Java 获取网络重定向URL(302重定向)

方法1：

 import java.net.HttpURLConnection;
 import java.net.URL;

 import org.junit.Assert;
 import org.junit.Test;

 public class GetRedirectUrlTest {
     @Test
     public void test_getRedirectUrl() throws Exception {
         String url="http://www.baidu.com/link?url=ByBJLpHsj5nXx6DESXbmMjIrU5W4Eh0yg5wCQpe3kCQMlJK_RJBmdEYGm0DDTCoTDGaz7rH80gxjvtvoqJuYxK";
         String expectUrl="http://www.zhihu.com/question/20583607/answer/16597802";
         String redictURL = getRedirectUrl(url);
         Assert.assertEquals(expectUrl, redictURL);
     }

     /**
      * 获取重定向地址
      * @param path
      * @return
      * @throws Exception
      */
     private String getRedirectUrl(String path) throws Exception {
         HttpURLConnection conn = (HttpURLConnection) new URL(path)
                 .openConnection();
         conn.setInstanceFollowRedirects(false);
         conn.setConnectTimeout(5000);
         return conn.getHeaderField("Location");
     }
 }

方法2：

 /**
      * 处理跳转链接，获取重定向地址
      * @param url   源地址
      * @return      目标网页的绝对地址
      */
     public String getAbsUrl(String url){
         CloseableHttpClient httpclient = HttpClients.createDefault();
         HttpClientContext context = HttpClientContext.create();
         HttpGet httpget = new HttpGet(url);
         CloseableHttpResponse response = null;
         String absUrl = null;
         try {
             response = httpclient.execute(httpget, context);
             HttpHost target = context.getTargetHost();
             List<URI> redirectLocations = context.getRedirectLocations();
             URI location = URIUtils.resolve(httpget.getURI(), target, redirectLocations);
             System.out.println("Final HTTP location: " + location.toASCIIString());
             absUrl = location.toASCIIString();
         }catch(IOException e){
             e.printStackTrace();
         }catch (URISyntaxException e) {
             e.printStackTrace();
         }finally {
             try {
                 httpclient.close();
                 response.close();
             } catch (IOException e) {
                 e.printStackTrace();
             }
         }
         return absUrl;
     }