JDBC

第一章 JDBC简介

1.1概念

概念：Java DataBase Connectivity Java 数据库连接 Java语言操作数据库
JDBC本质：其实是官方(SUN公司)定义的一套操作所有关系型数据库的规则，即接口。各个数据库厂商去实现这套接口，提供数据库驱动jar包。我们可以使用这套接口(JDBC)编程，真正执行的代码是驱动jar包中的实现类。

1.2步骤

1.导入驱动jar包

复制jar包到项目的libs目录下
右键–>Add As Library

2.注册驱动

3.获取数据库连接对象Connection

4.定义sql

5.获取执行sql语句的对象 Statement

6.执行sql，接受返回结果

7.处理结果

8.释放资源

1.3代码实现

package com.priv.demo01JDBC;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;

public class Demo01JDBC {
    public static void main(String[] args) throws Exception {
        //1.导入驱动jar包
        // 2.注册驱动
        Class.forName("com.mysql.cj.jdbc.Driver");
        //3.获取数据库连接对象Connection
        Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/students", "root", "填自己的数据库密码");
        //4.定义sql
        String sql="update account set balance=500 where username='张无忌'";
        //5.获取执行sql语句的对象 Statement
        Statement statement = connection.createStatement();
        //6.执行sql，接受返回结果
        int i = statement.executeUpdate(sql);
        //7.处理结果
        System.out.println(i);
        //8.释放资源
        statement.close();
        connection.close();
    }
}

结果

20211001181141

第二章详解各个对象

2.1DriverManager

驱动管理对象

1.功能

注册驱动：告诉程序该使用哪一个数据库驱动jar

** 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!");
     }
}

tips：mysql5之后的驱动jar包可以忽略注册驱动的步骤。

获取数据库连接

方法：

static Connection getConnection(String url,String user,String password);

参数：

1.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
例子：jdbc:mysql://localhost:3306/students
细节：如果连接的是本机mysql服务器，并且mysql服务默认端口是3306，则url可以简写为：jdbc:mysql:///数据库名称

2.user：用户名

3.password：密码

2.2Connection

数据库连接对象

一.功能

1.获取执行sql的对象

** Statement createStatement()**
** PreparedStatement prepareStatement(String sql)**

2.管理事务

开启事务：** setAutoCommit(boolean autoCommit)**：调用该方法设置参数为false，即开启事务
提交事务：** commit()**
回滚事务：** rollback()**

2.3Statement

执行sql的对象

1.执行sql

** boolean execute(String sql)**：可以执行任意的sql(了解)
** int executeUpdate(String sql)**：执行DML(insert、update、delete)语句、DDL(create、alter、drop)语句

返回值：影响的行数，可以通过这个影响的行数判断DML语句是否执行成功返回值>0的则执行成功，反之，则失败。

** ResultSet executeQuery(String sql)**：执行DQL(select)语句

2.4ResultSet

结果集对象

ResultSet：结果集对象，封装查询结果

next()：游标向下移动一行
getXXX(参数)：获取数据

Xxx：代表数据类型如：int getInt() String getString()

参数：

1.int：代表列的编号，从1开始如：getString(1)

2.String：代表列名称。如：getDouble(“balance”)

** boolean next()**：游标向下移动一行，判断当前行是否是最后一行末尾(是否有数据)，如果是，则返回false，如果不是则返回true
注意：

1.游标向下移动一行

2.判断是否有数据

3.获取数据

package com.priv.demo01JDBC;

import java.sql.*;
/**
 * 执行DQL语言
 */

public class Demo05JDBC {
    public static void main(String[] args) {
        Connection connection=null;
        Statement statement=null;
        ResultSet resultSet=null;
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            String sql="SELECT * FROM account";
            connection = DriverManager.getConnection("jdbc:mysql:///students", "root", "填自己的数据库密码");
            statement = connection.createStatement();
            resultSet = statement.executeQuery(sql);
            while(resultSet.next()){
                int anInt = resultSet.getInt(1);
                String username = resultSet.getString("username");
                double aDouble = resultSet.getDouble(3);
                System.out.println(anInt+"---"+username+"---"+aDouble);
            }

        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            try {
                resultSet.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
            try {
                statement.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
            try {
                connection.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }

