JDBC

时间：2021-08-30 01:57:11 阅读：30 评论：0 收藏：0 [点我收藏+]

JDBC

为了让开发人员对数据库的统一操作，提供了一个java操作数据库的规范。

1.jdbc程序

1.1数据准备

CREATE DATABASE jdbcStudy CHARACTER SET utf8 COLLATE utf8_general_ci;

USE jdbcStudy;

CREATE TABLE `users`(
	id INT PRIMARY KEY,
	NAME VARCHAR(40),
	PASSWORD VARCHAR(40),
	email VARCHAR(60),
	birthday DATE
);

INSERT INTO `users`(id,NAME,PASSWORD,email,birthday)
VALUES(1,‘zhansan‘,‘123456‘,‘zs@sina.com‘,‘1980-12-04‘),
(2,‘lisi‘,‘123456‘,‘lisi@sina.com‘,‘1981-12-04‘),
(3,‘wangwu‘,‘123456‘,‘wangwu@sina.com‘,‘1979-12-04‘)

1.2IDEA创建项目创建lib目录导入驱动

技术分享图片

1.3代码步骤

加载驱动
连接数据库DriverManager
获取执行sql的对象Statement
获取返回的结果集
释放连接（必须）

public static void main(String[] args) throws ClassNotFoundException, SQLException {
        //1.加载驱动
        Class.forName("com.mysql.jdbc.Driver");//固定写法，加载驱动
        //2.用户信息和url
        String url = "jdbc:mysql://localhost:3306/jdbcstudy?useUnicode=true&characterEncoding=utf8&useSSL=true";
        String username = "root";
        String password ="root123";
        //3.连接成功
        Connection connection = DriverManager.getConnection(url, username, password);
        //4.执行sql的对象 statement执行sql的对象
        Statement statement = connection.createStatement();
        //5.执行sql的对象去执行sql,可能存在结果，查看返回结果
        String sql ="select * from users";
        ResultSet resultSet = statement.executeQuery(sql); //返回结果集，结果存在所有的结果
        while (resultSet.next()){
            System.out.println("id="+resultSet.getObject("id"));
            System.out.println("name="+resultSet.getObject("name"));
            System.out.println("pwd="+resultSet.getObject("password"));
            System.out.println("email="+resultSet.getObject("email"));
            System.out.println("birthday="+resultSet.getObject("birthday"));
            System.out.println("=================================");
        }
        //6.释放连接(一定要关闭)
        resultSet.close();
        statement.close();
        connection.close();
    }

1.4DriverManager

//第一种写法
//DriverManager.registerDriver(new com.mysql.jdbc.Driver());
//第二种写法推荐写法
Class.forName("com.mysql.jdbc.Driver");//固定写法，加载驱动

//连接数据库
Connection connection = DriverManager.getConnection(url, username, password);
//提交
connection.commit();
//设置事务true或false
connection.setAutoCommit(false);
//回滚
connection.rollback();

1.5URL

mysql
驱动：com.mysql.jdbc.Driver
URL：jdbc:mysql://127.0.0.1:port/dbname
注：127.0.0.1:数据库所在机器的名称
port:端口号，默认是3306
dbname:数据库名称

oracle
驱动：oracle.jdbc.driver.OracleDriver
URL：jdbc:oracle:thin:127.0.0.1:port:dbname
注：127.0.0.1:数据库所在机器的名称
port:端口号，默认是1521
dbname:数据库名称

1.6statement执行sql对象 PreparedStatement执行sql对象

String sql ="select * from users"; //编写sql

statement.executeQuery()//查询
statement.execute()//执行任何sql
statement.executeUpdate()//增删改数据都是用这个
statement.executeBatch()//执行多条sql

1.7ResultSet查询结果集，封装了所有的查询结果

//不知道列类型使用
resultSet.getObject();
//如果知道列类型用以下函数
resultSet.getString();
resultSet.getInt();
resultSet.getDouble();
resultSet.getFloat();
resultSet.getDate();

