JDBC 为访问不同数据库提供了统一的接口,为使用者屏蔽了细节问题。
Java程序员使用JDBC,可以连接任何提供了JDBC驱动程序的数据库系统,从而完成对数据库的各种操作。
模拟JDBC
package com.xjs.jdbc.myjdbc;
/**
* @author 谢家升
* @version 1.0
* 我们规定的jdbc接口(方法)
*/
public interface JdbcInterface {
//连接
public Object getConnection() ;
//crud
public void crud();
//关闭连接
public void close();
}
package com.xjs.jdbc.myjdbc;
/**
* @author 谢家升
* @version 1.0
* mysql 数据库实现了jdbc接口 [模拟] 【mysql厂商开发】
*/
public class MysqlJdbcImpl implements JdbcInterface{
@Override
public Object getConnection() {
System.out.println("得到 mysql 的连接");
return null;
}
@Override
public void crud() {
System.out.println("完成 mysql 增删改查");
}
@Override
public void close() {
System.out.println("关闭 mysql 的连接");
}
}
package com.xjs.jdbc.myjdbc;
/**
* @author 谢家升
* @version 1.0
* 模拟oracle数据库实现 jdbc
*/
public class OracleJdbcImpl implements JdbcInterface {
@Override
public Object getConnection() {
System.out.println("得到 oracle的连接 升级");
return null;
}
@Override
public void crud() {
System.out.println("完成 对oracle的增删改查");
}
@Override
public void close() {
System.out.println("关闭 oracle的连接");
}
}
package com.xjs.jdbc.myjdbc;
import org.junit.jupiter.api.Test;
import java.io.FileInputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.Properties;
import java.util.Scanner;
/**
* @author 谢家升
* @version 1.0
*/
public class TestJDBC {
public static void main(String[] args) throws Exception {
//完成对mysql的操作
JdbcInterface jdbcInterface = new MysqlJdbcImpl();
jdbcInterface.getConnection(); //通过接口来调用实现类[动态绑定]
jdbcInterface.crud();
jdbcInterface.close();
//完成对oracle的操作
System.out.println("==============================");
jdbcInterface = new OracleJdbcImpl();
jdbcInterface.getConnection(); //通过接口来调用实现类[动态绑定]
jdbcInterface.crud();
jdbcInterface.close();
}
}
CREATE TABLE actor(
id INT PRIMARY KEY AUTO_INCREMENT,
`name` VARCHAR(32) NOT NULL DEFAULT '',
sex CHAR(1) NOT NULL DEFAULT '女',
borndate DATETIME,
phone VARCHAR(12)
)
SELECT * FROM actor
【前置工作】:将mysql 驱动引入到我们的项目中
视频链接: jdbc快速入门.
package com.xjs.jdbc;
import com.mysql.jdbc.Driver;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
/**
* @author 谢家升
* @version 1.0
* 这是第一个Jdbc 程序,完成简单的操作
*/
public class Jdbc01 {
public static void main(String[] args) throws SQLException {
//前置工作: 在项目下创建一个文件夹比如 libs
// 将 mysql.jar 拷贝到该目录下,点击 add as Library... 加入到项目中
//1. 注册驱动
Driver driver = new Driver(); //创建driver对象
//2. 得到连接
// 解读:
//(1) jdbc:mysql:// 规定好表示协议,通过jdbc的方式连接mysql
//(2) localhost 主机,可以是ip地址
//(3) 3306 表示mysql监听的端口
//(4) hsp_db02 连接到mysql dbms 的哪个数据库
//(5) mysql的连接本质就是前面学过的socket连接
String url = "jdbc:mysql://localhost:3306/hsp_db02";
//将 用户名和密码放入到Properties 对象
Properties properties = new Properties();
//说明 user 和 password 是规定好,后面的值根据实际情况写
properties.setProperty("user", "root");// 用户
properties.setProperty("password", "hsp"); //密码
Connection connect = driver.connect(url, properties);
//3. 执行sql
//String sql = "insert into actor values(null, '刘德华', '男', '1970-11-11', '110')";
//String sql = "update actor set name='周星驰' where id = 1";
String sql = "delete from actor where id = 1";
//statement 用于执行静态SQL语句并返回其生成的结果的对象
Statement statement = connect.createStatement();
int rows = statement.executeUpdate(sql); // 如果是 dml语句,返回的就是影响行数
System.out.println(rows > 0 ? "成功" : "失败");
//4. 关闭连接资源
statement.close();
connect.close();
}
}
//获取Driver实现类对象
Driver driver = new com.mysql.jdbc.Driver();
String url = "jdbc:mysql://localhost:3306/jdbc_db";
Properties info = new Properties();
info.setProperties("user","root");//用户名
info.setProperties("password","hsp");//密码
Connection conn = driver.connect(url,info);
System.out.println(conn);
//方式1 会直接使用 com.mysql.jdbc.Driver(),属于静态加载,灵活性差,依赖性强
//---推出---> 方式2
Calss aClass = Class.forName("com.mysql.jdbc.Driver");
Driver driver = (Driver) aClass.newInstance();
String url = "jdbc:mysql://localhost:3306/jdbc_db";
Properties info = new Properties();
info.setProperties("user","root");
info.setProperties("password","hsp");
Connection conn = driver.connect(url,info);
System.out.println(conn);
//使用DriverManager替换Driver
Class aClass = Class.forName("com.mysql.jdbc.Driver");
Driver driver = (Driver) aClass.newInstance();
String url = "jdbc:mysql://localhost:3306/hsp_db02";
String user = "root";
String password = "hsp";
DriverManager.registerDriver(driver);//注册Driver驱动
Connection conn = DriverManager.getConnection(url,user,password);
System.out.println(conn);
//使用Class.forName 自动完成注册驱动,简化代码 ==> 分析源码
Class.forName("com.mysql.jdbc.Driver");
String url = "jdbc:mysql://localhost:3306/hsp_db02";
String user = "root";
String password = "hsp";
Connection conn = DriverManager.getConnection(url,user,password);
System.out.println(conn);
> 特别提示:
> 1. mysql驱动5.1.6可以无需Class.forName("com.mysql.jdbc.Driver");
> 2. 从jdk1.5以后使用了jdbc4, 不再需要显示调用Class.forName()注册驱动,
> 而是自动调用驱动jar包下 META-INF\services\java.sql.Driver文本中的类名称去注册
> 3.建议还是写上 Class.forName("com.mysql.jdbc.Driver"),更加明确
//使用配置文件,连接数据库更灵活
1. Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/hsp_db02","user","hsp");
这其中的字符串 各个值,比如端口,数据库,用户名,密码为了方便,
我们可以将信息写入到 mysql.properties 配置文件中,方便操作
【配置文件 mysql.propertise 内容如下】
user=root
password=hsp
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/hsp_db02
//通过Properties对象获取配置文件的信息
Properties properties = new Properties();
properties.load(new FileInputStream("src\\mysql.properties"));
//获取相关的值
String user = properties.getProperty("user");
String password = properties.getProperty("password");
String driver = properties.getProperty("driver");
String url = properties.getProperty("url");
Class.forName(driver);//建议写上
Connection connection = DriverManager.getConnection(url, user, password);
System.out.println("方式5 " + connection);
【五种方式代码如下】
package com.xjs.jdbc;
import com.mysql.jdbc.Driver;
import org.junit.jupiter.api.Test;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;
/**
* @author 谢家升
* @version 1.0
* 分析java 连接mysql的5中方式
*/
public class JdbcConn {
//方式1
@Test
public void connect01() throws SQLException {
Driver driver = new Driver(); //创建driver对象
String url = "jdbc:mysql://localhost:3306/hsp_db02";
//将 用户名和密码放入到Properties 对象
