数据库连接池c3p0学习

这里只记录c3p0的数据源，不会涉及到其它方面和别的数据库连接池的对比

配置文件主要的实现方式有三种：

1.手写代码去加载一个配置文件

创建一个config.properties文件如下：

driverClass= com.mysql.jdbc.Driver
jdbcUrl = jdbc:mysql://127.0.0.1:3306/soc_db?autoReconnect=true&autoReconnectForPools=true
user = root
password = root
......

然后在java代码中：

     public void closeInputStream(InputStream inputStream){
         if(inputStream!=null){
             try {
                 inputStream.close();
             } catch (IOException e) {
                 e.printStackTrace();
             }
         }
     }

     public InputStream loadResource(String resource) {
         InputStream in = Thread.currentThread().getContextClassLoader().getResourceAsStream(resource);
         if (in == null) {
             in = PropertiesUtil.class.getResourceAsStream(resource);
         }
         return in;
     }

     public Properties getProperties(String resource){
         LOG.debug("[Method]   读取数据库配置信息");
         Properties properties = new Properties();
         InputStream in = null;
         try {
             in = loadResource(resource);
             if(in!=null){
                 properties.load(in);
             }
         } catch (IOException e) {
             LOG.error("load properties error",e);
         }finally {
             closeInputStream(in);
         }
         LOG.debug(properties.getProperty("url"));
         return properties;
     }

             Properties properties = PropertiesUtil.getInstance().getProperties("/resource/jindun.properties");
             c3p0DataSource.setDriverClass(properties.getProperty("driverClass"));
             c3p0DataSource.setDriverClass(properties.getProperty("jdbcUrl"));
             c3p0DataSource.setDriverClass(properties.getProperty("user"));
             c3p0DataSource.setDriverClass(properties.getProperty("password"));
             ......

2.在src下创建一个c3p0.properties文件（固定名字哦）

c3p0.driverClass=com.mysql.jdbc.Driver
c3p0.jdbcUrl=jdbc:mysql://10.30.79.10:3306/test
c3p0.user=root
c3p0.password=root
......

 ......
 ComboPooledDataSource c3p0DataSource = new ComboPooledDataSource()
 ......

这样就可以直接使用了，不需要再去说明。
3.在src下创建一个c3p0-config.xml文件

（1）XML格式更加直观

（2）可以在文件中配置多个数据源

<c3p0-config>
    <default-config>
        <property name="user">root</property>
        <property name="password">root</property>
        <property name="driverClass">com.mysql.jdbc.Driver</property>
        <property name="jdbcUrl">jdbc:mysql://127.0.0.1:3306/test</property>

        <property name="initialPoolSize">10</property>
        <property name="maxIdleTime">30</property>
        <property name="minPoolSize">10</property>
        <property name="maxPoolSize">500</property>

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

    </default-config>

    <!-- This app is jindun -->
    <named-config name="jinDunApp">
        <property name="user">root</property>
        <property name="password">root</property>
        <property name="driverClass">com.mysql.jdbc.Driver</property>
        <property name="jdbcUrl">jdbc:mysql://10.30.79.10:3306/HrINetDB?autoReconnect=true&amp;autoReconnectForPools=true</property>

        <property name="initialPoolSize">10</property>
        <property name="maxIdleTime">30</property>
        <property name="minPoolSize">10</property>
        <property name="maxPoolSize">500</property>

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

    </named-config>

    <!-- This app is Tianji -->
    <named-config name="tianJiApp">
        <property name="user">root</property>
        <property name="password">root</property>
        <property name="driverClass">com.mysql.jdbc.Driver</property>
        <property name="jdbcUrl">jdbc:mysql://10.30.67.95:3306/config_db?autoReconnect=true&amp;autoReconnectForPools=true</property>

        <property name="initialPoolSize">10</property>
        <property name="maxIdleTime">30</property>
        <property name="minPoolSize">10</property>
        <property name="maxPoolSize">500</property>

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

</c3p0-config>

     public static void main(String[] args) {
         // 默认配置
         ComboPooledDataSource comboPooledDataSource = new ComboPooledDataSource();
         // 固定名字配置
         ComboPooledDataSource comboPooledDataSource2 = new ComboPooledDataSource("jinDunApp");
         // 数据源使用
         PreparedStatement psta;
         ResultSet rs;
         try {
             // 这个的comboPooledDataSource改comboPooledDataSource2就执行jinDunApp配置了
             Connection conn = comboPooledDataSource.getConnection();
             psta = conn.prepareStatement("SELECT empName FROM t_sc_usermanager");
             rs = psta.executeQuery();
             while (rs.next() ){
                 System.out.println(rs.getString(1) + "\n");
             }
         } catch (SQLException e) {
             e.printStackTrace();
         }
     }

上面就是一个实例。

　　配置的参数列表如下（具体含义可以查看参考资料）：

参考资料：

http://haoran-10.iteye.com/blog/1753332

http://www.mchange.com/projects/c3p0/#c3p0-config.xml