非常简单的mysql数据库连接池

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/**
 * 连接池类
 */
package com.junones.test;
 
import java.sql.Connection;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
 
import com.mysql.jdbc.jdbc2.optional.MysqlDataSource;
 
public class MySQLPool {
    private static volatile MySQLPool pool;
    private MysqlDataSource ds;
    private Map map;
  
    private String url = "jdbc:mysql://localhost:3306/test";
    private String username = "root";
    private String password = "root1234";
    private int initPoolSize = 10;
    private int maxPoolSize = 200;
    private int waitTime = 100;
     
    private MySQLPool() {
        init();
    }
     
    public static MySQLPool getInstance() {
        if (pool == null) {
            synchronized (MySQLPool.class) {
                if(pool == null) {
                    pool = new MySQLPool();
                }
            }
        }
        return pool;
    }
     
    private void init() {
        try {
            ds = new MysqlDataSource();
            ds.setUrl(url);
            ds.setUser(username);
            ds.setPassword(password);
            ds.setCacheCallableStmts(true);
            ds.setConnectTimeout(1000);
            ds.setLoginTimeout(2000);
            ds.setUseUnicode(true);
            ds.setEncoding("UTF-8");
            ds.setZeroDateTimeBehavior("convertToNull");
            ds.setMaxReconnects(5);
            ds.setAutoReconnect(true);
            map = new HashMap();
            for (int i = 0; i < initPoolSize; i++) {
                map.put(getNewConnection(), true);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
     
    public Connection getNewConnection() {
        try {
            return ds.getConnection();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }
     
    public synchronized Connection getConnection() {
        Connection conn = null;
        try {
            for (Entry entry : map.entrySet()) {
                if (entry.getValue()) {
                    conn = entry.getKey();
                    map.put(conn, false);
                    break;
                }
            }
            if (conn == null) {
                if (map.size() < maxPoolSize) {
                    conn = getNewConnection();
                    map.put(conn, false);
                } else {
                    wait(waitTime);
                    conn = getConnection();
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return conn;
    }
     
    public void releaseConnection(Connection conn) {
        if (conn == null) {
            return;
        }
        try {
            if(map.containsKey(conn)) {
                if (conn.isClosed()) {
                    map.remove(conn);
                } else {
                    if(!conn.getAutoCommit()) {
                        conn.setAutoCommit(true);
                    }
                    map.put(conn, true);
                }
            } else {
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}
 
/**
 * 测试类
 */
package com.junones.test;
 
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
 
public class TestMySQLPool {
    private static volatile int a;
 
    private synchronized static void incr() {
        a++;
    }
 
    public static void main(String[] args) throws InterruptedException {
        int times = 10000;
        long start = System.currentTimeMillis();
        for (int i = 0; i < times; i++) {
            new Thread(new Runnable() {
 
                @Override
                public void run() {
 
                    MySQLPool pool = MySQLPool.getInstance();
                    Connection conn = pool.getConnection();
                    Statement stmt = null;
                    ResultSet rs = null;
                    try {
                        stmt = conn.createStatement();
                        rs = stmt.executeQuery("select id, name from t_test");
                        while (rs.next()) {
                            System.out.println(rs.getInt(1) + ", "
                                    + rs.getString(2));
                        }
                    } catch (SQLException e) {
                        e.printStackTrace();
                    } finally {
                        incr();
                        if (rs != null) {
                            try {
                                rs.close();
                            } catch (SQLException e) {
                                e.printStackTrace();
                            }
                        }
                        if (stmt != null) {
                            try {
                                stmt.close();
                            } catch (SQLException e) {
                            }
                        }
                        pool.releaseConnection(conn);
                    }
                }
            }).start();
        }
        while (true) {
            if (a == times) {
                System.out.println("finished, time:"
                        + (System.currentTimeMillis() - start));
                break;
            }
            Thread.sleep(100);
        }
    }
}