Properties properties = new Properties();
//说明 user 和 password 是规定好,后面的值根据实际情况写
properties.setProperty("user", "root");// 用户
properties.setProperty("password", "hsp"); //密码
Connection connect = driver.connect(url, properties);
System.out.println(connect); //com.mysql.jdbc.JDBC4Connection@6c629d6e
}
//方式2
@Test
public void connect02() throws ClassNotFoundException, IllegalAccessException, InstantiationException, SQLException {
//使用反射加载Driver类 , 动态加载,更加的灵活,减少依赖性
Class<?> aClass = Class.forName("com.mysql.jdbc.Driver");
Driver driver = (Driver)aClass.newInstance();
String url = "jdbc:mysql://localhost:3306/hsp_db02";
//将 用户名和密码放入到Properties 对象
Properties properties = new Properties();
//说明 user 和 password 是规定好,后面的值根据实际情况写
properties.setProperty("user", "root");// 用户
properties.setProperty("password", "hsp"); //密码
Connection connect = driver.connect(url, properties);
System.out.println("方式2=" + connect); //com.mysql.jdbc.JDBC4Connection@6c629d6e
}
//方式3 使用DriverManager 替代 driver 进行统一管理
@Test
public void connect03() throws IllegalAccessException, InstantiationException, ClassNotFoundException, SQLException {
//使用反射加载Driver
Class<?> aClass = Class.forName("com.mysql.jdbc.Driver");
Driver driver = (Driver) aClass.newInstance();
//创建url 和 user 和 password
String url = "jdbc:mysql://localhost:3306/hsp_db02";
String user = "root";
String password = "hsp";
DriverManager.registerDriver(driver);//注册Driver驱动
Connection connection = DriverManager.getConnection(url, user, password);
System.out.println("第三种方式=" + connection); //com.mysql.jdbc.JDBC4Connection@5ecddf8f
}
//方式4: 使用Class.forName 自动完成注册驱动,简化代码
//这种方式获取连接是使用的最多,推荐使用
@Test
public void connect04() throws ClassNotFoundException, SQLException {
//使用反射加载了 Driver类
//在加载 Driver类时,完成注册
/*
源码: 1. 静态代码块,在类加载时,会执行一次.
2. DriverManager.registerDriver(new Driver());
3. 因此注册driver的工作已经完成
static {
try {
DriverManager.registerDriver(new Driver());
} catch (SQLException var1) {
throw new RuntimeException("Can't register driver!");
}
}
*/
Class.forName("com.mysql.jdbc.Driver");
//创建url 和 user 和 password
String url = "jdbc:mysql://localhost:3306/hsp_db02";
String user = "root";
String password = "hsp";
Connection connection = DriverManager.getConnection(url, user, password);
System.out.println("第4种方式~ " + connection); //com.mysql.jdbc.JDBC4Connection@6c629d6e
}
//方式5 , 在方式4的基础上改进,增加配置文件,让连接mysql更加灵活
@Test
public void connect05() throws IOException, ClassNotFoundException, SQLException {
//通过Properties对象获取配置文件的信息
Properties properties = new Properties();
properties.load(new FileInputStream("src\\mysql.properties"));
//获取相关的值
String user = properties.getProperty("user");
String password = properties.getProperty("password");
String driver = properties.getProperty("driver");
String url = properties.getProperty("url");
Class.forName(driver);//建议写上
Connection connection = DriverManager.getConnection(url, user, password);
System.out.println("方式5 " + connection); //com.mysql.jdbc.JDBC4Connection@6c629d6e
}
}
参考前面的代码,使用方式5完成以下功能
package com.xjs.jdbc;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
/**
* @Author: 谢家升
* @Version: 1.0
*/
public class Exercise {
public static void main(String[] args) throws IOException, SQLException {
/*
参考前面的代码,使用==方式5==完成以下功能
1. 创建 news 表
2. 使用 JDBC 添加 5 条数据
3. 修改 id = 1 的记录,将 content 改成一个新的消息
4. 删除 id = 3 的记录
*/
//1.加载驱动
Properties properties = new Properties();
properties.load(new FileInputStream("src\\mysql.properties"));
String user = properties.getProperty("user");
String password = properties.getProperty("password");
String driver = properties.getProperty("driver");
String url = properties.getProperty("url");
//2.获得连接
Connection connection = DriverManager.getConnection(url, user, password);
//3.执行sql
//创建 news 表
//String sql = "create table news (id int primary key , content varchar(32) not null default '')";
//使用 JDBC 添加 5 条数据
//String sql = "insert into news values (1,'北京新闻'),(2,'上海新闻'),(3,'深圳新闻'),(4,'湖北新闻'),(5,'中央新闻')";
//修改 id = 1 的记录,将 content 改成一个新的消息
//String sql = "update news set content = '十堰新闻' where id = 1";
//删除 id = 3 的记录
String sql = "delete from news where id = 3";
Statement statement = connection.createStatement();
int i = statement.executeUpdate(sql);
System.out.println("i= "+i);
System.out.println(i>0?"操作成功~":"失败...");
//4.关闭连接释放资源
statement.close();
connection.close();
}
}
package com.xjs.jdbc.resultSet_;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.sql.*;
import java.util.Properties;
/**
* @Author: 谢家升
* @Version: 1.0
* 演示select 语句返回 ResultSet ,并取出结果
*/
@SuppressWarnings({"all"})
public class ResultSet_ {
public static void main(String[] args) throws IOException, ClassNotFoundException, SQLException {
//通过Properties对象获取配置文件的信息
//读取 mysql.properties 配置文件信息
Properties properties = new Properties();
properties.load(new FileInputStream("src\\mysql.properties"));
//获取相关信息
String user = properties.getProperty("user");
String password = properties.getProperty("password");
String driver = properties.getProperty("driver");
String url = properties.getProperty("url");
//1.注册驱动
Class.forName(driver);
//2.获取连接
Connection connection = DriverManager.getConnection(url, user, password);
//3.得到statement
Statement statement = connection.createStatement();
//4.执行sql
//先添加两条数据
//String sql = "insert into actor values (null,'刘德华','男','1970-12-12','111')";
//String sql = "insert into actor values (null,'周星驰','男','1974-1-1','222')";
//查询语句
String sql = "select id,name,sex,borndate from actor";
//执行给定的SQL语句,该语句返回单个 ResultSet对象
//dml语句
//int i = statement.executeUpdate(sql);
//System.out.println(i>0?"成功~":"失败...");
//执行给定的SQL语句,该语句返回单个 ResultSet对象
/*
+----+-----------+-----+---------------------+
| id | name | sex | borndate |
+----+-----------+-----+---------------------+
| 2 | 刘德华 | 男 | 1970-12-12 00:00:00 |
| 3 | 周星驰 | 男 | 1974-01-01 00:00:00 |
+----+-----------+-----+---------------------+
*/
/*
阅读debug 代码 resultSet 对象的结构
*/
//select语句
ResultSet resultSet = statement.executeQuery(sql);
//5. 使用while取出数据
while (resultSet.next()) {
