数据库连接池

1 package me.gacl.demo;
  2 
  3 import java.io.InputStream;
  4 import java.io.PrintWriter;
  5 import java.lang.reflect.InvocationHandler;
  6 import java.lang.reflect.Method;
  7 import java.lang.reflect.Proxy;
  8 import java.sql.Connection;
  9 import java.sql.DriverManager;
 10 import java.sql.SQLException;
 11 import java.util.LinkedList;
 12 import java.util.Properties;
 13 import javax.sql.DataSource;
 14 
 15 /**
 16 * @ClassName: JdbcPool
 17 * @Description:编写数据库连接池
 18 * @author: 孤傲苍狼
 19 * @date: 2014-9-30 下午11:07:23
 20 *
 21 */ 
 22 public class JdbcPool implements DataSource{
 23 
 24     /**
 25     * @Field: listConnections
 26     *         使用LinkedList集合来存放数据库链接，
 27     *        由于要频繁读写List集合，所以这里使用LinkedList存储数据库连接比较合适
 28     */ 
 29     private static LinkedList<Connection> listConnections = new LinkedList<Connection>();
 30     
 31     static{
 32         //在静态代码块中加载db.properties数据库配置文件
 33         InputStream in = JdbcPool.class.getClassLoader().getResourceAsStream("db.properties");
 34         Properties prop = new Properties();
 35         try {
 36             prop.load(in);
 37             String driver = prop.getProperty("driver");
 38             String url = prop.getProperty("url");
 39             String username = prop.getProperty("username");
 40             String password = prop.getProperty("password");
 41             //数据库连接池的初始化连接数大小
 42             int jdbcPoolInitSize =Integer.parseInt(prop.getProperty("jdbcPoolInitSize"));
 43             //加载数据库驱动
 44             Class.forName(driver);
 45             for (int i = 0; i < jdbcPoolInitSize; i++) {
 46                 Connection conn = DriverManager.getConnection(url, username, password);
 47                 System.out.println("获取到了链接" + conn);
 48                 //将获取到的数据库连接加入到listConnections集合中，listConnections集合此时就是一个存放了数据库连接的连接池
 49                 listConnections.add(conn);
 50             }
 51             
 52         } catch (Exception e) {
 53             throw new ExceptionInInitializerError(e);
 54         }
 55     }
 56     
 57     @Override
 58     public PrintWriter getLogWriter() throws SQLException {
 59         // TODO Auto-generated method stub
 60         return null;
 61     }
 62 
 63     @Override
 64     public void setLogWriter(PrintWriter out) throws SQLException {
 65         // TODO Auto-generated method stub
 66         
 67     }
 68 
 69     @Override
 70     public void setLoginTimeout(int seconds) throws SQLException {
 71         // TODO Auto-generated method stub
 72         
 73     }
 74 
 75     @Override
 76     public int getLoginTimeout() throws SQLException {
 77         // TODO Auto-generated method stub
 78         return 0;
 79     }
 80 
 81     @Override
 82     public <T> T unwrap(Class<T> iface) throws SQLException {
 83         // TODO Auto-generated method stub
 84         return null;
 85     }
 86 
 87     @Override
 88     public boolean isWrapperFor(Class<?> iface) throws SQLException {
 89         // TODO Auto-generated method stub
 90         return false;
 91     }
 92 
 93     /* 获取数据库连接
 94      * @see javax.sql.DataSource#getConnection()
 95      */
 96     @Override
 97     public Connection getConnection() throws SQLException {
 98         //如果数据库连接池中的连接对象的个数大于0
 99         if (listConnections.size()>0) {
100             //从listConnections集合中获取一个数据库连接
101             final Connection conn = listConnections.removeFirst();
102             System.out.println("listConnections数据库连接池大小是" + listConnections.size());
103             //返回Connection对象的代理对象
104             return (Connection) Proxy.newProxyInstance(JdbcPool.class.getClassLoader(), conn.getClass().getInterfaces(), new InvocationHandler(){
105                 @Override
106                 public Object invoke(Object proxy, Method method, Object[] args)
107                         throws Throwable {
108                     if(!method.getName().equals("close")){
109                         return method.invoke(conn, args);
110                     }else{
111                         //如果调用的是Connection对象的close方法，就把conn还给数据库连接池
112                         listConnections.add(conn);
113                         System.out.println(conn + "被还给listConnections数据库连接池了！！");
114                         System.out.println("listConnections数据库连接池大小为" + listConnections.size());
115                         return null;
116                     }
117                 }
118             });
119         }else {
120             throw new RuntimeException("对不起，数据库忙");
121         }
122     }
123 
124     @Override
125     public Connection getConnection(String username, String password)
126             throws SQLException {
127         return null;
128     }
129 }