */ public abstract class MyAdapter implements Connection { // 定义数据库连接对象的变量 private Connection con; // 通过构造方法赋值 public MyAdapter(Connection con) { this.con = con; } // 所有的方法，均调用mysql的连接对象实现 @Override public Statement createStatement() throws SQLException { return con.createStatement(); } @Override public PreparedStatement prepareStatement(String sql) throws SQLException { return con.prepareStatement(sql); } @Override public CallableStatement prepareCall(String sql) throws SQLException { return con.prepareCall(sql); } @Override public String nativeSQL(String sql) throws SQLException { return con.nativeSQL(sql); } @Override public void setAutoCommit(boolean autoCommit) throws SQLException { con.setAutoCommit(autoCommit); } @Override public boolean getAutoCommit() throws SQLException { return con.getAutoCommit(); } @Override public void commit() throws SQLException { con.commit(); } @Override public void rollback() throws SQLException { con.rollback(); } @Override public boolean isClosed() throws SQLException { return con.isClosed(); } @Override public DatabaseMetaData getMetaData() throws SQLException { return con.getMetaData(); } @Override public void setReadOnly(boolean readOnly) throws SQLException { con.setReadOnly(readOnly); } @Override public boolean isReadOnly() throws SQLException { return con.isReadOnly(); } @Override public void setCatalog(String catalog) throws SQLException { con.setCatalog(catalog); } @Override public String getCatalog() throws SQLException { return con.getCatalog(); } @Override public void setTransactionIsolation(int level) throws SQLException { con.setTransactionIsolation(level); } @Override public int getTransactionIsolation() throws SQLException { return con.getTransactionIsolation(); } @Override public SQLWarning getWarnings() throws SQLException { return con.getWarnings(); } @Override public void clearWarnings() throws SQLException { con.clearWarnings(); } @Override public Statement createStatement(int resultSetType, int resultSetConcurrency) throws SQLException { return con.createStatement(resultSetType,resultSetConcurrency); } @Override public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency) throws SQLException { return con.prepareStatement(sql,resultSetType,resultSetConcurrency); } @Override public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency) throws SQLException { return con.prepareCall(sql,resultSetType,resultSetConcurrency); } @Override public Map<String, Class<?>> getTypeMap() throws SQLException { return con.getTypeMap(); } @Override public void setTypeMap(Map<String, Class<?>> map) throws SQLException { con.setTypeMap(map); } @Override public void setHoldability(int holdability) throws SQLException { con.setHoldability(holdability); } @Override public int getHoldability() throws SQLException { return con.getHoldability(); } @Override public Savepoint setSavepoint() throws SQLException { return con.setSavepoint(); } @Override public Savepoint setSavepoint(String name) throws SQLException { return con.setSavepoint(name); } @Override public void rollback(Savepoint savepoint) throws SQLException { con.rollback(savepoint); } @Override public void releaseSavepoint(Savepoint savepoint) throws SQLException { con.releaseSavepoint(savepoint); } @Override public Statement createStatement(int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException { return con.createStatement(resultSetType,resultSetConcurrency,resultSetHoldability); } @Override