int id = resultSet.getInt(1);//获取该行的第1列值
//int id = resultSet.getInt("id"); 通过列名来获取值, 推荐
String name = resultSet.getString(2);//获取该行的第2列值
String sex = resultSet.getString(3);
Date borndate = resultSet.getDate(4);
//输出
System.out.println(id + "\t" + name + "\t" + sex + "\t" + borndate);
}
//6.关闭资源
statement.close();
connection.close();
}
}
【阅读debug 代码 resultSet 对象的结构】如下图所示:
-- 演示sql 注入
-- 创建一张表
CREATE TABLE admin ( -- 管理员表
NAME VARCHAR(32) NOT NULL UNIQUE,
pwd VARCHAR(32) NOT NULL DEFAULT '') CHARACTER SET utf8;
-- 添加数据
INSERT INTO admin VALUES('tom', '123');
-- 查找某个管理是否存在
SELECT *
FROM admin
WHERE NAME = 'tom' AND pwd = '123'
-- SQL
-- 输入用户名 为 1' or
-- 输入万能密码 为 or '1'= '1
SELECT *
FROM admin
WHERE NAME = '1' OR' AND pwd = 'OR '1'= '1'
SELECT * FROM admin
【说明】scanner.next()
:当接收到 空格或者 '就是表示结束, 而scanner.nextLine()
是接收到回车表示结束
package com.xjs.jdbc.statement_;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.sql.*;
import java.util.Properties;
import java.util.Scanner;
/**
* @author 谢家升
* @version 1.0
* 演示statement 的注入问题
*/
@SuppressWarnings({"all"})
public class Statement_ {
public static void main(String[] args) throws Exception {
Scanner scanner = new Scanner(System.in);
//让用户输入管理员名和密码
System.out.print("请输入管理员的名字: ");
//next(): 当接收到 空格或者 '就是表示结束, 而nextLine()是接收到回车表示结束
String admin_name = scanner.nextLine(); // 特别说明,如果希望看到SQL注入,这里需要用nextLine
System.out.print("请输入管理员的密码: ");
String admin_pwd = scanner.nextLine();
//通过Properties对象获取配置文件的信息
Properties properties = new Properties();
properties.load(new FileInputStream("src\\mysql.properties"));
//获取相关的值
String user = properties.getProperty("user");
String password = properties.getProperty("password");
String driver = properties.getProperty("driver");
String url = properties.getProperty("url");
//1. 注册驱动
Class.forName(driver);//建议写上
//2. 得到连接
Connection connection = DriverManager.getConnection(url, user, password);
//3. 得到Statement
Statement statement = connection.createStatement();
//4. 组织SqL
String sql = "select name , pwd from admin where name ='"
+ admin_name + "' and pwd = '" + admin_pwd + "'";
ResultSet resultSet = statement.executeQuery(sql);
if (resultSet.next()) { //如果查询到一条记录,则说明该管理存在
System.out.println("恭喜, 登录成功");
} else {
System.out.println("对不起,登录失败");
}
//关闭连接
resultSet.close();
statement.close();
connection.close();
}
}
package com.xjs.jdbc.preparedstatement_;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.sql.*;
import java.util.Properties;
import java.util.Scanner;
/**
* @author 谢家升
* @version 1.0
* 演示PreparedStatement使用
*/
@SuppressWarnings({"all"})
public class PreparedStatement_ {
public static void main(String[] args) throws Exception {
Scanner scanner = new Scanner(System.in);
//让用户输入管理员名和密码
System.out.print("请输入管理员的名字: "); //next(): 当接收到 空格或者 '就是表示结束
String admin_name = scanner.nextLine(); // 说明,如果希望看到SQL注入,这里需要用nextLine
System.out.print("请输入管理员的密码: ");
String admin_pwd = scanner.nextLine();
//通过Properties对象获取配置文件的信息
Properties properties = new Properties();
properties.load(new FileInputStream("src\\mysql.properties"));
//获取相关的值
String user = properties.getProperty("user");
String password = properties.getProperty("password");
String driver = properties.getProperty("driver");
String url = properties.getProperty("url");
//1. 注册驱动
Class.forName(driver);//建议写上
//2. 得到连接
Connection connection = DriverManager.getConnection(url, user, password);
//3. 得到PreparedStatement
//3.1 组织SqL , Sql 语句的 ? 就相当于占位符
String sql = "select name , pwd from admin where name =? and pwd = ?";
//3.2 preparedStatement 对象是实现了 PreparedStatement 接口的实现类的对象
PreparedStatement preparedStatement = connection.prepareStatement(sql);
//3.3 给 ? 赋值
preparedStatement.setString(1, admin_name);
preparedStatement.setString(2, admin_pwd);
//4. 执行 select 语句使用 executeQuery
// 如果执行的是 dml(update, insert ,delete) executeUpdate()
// 这里执行 executeQuery ,不要在写 sql,
ResultSet resultSet = preparedStatement.executeQuery();
if (resultSet.next()) { //如果查询到一条记录,则说明该管理存在
System.out.println("恭喜, 登录成功");
} else {
System.out.println("对不起,登录失败");
}
//关闭连接
resultSet.close();
preparedStatement.close();
connection.close();
}
}
package com.xjs.jdbc.preparedstatement_;
import java.io.FileInputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.Properties;
import java.util.Scanner;
/**
* @author 谢家升
* @version 1.0
* 演示PreparedStatement使用 dml语句
*/
@SuppressWarnings({"all"})
public class PreparedStatementDML_ {
public static void main(String[] args) throws Exception {
//看 PreparedStatement类图
Scanner scanner = new Scanner(System.in);
//让用户输入管理员名和密码
System.out.print("请输删除管理员的名字: "); //next(): 当接收到 空格或者 '就是表示结束
String admin_name = scanner.nextLine(); // 说明,如果希望看到SQL注入,这里需要用nextLine
// System.out.print("请输入管理员的新密码: ");
// String admin_pwd = scanner.nextLine();
//通过Properties对象获取配置文件的信息
Properties properties = new Properties();
properties.load(new FileInputStream("src\\mysql.properties"));
//获取相关的值
String user = properties.getProperty("user");
String password = properties.getProperty("password");
String driver = properties.getProperty("driver");
String url = properties.getProperty("url");
//1. 注册驱动
Class.forName(driver);//建议写上
//2. 得到连接
Connection connection = DriverManager.getConnection(url, user, password);
//3. 得到PreparedStatement
//3.1 组织SqL , Sql 语句的 ? 就相当于占位符
//添加记录
//String sql = "insert into admin values(?, ?)";
//String sql = "update admin set pwd = ? where name = ?";
String sql = "delete from admin where name = ?";
//3.2 preparedStatement 对象实现了 PreparedStatement 接口的实现类的对象
PreparedStatement preparedStatement = connection.prepareStatement(sql);
//3.3 给 ? 赋值
preparedStatement.setString(1, admin_name);
//preparedStatement.setString(2, admin_name);
//4. 执行 dml 语句使用 executeUpdate
int rows = preparedStatement.executeUpdate();
System.out.println(rows > 0 ? "执行成功" : "执行失败");
//关闭连接
preparedStatement.close();
connection.close();
}
}
要求:
package com.xjs.jdbc.preparedStatement_;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.sql.*;
import java.util.Properties;
import java.util.Scanner;
/**
* @Author: 谢家升
* @Date: 2022/1/26-01-26-15:37