遍历，指针

resultSet.beforeFirst();//移动到最前面
resultSet.afterLast();//移动到最后面
resultSet.next();//移动到下一个
resultSet.previous();//移动到前一行
resultSet.absolute();//移动到指定行

1.8释放资源

//必须释放（占用资源大）顺序resultSet>>statement>>connection
resultSet.close();
statement.close();
connection.close();

1.8statement对象

1.81代码实现

提取工具类

//db.properties
driver = com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/jdbcstudy?useUnicode=true&characterEncoding=utf8&useSSL=true
username = root
password =root123

//jdbcUtils.java
import java.io.*;
import java.sql.*;
import java.util.*;
public class jdbcUtils {
    private static String driver=null;
    private static String url=null;
    private static String username=null;
    private static String password=null;
    static {
        try {
            InputStream in = jdbcUtils.class.getClassLoader().getResourceAsStream("db.properties");
            Properties properties = new Properties();
            properties.load(in);

            driver = properties.getProperty("driver");
            url = properties.getProperty("url");
            username = properties.getProperty("username");
            password = properties.getProperty("password");

            //1.驱动只加载异常
            Class.forName(driver);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    //获取连接
    public  static Connection getConnection() throws SQLException {
        return DriverManager.getConnection(url, username, password);
    }

    //释放连接
    public static  void release(Connection connection,Statement statement,ResultSet resultSet){
        if (resultSet !=null){
            try {
                resultSet.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (statement !=null){
            try {
                statement.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }if (connection !=null){
            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }


    }

}

1.82编写增删改的方法（executeUpdate）

增加数据

import xiaozhi.jd1.utils.jdbcUtils;
import java.sql.*;

public class TestUtilAdd {
    public static void main(String[] args) {
        Connection conn =null;
        Statement st = null;
        ResultSet rs = null;
        try {
            conn = jdbcUtils.getConnection();//获取连接
            st = conn.createStatement();//获取执行对象
            //插入语句
            String sql ="INSERT INTO users(name,password,email,birthday) VALUES(‘zhangsan‘,‘1253348‘,‘11222243464@qq.com‘,‘2021-3-18‘)";
            int i = st.executeUpdate(sql);
            if (i>0){
                System.out.println("插入成功");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            jdbcUtils.release(conn,st,rs);
        }
    }
}

更改数据

package xiaozhi.jd1;

import xiaozhi.jd1.utils.jdbcUtils;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class TestUtilUpdate {
    public static void main(String[] args) {
        Connection conn =null;
        Statement st = null;
        ResultSet rs = null;
        try {
            conn = jdbcUtils.getConnection();//获取连接
            st = conn.createStatement();//获取执行对象
            //插入语句
            String sql ="UPDATE users SET NAME=‘李五‘ WHERE name =‘zhangsahn‘ ";
            int i = st.executeUpdate(sql);
            if (i>0){
                System.out.println("更新成功");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            jdbcUtils.release(conn,st,rs);
        }
    }
}

删除数据

package xiaozhi.jd1;

import xiaozhi.jd1.utils.jdbcUtils;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class TestUtilDel {
    public static void main(String[] args) {
        Connection conn =null;
        Statement st = null;
        ResultSet rs = null;
        try {
            conn = jdbcUtils.getConnection();//获取连接
            st = conn.createStatement();//获取执行对象
            //插入语句
            String sql ="DELETE FROM users WHERE NAME=‘李五‘";
            int i = st.executeUpdate(sql);
            if (i>0){
                System.out.println("删除成功");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            jdbcUtils.release(conn,st,rs);
        }
    }
}