public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException { return con.prepareStatement(sql,resultSetType,resultSetConcurrency,resultSetHoldability); } @Override public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException { return con.prepareCall(sql,resultSetType,resultSetConcurrency,resultSetHoldability); } @Override public PreparedStatement prepareStatement(String sql, int autoGeneratedKeys) throws SQLException { return con.prepareStatement(sql,autoGeneratedKeys); } @Override public PreparedStatement prepareStatement(String sql, int[] columnIndexes) throws SQLException { return con.prepareStatement(sql,columnIndexes); } @Override public PreparedStatement prepareStatement(String sql, String[] columnNames) throws SQLException { return con.prepareStatement(sql,columnNames); } @Override public Clob createClob() throws SQLException { return con.createClob(); } @Override public Blob createBlob() throws SQLException { return con.createBlob(); } @Override public NClob createNClob() throws SQLException { return con.createNClob(); } @Override public SQLXML createSQLXML() throws SQLException { return con.createSQLXML(); } @Override public boolean isValid(int timeout) throws SQLException { return con.isValid(timeout); } @Override public void setClientInfo(String name, String value) throws SQLClientInfoException { con.setClientInfo(name,value); } @Override public void setClientInfo(Properties properties) throws SQLClientInfoException { con.setClientInfo(properties); } @Override public String getClientInfo(String name) throws SQLException { return con.getClientInfo(name); } @Override public Properties getClientInfo() throws SQLException { return con.getClientInfo(); } @Override public Array createArrayOf(String typeName, Object[] elements) throws SQLException { return con.createArrayOf(typeName,elements); } @Override public Struct createStruct(String typeName, Object[] attributes) throws SQLException { return con.createStruct(typeName,attributes); } @Override public void setSchema(String schema) throws SQLException { con.setSchema(schema); } @Override public String getSchema() throws SQLException { return con.getSchema(); } @Override public void abort(Executor executor) throws SQLException { con.abort(executor); } @Override public void setNetworkTimeout(Executor executor, int milliseconds) throws SQLException { con.setNetworkTimeout(executor,milliseconds); } @Override public int getNetworkTimeout() throws SQLException { return con.getNetworkTimeout(); } @Override public <T> T unwrap(Class<T> iface) throws SQLException { return con.unwrap(iface); } @Override public boolean isWrapperFor(Class<?> iface) throws SQLException { return con.isWrapperFor(iface); } }- 自定义连接类
/* 自定义Connection连接类。通过适配器设计模式。完成close()方法的重写 1.定义一个类，继承适配器父类 2.定义Connection连接对象和连接池容器对象的变量 3.提供有参构造方法，接收连接对象和连接池对象，对变量赋值 4.在close()方法中，完成连接的归还 */ public class MyConnection3 extends MyAdapter { //2.定义Connection连接对象和连接池容器对象的变量 private Connection con; private List<Connection> pool; //3.提供有参构造方法，接收连接对象和连接池对象，对变量赋值 public MyConnection3(Connection con,List<Connection> pool) { super(con); // 将接收的数据库连接对象给适配器父类传递 this.con = con; this.pool = pool; } //4.在close()方法中，完成连接的归还 @Override public void close() throws SQLException { pool.add(con); } }- 自定义连接池类
