Java实现C3P0数据库连接池

maven 下载依赖包

<dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.38</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/c3p0/c3p0 -->
    <dependency>
      <groupId>c3p0</groupId>
      <artifactId>c3p0</artifactId>
      <version>0.9.1.2</version>
    </dependency>

创建c3p0-config.xml 配置文件

<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
    <!--默认配置-->
    <default-config>
        <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>

    <!--配置连接池mysql-->
    <named-config name="mysql">
        <property name="driverClass">com.mysql.jdbc.Driver</property>
        <property name="jdbcUrl">jdbc:mysql://192.168.146.222:3306/school</property>
        <property name="user">root</property>
        <property name="password">1</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>
    </named-config>

    <!--配置连接池2-->
    ......
    <!--配置连接池3-->
    ......
    <!--配置连接池4-->
    ......
</c3p0-config>

实现代码

这里需要注意的地方是，ComboPooledDataSource(“mysql”); 里面写的名称需要和 xml配置文件内 named-config name=“mysql” 保持一致，否则无法调用成功。

public class C3P0Utils {

    //通过标识名来创建相应连接池
    static ComboPooledDataSource dataSource=new ComboPooledDataSource("mysql");
    //从连接池中取用一个连接
    public static Connection getConnection(){
        Connection connection =null;
        try {
            connection = dataSource.getConnection();

        } catch (Exception e) {
           e.printStackTrace();
        }
        return connection;
    }

    public static void main(String[] args) {
        Connection connection1 = C3P0Utils.getConnection();
        Connection connection2 = C3P0Utils.getConnection();
        if (connection1==connection2){
            System.out.println("true");
        }else {
            System.out.println("false");
        }
        try {
            connection1.close();
            connection2.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    //释放资源
    public static void close(Connection conn, PreparedStatement pstmt, ResultSet rs){
        if (rs!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (pstmt!=null){
            try {
                pstmt.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (conn!=null){
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}