* @Version: 1.0
*/
@SuppressWarnings({"all"})
public class Exercise {
public static void main(String[] args) throws IOException, ClassNotFoundException, SQLException {
//接收用户输入
Scanner scanner = new Scanner(System.in);
// System.out.println("请输入用户名:");
// String admin_name = scanner.nextLine();
// System.out.println("请输入密码:");
// String admin_pwd = scanner.nextLine();
//通过properties对象读取配置文件
Properties properties = new Properties();
properties.load(new FileInputStream("src\\mysql.properties"));
//读取相关信息
String user = properties.getProperty("user");
String password = properties.getProperty("password");
String url = properties.getProperty("url");
String driver = properties.getProperty("driver");
//1.注册driver驱动
Class.forName(driver);
//2.得到连接
Connection connection = DriverManager.getConnection(url, user, password);
//3.组织sql语句
//① 创建admin表
// String sql = "create table admin (name varchar(32) not null unique," +
// "pwd varchar(32) not null default '')";
//② 使用 preparedStatement 添加 5 条数据
// String sql = "insert into admin values (?,?)";
//③ 修改 tom 的记录,将 name 改成 king
// String sql = "update admin set name = ? where name = ?";
//④ 删除一条记录
// String sql = "delete from admin where name = ?";
//⑤ 查询全部记录,并显示在控制台
String sql = "select * from admin";
//3.2得到preparedStatement
PreparedStatement preparedStatement = connection.prepareStatement(sql);
//3.3 给?赋值
//preparedStatement.setString(1,admin_name);
//preparedStatement.setString(2,admin_pwd);
//4.执行sql
//dml语句
// int i = preparedStatement.executeUpdate();
// System.out.println(i>0?"执行成功":"执行失败");
//select语句
ResultSet resultSet = preparedStatement.executeQuery();
while (resultSet.next()) {
String name = resultSet.getString(1);//获取该行第1列数据
String pwd = resultSet.getString(2);//获取该行第2列数据
System.out.println(name+"\t"+pwd);
}
//5.关闭资源
resultSet.close();
preparedStatement.close();
connection.close();
}
}
在 jdbc 操作中,获取连接和释放资源是经常使用到的,可以将其封装到 JDBC 连接的工具类 JDBCUtils
package com.xjs.jdbc.utils;
import java.io.FileInputStream;
import java.io.IOException;
import java.sql.*;
import java.util.Properties;
/**
* @author 谢家升
* @version 1.0
* 这是一个工具类,完成 mysql的连接和关闭资源
*/
public class JDBCUtils {
//定义相关的属性(4个), 因为只需要一份,因此,我们做出static
private static String user; //用户名
private static String password; //密码
private static String url; //url
private static String driver; //驱动名
//在static代码块去初始化
static {
try {
Properties properties = new Properties();
properties.load(new FileInputStream("src\\mysql.properties"));
//读取相关的属性值
user = properties.getProperty("user");
password = properties.getProperty("password");
url = properties.getProperty("url");
driver = properties.getProperty("driver");
} catch (IOException e) {
//在实际开发中,我们可以这样处理
//1. 将编译异常转成 运行异常
//2. 调用者,可以选择捕获该异常,也可以选择默认处理该异常,比较方便.
throw new RuntimeException(e);
}
}
//连接数据库, 返回Connection
public static Connection getConnection() {
try {
return DriverManager.getConnection(url, user, password);
} catch (SQLException e) {
//1. 将编译异常转成 运行异常
//2. 调用者,可以选择捕获该异常,也可以选择默认处理该异常,比较方便.
throw new RuntimeException(e);
}
}
//关闭相关资源
/*
1. ResultSet 结果集
2. Statement 或者 PreparedStatement
3. Connection
4. 如果需要关闭资源,就传入对象,否则传入 null
*/
public static void close(ResultSet set, Statement statement, Connection connection) {
//判断是否为null
try {
if (set != null) {
set.close();
}
if (statement != null) {
statement.close();
}
if (connection != null) {
connection.close();
}
} catch (SQLException e) {
//将编译异常转成运行异常抛出
throw new RuntimeException(e);
}
}
}
package com.xjs.jdbc.utils;
import org.junit.Test;
import java.sql.*;
/**
* @Author: 谢家升
* @Date: 2022/1/26-01-26-21:11
* @Version: 1.0
*/
@SuppressWarnings({"all"})
public class JDBCUtilsUse {
@Test
public void testDML() {
//1.得到连接
Connection connection = null;
//2.组织sql
String sql = "update actor set name = ? where id = ?";
//得到preparedStatement对象
PreparedStatement preparedStatement = null;
try {
connection = JDBCUtils.getConnection();
preparedStatement = connection.prepareStatement(sql);
//给?占位符赋值,(将刘德华改为黄渤)
preparedStatement.setString(1, "黄渤");
preparedStatement.setInt(2, 2);
//执行
int i = preparedStatement.executeUpdate();
System.out.println("受影响行数= " + i);
} catch (SQLException e) {
e.printStackTrace();
} finally {
//关闭资源
JDBCUtils.close(null, preparedStatement, connection);
}
}
@Test
public void testSelect() {
//1.连接数据库
Connection connection = null;
//2.组织Sql
String sql = "select * from actor where id = ?";
//3.得到preparedStstement
PreparedStatement preparedStatement = null;
//得到结果集
ResultSet resultSet = null;
try {
connection = JDBCUtils.getConnection();
preparedStatement = connection.prepareStatement(sql);
preparedStatement.setInt(1, 3);//给?号赋值
//执行查询,得到resultSet
resultSet = preparedStatement.executeQuery();
while (resultSet.next()) {
//int id = resultSet.getInt(1);
int id = resultSet.getInt("id");//推荐
//String name = resultSet.getString(2);
String name = resultSet.getString("name");//推荐
//String sex = resultSet.getString(3);
String sex = resultSet.getString("sex");
//Date borndate = resultSet.getDate(4);
Date borndate = resultSet.getDate("borndate");
//String phone = resultSet.getString(5);
String phone = resultSet.getString("phone");
System.out.println(id + "\t" + name + "\t" + sex + "\t" + borndate + "\t" + phone);
/*
表所有数据:
2 黄渤 男 1970-12-12 111
3 周星驰 男 1974-01-01 222
*/
/*控制台输出结果:
3 周星驰 男 1974-01-01 222
*/
}
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.close(resultSet,preparedStatement,connection);
}
}
}
setAutoCommit(false)
可以取消自动提交事务commit()
方法提交事务rollback()
方法回滚事务模拟经典的转账业务
create table account(
id int primary key auto_increment,
name varchar(32) not null default '',
balance double not null default 0
) character set utf8;
insert into account values(null,'马云',3000);
insert into account values(null,'马化腾',10000);
package com.xjs.jdbc.transaction_;
import com.xjs.jdbc.utils.JDBCUtils;
import org.junit.Test;
import java.sql.Connection;
import java.sql.PreparedStatement;
/**
* @Author: 谢家升
* @Date: 2022/1/27-01-27-8:42
* @Version: 1.0
* 演示 JDBC 中事务的使用
*/
@SuppressWarnings({"all"})
public class Transaction_ {
//没有使用事务.
