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Spring 动态代理 part1
实现接口InvocationHandler
public class UserHandler implements InvocationHandler {
private Object obj;
public UserHandler(Object obj) {
this.obj = obj;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
System.out.println("before");
Object result = method.invoke(obj, args);
System.out.println("after");
return result;
}
}
数据库连接池核心代码
/**
*
*/
package com.hpe.util;
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.sql.SQLFeatureNotSupportedException;
import java.util.LinkedList;
import java.util.List;
import java.util.Properties;
import java.util.logging.Logger;
import javax.sql.DataSource;
/**
* 类描述：
* 作者：Λrisa
* 创建日期：2018年10月15日
*/
public class DataSourcePoolProxy implements DataSource{
private static LinkedList<Connection> List =new LinkedList<Connection>();
static{
InputStream in = DataSourcePoolProxy.class.getClassLoader().getResourceAsStream("db.properties");
Properties prop = new Properties();
try {
prop.load(in);
String driver = prop.getProperty("driver");
System.out.println(driver);
String url = prop.getProperty("url");
String user = prop.getProperty("user");
String password = prop.getProperty("password");
Class.forName(driver);
// 初始化10个Connection
for (int i = 0; i < 10; i++) {
Connection conn = DriverManager.getConnection(url, user, password);
List.add(conn); // 将conn对象添加容器中
}
} catch (Exception e) {
e.printStackTrace();
throw new ExceptionInInitializerError(e);
}
}
/* (non-Javadoc)
* @see javax.sql.CommonDataSource#getLogWriter()
*/
@Override
public PrintWriter getLogWriter() throws SQLException {
// TODO Auto-generated method stub
return null;
}
/* (non-Javadoc)
* @see javax.sql.CommonDataSource#setLogWriter(java.io.PrintWriter)
*/
@Override
public void setLogWriter(PrintWriter out) throws SQLException {
// TODO Auto-generated method stub
}
/* (non-Javadoc)
* @see javax.sql.CommonDataSource#setLoginTimeout(int)
*/
@Override
public void setLoginTimeout(int seconds) throws SQLException {
// TODO Auto-generated method stub
}
/* (non-Javadoc)
* @see javax.sql.CommonDataSource#getLoginTimeout()
*/
@Override
public int getLoginTimeout() throws SQLException {
// TODO Auto-generated method stub
return 0;
}
/* (non-Javadoc)
* @see javax.sql.CommonDataSource#getParentLogger()
*/
@Override
public Logger getParentLogger() throws SQLFeatureNotSupportedException {
// TODO Auto-generated method stub
return null;
}
/* (non-Javadoc)
* @see java.sql.Wrapper#unwrap(java.lang.Class)
*/
@Override
public <T> T unwrap(Class<T> iface) throws SQLException {
// TODO Auto-generated method stub
return null;
}
/* (non-Javadoc)
* @see java.sql.Wrapper#isWrapperFor(java.lang.Class)
*/
@Override
public boolean isWrapperFor(Class<?> iface) throws SQLException {
// TODO Auto-generated method stub
return false;
}
/* (non-Javadoc)
* @see javax.sql.DataSource#getConnection()
*/
@Override
public Connection getConnection() throws SQLException {
//说明有可用的链接
synchronized(List){
if(List.size()>0){
/**
* 如果调用的方法主要使用子类实现的方法，不用向上转型
* 如果主要使用父类 父接口的方法 则使用向上转型
*/
final Connection conn=List.removeFirst();
Object obj=Proxy.newProxyInstance(DataSourcePoolProxy.class.getClassLoader(),new Class[]{Connection.class}, new InvocationHandler(){
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
if("close".equals(method.getName())){
List.add(conn);
return null;
}else{
return method.invoke(conn, args);
}
}
});
return (Connection) obj;
}
return null;
}
}
/* (non-Javadoc)
* @see javax.sql.DataSource#getConnection(java.lang.String, java.lang.String)
*/
@Override
public Connection getConnection(String username, String password) throws SQLException {
return null;
}
}
