心得2--自定义连接池与开源组织编写的连接池案例分析

1.自己编写的连接池案例package com.csdn.uil;import java.io.IOException;import java.io.InputStream;import java.io.PrintWriter;import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;import java.lang.reflect.Proxy;import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;import java.util.LinkedList;import java.util.Properties;import javax.sql.DataSource;/** * 自己编写一个连接池，模拟dbcp、c3p0等连接池；实现了DataSourc接口 */public class DBPool implements DataSource {private static String driver;private static String url;private static String username;private static String password;private static Connection con;    //这里用LinkedList是因为取出放回的时候要按顺序取出，顺序放回private static LinkedList<Connection> list = new LinkedList<Connection>();static {InputStream in = DBManager.class.getClassLoader().getResourceAsStream("db.properties");Properties pro = new Properties();try {pro.load(in);driver = pro.getProperty("driver");url = pro.getProperty("url");username = pro.getProperty("username");password = pro.getProperty("password");Class.forName(driver);//手动设置向连接池加入10个连接for (int i = 0; i < 10; i++) {con = DriverManager.getConnection(url, username, password);System.out.println("向连接池中加入了" + con);list.add(con);}} catch (IOException e) {e.printStackTrace();} catch (ClassNotFoundException e) {e.printStackTrace();} catch (SQLException e) {e.printStackTrace();}}@Overridepublic Connection getConnection() throws SQLException {if(list.size()>0){//这里不用get的原因是这里取出一个连接，是取出（连接池里没有了），用get连接池里还有final Connection con = list.removeFirst();System.out.println("用户从池中取走了:"+con);System.out.println("池的大小为："+list.size());return (Connection)Proxy.newProxyInstance(DBPool.class.getClassLoader(), new Class[]{Connection.class}, new InvocationHandler() {@Overridepublic Object invoke(Object proxy, Method method, Object[] args)throws Throwable {if(!method.getName().equalsIgnoreCase("close")){return method.invoke(con, args);}System.out.println(con+"被放回了");list.add(con);System.out.println("池的大小为："+list.size());return null;}});}else{//throw new RuntimeException("对不起，请稍等！");return null;}}@Overridepublic Connection getConnection(String username, String password)throws SQLException {return null;}@Overridepublic PrintWriter getLogWriter() throws SQLException {return null;}@Overridepublic int getLoginTimeout() throws SQLException {return 0;}@Overridepublic void setLogWriter(PrintWriter out) throws SQLException {}@Overridepublic void setLoginTimeout(int seconds) throws SQLException {}@Overridepublic boolean isWrapperFor(Class<?> iface) throws SQLException {return false;}@Overridepublic <T> T unwrap(Class<T> iface) throws SQLException {return null;}}2．Apache组织的连接池：dbcppackage com.csdn.uil;import java.io.IOException;import java.io.InputStream;import java.sql.Connection;import java.sql.SQLException;import java.util.Properties;import javax.sql.DataSource;import org.apache.commons.dbcp.BasicDataSourceFactory;public class DBManager_dbcp {private static DataSource ds;static{InputStream in = DBManager_dbcp.class.getClassLoader().getResourceAsStream("dbcpconfig.properties");Properties pro = new Properties();try {pro.load(in);BasicDataSourceFactory factory = new BasicDataSourceFactory();ds = factory.createDataSource(pro);} catch (IOException e) {e.printStackTrace();} catch (Exception e) {e.printStackTrace();}}public static Connection getConnection() throws SQLException{return ds.getConnection();}}3. c3p0连接池package com.csdn.uil;import java.sql.Connection;import java.sql.SQLException;import com.mchange.v2.c3p0.ComboPooledDataSource;public class DBManager_c3p0 {private static ComboPooledDataSource ds = null;static{//这里要注意的是：xml配置文件的名字一定要是c3p0-config.xml，可以doc参考帮助，帮助中有命名，如果名字写错了会无法加载驱动，空指针的错ds = new ComboPooledDataSource("mysql");/*try {ds =new ComboPooledDataSource();ds.setDriverClass("com.mysql.jdbc.Driver");//自己写的时候一定要区分com.mysql.jdbc和jdbc:mysql:的顺序区别，写错之后会出无法加载driver驱动的错ds.setJdbcUrl("jdbc:mysql://localhost:3306/login");ds.setUser("root");ds.setPassword("root");ds.setInitialPoolSize(10);ds.setMaxPoolSize(20);ds.setMinPoolSize(5);} catch (PropertyVetoException e) {e.printStackTrace();}*/}    public static Connection getCon() throws SQLException{    return ds.getConnection();    }}   这里要注意的是：c3p0连接池需要一个xml配置文件c3p0-config.xml;而且名字是固定的，一定是c3p0-config，中连线不是下划线，错了会出错<c3p0-config><default-config><property name="driverClass">com.mysql.jdbc.Driver</property><property name="jdbcUrl">jdbc:mysql://localhost:3306/login</property><property name="user">root</property><property name="password">root</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></default-config><named-config name="mysql"><property name="driverClass">com.mysql.jdbc.Driver</property><property name="jdbcUrl">jdbc:mysql://localhost:3306/login</property><property name="user">root</property><property name="password">root</property><property name="acquireIncrement">5</property><property name="initialPoolSize">10</property><property name="minPoolSize">50</property><property name="maxPoolSize">1000</property></named-config></c3p0-config>