    }
}

2.5PreparedStatement

执行sql的对象

1.SQL注入问题：在拼接sql时，有一些sql的特殊关键字参与字符串的拼接。会造成安全性问题

输入用户随便，输入密码：a’ or ‘a’=’a
sql：SELECT * FROM USER WHERE username=’fhjjhishaid’and password=’a’ or ‘a’=’a’

2.解决sql注入问题：使用PreparedStatement对象来解决

package com.priv.demo01JDBC;

import com.priv.demo03util.Demo01JDBCUtils;

import java.sql.*;
import java.util.Scanner;

public class Demo09JDBC {
    public static void main(String[] args) {
        Scanner scanner=new Scanner(System.in);
        System.out.println("请输入用户名：");
        String username = scanner.nextLine();
        System.out.println("请输入密码：");
        String password = scanner.nextLine();
        boolean login = new Demo08JDBC().login(username, password);
        if(login){
            System.out.println("登录成功！");
        }else{
            System.out.println("******用户名或密码错误！******");
        }
    }

    public boolean login(String username,String password){
        Connection connection=null;
        PreparedStatement preparedStatement=null;
        ResultSet resultSet=null;
        if(username==null||password==null){
            return false;
        }
        try {
            connection = Demo01JDBCUtils.getConnection();
            String sql="SELECT * FROM USER  WHERE username= ? and password= ? ";
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setString(1,username);
            preparedStatement.setString(2,password);
            resultSet = preparedStatement.executeQuery();
            return resultSet.next();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            Demo01JDBCUtils.close(resultSet,preparedStatement,connection);
        }
        return false;
    }
}

tips：后期都会使用preparedStatement来完成增删改查的所有操作

可以防止SQL注入

效率更高

第三章 JDBC练习

3.1insert语句

package com.priv.demo01JDBC;

import java.sql.*;
/**
 * account表 添加一条记录 insert语句
 */
public class Demo02JDBC {
    public static void main(String[] args) {
        Connection connection =null;
        Statement  statement =null;
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            String sql="insert into account values(NULL,'张三',1800)";
            connection = DriverManager.getConnection("jdbc:mysql:///students", "root", "填自己的数据库密码");
            statement = connection.createStatement();
            int count = statement.executeUpdate(sql);
            System.out.println(count);
            if(count>0){
                System.out.println("添加成功！");
            }else{
                System.out.println("添加失败！");
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            //避免空指针异常
            if(connection!=null){
                try {
                    connection.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
            if(statement!=null){
                try {
                    statement.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
        }
    }
}

3.2update语句

package com.priv.demo01JDBC;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
/**
 * account表 修改一条记录 update语句
 */
public class Demo03JDBC {
    public static void main(String[] args) {
        Connection connection =null;
        Statement statement=null;
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            String sql="update account set balance=500 where username='张三'";
            connection = DriverManager.getConnection("jdbc:mysql:///students", "root", "填自己的数据库密码");
            statement = connection.createStatement();
            int i = statement.executeUpdate(sql);
            System.out.println(i);
            if(i>0){
                System.out.println("修改成功！");
            }else {
                System.out.println("修改失败！");
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            if(statement!=null){
                try {
                    statement.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
            if(connection!=null){
                try {
                    connection.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
        }
    }
}

3.3delete语句

package com.priv.demo01JDBC;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
/**
 * account表 删除一条记录 delete语句
 */
public class Demo04JDBC {
    public static void main(String[] args) {
        Connection connection=null;
        Statement statement=null;
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            String sql="DELETE FROM ACCOUNT WHERE USERNAME='张三'";
            connection = DriverManager.getConnection("jdbc:mysql:///students", "root", "填自己的数据库密码");
            statement = connection.createStatement();
            int count = statement.executeUpdate(sql);
            System.out.println(count);
            if(count>0){
                System.out.println("删除成功");
            }else{
                System.out.println("删除失败");
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            try {
                statement.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
            try {
                connection.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }

    }
}

tips：返回的count值是受影响的行数

3.4select语句

package com.priv.demo02JDBC;

import java.util.Date;

public class employees {
    private int employee_id;
    private String first_name;
    private String last_name;
    private String email;
    private String phone_number;
    private String job_id;
    private double salary;
    private double commission_pct;
    private int manager_id;
    private int department_id;
    private Date hiredate;

    public employees() {

    }

    public int getEmployee_id() {
        return employee_id;
    }

    public void setEmployee_id(int employee_id) {
        this.employee_id = employee_id;
    }

    public String getFirst_name() {
        return first_name;
    }

    public void setFirst_name(String first_name) {
        this.first_name = first_name;
    }

    public String getLast_name() {
        return last_name;
    }

    public void setLast_name(String last_name) {
        this.last_name = last_name;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getPhone_number() {
        return phone_number;
    }

    public void setPhone_number(String phone_number) {
        this.phone_number = phone_number;
    }

    public String getJob_id() {
        return job_id;
    }

    public void setJob_id(String job_id) {
        this.job_id = job_id;
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

    public double getCommission_pct() {
        return commission_pct;
    }

    public void setCommission_pct(double commission_pct) {
        this.commission_pct = commission_pct;
    }

    public int getManager_id() {
        return manager_id;
    }

    public void setManager_id(int manager_id) {
        this.manager_id = manager_id;
    }

    public int getDepartment_id() {
        return department_id;
    }

    public void setDepartment_id(int department_id) {
        this.department_id = department_id;
    }

    public Date getHiredate() {
        return hiredate;
    }

    public void setHiredate(Date hiredate) {
        this.hiredate = hiredate;
    }

    @Override
    public String toString() {
        return "Demo01List{" +
                "employee_id=" + employee_id +
                ", first_name='" + first_name + '\'' +
                ", last_name='" + last_name + '\'' +
                ", emile='" + email + '\'' +
                ", phone_number='" + phone_number + '\'' +
                ", job_id='" + job_id + '\'' +
                ", salary=" + salary +
                ", commission_pct=" + commission_pct +
                ", manager_id=" + manager_id +
                ", department_id=" + department_id +
                ", hiredate='" + hiredate + '\'' +
                '}';
    }

    public employees(int employee_id, String first_name, String last_name, String emile, String phone_number, String job_id, float salary, float commission_pct, int manager_id, int department_id, Date hiredate) {
        this.employee_id = employee_id;
        this.first_name = first_name;
        this.last_name = last_name;
        this.email = email;
        this.phone_number = phone_number;
        this.job_id = job_id;
        this.salary = salary;
        this.commission_pct = commission_pct;
        this.manager_id = manager_id;
        this.department_id = department_id;
        this.hiredate = hiredate;
    }
}

package com.priv.demo01JDBC;

import com.priv.demo02JDBC.employees;

import java.sql.*;
import java.util.ArrayList;
import java.util.Date;
import java.util.Iterator;
import java.util.List;

public class Demo06JDBC {
    public static void main(String[] args) {
        List<employees> all = new Demo06JDBC().findAll();
        Iterator<employees> iterator=all.iterator();
        while (iterator.hasNext()){
            System.out.println(iterator.next());
        }
    }
    /**
     *查询所有employees对象
     * @return
     */
    public List<employees> findAll(){
        Connection connection=null;
        Statement statement=null;
        ResultSet resultSet=null;
        List<employees> list=null;
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            String sql="SELECT * FROM EMPLOYEES";
            connection = DriverManager.getConnection("jdbc:mysql:///myemployees", "root", "填自己的数据库密码");
            statement = connection.createStatement();
            resultSet = statement.executeQuery(sql);
            employees employees=null;
            list=new ArrayList<>();

            while (resultSet.next()){
                int employee_id = resultSet.getInt(1);
                String first_name = resultSet.getString("first_name");
                String last_name = resultSet.getString("last_name");
                String email = resultSet.getString("email");
                String phone_number = resultSet.getString("phone_number");
                String job_id = resultSet.getString("job_id");
                double salary = resultSet.getDouble(7);
                double commission_pct = resultSet.getDouble(8);
                int manager_id = resultSet.getInt(9);
                int department_id = resultSet.getInt(10);
                Date hiredate = resultSet.getDate("hiredate");
                employees=new employees();
                employees.setEmployee_id(employee_id);
                employees.setFirst_name(first_name);
                employees.setLast_name(last_name);
                employees.setEmail(email);
                employees.setPhone_number(phone_number);
                employees.setJob_id(job_id);
                employees.setSalary(salary);
                employees.setCommission_pct(commission_pct);
                employees.setManager_id(manager_id);
                employees.setDepartment_id(department_id);
                employees.setHiredate(hiredate);
                list.add(employees);