public class MyDataSource implements DataSource{ //定义集合容器，用于保存多个数据库连接对象 private static List<Connection> pool = Collections.synchronizedList(new ArrayList<Connection>()); //静态代码块，生成10个数据库连接保存到集合中 static { for (int i = 0; i < 10; i++) { Connection con = JDBCUtils.getConnection(); pool.add(con); } } //返回连接池的大小 public int getSize() { return pool.size(); } //从池中返回一个数据库连接 @Override public Connection getConnection() { if(pool.size() > 0) { //从池中获取数据库连接 Connection con = pool.remove(0); //通过自定义连接对象进行包装 //MyConnection2 mycon = new MyConnection2(con,pool); MyConnection3 mycon = new MyConnection3(con,pool); //返回包装后的连接对象 return mycon; }else { throw new RuntimeException("连接数量已用尽"); } } }动态代理
- 经过我们适配器模式的改进，自定义连接类中的方法已经很简洁了。剩余所有的方法已经抽取到了适配器类中。但是适配器这个类还是我们自己编写的，也比较麻烦！所以可以使用动态代理的方式来改进。
- 自定义数据库连接池类
public class MyDataSource implements DataSource{ //定义集合容器，用于保存多个数据库连接对象 private static List<Connection> pool = Collections.synchronizedList(new ArrayList<Connection>()); //静态代码块，生成10个数据库连接保存到集合中 static { for (int i = 0; i < 10; i++) { Connection con = JDBCUtils.getConnection(); pool.add(con); } } //返回连接池的大小 public int getSize() { return pool.size(); } //动态代理方式 @Override public Connection getConnection() { if(pool.size() > 0) { //从池中获取数据库连接 Connection con = pool.remove(0); Connection proxyCon = (Connection)Proxy.newProxyInstance(con.getClass().getClassLoader(), new Class[]{Connection.class}, new InvocationHandler() { /* 执行Connection实现类所有方法都会经过invoke 如果是close方法，则将连接还回池中 如果不是，直接执行实现类的原有方法 */ @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { if(method.getName().equals("close")) { pool.add(con); return null; }else { return method.invoke(con,args); } } }); return proxyCon; }else { throw new RuntimeException("连接数量已用尽"); } } //从池中返回一个数据库连接 /*@Override public Connection getConnection() { if(pool.size() > 0) { //从池中获取数据库连接 Connection con = pool.remove(0); //通过自定义连接对象进行包装 //MyConnection2 mycon = new MyConnection2(con,pool); MyConnection3 mycon = new MyConnection3(con,pool); //返回包装后的连接对象 return mycon; }else { throw new RuntimeException("连接数量已用尽"); } }*/ }
5.开源连接池的使用
C3P0
- 基本使用
/* 使用C3P0连接池 1.导入jar包 2.导入配置文件到src目录下 3.创建c3p0连接池对象 4.获取数据库连接进行使用 */ public class C3P0Demo1 { public static void main(String[] args) throws Exception{ //创建c3p0连接池对象 DataSource dataSource = new ComboPooledDataSource(); //获取数据库连接进行使用 Connection con = dataSource.getConnection(); //查询全部学生信息 String sql = "SELECT * FROM student"; PreparedStatement pst = con.prepareStatement(sql); ResultSet rs = pst.executeQuery(); while(rs.next()) { System.out.println(rs.getInt("sid") + "\t" + rs.getString("name") + "\t" + rs.getInt("age") + "\t" + rs.getDate("birthday")); } //释放资源 rs.close(); pst.close(); con.close(); // 将连接对象归还池中 } }- 配置演示
public class C3P0Demo2 { public static void main(String[] args) throws Exception{ //创建c3p0连接池对象 DataSource dataSource = new ComboPooledDataSource(); //获取数据库连接进行使用 for(int i = 1; i <= 11; i++) { Connection con = dataSource.getConnection(); System.out.println(i + ":" + con); if(i == 5) { con.close(); } } } }Druid
- 基本使用
/* Druid连接池 1.导入jar包 2.编写配置文件，放在src目录下 3.通过Properties集合加载配置文件 4.通过Druid连接池工厂类获取数据库连接池对象 5.获取数据库连接，进行使用 */ public class DruidDemo1 { public static void main(String[] args) throws Exception{ //通过Properties集合加载配置文件 InputStream is = DruidDemo1.class.getClassLoader().getResourceAsStream("druid.properties"); Properties prop = new Properties(); prop.load(is); //通过Druid连接池工厂类获取数据库连接池对象 DataSource dataSource = DruidDataSourceFactory.createDataSource(prop); //获取数据库连接，进行使用 Connection con = dataSource.getConnection(); //查询全部学生信息 String sql = "SELECT * FROM student"; PreparedStatement pst = con.prepareStatement(sql); ResultSet rs = pst.executeQuery(); while(rs.next()) { System.out.println(rs.getInt("sid") + "\t" + rs.getString("name") + "\t" + rs.getInt("age") + "\t" + rs.getDate("birthday")); } //释放资源 rs.close(); pst.close(); con.close(); // 将连接对象归还池中 } }- 抽取工具类