1.83查的方法executeQuery

package xiaozhi.jd1;

import xiaozhi.jd1.utils.jdbcUtils;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class TestUtilSelect {
    public static void main(String[] args) {
        Connection conn =null;
        Statement st = null;
        ResultSet rs = null;
        try {
            conn = jdbcUtils.getConnection();//获取连接
            st = conn.createStatement();//获取执行对象
            //插入语句
            String sql ="select * from users where id=2";
            rs = st.executeQuery(sql);
            while (rs.next()){
                System.out.println("id="+rs.getObject("id"));
                System.out.println("name="+rs.getObject("name"));
                System.out.println("pwd="+rs.getObject("password"));
                System.out.println("email="+rs.getObject("email"));
                System.out.println("birthday="+rs.getObject("birthday"));
                System.out.println("=================================");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            jdbcUtils.release(conn,st,rs);
        }
    }
}

1.84sql注入

mysql存在的问题，会导致数据泄露

package xiaozhi.jd1;

import xiaozhi.jd1.utils.jdbcUtils;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class TestUtilLogin {
    public static void main(String[] args) {

//        login("wangwu","123456");
        //sql注入
        login("‘or ‘1=1","123456");
    }
    public static void login(String username,String pwd){
        Connection conn =null;
        Statement st = null;
        ResultSet rs = null;
        try {
            conn = jdbcUtils.getConnection();//获取连接
            st = conn.createStatement();//获取执行对象
            //插入语句
            String sql ="select * from users WHERE name = ‘"+username+"‘and password =‘"+pwd+"‘";
            rs = st.executeQuery(sql);
            if (rs.next()){
                System.out.println("登录成功");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            jdbcUtils.release(conn,st,rs);
        }
    }
}

1.9PreparedStatement对象

该对象可以防止sql注入，效率更好

1.91新增

package xiaozhi.PreparedStatementDemo;
import xiaozhi.jd1.utils.jdbcUtils;
import java.util.Date;
import java.sql.*;
import java.sql.PreparedStatement;

public class TestInsert{
    public static void main(String[] args) {
        Connection conn =null;
        PreparedStatement st = null;
        ResultSet rs = null;
        try {
            conn = jdbcUtils.getConnection();//获取连接
            //插入语句 用？做占位符
            String sql ="insert into users(name,password,email,birthday) value(?,?,?,?)";

            st = conn.prepareStatement(sql);//预编译sql,先写sql，不执行
            //手动赋值
            st.setString(1,"xiaoou");
            st.setString(2,"5223556");
            st.setString(3,"522365122@qq.com");
            st.setDate(4,new java.sql.Date(new Date().getTime()));
            //执行 不需要再写入sql
            int i = st.executeUpdate();
            if (i>0){
                System.out.println("插入成功");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            jdbcUtils.release(conn,st,rs);
        }
    }
}

1.92更新

package xiaozhi.PreparedStatementDemo;

import xiaozhi.jd1.utils.jdbcUtils;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Date;

public class TestUpdate {
    public static void main(String[] args) {
        Connection conn =null;
        PreparedStatement st = null;
        ResultSet rs = null;
        try {
            conn = jdbcUtils.getConnection();//获取连接
            //插入语句 用？做占位符
            String sql ="update users set name = ? where name=?";

            st = conn.prepareStatement(sql);//预编译sql,先写sql，不执行
            //手动赋值
            st.setString(1,"xiaozhi");
            st.setString(2,"xiaoou");
            //执行 不需要再写入sql
            int i = st.executeUpdate();
            if (i>0){
                System.out.println("修改成功");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            jdbcUtils.release(conn,st,rs);
        }
    }
}

1.93删除

package xiaozhi.PreparedStatementDemo;

import xiaozhi.jd1.utils.jdbcUtils;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class TestDelete {
    public static void main(String[] args) {
        Connection conn =null;
        PreparedStatement st = null;
        ResultSet rs = null;
        try {
            conn = jdbcUtils.getConnection();//获取连接
            //插入语句 用？做占位符
            String sql ="delete from users where name = ?";

            st = conn.prepareStatement(sql);//预编译sql,先写sql，不执行
            //手动赋值
            st.setString(1,"xiaozhi");
            //执行 不需要再写入sql
            int i = st.executeUpdate();
            if (i>0){
                System.out.println("删除成功");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            jdbcUtils.release(conn,st,rs);
        }
    }
}

