本文源码：GitHub·点这里 || GitEE·点这里

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。

<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}

GitHub·地址https://github.com/cicadasmile/java-base-parentGitEE·地址https://gitee.com/cicadasmile/java-base-parent