/* 数据库连接池工具类 */ public class DataSourceUtils { //1.私有构造方法 private DataSourceUtils(){} //2.定义DataSource数据源变量 private static DataSource dataSource; //3.提供静态代码块，完成配置文件的加载和获取连接池对象 static { try{ //加载配置文件 InputStream is = DruidDemo1.class.getClassLoader().getResourceAsStream("druid.properties"); Properties prop = new Properties(); prop.load(is); //获取数据库连接池对象 dataSource = DruidDataSourceFactory.createDataSource(prop); } catch(Exception e) { e.printStackTrace(); } } //4.提供获取数据库连接的方法 public static Connection getConnection() { Connection con = null; try { con = dataSource.getConnection(); } catch (SQLException e) { e.printStackTrace(); } return con; } //5.提供获取数据库连接池的方法 public static DataSource getDataSource() { return dataSource; } //6.提供释放资源的方法 public static void close(Connection con, Statement stat, ResultSet rs) { if(con != null) { try { con.close(); } catch (SQLException e) { e.printStackTrace(); } } if(stat != null) { try { stat.close(); } catch (SQLException e) { e.printStackTrace(); } } if(rs != null) { try { rs.close(); } catch (SQLException e) { e.printStackTrace(); } } } public static void close(Connection con, Statement stat) { close(con,stat,null); } }
八、JDBC框架(JDBCTemplate)
1.分析前一天案例中的重复代码
- dao层的重复代码
- 定义必要的信息、获取数据库的连接、释放资源都是重复的代码！
- 而我们最终的核心功能仅仅只是执行一条sql语句而已啊！
- 所以我们可以抽取出一个JDBC模板类，来封装一些方法(update、query)，专门帮我们执行增删改查的sql语句！
- 将之前那些重复的操作，都抽取到模板类中的方法里。就能大大简化我们的使用步骤！
2.自定义JDBC框架
2.1数据库的源信息
- DataBaseMetaData(了解)：数据库的源信息
- java.sql.DataBaseMetaData：封装了整个数据库的综合信息
- 例如：
- String getDatabaseProductName()：获取数据库产品的名称
- int getDatabaseProductVersion()：获取数据库产品的版本号
- ParameterMetaData：参数的源信息
- java.sql.ParameterMetaData：封装的是预编译执行者对象中每个参数的类型和属性
- 这个对象可以通过预编译执行者对象中的getParameterMetaData()方法来获取
- 核心功能：
- int getParameterCount()：获取sql语句中参数的个数
- ResultSetMetaData：结果集的源信息
- java.sql.ResultSetMetaData：封装的是结果集对象中列的类型和属性
- 这个对象可以通过结果集对象中的getMetaData()方法来获取
- 核心功能：
- int getColumnCount()：获取列的总数
- String getColumnName(int i)：获取列名
2.2JDBCTemplate类增删改功能的编写
public class JDBCTemplate {
private DataSource dataSource;
private Connection con;
private PreparedStatement pst;
private ResultSet rs;
public JDBCTemplate(DataSource dataSource) {
this.dataSource = dataSource;
}
//专用于执行增删改sql语句的方法
public int update(String sql,Object...objs) {
int result = 0;
try{
con = dataSource.getConnection();
pst = con.prepareStatement(sql);
//获取sql语句中的参数源信息
ParameterMetaData pData = pst.getParameterMetaData();
//获取sql语句中参数的个数
int parameterCount = pData.getParameterCount();
//判断参数个数是否一致
if(parameterCount != objs.length) {
throw new RuntimeException("参数个数不匹配");
}
//为sql语句中的?占位符赋值
for (int i = 0; i < objs.length; i++) {
pst.setObject(i+1,objs[i]);
}
//执行sql语句
result = pst.executeUpdate();
} catch(Exception e) {
e.printStackTrace();
} finally {
//释放资源
DataSourceUtils.close(con,pst);
}
//返回结果
return result;
}
}
2.3JDBCTemplate类查询功能的编写
- 实体类
/*
学生实体类
*/
public class Student {
private Integer sid;
private String name;
private Integer age;
private Date birthday;
public Student() {
}
public Student(Integer sid, String name, Integer age, Date birthday) {
this.sid = sid;