@Test
public void noTransaction() {
//操作转账的业务
//1. 得到连接
Connection connection = null;
//2. 组织sql
String sql = "update account set balance = balance - 100 where id = 1";
String sql2 = "update account set balance = balance + 100 where id = 2";
//3.创建 preparedStatement 对象
PreparedStatement preparedStatement = null;
try {
connection = JDBCUtils.getConnection();// 在默认情况下,connection是默认自动提交事务
//执行sql
preparedStatement = connection.prepareStatement(sql);
preparedStatement.executeUpdate();//执行第1条Sql
int i = 1/0;//这里会抛出一个异常,下面的第2条sql将无法执行...
preparedStatement = connection.prepareStatement(sql2);
preparedStatement.executeUpdate();//执行第2条Sql
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.close(null,preparedStatement,connection);
}
}
}
package com.xjs.jdbc.transaction_;
import com.xjs.jdbc.utils.JDBCUtils;
import org.junit.Test;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
/**
* @Author: 谢家升
* @Date: 2022/1/27-01-27-8:42
* @Version: 1.0
* 演示 JDBC 中事务的使用
*/
@SuppressWarnings({"all"})
public class Transaction_ {
//使用事务处理
@Test
public void useTransaction () {
//操作转账的业务
//1. 得到连接
Connection connection = null;
//2. 组织sql
String sql = "update account set balance = balance - 100 where id = 1";
String sql2 = "update account set balance = balance + 100 where id = 2";
//3.创建 preparedStatement 对象
PreparedStatement preparedStatement = null;
try {
connection = JDBCUtils.getConnection();// 在默认情况下,connection是默认自动提交事务
//这里我们将connection设置为不自动提交事务
connection.setAutoCommit(false);//此时相当于开启了一个事务
//执行sql
preparedStatement = connection.prepareStatement(sql);
preparedStatement.executeUpdate();//执行第1条Sql
int i = 1/0;//这里会抛出一个异常,下面的第2条sql将无法执行...
preparedStatement = connection.prepareStatement(sql2);
preparedStatement.executeUpdate();//执行第2条Sql
//这里提交事务
connection.commit();
} catch (Exception e) {
//如果程序发生异常,在这里我们有机会回滚撤销
System.out.println("执行发生了异常,撤销执行的sql");
try {
//rollback()方法如果没有指定参数(savepoint),默认回滚到事务开启的状态
connection.rollback();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
e.printStackTrace();
} finally {
JDBCUtils.close(null,preparedStatement,connection);
}
}
}
addBatch()
:添加需要批量处理的SQL语句或参数executeBatch()
:执行批量处理语句clearBatch()
:清空批处理包的语句create table admin2(
id int primary key auto_increment,
username varchar(32) not null,
password varchar(32) not null);
package com.xjs.jdbc.batch_;
import com.xjs.jdbc.utils.JDBCUtils;
import org.junit.Test;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
/**
* @Author: 谢家升
* @Date: 2022/1/27-01-27-10:19
* @Version: 1.0
* 演示 Java 批处理
*/
@SuppressWarnings({"all"})
public class Batch_ {
//传统方法,添加5000条数据到admin2
@Test
public void noBatch() throws SQLException {
Connection connection = JDBCUtils.getConnection();
String sql = "insert into admin2 values(null,?,?)";
PreparedStatement preparedStatement = connection.prepareStatement(sql);
System.out.println("开始执行...");
long start = System.currentTimeMillis();//开始计时
for (int i = 0; i < 5000; i++) {//循环执行5000次
preparedStatement.setString(1, "jack" + i);
preparedStatement.setString(2, "666");
preparedStatement.executeUpdate();//执行
}
System.out.println("执行完成~");
long end = System.currentTimeMillis();
System.out.println("传统方式共耗时=" + (end - start));//传统方式共耗时=3377
//关闭连接
JDBCUtils.close(null, preparedStatement, connection);
}
//使用批处理
@Test
public void useBath() throws SQLException {
Connection connection = JDBCUtils.getConnection();
String sql = "insert into admin2 values(null,?,?)";
PreparedStatement preparedStatement = connection.prepareStatement(sql);
System.out.println("开始执行...");
long start = System.currentTimeMillis();//开始计时
for (int i = 0; i < 5000; i++) {//添加5000条数据
preparedStatement.setString(1, "jack" + i);
preparedStatement.setString(2, "666");
//将sql语句储到批处理包中
preparedStatement.addBatch();
//看底层源码,debug---> addBatch();
/*
//1. //第一就创建 ArrayList - elementData => Object[]
//2. elementData => Object[] 就会存放我们预处理的sql语句
//3. 当elementData满后,就按照1.5扩容
//4. 当添加到指定的值后,就executeBatch
//5. 批量处理会减少我们发送sql语句的网络开销,而且减少编译次数,因此效率提高
public void addBatch() throws SQLException {
synchronized(this.checkClosed().getConnectionMutex()) {
if (this.batchedArgs == null) {
this.batchedArgs = new ArrayList();
}
for(int i = 0; i < this.parameterValues.length; ++i) {
this.checkAllParametersSet(this.parameterValues[i], this.parameterStreams[i], i);
}
this.batchedArgs.add(new PreparedStatement.BatchParams(this.parameterValues, this.parameterStreams, this.isStream, this.streamLengths, this.isNull));
}
}
*/
if ((i + 1) % 1000 == 0) {
preparedStatement.executeBatch();//批量执行1000条数据
preparedStatement.clearBatch();//清空批处理包数据
}
}
System.out.println("执行完成~");
long end = System.currentTimeMillis();//结束时间
System.out.println("使用批处理共耗时=" + (end - start));//使用批处理共耗时=94
//关闭连接
JDBCUtils.close(null, preparedStatement, connection);
}
}
package com.xjs.jdbc.datasource;
import com.xjs.jdbc.utils.JDBCUtils;
import org.junit.Test;
import java.sql.Connection;
/**
* @Author: 谢家升
* @Date: 2022/1/27-01-27-17:21
* @Version: 1.0
*/
public class ConQuestion {
//代码 连接mysql 5000次
@Test
public void testCon() {
//看看连接-关闭 connection 会耗用多久
long start = System.currentTimeMillis();
System.out.println("开始连接.....");
for (int i = 0; i < 5000; i++) {
//使用传统的jdbc方式,得到连接
Connection connection = JDBCUtils.getConnection();
//做一些工作,比如得到PreparedStatement ,发送sql
//..........
//关闭
JDBCUtils.close(null, null, connection);
}
long end = System.currentTimeMillis();
System.out.println("传统方式5000次 耗时=" + (end - start));//传统方式5000次 耗时=7099
}
}
韩老师视频链接: C3P0测试.