            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            try {
                resultSet.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
            try {
                statement.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
            try {
                connection.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
        return list;
    }
}

第四章 JDBC工具类

4.1工具类实现

url=jdbc:mysql:///students
user=root
password=填自己的数据库密码
driver=com.mysql.cj.jdbc.Driver

package com.priv.demo03util;

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.net.URL;
import java.sql.*;
import java.util.Properties;

public class Demo01JDBCUtils {
    private static String url;
    private static String user;
    private static String password;
    private static String driver;

    static{
        try {
            Properties properties = new Properties();
            ClassLoader classLoader = Demo01JDBCUtils.class.getClassLoader();
            URL resource = classLoader.getResource("jdbc.properties");
            String path = resource.getPath();
            properties.load(new FileReader(path));
            url=properties.getProperty("url");
            user=properties.getProperty("user");
            password=properties.getProperty("password");
            driver=properties.getProperty("driver");
            Class.forName(driver);
        } catch (ClassNotFoundException | FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    /**
     *获取连接
     * @return 连接对象
     */

    public static Connection getConnection() throws SQLException {
        return DriverManager.getConnection(url,user,password);
    }

    /**
     * 释放资源
     * @param statement
     * @param connection
     */
    public static void close(Statement statement,Connection connection){
        if(statement!=null){
            try {
                statement.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
        if(connection!=null){
            try {
                connection.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
    }

    public static void close(ResultSet resultSet,Statement statement, Connection connection){
        if(resultSet!=null){
            try {
                resultSet.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
        if(statement!=null){
            try {
                statement.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
        if(connection!=null){
            try {
                connection.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
    }

}

package com.priv.demo01JDBC;

import com.priv.demo02JDBC.employees;
import com.priv.demo03util.Demo01JDBCUtils;

import java.sql.*;
import java.util.ArrayList;
import java.util.Date;
import java.util.Iterator;
import java.util.List;

public class Demo07JDBC {
    public static void main(String[] args) {
        List<employees> all = new Demo06JDBC().findAll();
        Iterator<employees> iterator=all.iterator();
        while (iterator.hasNext()){
            System.out.println(iterator.next());
        }
    }
    /**
     *演示JDBC工具类
     * @return
     */
    public List<employees> findAll(){
        Connection connection=null;
        Statement statement=null;
        ResultSet resultSet=null;
        List<employees> list=null;
        try {
            Connection connection1 = Demo01JDBCUtils.getConnection();
            String sql="SELECT * FROM EMPLOYEES";
            statement = connection.createStatement();
            resultSet = statement.executeQuery(sql);
            employees employees=null;
            list=new ArrayList<>();

            while (resultSet.next()){
                int employee_id = resultSet.getInt(1);
                String first_name = resultSet.getString("first_name");
                String last_name = resultSet.getString("last_name");
                String email = resultSet.getString("email");
                String phone_number = resultSet.getString("phone_number");
                String job_id = resultSet.getString("job_id");
                double salary = resultSet.getDouble(7);
                double commission_pct = resultSet.getDouble(8);
                int manager_id = resultSet.getInt(9);
                int department_id = resultSet.getInt(10);
                Date hiredate = resultSet.getDate("hiredate");
                employees=new employees();
                employees.setEmployee_id(employee_id);
                employees.setFirst_name(first_name);
                employees.setLast_name(last_name);
                employees.setEmail(email);
                employees.setPhone_number(phone_number);
                employees.setJob_id(job_id);
                employees.setSalary(salary);
                employees.setCommission_pct(commission_pct);
                employees.setManager_id(manager_id);
                employees.setDepartment_id(department_id);
                employees.setHiredate(hiredate);
                list.add(employees);

            }
        }catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        Demo01JDBCUtils.close(resultSet,statement,connection);
        return list;
    }
}

4.2登录案例

package com.priv.demo01JDBC;

import com.priv.demo03util.Demo01JDBCUtils;