this.name = name;
this.age = age;
this.birthday = birthday;
}
public Integer getSid() {
return sid;
}
public void setSid(Integer sid) {
this.sid = sid;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
@Override
public String toString() {
return "Student{" +
"sid=" + sid +
", name='" + name + '\'' +
", age=" + age +
", birthday=" + birthday +
'}';
}
}
- ResultSetHandler接口
/*
用于处理结果集的接口
*/
public interface ResultSetHandler<T> {
//处理结果集的抽象方法。
<T> T handler(ResultSet rs);
}
- BeanHandler实现类
/*
实现类1：用于完成将查询出来的一条记录，封装到Student对象中
*/
public class BeanHandler<T> implements ResultSetHandler<T> {
//1.声明对象类型变量
private Class<T> beanClass;
//2.有参构造对变量赋值
public BeanHandler(Class<T> beanClass) {
this.beanClass = beanClass;
}
/*
将ResultSet结果集中的数据封装到beanClass类型对象中
*/
@Override
public T handler(ResultSet rs) {
//3.声明对象
T bean = null;
try{
//4.创建传递参数的对象
bean = beanClass.newInstance();
//5.判断是否有结果集
if(rs.next()) {
//6.得到所有的列名
//6.1先得到结果集的源信息
ResultSetMetaData rsmd = rs.getMetaData();
//6.2还要得到有多少列
int columnCount = rsmd.getColumnCount();
//6.3遍历列数
for(int i = 1; i <= columnCount; i++) {
//6.4得到每列的列名
String columnName = rsmd.getColumnName(i);
//6.5通过列名获取数据
Object columnValue = rs.getObject(columnName);
//6.6列名其实就是对象中成员变量的名称。于是就可以使用列名得到对象中属性的描述器(get和set方法)
PropertyDescriptor pd = new PropertyDescriptor(columnName.toLowerCase(),beanClass);
//6.7获取set方法
Method writeMethod = pd.getWriteMethod();
//6.8执行set方法，给成员变量赋值
writeMethod.invoke(bean,columnValue);
}
}
} catch (Exception e) {
e.printStackTrace();
}
//7.将对象返回
return bean;
}
}
- BeanListHandler实现类
/*
实现类2：用于将结果集封装到集合中
*/
public class BeanListHandler<T> implements ResultSetHandler<T> {
//1.声明对象变量
private Class<T> beanClass;
//2.有参构造为变量赋值
public BeanListHandler(Class<T> beanClass) {
this.beanClass = beanClass;
}
@Override
public List<T> handler(ResultSet rs) {
//3.创建集合对象
List<T> list = new ArrayList<>();
try{
//4.遍历结果集对象
while(rs.next()) {
//5.创建传递参数的对象
T bean = beanClass.newInstance();
//6.得到所有的列名
//6.1先得到结果集的源信息
ResultSetMetaData rsmd = rs.getMetaData();
//6.2还要得到有多少列
int columnCount = rsmd.getColumnCount();
//6.3遍历列数
for(int i = 1; i <= columnCount; i++) {
//6.4得到每列的列名
String columnName = rsmd.getColumnName(i);
//6.5通过列名获取数据
Object columnValue = rs.getObject(columnName);
//6.6列名其实就是对象中成员变量的名称。于是就可以使用列名得到对象中属性的描述器(get和set方法)
PropertyDescriptor pd = new PropertyDescriptor(columnName.toLowerCase(),beanClass);
//6.7获取set方法
Method writeMethod = pd.getWriteMethod();
//6.8执行set方法，给成员变量赋值
writeMethod.invoke(bean,columnValue);
}
//7.将对象保存到集合中
list.add(bean);
}
} catch (Exception e) {
e.printStackTrace();
}
//8.返回结果
return list;
}
}
- ScalarHandler实现类
/*
实现类3：用于返回一个聚合函数的查询结果
*/
public class ScalarHandler<T> implements ResultSetHandler<T> {
@Override
public Long handler(ResultSet rs) {
//1.声明一个变量
Long value = null;
try{
//2.判断是否有结果
if(rs.next()) {
//3.获取结果集的源信息
ResultSetMetaData rsmd = rs.getMetaData();
//4.获取第一列的列名
String columnName = rsmd.getColumnName(1);
//5.根据列名获取值
value = rs.getLong(columnName);
}
} catch(Exception e) {
e.printStackTrace();
}
//6.将结果返回
return value;
}
}
- JDBCTemplate类
public class JDBCTemplate {
private DataSource dataSource;
private Connection con;
private PreparedStatement pst;
private ResultSet rs;
public JDBCTemplate(DataSource dataSource) {
this.dataSource = dataSource;
}
/*
专用于执行聚合函数sql语句的方法
*/
public Long queryForScalar(String sql, ResultSetHandler<Long> rsh, Object...objs) {
Long result = null;
try{
