ThreadLocal學習----簡單例子應用。

    1. ThreadLocal的解釋，參見
       http://my.oschina.net/u/1989867/blog/528047
    2. ThreadLocal的簡單應用：利用ThreadLocal隔離局部變量的特色實現爲每一個線程提供本身的數據庫連接
       ConnectionResource.java ------------------------------------------產生數據庫連接的資源類

package com.lxh.ThreadLocal;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

// 資源類
public class ConnectionResource {
	// 屬性
	public static String userName = "root";
	public static String userPass = "admin123";
	public static String url = "jdbc:mysql://localhost:3306/user";
	public static String driverName = "com.mysql.jdbc.Driver";
	// 獲取數據庫連接
	public Connection getConnection(){
		Connection conn = null;
		try {
			Class.forName(driverName);
			conn = DriverManager.getConnection(url, userName, userPass);
		} catch (SQLException e) {
			System.out.println("獲取數據庫連接失敗..."+e.getMessage());
		} catch (ClassNotFoundException e) {
			System.out.println("獲取數據庫加載類失敗..."+e.getMessage());
			e.printStackTrace();
		}
		return conn;
	}
}

       ConnectionThread.java   ------------------------------------------模擬多個線程實現屢次獲取數據庫連接

package com.lxh.ThreadLocal;

import java.sql.Connection;

// 
public class ConnectionThread implements Runnable {
	// 
	public ThreadLocal<Connection> tl = new ThreadLocal<Connection>() {
		@Override
		protected Connection initialValue() {
			ConnectionResource cr = new ConnectionResource();
			return cr.getConnection();
		}
	};

	@Override
	public void run() {
		// 連接對象
		Connection conn = null;
		// 循環獲取線程的連接對象
		for (int i = 0; i < 5; i++) {
			conn = tl.get();
			System.out.println("***當前線程【" + Thread.currentThread().getName()
					+ "】獲取的連接資源:" + conn + "***");
		}
	}

}

       Test.java               ------------------------------------------測試類

package com.lxh.ThreadLocal;

/**
 * 使用ThreadLocal解決多線程問題
 */
public class Test {

	public static void main(String[] args) {

		ConnectionThread ct = new ConnectionThread();

		Thread t0 = new Thread(ct);
		Thread t1 = new Thread(ct);
		Thread t2 = new Thread(ct);
		Thread t3 = new Thread(ct);

		t0.start();
		t1.start();
		t2.start();
		t3.start();
	}
}

    3. 測試結果
    4. 測試結果分析        咱們經過"測試結果"能夠清晰地看到，同一個線程，不管請求多少次，其獲取到的數據庫連接都是同樣的，這符合咱們的預期----不讓同一個線程獲取多個數據庫連接以減小資源消耗。