1.94查询

package xiaozhi.PreparedStatementDemo;

import xiaozhi.jd1.utils.jdbcUtils;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class TestSelect {
    public static void main(String[] args) {
        Connection conn =null;
        PreparedStatement st = null;
        ResultSet rs = null;
        try {
            conn = jdbcUtils.getConnection();//获取连接
            //插入语句 用？做占位符
            String sql ="select * from users WHERE NAME = ?";

            st = conn.prepareStatement(sql);//预编译sql,先写sql，不执行
            //手动赋值
            st.setString(1,"zhansan");
            //执行 不需要再写入sql
            rs= st.executeQuery();
            if (rs.next()){
                System.out.println("查询成功"+rs.getString("name"));
                System.out.println("==============");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            jdbcUtils.release(conn,st,rs);
        }
    }
}

1.95sql注入测试

package xiaozhi.PreparedStatementDemo;

import xiaozhi.jd1.utils.jdbcUtils;

import java.sql.*;

public class TestUtilLogin {
    public static void main(String[] args) {

//        login("wangwu","123456");
//        //sql注入
        login("‘or ‘1=1","123456");
    }
    public static void login(String username,String pwd){
        Connection conn =null;
        PreparedStatement st = null;
        ResultSet rs = null;
        try {
            conn = jdbcUtils.getConnection();//获取连接

            //插入语句
            String sql ="select * from users WHERE name = ? and password =?";
            st = conn.prepareStatement(sql);//获取执行对象 先转义字符
            st.setString(1,username);
            st.setString(2,pwd);
            rs = st.executeQuery();
            if (rs.next()){
                System.out.println("登录成功");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            jdbcUtils.release(conn,st,rs);
        }
    }
}

2.IDEA连接数据库mysql

技术分享图片

如果出现如下错误

Server returns invalid timezone. Go to ‘Advanced’ tab and set ‘serverTimezone’ property manually.

技术分享图片

serverTimezone设置为CST

GMT（Greenwich Mean Time）：格林威治标准时间
UTC：世界标准时间
CST（China Standard Time）：中国标准时间

GMT + 8 = UTC + 8 = CST

技术分享图片

3.jdbc事务

要么都成功，要么都失败

3.1ACID原则

原子性：要么全部完成，要么都不完成

一致性：总数不变

隔离性：多个进程互不干扰

持久性：一旦提交不可逆，持久化到数据库

隔离性的问题：

脏读：一个事务读取了另一个没有提交的事务

不可重复读：在同一个事务内，重复读取表中的数据，表数据发生了改变

虚读（幻读）：在一个事务内，读取到了别人插入的数据，导致前后读出来结果不一致

package xiaozhi.transactionDemo;

import xiaozhi.jd1.utils.jdbcUtils;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Date;

public class Tdemo2 {
    public static void main(String[] args) {
        Connection conn =null;
        PreparedStatement st = null;
        PreparedStatement st1 = null;
        ResultSet rs = null;
        try {
            conn = jdbcUtils.getConnection();//获取连接
            //关闭数据库的自动提交，自动会开启事务注意是InnoDB
            conn.setAutoCommit(false);//开启事务

            //插入语句 用？做占位符
            String sql ="update account set money = money-500 where name=?";
            st = conn.prepareStatement(sql);//预编译sql,先写sql，不执行
            st.setString(1, "A");
            st.executeUpdate();

            int x=1/0;

            String sql1 ="update account set money = money+500 where name=?";
            st1 = conn.prepareStatement(sql1);//预编译sql,先写sql，不执行
            //手动赋值
            st1.setString(1, "B");
            //执行 不需要再写入sql
            st1.executeUpdate();
        } catch (Exception e) {
            // 回滚事务:
            try {
                conn.rollback();
            } catch (SQLException e1) {
                e1.printStackTrace();
            }
            e.printStackTrace();
        } finally {
            jdbcUtils.release(conn,st,rs);
        }
    }
}

