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;
    }