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

public class Demo08JDBC {
    public static void main(String[] args) {
        Scanner scanner=new Scanner(System.in);
        System.out.println("请输入用户名：");
        String username = scanner.nextLine();
        System.out.println("请输入密码：");
        String password = scanner.nextLine();
        boolean login = new Demo08JDBC().login(username, password);
        if(login){
            System.out.println("登录成功！");
        }else{
            System.out.println("******用户名或密码错误！******");
        }
    }

    public boolean login(String username,String password){
        Connection connection=null;
        Statement statement=null;
        ResultSet resultSet=null;
        if(username==null||password==null){
            return false;
        }
        try {
            connection = Demo01JDBCUtils.getConnection();
            String sql="SELECT * FROM USER  WHERE username='"+username+"'and password='"+password+"'";
            statement = connection.createStatement();
            resultSet = statement.executeQuery(sql);
            return resultSet.next();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            Demo01JDBCUtils.close(resultSet,statement,connection);
        }
        return false;
    }
}

第五章 JDBC控制事务

5.1概述

1.事务：一个包含多个步骤的业务操作。如果这个业务操作被事务管理，则这多个步骤要么同时成功，要么同时失败。

2.操作：

开启事务
提交事务
回滚事务

3.使用Connection对象来管理事务

开启事务：** setAutoCommit(boolean autoCommit)**：调用该方法设置参数为false，即开启事务

在执行sql之前开启事务
提交事务：** commit()**

当所有sql都执行完提交事务
回滚事务：** rollback()**

在catch中回滚事务

5.2实现案例

package com.priv.demo01JDBC;

import com.priv.demo03util.Demo01JDBCUtils;

import java.sql.*;

/**
 *事务操作：转账
 */
public class Demo10JDBC {
    public static void main(String[] args) {
        Connection connection=null;
        PreparedStatement preparedStatement1=null;
        PreparedStatement preparedStatement2=null;
        ResultSet resultSet=null;
        try {
            connection = Demo01JDBCUtils.getConnection();
            //开启事务
            connection.setAutoCommit(false);
            String sql1="update account set balance=balance-? where id=?";
            String sql2="update account set balance=balance+? where id=?";
            preparedStatement1 = connection.prepareStatement(sql1);
            preparedStatement2 = connection.prepareStatement(sql2);
            preparedStatement1.setDouble(1,500);
            preparedStatement1.setInt(2,1);

            preparedStatement2.setDouble(1,500);
            preparedStatement2.setInt(2,2);

            preparedStatement1.executeUpdate();
            //手动制造异常
            int i=3/0;
            preparedStatement2.executeUpdate();
            //提交事务
            connection.commit();
        } catch (SQLException throwables) {
            //事务回滚
            try {
                if(connection!=null) {
                    connection.rollback();
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
            throwables.printStackTrace();
        }finally {
            Demo01JDBCUtils.close(preparedStatement1,connection);
            Demo01JDBCUtils.close(preparedStatement2,null);
        }

    }
}

第六章数据库连接池

6.1概述

1.概念：其实就是一个容器(集合)，存放数据库连接的容器。当系统初始化好后，容器被创建，容器中会申请一些连接对象，当用户来访问数据库时，从容器中获取连接对象，用户访问完之后，会将连接对象归还给容器。

2.好处：

节约资源
用户访问高效

3.实现

1.标准接口：DataSource javax.sql包下

1.方法：

获取连接：getConnection()

归还连接：Connection.close() 如果连接对象Connection时从连接池中获取的，那么调用Connection.close()方法，则不会再关闭连接了。而是归还连接

2.一般我们不去实现它，由数据库厂商来实现

C3P0：数据库连接池技术
Druid：数据库连接池实现技术，由阿里巴巴提供

6.2C3P0

步骤：

1.导入jar包：两个 c3p0-0.9.5.5.jar和mchange-commons-java-0.2.19.jar

2.定义配置文件：

名称：c3p0.properties或者c3p0-config.xml
路径：直接将文件放在src目录下即可。

3.创建核心对象数据库连接池对象 ComboPooledDataSource

4.获取连接：getConnection

package com.priv.demo04JDBCTemplate;

import com.mchange.v2.c3p0.ComboPooledDataSource;

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.SQLException;

/**
 * C3P0的演示
 */
public class Demo01C3P0 {
    public static void main(String[] args) throws SQLException {
        //创建数据库连接池对象
        DataSource ds = new ComboPooledDataSource();
        Connection connection = ds.getConnection();
        System.out.println(connection);
    }
}

6.3Druid

步骤：

1.导入jar包：druid-1.0.9.jar

2.定义配置文件

是properties形式的
可以叫任意名称，可以放在任意目录下

3.获取数据库连接池对象：通过工厂类来获取 DruidDataSourceFactory

4.获取连接：getConnection

package com.priv.demo04JDBCTemplate;

import com.alibaba.druid.pool.DruidDataSourceFactory;

