JDBC学习笔记(17)：连接池

 1 package com.xxyh.jdbc.datasource;
 2 import java.sql.Connection;
 3 import java.sql.DriverManager;
 4 import java.sql.SQLException;
 5 import java.util.LinkedList;
 6 public class MyDataSource {
 7     private static String url = "jdbc:mysql://localhost:3306/jdbc?generateSimpleParameterMetadata=true";
 8     private static String user = "root";
 9     private static String password = "1234";
10     
11     private LinkedList<Connection> connectionsPool = new LinkedList<>();
12     
13     public MyDataSource() {
14         try {
15             // 创建 5 个连接
16             for (int i = 0; i < 5; i++)
17                 this.connectionsPool.addLast(this.createConnection());
18         } catch (SQLException e) {
19             throw new ExceptionInInitializerError(e);
20         }
21     }
22     
23     private Connection createConnection() throws SQLException {
24         return DriverManager.getConnection(url, user, password);
25     }
26     
27     public void free(Connection conn) {
28         // 释放一个连接，将它放回连接池
29         this.connectionsPool.addLast(conn);
30     }
31     
32     public Connection getConnection() {
33         // 从连接池中获取一个连接
34         return this.connectionsPool.removeFirst();
35     }
36 }

 1 package com.xxyh.jdbc;
 2 import java.sql.Connection;
 3 import java.sql.ResultSet;
 4 import java.sql.SQLException;
 5 import java.sql.Statement;
 6 public class JdbcUtils {
 7     private static MyDataSource myDataSource = null;
 8     
 9     private JdbcUtils() {
10     }
11     
12     static {
13         try {
14             // 将注册驱动放在静态代码块中只需执行一次
15             Class.forName("com.mysql.jdbc.Driver");
16             myDataSource = new MyDataSource();
17         } catch(ClassNotFoundException e) {
18             throw new ExceptionInInitializerError(e);
19         } 
20     }
21     
22     public static Connection getConnection() throws SQLException {
23 //        return DriverManager.getConnection(url, user, password);
24         // 当需要连接的时候，不再创建，而是从连接池中获取
25         return myDataSource.getConnection();
26     }
27     
28     public static void close(ResultSet rs, Statement stmt, Connection conn) {
29         try {
30             if (rs != null) {
31                 rs.close();
32             }
33         } catch (SQLException e) {
34             e.printStackTrace();
35         } finally {
36             try {
37                 if (stmt != null) {
38                     stmt.close();
39                 }
40             } catch (SQLException e) {
41                 e.printStackTrace();
42             } finally {
43                 if (conn != null) {
44                     try {
45                         //conn.close();
46                         // 将连接放回连接池，而不是关闭连接
47                         myDataSource.free(conn);
48                     } catch (Exception e) {
49                         e.printStackTrace();
50                     }
51                 }
52             }
53         }
54     }
55 }

 1 package com.xxyh.jdbc;
 2 import java.sql.Connection;
 3 import java.sql.DriverManager;
 4 import java.sql.ResultSet;
 5 import java.sql.SQLException;
 6 import java.sql.Statement;
 7 public class Base {
 8     public static void main(String[] args) throws ClassNotFoundException, SQLException {
 9         //test();
10 //        template();
11         for (int i = 0; i < 10; i++) {
12             Connection conn = JdbcUtils.getConnection();
13             System.out.println(conn);
14             JdbcUtils.close(null, null, conn);
15         }
16     }
17 }