本文源码：GitHub·点这里 || GitEE·点这里

一、C3P0连接池

1、C3P0简介

C3P0是一个开源的JDBC连接池，应用程序根据C3P0配置来初始化数据库连接，可以自动回收空闲连接的功能。

2、核心依赖

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>${mysql.version}</version>
</dependency>
<dependency>
    <groupId>com.mchange</groupId>
    <artifactId>c3p0</artifactId>
    <version>${c3p0.version}</version>
</dependency>

3、配置文件

配置文件位置：放在resources目录下，这样C3P0组件会自动加载该配置。

<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
    <default-config>
        <!-- 核心参数配置 -->
        <property name="jdbcUrl">jdbc:mysql://localhost:3306/servlet-jdbc</property>
        <property name="driverClass">com.mysql.jdbc.Driver</property>
        <property name="user">root</property>
        <property name="password">123</property>
        <!-- 池参数配置 -->
        <property name="acquireIncrement">3</property>
        <property name="initialPoolSize">10</property>
        <property name="minPoolSize">2</property>
        <property name="maxPoolSize">10</property>
    </default-config>
</c3p0-config>

4、编写工具类

该工具类用来获取数据库连接，和释放相关连接。

public class C3P0Pool {
    private static DataSource dataSource = new ComboPooledDataSource();
    public static DataSource getDataSource() {
        return dataSource ;
    }
    /**
     * 获取连接
     */
    public static Connection getConnection() throws SQLException {
        return dataSource.getConnection();
    }
    /**
     * 释放连接
     */
    public static void close(ResultSet resultSet, PreparedStatement pst, Connection connection) {
        if (resultSet != null) {
            try {
                resultSet.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (pst != null) {
            try {
                pst.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (connection != null) {
            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

二、数据操作封装

1、新增数据

public class UserJdbcInsert {
    public static void insertUser (UserInfo userInfo){
        try {
            Connection connection = C3P0Pool.getConnection();
            String sql = "INSERT INTO user_info (user_name,user_age) VALUES (?,?)" ;
            PreparedStatement statement = connection.prepareStatement(sql);
            statement.setString(1,userInfo.getUserName());
            statement.setString(2,userInfo.getUserAge().toString());
            statement.execute() ;
            C3P0Pool.close(null, statement, connection);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public static void batchInsertUser (List<UserInfo> userInfoList){
        try {
            Connection connection = C3P0Pool.getConnection();
            String sql = "INSERT INTO user_info (user_name,user_age) VALUES (?,?)" ;
            PreparedStatement statement = connection.prepareStatement(sql);
            for (UserInfo userInfo:userInfoList){
                statement.setString(1,userInfo.getUserName());
                statement.setString(2,userInfo.getUserAge().toString());
                statement.addBatch();
            }
            statement.executeBatch() ;
            C3P0Pool.close(null, statement, connection);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

2、查询数据

public class UserJdbcQuery {
    public static UserInfo queryUser (String userName){
        UserInfo userInfo = null ;
        try {
            Connection connection = C3P0Pool.getConnection();
            String sql = "SELECT * FROM user_info WHERE user_name=?" ;
            PreparedStatement statement = connection.prepareStatement(sql);
            statement.setString(1,userName);
            ResultSet resultSet = statement.executeQuery() ;
            while (resultSet.next()){
                int id = resultSet.getInt("id");
                String name = resultSet.getString("user_name");
                int age = resultSet.getInt("user_age");
                System.out.println("ID:"+id+";name:"+name+";age:"+age);
                userInfo = new UserInfo(name,age) ;
            }
            C3P0Pool.close(resultSet, statement, connection);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return userInfo ;
    }
}

3、更新数据

public class UserJdbcUpdate {
    public static void updateUser (String name,Integer age,Integer id){
        try {
            Connection connection = C3P0Pool.getConnection();
            String sql = "UPDATE user_info SET user_name=?,user_age=? WHERE id=?" ;
            PreparedStatement statement = connection.prepareStatement(sql);
            statement.setString(1,name);
            statement.setInt(2,age);
            statement.setInt(3,id);
            statement.executeUpdate() ;
            C3P0Pool.close(null, statement, connection);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

4、删除数据

public class UserJdbcDelete {
    public static void deleteUser (Integer id){
        try {
            Connection connection = C3P0Pool.getConnection();
            String sql = "DELETE FROM user_info WHERE id=?" ;
            PreparedStatement statement = connection.prepareStatement(sql);
            statement.setInt(1,id);
            statement.executeUpdate() ;
            C3P0Pool.close(null, statement, connection);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

三、Servlet接口

public class JdbcServletImpl extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String userName = request.getParameter("userName") ;
        UserInfo userInfo = UserJdbcQuery.queryUser(userName) ;
        response.setContentType("text/html;charset=utf-8");
        response.getWriter().print("用户信息:"+userInfo);
    }
}

测试访问：

http://localhost:6003/jdbcServletImpl?userName=LiSi

页面打印：

用户信息:UserInfo{userName='LiSi', userAge=22}