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

public class Demo02Druid {
    public static void main(String[] args) throws Exception {
        //1.导入jar包
        //2.定义配置文件
        //3.加载配置文件
        Properties properties = new Properties();
        ClassLoader classLoader = Demo02Druid.class.getClassLoader();
        InputStream resourceAsStream = classLoader.getResourceAsStream("druid.properties");
        properties.load(resourceAsStream);
        //4.获取连接池对象
        DataSource dataSource = DruidDataSourceFactory.createDataSource(properties);
        //5.获取连接
        Connection connection = dataSource.getConnection();
        System.out.println(connection);
    }
}

工具类

1.定义一个类 JDBCUtils

2.提供静态代码块加载配置文件，初始化连接池对象

3.提供方法

获取连接方法：通过数据库连接池获取连接
释放资源
获取连接池的方法

package com.priv.demo04JDBCTemplate;
/**
 * Druid工具类
 */

import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;
import java.io.IOException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

public class JDBCUtils {
    private static DataSource dataSource;
    static {

        try {
            Properties properties=new Properties();
            properties.load(JDBCUtils.class.getResourceAsStream("druid.properties"));
            dataSource= DruidDataSourceFactory.createDataSource(properties);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     *获取连接
     */
    public static Connection getConnection() throws SQLException {

        return dataSource.getConnection();
    }
    /**
     * 释放资源
     */
    public static void close(Statement statement,Connection connection){
        if(statement!=null){
            try {
                statement.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
        if(connection!=null){
            try {
                connection.close();//归还连接
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
    }

    public static void close(ResultSet resultSet,Statement statement, Connection connection){
        if(resultSet!=null){
            try {
                resultSet.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
        close(statement, connection);
    }

    /**
     * 获取连接池方法
     */
    public static DataSource getDataSource(){
        return dataSource;
    }
}

实现

package com.priv.demo04JDBCTemplate;

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

/**
 * 使用新的工具类
 */
public class Demo03Druid {
    public static void main(String[] args) {
        Connection connection =null;
        PreparedStatement preparedStatement =null;
        try {
            connection = JDBCUtils.getConnection();
            String sql="insert into account value(null,?,?) ";
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setString(1,"张飞");
            preparedStatement.setInt(2,1000);
            int count = preparedStatement.executeUpdate();
            System.out.println(count);
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            JDBCUtils.close(preparedStatement,connection);
        }

    }
}

第七章 Spring JDBC

7.1JDBCTemplate简介

Spring框架对JDBC的简单封装。提供了一个JDBCTemplate对象简化JDBC的开发

步骤：

1.导入jar包

2.创建JDBCTemplate对象。依赖于数据源DataSource

```java
JdbcTemplate jdbcTemplate=new JdbcTemplate(ds);


3.调用JDBCTemplate的方法来完成CRUD的操作

* ** `update():`**执行DML语句。增、删、改语句
* ** `queryForMap():`**查询结果将结果集封装为Map集合

注意：这个方法查询的结果集长度只能是1

* ** `queryForList():`**查询结果将结果集封装为List集合

注意：将每一条记录封装为一个Map集合，再将Map集合装载到List集合中

* ** `query():`**查询结果将结果集封装为JavaBean集合

query的参数：RowMapper

一般我们使用BeanPropertyRowMapper实现类。可以完成数据到JavaBean的自动封装

new BeanPropertyRowMapper<类型>(类型.class)

* ** `queryForObject():`**查询结果将结果集封装为对象

一般用于聚合函数的查询

```java
package com.priv.demo04JDBCTemplate;

import org.springframework.jdbc.core.JdbcTemplate;

/**
 * JDBCTemplate入门
 */
public class Demo04JDBCTemplate {
    public static void main(String[] args) {
        //导入jar包
        //创建JdbcTemplate对象
        JdbcTemplate jdbcTemplate=new JdbcTemplate(JDBCUtils.getDataSource());
        String sql="update account set balance=5000 where id=?";
        //调用方法
        int count = jdbcTemplate.update(sql,3);
        System.out.println(count);
    }
}

7.2JDBCTemplate执行DML语句

package com.priv.demo04JDBCTemplate;

import org.junit.Test;
import org.springframework.jdbc.core.JdbcTemplate;