使用代码实现C3P0数据库连接池,配置文件(c3p0.config.xml)放在src目录下
package com.xjs.jdbc.datasource;
import com.mchange.v2.c3p0.ComboPooledDataSource;
import org.junit.Test;
import java.beans.PropertyVetoException;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;
/**
* @Author: 谢家升
* @Date: 2022/1/27-01-27-20:28
* @Version: 1.0
* 演示 C3P0 的使用
*/
@SuppressWarnings({"all"})
public class C3P0_ {
//方式1: 相关参数,在程序中指定user, url , password等
@Test
public void testC3P0_01() throws Exception {
//1. 创建一个数据源对象
ComboPooledDataSource comboPooledDataSource = new ComboPooledDataSource();
//2. 通过配置文件mysql.properties 获取相关连接的信息
Properties properties = new Properties();
properties.load(new FileInputStream("src\\mysql.properties"));
//读取相关的属性值
String user = properties.getProperty("user");
String password = properties.getProperty("password");
String url = properties.getProperty("url");
String driver = properties.getProperty("driver");
//给数据源 comboPooledDataSource 设置相关的参数
//注意:连接管理是由 comboPooledDataSource 来管理
comboPooledDataSource.setDriverClass(driver);
comboPooledDataSource.setJdbcUrl(url);
comboPooledDataSource.setUser(user);
comboPooledDataSource.setPassword(password);
//设置初始化连接数
comboPooledDataSource.setInitialPoolSize(10);
//最大连接数
comboPooledDataSource.setMaxPoolSize(50);
//测试连接池的效率, 测试对mysql 5000次操作
long start = System.currentTimeMillis();
for (int i = 0; i < 5000; i++) {
Connection connection = comboPooledDataSource.getConnection(); //这个方法就是从 DataSource 接口实现的
//System.out.println("连接OK");
connection.close();
}
long end = System.currentTimeMillis();
//c3p0 5000次连接mysql 耗时=438
System.out.println("c3p0 5000次连接mysql 耗时=" + (end - start));
}
//第二种方式 使用配置文件模板来完成
//1. 将c3p0 提供的 c3p0.config.xml 拷贝到 src目录下
//2. 该文件指定了连接数据库和连接池的相关参数
@Test
public void testC3P0_02() throws SQLException {
ComboPooledDataSource comboPooledDataSource = new ComboPooledDataSource("xjs");
//测试5000次连接mysql
long start = System.currentTimeMillis();
System.out.println("开始执行....");
for (int i = 0; i < 500000; i++) {
Connection connection = comboPooledDataSource.getConnection();
//System.out.println("连接OK~");
connection.close();
}
long end = System.currentTimeMillis();
//c3p0的第二种方式 耗时=375
System.out.println("c3p0的第二种方式(500000) 耗时=" + (end - start));//1970
}
}
【将c3p0 提供的 c3p0.config.xml 拷贝到 src目录下】
<c3p0-config>
<!-- 数据源名称代表连接池 -->
<named-config name="xjs">
<!-- 驱动类 -->
<property name="driverClass">com.mysql.jdbc.Driver</property>
<!-- url-->
<property name="jdbcUrl">jdbc:mysql://127.0.0.1:3306/hsp_db02</property>
<!-- 用户名 -->
<property name="user">root</property>
<!-- 密码 -->
<property name="password">hsp</property>
<!-- 每次增长的连接数-->
<property name="acquireIncrement">5</property>
<!-- 初始的连接数 -->
<property name="initialPoolSize">10</property>
<!-- 最小连接数 -->
<property name="minPoolSize">5</property>
<!-- 最大连接数 -->
<property name="maxPoolSize">50</property>
<!-- 可连接的最多的命令对象数 -->
<property name="maxStatements">5</property>
<!-- 每个连接对象可连接的最多的命令对象数 -->
<property name="maxStatementsPerConnection">2</property>
</named-config>
</c3p0-config>
韩老师视频链接: Druid测试.
使用代码实现Druid(德鲁伊)数据库连接池
【加入 配置文件 druid.properties , 将该文件拷贝项目的 src 目录】
#key=value
driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/hsp_db02?rewriteBatchedStatements=true
username=root
password=hsp
#initial connection Size
initialSize=10
#min idle connection size
minIdle=5
#max active connection size
maxActive=20
#max wait time (5000 mil seconds)
maxWait=5000
package com.xjs.jdbc.datasource;
import com.alibaba.druid.pool.DruidDataSourceFactory;
import org.junit.Test;
import javax.sql.DataSource;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.sql.Connection;
import java.util.Properties;
/**
* @Author: 谢家升
* @Date: 2022/1/27-01-27-21:36
* @Version: 1.0
* 测试 Druid (德鲁伊)的使用
*/
@SuppressWarnings({"all"})
public class Druid_ {
@Test
public void testDruid() throws Exception {
//1. 加入 Druid jar包
//2. 加入 配置文件 druid.properties , 将该文件拷贝项目的src目录
//3. 创建Properties对象, 读取配置文件
Properties properties = new Properties();
properties.load(new FileInputStream("src\\druid.properties"));
//4. 创建一个指定参数的数据库连接池, Druid连接池
DataSource dataSource =
DruidDataSourceFactory.createDataSource(properties);
long start = System.currentTimeMillis();
for (int i = 0; i < 500000; i++) {
Connection connection = dataSource.getConnection();
System.out.println(connection.getClass());
//System.out.println("连接成功!");
connection.close();
}
long end = System.currentTimeMillis();
//druid连接池 操作5000 耗时=359
System.out.println("druid连接池 操作500000 耗时=" + (end - start));//510
}
}
package com.xjs.jdbc.datasource;
import com.alibaba.druid.pool.DruidDataSourceFactory;
import javax.sql.DataSource;
import java.io.FileInputStream;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
/**
* @Author: 谢家升
* @Date: 2022/1/28-01-28-8:53
* @Version: 1.0
* 基于druid数据库连接池的工具类
*/
@SuppressWarnings({"all"})
public class JDBCUtilsByDruid {
private static DataSource dataSource;
//在静态代码块完成 dataSource初始化
static {
Properties properties = new Properties();
try {
properties.load(new FileInputStream("src\\druid.properties"));
dataSource = DruidDataSourceFactory.createDataSource(properties);
} catch (Exception e) {
throw new RuntimeException(e);
}
}
//编写getConnection方法
public static Connection getConnection() {
try {
return dataSource.getConnection();
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
//关闭连接, 再次强调: 在数据库连接池技术中,close 不是真的断掉连接
//而是把使用的Connection对象放回连接池
//由于Connection接口的实现类不同,所以处理方式也就不同
public static void close(ResultSet resultSet, Statement statement, Connection connection) {
try {
if (resultSet != null) {
resultSet.close();
}
if (statement != null) {
statement.close();
}
if (connection != null) {
connection.close();
}
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
}
测试该工具类的使用:
package com.xjs.jdbc.datasource;
import org.junit.Test;
import java.sql.Connection;
import java.sql.Date;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
/**
* @Author: 谢家升
* @Date: 2022/1/28-01-28-9:09
* @Version: 1.0
*/
@SuppressWarnings({"all"})
public class JDBCUtilsByDruidUse {
@Test
public void TestSelect() {
//1.得到连接
Connection connection = null;
//2.组织sql
String sql = "select * from actor where id >= ?";
//3.得到preparedStatement
PreparedStatement preparedStatement = null;
//4.得到resultSet结果集
ResultSet resultSet = null;
try {
connection = JDBCUtilsByDruid.getConnection();
System.out.println(connection.getClass());
//此处connection的运行类型: com.alibaba.druid.pool.DruidPooledConnection
preparedStatement = connection.prepareStatement(sql);
preparedStatement.setInt(1,3);//给?赋值
resultSet = preparedStatement.executeQuery();
while (resultSet.next()) {
int id = resultSet.getInt("id");
String name = resultSet.getString("name");
String sex = resultSet.getString("sex");
Date borndate = resultSet.getDate("borndate");
String phone = resultSet.getString("phone");
System.out.println(id+"\t"+name+"\t"+sex+"\t"+borndate+"\t"+phone);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtilsByDruid.close(resultSet,preparedStatement,connection);
}
}
}
韩老师链接: link.