con = dataSource.getConnection();
pst = con.prepareStatement(sql);
//获取sql语句中的参数源信息
ParameterMetaData pData = pst.getParameterMetaData();
int parameterCount = pData.getParameterCount();
//判断参数个数是否一致
if(parameterCount != objs.length) {
throw new RuntimeException("参数个数不匹配");
}
//为sql语句中的?占位符赋值
for (int i = 0; i < objs.length; i++) {
pst.setObject(i+1,objs[i]);
}
//执行sql语句
rs = pst.executeQuery();
//通过ScalarHandler方式对结果进行处理
result = rsh.handler(rs);
} catch(Exception e) {
e.printStackTrace();
} finally {
//释放资源
DataSourceUtils.close(con,pst,rs);
}
//将结果返回
return result;
}
/*
专用于查询所有记录sql语句的方法
*/
public <T> List<T> queryForList(String sql, ResultSetHandler<T> rsh, Object...objs) {
List<T> list = new ArrayList<>();
try{
con = dataSource.getConnection();
pst = con.prepareStatement(sql);
//获取sql语句中的参数源信息
ParameterMetaData pData = pst.getParameterMetaData();
int parameterCount = pData.getParameterCount();
//判断参数个数是否一致
if(parameterCount != objs.length) {
throw new RuntimeException("参数个数不匹配");
}
//为sql语句中的?占位符赋值
for (int i = 0; i < objs.length; i++) {
pst.setObject(i+1,objs[i]);
}
//执行sql语句
rs = pst.executeQuery();
//通过BeanListHandler方式对结果进行处理
list = rsh.handler(rs);
} catch(Exception e) {
e.printStackTrace();
} finally {
//释放资源
DataSourceUtils.close(con,pst,rs);
}
//将结果返回
return list;
}
/*
专用于执行查询一条记录sql语句的方法
*/
public <T> T queryForObject(String sql, ResultSetHandler<T> rsh, Object...objs) {
T obj = null;
try{
con = dataSource.getConnection();
pst = con.prepareStatement(sql);
//获取sql语句中的参数源信息
ParameterMetaData pData = pst.getParameterMetaData();
int parameterCount = pData.getParameterCount();
//判断参数个数是否一致
if(parameterCount != objs.length) {
throw new RuntimeException("参数个数不匹配");
}
//为sql语句中的?占位符赋值
for (int i = 0; i < objs.length; i++) {
pst.setObject(i+1,objs[i]);
}
//执行sql语句
rs = pst.executeQuery();
//通过BeanHandler方式对结果进行处理
obj = rsh.handler(rs);
} catch(Exception e) {
e.printStackTrace();
} finally {
//释放资源
DataSourceUtils.close(con,pst,rs);
}
//将结果返回
return obj;
}
}
2.4测试自定义JDBC框架的使用
public class JDBCTemplateTest {
//创建JDBCTemplate对象
JDBCTemplate template = new JDBCTemplate(DataSourceUtils.getDataSource());
@Test
public void selectScalar() {
//查询student表的记录条数
String sql = "SELECT COUNT(*) FROM student";
Long count = template.queryForScalar(sql, new ScalarHandler<Long>());
System.out.println(count);
}
@Test
public void selectAll() {
//查询所有学生信息
String sql = "SELECT * FROM student";
List<Student> list = template.queryForList(sql, new BeanListHandler<Student>(Student.class));
for(Student stu : list) {
System.out.println(stu);
}
}
@Test
public void selectOne() {
//查询张三这条记录
String sql = "SELECT * FROM student WHERE sid=?";
//通过BeanHandler将结果封装成一个Student对象
Student stu = template.queryForObject(sql, new BeanHandler<Student>(Student.class), 1);
System.out.println(stu);
}
@Test
public void insert() {
//新增周七记录
String sql = "INSERT INTO student VALUES (?,?,?,?)";
Object[] params = {5,"周七",27,"2007-07-07"};
int result = template.update(sql, params);
System.out.println(result);
}
@Test
public void delete() {
//删除周七这条记录
String sql = "DELETE FROM student WHERE sid=?";
int result = template.update(sql, 5);
System.out.println(result);
}
@Test
public void update() {
//修改张三的年龄为33
String sql = "UPDATE student SET age=? WHERE name=?";
Object[] params = {33,"张三"};
int result = template.update(sql,params);
System.out.println(result);
}
}
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