java 检测一个URL地址是否有效

package com.hety.util;

import java.io.IOException;

import java.net.HttpURLConnection;

import java.net.MalformedURLException;

import java.net.URL;

/**

*

*检测一个URL地址是否有效

* @author hety

* @version 1.0 2015-7-1 上午11:03:08

*/

public class URLAvailability {

private static URL url=null;

private static HttpURLConnection connection;

private static String succ="";

private static int statusCode = -1;

private static int testCounts = 5;//尝试链接次数

/**

* 功能描述 : 检测当前URL是否可连接或是否有效,

* 最多连接网络 5 次, 如果 5 次都不成功说明该地址不存在或视为无效地址.

*

* @param urlStr

* 指定URL网络地址

*

* @return String

*/

private synchronized String isConnectable(String urlStr) {

int counts = 0;

if (urlStr == null || urlStr.length() <= 0) {

return succ;

}

while (counts < testCounts) {

try {//非格式,io错误的链接

url = new URL(urlStr);

connection = (HttpURLConnection) url.openConnection();

statusCode = connection.getResponseCode();

if (statusCode == 200) {

succ = connection.getURL().toString();

break;

}

counts++;

System.out.println("连接次数："+counts);

} catch (Exception ex) {//格式,io错误的链接

counts++;

System.out.println("连接次数："+counts);

}

}

return succ;

}

/**

* 功能：检测当前URL是否可连接或是否有效,

* 描述：最多连接网络 5 次, 如果 5 次都不成功，视为该地址不可用

* @param urlStr 指定URL网络地址

* @return URL

*/

public synchronized URL isConnect(String urlStr) {

int counts = 1;

if (urlStr == null || urlStr.length() <= 0) {

return null;

}

while (counts <= testCounts) {

try {

url = new URL(urlStr);

connection = (HttpURLConnection) url.openConnection();

statusCode = connection.getResponseCode();

System.out.println("第"+(counts) +"/"+testCounts+"次链接， statusCode:"+statusCode);

counts++;

//非格式错误链接

if (statusCode == 200) {//可连接

System.out.println("URL可用！");

break;

}else{//不可连接

url = null;

}

} catch (MalformedURLException e) {//格式错误

System.out.println("URL不可用，尝试连接第"+(counts) +"/"+testCounts+"次");

url = null;

counts++;

continue;

} catch (IOException e) {//io错误

System.out.println("URL不可用，尝试连接第"+(counts) +"/"+testCounts+"次");

url = null;

counts++;

}

}

return url;

}

/**

* 功能：检测当前URL是否可连接或是否有效,

* 描述：最多连接网络 5 次, 如果 5 次都不成功，视为该地址不可用

* @param urlStr 指定URL网络地址

* @return URL

*/

public synchronized boolean isConnected(String urlStr) {

int counts = 1;

boolean connected = false;

if (urlStr == null || urlStr.length() <= 0) {

return false;

}

while (counts <= testCounts) {

try {

url = new URL(urlStr);

connection = (HttpURLConnection) url.openConnection();

statusCode = connection.getResponseCode();

System.out.println("第"+(counts) +"/"+testCounts+"次链接， statusCode:"+statusCode);

counts++;

//非格式错误链接

if (statusCode == 200) {//可连接

System.out.println("URL可用！");

connected= true;

break;

}else{//不可连接

connected= false;

}

} catch (Exception e) {//io,malformed error

System.out.println("URL不可用，尝试连接第"+(counts) +"/"+testCounts+"次");

connected =false;

counts++;

}

}

return connected;

}

/**

* @param args

*/

public static void main(String[] args) {

String url1="httpp://www.jb51.net/logo.gif";

URLAvailability ua = new URLAvailability();

// URL url = ua.isConnect(url1);

// System.out.println(url==null?"无效":"有效");

System.out.println("+++++++++++++++");

//String urlStr = ua.isConnectable(url1);

// System.out.println("urlStr:"+urlStr);

System.out.println("+++++++++++++++");

boolean flag = ua.isConnected(url1);

System.out.println("flag:"+flag);

}

}