先创建 Actor 类,用于封装 actor表中各列信息
package com.xjs.jdbc.datasource;
import java.util.Date;
/**
* @Author: 谢家升
* @Date: 2022/1/28-01-28-11:21
* @Version: 1.0
* Actor 对象和 actor表的记录对应
*/
@SuppressWarnings({"all"})
public class Actor {//Javabean, POJO, Domain对象
private Integer id;
private String name;
private String sex;
private Date borndate;
private String phone;
public Actor() {//一定要给一个无参构造器[反射需要]
}
public Actor(Integer id, String name, String sex, Date borndate, String phone) {
this.id = id;
this.name = name;
this.sex = sex;
this.borndate = borndate;
this.phone = phone;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public Date getBorndate() {
return borndate;
}
public void setBorndate(Date borndate) {
this.borndate = borndate;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
@Override
public String toString() {
return "\nActor{" +
"id=" + id +
", name='" + name + '\'' +
", sex='" + sex + '\'' +
", borndate=" + borndate +
", phone='" + phone + '\'' +
'}';
}
}
测试方法如下:
package com.xjs.jdbc.datasource;
import org.junit.Test;
import java.sql.*;
import java.util.ArrayList;
/**
* @Author: 谢家升
* @Date: 2022/1/28-01-28-9:09
* @Version: 1.0
*/
@SuppressWarnings({"all"})
public class JDBCUtilsByDruidUse {
//注意:@Test 测试的方法不能有返回值,否则将报一个异常,
//这里我选择写一次main方法来测试
public static void main(String[] args) {
new JDBCUtilsByDruidUse().testSelectToArrayList();
}
//使用土方法来解决ResultSet =封装=> Arraylist
//@Test
public ArrayList<Actor> testSelectToArrayList() {
//1.得到连接
Connection connection = null;
//2.组织sql
String sql = "select * from actor where id >= ?";
//3.得到preparedStatement
PreparedStatement preparedStatement = null;
//4.得到resultSet结果集
ResultSet resultSet = null;
//创建ArrayList对象,存放actor对象
ArrayList<Actor> arrayList = new ArrayList<>();
try {
connection = JDBCUtilsByDruid.getConnection();
System.out.println(connection.getClass());
//此处connection的运行类型: com.alibaba.druid.pool.DruidPooledConnection
preparedStatement = connection.prepareStatement(sql);
preparedStatement.setInt(1,1);//给?赋值
resultSet = preparedStatement.executeQuery();
while (resultSet.next()) {
int id = resultSet.getInt("id");
String name = resultSet.getString("name");
String sex = resultSet.getString("sex");
Date borndate = resultSet.getDate("borndate");
String phone = resultSet.getString("phone");
//把得到的resultset 的记录,封装到 Actor对象,放入到list集合
arrayList.add(new Actor(id,name,sex,borndate,phone));
}
System.out.println("arraylist集合数据:"+arrayList);
for(Actor actor : arrayList) {//可以选择性的只取出我们需要的字段信息
System.out.println("id=" + actor.getId() + "\t" + actor.getName());
}
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtilsByDruid.close(resultSet,preparedStatement,connection);
}
//因为ArrayList 和 connection 没有任何关联,所以该集合可以复用.
return arrayList;
}
}
使用 DBUtils + 数据库连接池(德鲁伊)方式,完成对表 actor 的 crud
package com.xjs.jdbc.datasource;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;
import org.junit.jupiter.api.Test;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
/**
* @author 谢家升
* @Date: 2022/1/28-01-28-13:58
* @version 1.0
*/
@SuppressWarnings({"all"})
public class DBUtils_USE {
//使用apache-DBUtils 工具类 + druid 完成对表的crud操作
@Test
public void testQueryMany() throws SQLException { //返回结果是多行的情况
//1. 得到 连接 (druid)
Connection connection = JDBCUtilsByDruid.getConnection();
//2. 使用 DBUtils 类和接口 , 先引入DBUtils 相关的jar , 加入到本Project
//3. 创建 QueryRunner
QueryRunner queryRunner = new QueryRunner();
//4. 就可以执行相关的方法,返回ArrayList 结果集
//String sql = "select * from actor where id >= ?";
// 注意: sql 语句也可以查询部分列
String sql = "select id, name from actor where id >= ?";
// 解读:
//(1) query 方法就是执行sql 语句,得到resultset ---封装到 --> ArrayList 集合中
//(2) 然后返回该集合
//(3) connection: 连接
//(4) sql : 执行的sql语句
//(5) new BeanListHandler<>(Actor.class): 在将resultset -> Actor 对象 -> 封装到 ArrayList
// 底层使用反射机制 去获取Actor 类的属性,然后进行封装
//(6) 1: 就是给 sql 语句中的? 赋值,可以有多个值,因为是可变参数Object... params
//(7) 底层得到的resultset ,会在query 关闭, 同时也会关闭PreparedStatment
/**
* 分析 queryRunner.query方法:
* public T query(Connection conn, String sql, ResultSetHandler rsh, Object... params) throws SQLException {
* PreparedStatement stmt = null;//定义PreparedStatement
* ResultSet rs = null;//接收返回的 ResultSet
* Object result = null;//返回ArrayList
*
* try {
* stmt = this.prepareStatement(conn, sql);//创建PreparedStatement
* this.fillStatement(stmt, params);//对sql 进行 ? 赋值
* rs = this.wrap(stmt.executeQuery());//执行sql,返回resultset
* result = rsh.handle(rs);//返回的resultset --封装--> arrayList[result] [使用到反射,对传入class对象处理]
* } catch (SQLException var33) {
* this.rethrow(var33, sql, params);
* } finally {
* try {
* this.close(rs);//关闭resultset
* } finally {
* this.close((Statement)stmt);//关闭preparedstatement对象
* }
* }
*
* return result;
* }
*/
List<Actor> list =
queryRunner.query(connection, sql, new BeanListHandler<>(Actor.class), 1);
System.out.println("输出集合的信息");
for (Actor actor : list) {
System.out.print(actor);
}
//释放资源
JDBCUtilsByDruid.close(null, null, connection);
}
//演示 apache-dbutils + druid 完成 返回的结果是单行记录(单个对象)
@Test
public void testQuerySingle() throws SQLException {
//1. 得到 连接 (druid)
Connection connection = JDBCUtilsByDruid.getConnection();
//2. 使用 DBUtils 类和接口 , 先引入DBUtils 相关的jar , 加入到本Project
//3. 创建 QueryRunner
QueryRunner queryRunner = new QueryRunner();
//4. 就可以执行相关的方法,返回单个对象
String sql = "select * from actor where id = ?";
// 解读:
// 因为我们返回的单行记录<--->单个对象 , 使用的Hander 是 BeanHandler
Actor actor = queryRunner.query(connection, sql, new BeanHandler<>(Actor.class), 3);
System.out.println(actor);
// 释放资源
JDBCUtilsByDruid.close(null, null, connection);
}
//演示apache-dbutils + druid 完成查询结果是单行单列-返回的就是object
@Test
public void testScalar() throws SQLException {
//1. 得到 连接 (druid)
Connection connection = JDBCUtilsByDruid.getConnection();
//2. 使用 DBUtils 类和接口 , 先引入DBUtils 相关的jar , 加入到本Project
//3. 创建 QueryRunner
QueryRunner queryRunner = new QueryRunner();
//4. 就可以执行相关的方法,返回单行单列 , 返回的就是Object
String sql = "select name from actor where id = ?";
//解读: 因为返回的是一个对象, 使用的handler 就是 ScalarHandler
Object obj = queryRunner.query(connection, sql, new ScalarHandler(), 3);
System.out.println(obj);
// 释放资源
