HttpClients 如何自动处理重定向


首先说说HttpClient和浏览器的区别

       我们从浏览器发起一笔请求，浏览器则会帮你处理重定向、缓存等事情。这也就是为什么用浏览器表单post提交后，不管服务端如何重定向，都能正常接收到服务端返回的数据。

       但是用HttpClient呢，你会发现，请求后，会返回302，因为POST方式提交HttpClient是不会帮你处理重定向的。这时候怎么办呢？

       方法一：（自己手动处理）

        HttpClient httpClient = HttpClients.createDefault();

        HttpPost httpPost= new HttpPost(http://ip:port/xxx);

        CloseableHttpResponse response = httpclient.execute(httpPost);

        int statusCode = response.getStatusLine().getStatusCode();

        System.out.println("statusCode=="+statusCode); //返回码

        Header header=response.getFirstHeader("Location");

        //重定向地址

        String location =  header.getValue();

        System.out.println(location);

        //然后再对新的location发起请求即可

        HttpGet httpGet = new HttpGet(location);

        CloseableHttpResponse response2 = httpclient.execute(httpGet);

        System.out.println("返回报文"+EntityUtils.toString(response2.getEntity(), "UT-F-8"));

       方法二：（已有工具类）

       HttpClientBuilder builder = HttpClients.custom()

            .disableAutomaticRetries() //关闭自动处理重定向

            .setRedirectStrategy(new LaxRedirectStrategy());//利用LaxRedirectStrategy处理POST重定向问题

       CloseableHttpClient client = builder.build();

        HttpPost httpPost= new HttpPost(http://ip:port/xxx);

        CloseableHttpResponse response = client.execute(httpPost);

        int statusCode = response.getStatusLine().getStatusCode();

        System.out.println("statusCode=="+statusCode); //返回码

         System.out.println("返回报文"+EntityUtils.toString(response.getEntity(), "UT-F-8"));