4.数据库连接池dbcp和c3p0

4.1dbcp

架包

技术分享图片

dbcpconfig.properties

#连接设置
driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/jdbcstudy?useUnicode=true&characterEncoding=utf8&useSSL=true
username=root
password=root123

#<!-- 初始化连接 -->
initialSize=10

#最大连接数量
maxActive=50

#<!-- 最大空闲连接 -->
maxIdle=20

#<!-- 最小空闲连接 -->
minIdle=5

#<!-- 超时等待时间以毫秒为单位 6000毫秒/1000等于60秒 -->
maxWait=60000
#JDBC驱动建立连接时附带的连接属性属性的格式必须为这样：【属性名=property;】
#注意："user" 与 "password" 两个属性会被明确地传递，因此这里不需要包含他们。
connectionProperties=useUnicode=true;characterEncoding=UTF8

#指定由连接池所创建的连接的自动提交（auto-commit）状态。
defaultAutoCommit=true

#driver default 指定由连接池所创建的连接的只读（read-only）状态。
#如果没有设置该值，则“setReadOnly”方法将不被调用。（某些驱动并不支持只读模式，如：Informix）
defaultReadOnly=

#driver default 指定由连接池所创建的连接的事务级别（TransactionIsolation）。
#可用值为下列之一：（详情可见javadoc。）NONE,READ_UNCOMMITTED, READ_COMMITTED, REPEATABLE_READ, SERIALIZABLE
defaultTransactionIsolation=READ_UNCOMMITTED

jdbc_Utils

package xiaozhi.JdbcDemo.utils;

import org.apache.commons.dbcp.BasicDataSourceFactory;

import javax.sql.DataSource;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

public class jdbc_Utils {
    private static String driver=null;
    private static String url=null;
    private static String username=null;
    private static String password=null;
    private static DataSource dataSource=null;
    static {
        try {
            InputStream in = jdbc_Utils.class.getClassLoader().getResourceAsStream("dbcpconfig.properties");
            Properties properties = new Properties();
            properties.load(in);

            //创建数据源
            dataSource = BasicDataSourceFactory.createDataSource(properties);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    //获取连接
    public  static Connection getConnection() throws SQLException {
        return dataSource.getConnection();//从数据源中获取
    }

    //释放连接
    public static  void release(Connection connection,Statement statement,ResultSet resultSet){
        if (resultSet !=null){
            try {
                resultSet.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (statement !=null){
            try {
                statement.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }if (connection !=null){
            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }


    }

}

test

package xiaozhi.JdbcDemo.test;

import xiaozhi.JdbcDemo.utils.jdbc_Utils;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class TestUtilAdd {
    public static void main(String[] args) {
        Connection conn =null;
        Statement st = null;
        ResultSet rs = null;
        try {
            conn = jdbc_Utils.getConnection();//获取连接
            st = conn.createStatement();//获取执行对象
            //插入语句
            String sql ="INSERT INTO users(name,password,email,birthday) VALUES(‘zhangsan‘,‘1253348‘,‘11222243464@qq.com‘,‘2021-3-18‘)";
            int i = st.executeUpdate(sql);
            if (i>0){
                System.out.println("插入成功");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            jdbc_Utils.release(conn,st,rs);
        }
    }
}

4.2C3P0

架包

技术分享图片

c3p0-config.xml

<c3p0-config>
    <default-config>
        <property name="driverClass">com.mysql.jdbc.Driver</property>
        <property name="jdbcUrl">jdbc:mysql://localhost:3306/jdbcstudy?useUnicode=true&amp;characterEncoding=utf8&amp;useSSL=true</property>
        <property name="user">root</property>
        <property name="password">root123</property>