JDBCUtilsByDruid.close(null, null, connection);
}
//演示apache-dbutils + druid 完成 dml (update, insert ,delete)
@Test
public void testDML() throws SQLException {
//1. 得到 连接 (druid)
Connection connection = JDBCUtilsByDruid.getConnection();
//2. 使用 DBUtils 类和接口 , 先引入DBUtils 相关的jar , 加入到本Project
//3. 创建 QueryRunner
QueryRunner queryRunner = new QueryRunner();
//4. 这里组织sql 完成 update, insert delete
//String sql = "update actor set name = ? where id = ?";
//String sql = "insert into actor values(null, ?, ?, ?, ?)";
String sql = "delete from actor where id = ?";
//解读:
//(1) 执行dml 操作是 queryRunner.update()
//(2) 返回的值是受影响的行数 (affected: 受影响)
//int affectedRow = queryRunner.update(connection, sql, "林青霞", "女", "1966-10-10", "116");
int affectedRow = queryRunner.update(connection, sql, 1000 );
System.out.println(affectedRow > 0 ? "执行成功" : "执行没有影响到表");
// 释放资源
JDBCUtilsByDruid.close(null, null, connection);
}
}
apache-dbutils + Druid 简化了 JDBC 开发,但还有不足:
完成简单设计
com.xjs.dao_
package com.xjs.dao_.utils;
import com.alibaba.druid.pool.DruidDataSourceFactory;
import javax.sql.DataSource;
import java.io.FileInputStream;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
/**
* @author xjs
* @version 1.0
* 基于druid数据库连接池的工具类
*/
public class JDBCUtilsByDruid {
private static DataSource ds;
//在静态代码块完成 ds初始化
static {
Properties properties = new Properties();
try {
properties.load(new FileInputStream("src\\druid.properties"));
ds = DruidDataSourceFactory.createDataSource(properties);
} catch (Exception e) {
e.printStackTrace();
}
}
//编写getConnection方法
public static Connection getConnection() throws SQLException {
return ds.getConnection();
}
//关闭连接, 再次强调: 在数据库连接池技术中,close 不是真的断掉连接
//而是把使用的Connection对象放回连接池
public static void close(ResultSet resultSet, Statement statement, Connection connection) {
try {
if (resultSet != null) {
resultSet.close();
}
if (statement != null) {
statement.close();
}
if (connection != null) {
connection.close();
}
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
}
package com.xjs.dao_.domain;
import java.util.Date;
/**
* @author 谢家升
* @version 1.0
* Actor 对象和 actor表的记录对应
*
*/
public class Actor { //Javabean, POJO, Domain对象
private Integer id;
private String name;
private String sex;
private Date borndate;
private String phone;
public Actor() { //一定要给一个无参构造器[反射需要]
}
public Actor(Integer id, String name, String sex, Date borndate, String phone) {
this.id = id;
this.name = name;
this.sex = sex;
this.borndate = borndate;
this.phone = phone;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public Date getBorndate() {
return borndate;
}
public void setBorndate(Date borndate) {
this.borndate = borndate;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
@Override
public String toString() {
return "\nActor{" +
"id=" + id +
", name='" + name + '\'' +
", sex='" + sex + '\'' +
", borndate=" + borndate +
", phone='" + phone + '\'' +
'}';
}
}
package com.xjs.dao_.dao;
import com.xjs.dao_.utils.JDBCUtilsByDruid;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;
/**
* @author 谢家升
* @version 1.0
* 开发BasicDAO , 是其他DAO的父类
*/
public class BasicDAO<T> { //泛型指定具体类型
private QueryRunner qr = new QueryRunner();
//开发通用的dml方法, 针对任意的表
public int update(String sql, Object... parameters) {
Connection connection = null;
try {
connection = JDBCUtilsByDruid.getConnection();
int update = qr.update(connection, sql, parameters);
return update;
} catch (SQLException e) {
throw new RuntimeException(e); //将编译异常->运行异常 ,抛出
} finally {
JDBCUtilsByDruid.close(null, null, connection);
}
}
//返回多个对象(即查询的结果是多行), 针对任意表
/**
*
* @param sql sql 语句,可以有 ?
* @param clazz 传入一个类的Class对象 比如 Actor.class
* @param parameters 传入 ? 的具体的值,可以是多个
* @return 根据Actor.class 返回对应的 ArrayList 集合
*/
public List<T> queryMulti(String sql, Class<T> clazz, Object... parameters) {
Connection connection = null;
try {
connection = JDBCUtilsByDruid.getConnection();
return qr.query(connection, sql, new BeanListHandler<T>(clazz), parameters);
} catch (SQLException e) {
throw new RuntimeException(e); //将编译异常->运行异常 ,抛出
} finally {
JDBCUtilsByDruid.close(null, null, connection);
}
}
//查询单行结果 的通用方法
public T querySingle(String sql, Class<T> clazz, Object... parameters) {
Connection connection = null;
try {
connection = JDBCUtilsByDruid.getConnection();
return qr.query(connection, sql, new BeanHandler<T>(clazz), parameters);
} catch (SQLException e) {
throw new RuntimeException(e); //将编译异常->运行异常 ,抛出
} finally {
JDBCUtilsByDruid.close(null, null, connection);
}
}
//查询单行单列的方法,即返回单值的方法
public Object queryScalar(String sql, Object... parameters) {
Connection connection = null;
try {
connection = JDBCUtilsByDruid.getConnection();
return qr.query(connection, sql, new ScalarHandler(), parameters);
} catch (SQLException e) {
throw new RuntimeException(e); //将编译异常->运行异常 ,抛出
} finally {
JDBCUtilsByDruid.close(null, null, connection);
}
}
}
package com.xjs.dao_.dao;
import com.xjs.dao_.domain.Actor;
/**
* @author 谢家升
* @version 1.0
*/
public class ActorDAO extends BasicDAO<Actor> {
//由于继承了 BasicDAO,所以:
//1. 就有 BasicDAO 的方法
//2. 根据业务需求,可以编写特有的方法.
}
package com.xjs.dao_.test;
import com.xjs.dao_.dao.ActorDAO;
import com.xjs.dao_.domain.Actor;
import org.junit.jupiter.api.Test;
import java.util.List;
/**
* @author 谢家升
* @version 1.0
*/
public class TestDAO {
//测试ActorDAO 对actor表crud操作
@Test
public void testActorDAO() {
ActorDAO actorDAO = new ActorDAO();
//1. 查询
List<Actor> actors = actorDAO.queryMulti("select * from actor where id >= ?", Actor.class, 1);
System.out.println("===查询结果===");
for (Actor actor : actors) {
System.out.println(actor);
}
//2. 查询单行记录
Actor actor = actorDAO.querySingle("select * from actor where id = ?", Actor.class, 6);
System.out.println("====查询单行结果====");
System.out.println(actor);
//3. 查询单行单列
Object o = actorDAO.queryScalar("select name from actor where id = ?", 6);
System.out.println("====查询单行单列值===");
System.out.println(o);
//4. dml操作 insert ,update, delete
int update = actorDAO.update("insert into actor values(null, ?, ?, ?, ?)", "张无忌", "男", "2000-11-11", "999");
System.out.println(update > 0 ? "执行成功" : "执行没有影响表");
}
}