手写数据库连接池（动态代理）

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package com.zhangbz.jdbc;   import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException;   import com.zhangbz.pool.MyPool;   public class JDBCDemo1 {     public static void main(String[] args) {         Connection conn = null;         PreparedStatement ps = null;         ResultSet rs = null;         MyPool pool = new MyPool();         try {             conn = pool.getConnection();             ps = conn.prepareStatement("select * from account");             rs = ps.executeQuery();             while(rs.next()) {                 String name = rs.getString("name");                 System.out.println(name);             }         } catch(Exception e) {             e.printStackTrace();         } finally {             if (rs != null) {                 try {                     rs.close();                 } catch (SQLException e) {                     e.printStackTrace();                 } finally {                     rs = null;                 }             }             if (ps != null) {                 try {                     ps.close();                 } catch (SQLException e) {                     e.printStackTrace();                 } finally {                     ps = null;                 }             }             if (conn != null) {                 try {                     conn.close();                 } catch (SQLException e) {                     e.printStackTrace();                 } finally {                     conn = null;                 }             }         }     } }

MyPool.java

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package com.zhangbz.pool;     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.List;   import javax.sql.DataSource;   public class MyPool implements DataSource{     private static List<Connection> pool = new LinkedList<Connection>();     static {         try {             Class.forName("com.mysql.jdbc.Driver");             for (int i = 0; i < 5; i++) {                 Connection conn = DriverManager.getConnection("jdbc:mysql:///Day11", "root", "root");                 pool.add(conn);             }         } catch (Exception e) {              e.printStackTrace();              throw new RuntimeException(e);         }     }     public Connection getConnection() throws SQLException {         if (pool.size() == 0) {             for(int i = 0; i < 3; i++) {                 Connection conn = DriverManager.getConnection("jdbc:mysql:///Day11", "root", "root");                 pool.add(conn);             }         }         final Connection conn = pool.remove(0);         //--利用动态代理改造close方法（还可以使用继承和装饰）         Connection proxy = (Connection) Proxy.newProxyInstance(conn.getClass().getClassLoader(), conn.getClass().getInterfaces(), new  InvocationHandler() {               public Object invoke(Object proxy, Method method, Object[] args)                     throws Throwable {                 if ("close".equals(method.getName())) {                     //对于想要改造的方法我们自己写                     retConn(conn);                     return null;                 } else {                     //对于不想改造的方法，调用被代理者身上的方法                     return method.invoke(conn, args);                 }             }         });         System.out.println("获取了一个连接，池里还剩余" +pool.size()+ "个连接");         return proxy;     }           private  void retConn(Connection conn) {         try {             if (conn != null && !conn.isClosed()) {                 pool.add(conn);                 System.out.println("换回来一个连接，池里还剩余" +pool.size()+ "个连接");             }         } catch (SQLException e) {             e.printStackTrace();         }     }       public Connection getConnection(String arg0, String arg1)             throws SQLException {         // TODO Auto-generated method stub         return null;     }       public PrintWriter getLogWriter() throws SQLException {         // TODO Auto-generated method stub         return null;     }       public int getLoginTimeout() throws SQLException {         // TODO Auto-generated method stub         return 0;     }       public void setLogWriter(PrintWriter arg0) throws SQLException {         // TODO Auto-generated method stub               }       public void setLoginTimeout(int arg0) throws SQLException {         // TODO Auto-generated method stub               }   }