Httpclient 4，錯誤302.如何重定向？

Question

我想要訪問首先需要（tomcat服務器）身份驗證的一個站點，然後使用POST請求登錄並讓該用戶查看該站點的頁面。我使用的HttpClient 4.0.1

第一認證工作正常，但並不總是抱怨這個錯誤的登錄：「302臨時移動」

我把餅乾&我保持一個方面，但一無所獲。實際上，登錄似乎有效，因爲如果我寫入不正確的參數或用戶||密碼，我會看到登錄頁面。所以我猜想什麼是不工作的自動重定向。

繼我的代碼，它總是拋出IOException異常，302：

DefaultHttpClient httpclient = new DefaultHttpClient(); 
    CookieStore cookieStore = new BasicCookieStore(); 
    httpclient.getParams().setParameter(
     ClientPNames.COOKIE_POLICY, CookiePolicy.BROWSER_COMPATIBILITY); 
    HttpContext context = new BasicHttpContext(); 
    context.setAttribute(ClientContext.COOKIE_STORE, cookieStore); 
    //ResponseHandler<String> responseHandler = new BasicResponseHandler(); 

    Credentials testsystemCreds = new UsernamePasswordCredentials(TESTSYSTEM_USER, TESTSYSTEM_PASS); 
    httpclient.getCredentialsProvider().setCredentials(
      new AuthScope(AuthScope.ANY_HOST, AuthScope.ANY_PORT), 
      testsystemCreds); 

    HttpPost postRequest = new HttpPost(cms + "/login"); 
    List<NameValuePair> formparams = new ArrayList<NameValuePair>(); 
    formparams.add(new BasicNameValuePair("pUserId", user)); 
    formparams.add(new BasicNameValuePair("pPassword", pass)); 
    postRequest.setEntity(new UrlEncodedFormEntity(formparams, "UTF-8")); 
    HttpResponse response = httpclient.execute(postRequest, context); 
    System.out.println(response); 

    if (response.getStatusLine().getStatusCode() != HttpStatus.SC_OK) 
     throw new IOException(response.getStatusLine().toString()); 

    HttpUriRequest currentReq = (HttpUriRequest) context.getAttribute( 
      ExecutionContext.HTTP_REQUEST); 
    HttpHost currentHost = (HttpHost) context.getAttribute( 
      ExecutionContext.HTTP_TARGET_HOST); 
    String currentUrl = currentHost.toURI() + currentReq.getURI();   
    System.out.println(currentUrl); 

    HttpEntity entity = response.getEntity(); 
    if (entity != null) { 
     long len = entity.getContentLength(); 
     if (len != -1 && len < 2048) { 
      System.out.println(EntityUtils.toString(entity)); 
     } else { 
      // Stream content out 
     } 
    } 

Answer 1

對於4.1版本：

DefaultHttpClient httpclient = new DefaultHttpClient(); 
    httpclient.setRedirectStrategy(new DefaultRedirectStrategy() {     
     public boolean isRedirected(HttpRequest request, HttpResponse response, HttpContext context) { 
      boolean isRedirect=false; 
      try { 
       isRedirect = super.isRedirected(request, response, context); 
      } catch (ProtocolException e) { 
       // TODO Auto-generated catch block 
       e.printStackTrace(); 
      } 
      if (!isRedirect) { 
       int responseCode = response.getStatusLine().getStatusCode(); 
       if (responseCode == 301 || responseCode == 302) { 
        return true; 
       } 
      } 
      return isRedirect; 
     } 
    }); 

Answer 2

httpclient.setRedirectHandler(new DefaultRedirectHandler()); 

見的HttpClient Javadoc

Answer 3

你要實現自定義的重定向處理程序，將指示POST這種反應是重定向。這可以通過覆蓋isRedirectRequested（）方法來完成，如下所示。

DefaultHttpClient client = new DefaultHttpClient(); 
client.setRedirectHandler(new DefaultRedirectHandler() {     
    @Override 
    public boolean isRedirectRequested(HttpResponse response, HttpContext context) { 
     boolean isRedirect = super.isRedirectRequested(response, context); 
     if (!isRedirect) { 
      int responseCode = response.getStatusLine().getStatusCode(); 
      if (responseCode == 301 || responseCode == 302) { 
       return true; 
      } 
     } 
     return isRedirect; 
    } 
}); 

在以後的HttpClient的版本，類名是DefaultRedirectStrategy，但類似的解決方案可以在那裏使用。

Answer 4

重定向不會自動的HttpClient 4.1其他方法比GET和PUT處理。

Answer 5

在HttpClient的更高版本（4.1以上版本），你可以這樣做：

DefaultHttpClient client = new DefaultHttpClient() 
client.setRedirectStrategy(new LaxRedirectStrategy()) 

LaxRedirectStrategy將自動重定向HEAD，GET，和POST請求。對於更嚴格的實現，請使用DefaultRedirectStrategy。

Answer 6

Extend the DefaultRedirectStrategy class and override the methods. 
@Override 
    protected URI createLocationURI(String arg0) throws ProtocolException { 
     // TODO Auto-generated method stub 
     return super.createLocationURI(arg0); 
    } 

    @Override 
    protected boolean isRedirectable(String arg0) { 
     // TODO Auto-generated method stub 
     return true; 
    } 

    @Override 
    public URI getLocationURI(HttpRequest arg0, HttpResponse arg1, 
      HttpContext arg2) throws ProtocolException { 
     // TODO Auto-generated method stub 
     return super.getLocationURI(arg0, arg1, arg2); 
    } 

    @Override 
    public HttpUriRequest getRedirect(HttpRequest request, 
      HttpResponse response, HttpContext context) 
      throws ProtocolException { 
      URI uri = getLocationURI(request, response, context); 
      String method = request.getRequestLine().getMethod(); 
      if (method.equalsIgnoreCase(HttpHead.METHOD_NAME)) { 
       return new HttpHead(uri); 
      } else { 
       return new HttpPost(uri); 
      } 

    } 

    @Override 
    public boolean isRedirected(HttpRequest request, HttpResponse response, 
      HttpContext context) throws ProtocolException { 
     // TODO Auto-generated method stub 
     return super.isRedirected(request, response, context); 
    } 

in this case isRedirectable method will always return true and getRedirect method will return post request in place of get request. 

Answer 7

對於HttpClient的版本4.3.x：

HttpClient httpClient = HttpClientBuilder.create().setRedirectStrategy(new LaxRedirectStrategy()).build();