        <property name="initialPoolSize">10</property>
        <property name="maxIdleTime">30</property>
        <property name="maxPoolSize">100</property>
        <property name="minPoolSize">10</property>
        <property name="maxStatements">200</property>
    </default-config>

    <!-- This app is massive! -->
    <named-config name="intergalactoApp">
        <property name="acquireIncrement">50</property>
        <property name="initialPoolSize">100</property>
        <property name="minPoolSize">50</property>
        <property name="maxPoolSize">1000</property>

        <!-- intergalactoApp adopts a different approach to configuring statement caching -->
        <property name="maxStatements">0</property>
        <property name="maxStatementsPerConnection">5</property>

        <!-- he‘s important, but there‘s only one of him -->
        <user-overrides user="master-of-the-universe">
            <property name="acquireIncrement">1</property>
            <property name="initialPoolSize">1</property>
            <property name="minPoolSize">1</property>
            <property name="maxPoolSize">5</property>
            <property name="maxStatementsPerConnection">50</property>
        </user-overrides>
    </named-config>
</c3p0-config>

jdbc_Utils

package xiaozhi.c3p0Demo.utils;


import com.mchange.v2.c3p0.ComboPooledDataSource;
import javax.sql.DataSource;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

public class jdbc_Utils {
    private static String driver=null;
    private static String url=null;
    private static String username=null;
    private static String password=null;
    private static DataSource dataSource=null;
    private static ComboPooledDataSource comboPooledDataSource=null;
    static {
        try {
            InputStream in = jdbc_Utils.class.getClassLoader().getResourceAsStream("c3p0-config.xml");
            Properties properties = new Properties();
            properties.load(in);

            //创建数据源
//            dataSource = BasicDataSourceFactory.createDataSource(properties);
            comboPooledDataSource = new ComboPooledDataSource();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    //获取连接
    public  static Connection getConnection() throws SQLException {
        return comboPooledDataSource.getConnection();//从数据源中获取
    }

    //释放连接
    public static  void release(Connection connection,Statement statement,ResultSet resultSet){
        if (resultSet !=null){
            try {
                resultSet.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (statement !=null){
            try {
                statement.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }if (connection !=null){
            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }


    }

}

test

package xiaozhi.c3p0Demo.test;

import xiaozhi.c3p0Demo.utils.jdbc_Utils;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class TestUtilAdd {
    public static void main(String[] args) {
        Connection conn =null;
        Statement st = null;
        ResultSet rs = null;
        try {
            conn = jdbc_Utils.getConnection();//获取连接
            st = conn.createStatement();//获取执行对象
            //插入语句
            String sql ="INSERT INTO users(name,password,email,birthday) VALUES(‘zhangsan‘,‘1253348‘,‘11222243464@qq.com‘,‘2021-3-18‘)";
            int i = st.executeUpdate(sql);
            if (i>0){
                System.out.println("插入成功");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            jdbc_Utils.release(conn,st,rs);
        }
    }
}

JDBC

原文：https://www.cnblogs.com/xiaozhizxj/p/15195386.html

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JDBC

JDBC

1.jdbc程序

1.1数据准备

1.2IDEA创建项目 创建lib目录导入驱动

1.3代码步骤

1.4DriverManager

1.5URL

1.6statement执行sql对象 PreparedStatement执行sql对象

1.7ResultSet查询结果集，封装了所有的查询结果

1.8statement对象

1.81代码实现

1.82编写增删改的方法（executeUpdate）

1.83查的方法executeQuery

1.84sql注入

1.9PreparedStatement对象

2.IDEA连接数据库mysql

如果出现如下错误

Server returns invalid timezone. Go to ‘Advanced’ tab and set ‘serverTimezone’ property manually.

3.jdbc事务

3.1ACID原则

4.数据库连接池dbcp和c3p0

4.1dbcp

4.2C3P0

1.2IDEA创建项目创建lib目录导入驱动