/**
 * 案例一：修改1号数据的balance为5000
 */
public class Demo05JDBCTemplateP {
    @Test
    public void test1() {
        JdbcTemplate jdbcTemplate=new JdbcTemplate(JDBCUtils.getDataSource());
        String sql="update account set balance=5000 where id=?";
        int update = jdbcTemplate.update(sql, 1);
        System.out.println(update);
    }
/**
 * 案例二：添加一条记录
 */
    @Test
    public void test2() {
        JdbcTemplate jdbcTemplate=new JdbcTemplate(JDBCUtils.getDataSource());
        String sql="insert into account value(null ,?,?)";
        int count = jdbcTemplate.update(sql, "郭靖", "1000");
        System.out.println(count);
    }

/**
 * 案例三：删除刚才添加的记录
 */
    @Test
    public void test3() {
        JdbcTemplate jdbcTemplate=new JdbcTemplate(JDBCUtils.getDataSource());
        String sql="delete from account where id=?";
        int count = jdbcTemplate.update(sql, "4");
        System.out.println(count);
}
}

7.3JDBCTemplate执行DQL语句

package com.priv.demo04JDBCTemplate;

import org.junit.Test;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;
import java.util.Map;

public class Demo06JDBCTemplateP2 {
    /**
     * 案例一：查询id为1的记录，将其封装为Map集合
     */
    @Test
    public void Test1(){
        JdbcTemplate jdbcTemplate=new JdbcTemplate(JDBCUtils.getDataSource());
        String sql="select * from account where id=?";
        Map<String, Object> stringObjectMap = jdbcTemplate.queryForMap(sql, "1");
        System.out.println(stringObjectMap);
    }

    /**
     * 案例二：查询所有记录，将其封装为List集合
     */
    @Test
    public void Test2(){
        JdbcTemplate jdbcTemplate=new JdbcTemplate(JDBCUtils.getDataSource());
        String sql="select * from account";
        List<Map<String, Object>> maps = jdbcTemplate.queryForList(sql);
        for(Map<String, Object> stringObjectMap:maps){
            System.out.println(stringObjectMap);
        }
    }

    /**
     *案例三：查询所有记录，将其封装为account对象的List集合
     */
    @Test
    public void Test3(){
        JdbcTemplate jdbcTemplate=new JdbcTemplate(JDBCUtils.getDataSource());
        String sql="select * from account";
        List<account> list=jdbcTemplate.query(sql, new RowMapper<account>() {
            @Override
            public account mapRow(ResultSet resultSet, int i) throws SQLException {
                account account=new account();
                int id = account.getId("id");
                String username = account.getUsername();
                int balance = account.getBalance();

                account.setId(id);
                account.setUsername(username);
                account.setBalance(balance);
                return null;
            }
        });
        for(account account:list){
            System.out.println(account);
        }
    }

    @Test
    public void Test4(){
        JdbcTemplate jdbcTemplate=new JdbcTemplate(JDBCUtils.getDataSource());
        String sql="select * from account";
        List<account> query = jdbcTemplate.query(sql, new BeanPropertyRowMapper<account>(account.class));
        for(account account:query){
            System.out.println(account);
        }
    }

    /**
     *案例四：查询总记录数
     */
    @Test
    public void Test5(){
        JdbcTemplate jdbcTemplate=new JdbcTemplate(JDBCUtils.getDataSource());
        String sql="select count(id) from account";
        Long aLong = jdbcTemplate.queryForObject(sql, long.class);
        System.out.println(aLong);
    }
}

JDBC

第一章 JDBC简介

1.1概念

1.2步骤

1.3代码实现

第二章 详解各个对象

2.1DriverManager

2.2Connection

2.3Statement

2.4ResultSet

2.5PreparedStatement

第三章 JDBC练习

3.1insert语句

3.2update语句

3.3delete语句

3.4select语句

第四章 JDBC工具类

4.1工具类实现

4.2登录案例

第五章 JDBC控制事务

5.1概述

5.2实现案例

第六章 数据库连接池

6.1概述

6.2C3P0

6.3Druid

第七章 Spring JDBC

7.1JDBCTemplate简介

7.2JDBCTemplate执行DML语句

7.3JDBCTemplate执行DQL语句

第二章详解各个对象

第六章数据库连接池