Question

我正在从Java内部进行POST调用，我不确定为什么它不会通过。代码如下：

String screencastStartURL = "......";                            
List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(1);   
nameValuePairs.add(new BasicNameValuePair("stateID", s_id));
nameValuePairs.add(new BasicNameValuePair("startTime", screencastStartTime));   
nameValuePairs.add(new BasicNameValuePair("identifier", screencastId));
System.out.println("about to make postCall"); 
String postResponse = Commons.postCall(screencastStartURL, nameValuePairs);
out.println(postResponse); // out is an earlier instantiated PrintWriter

postCall方法如下：

public static String postCall(String url, List<NameValuePair> nameValuePairs)   {
        System.out.println("Within postCall method");
        String ans = "";
        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httppost = new HttpPost(url);

        try {
          System.out.println("Within postCall method 2");
          httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
          HttpResponse response = httpclient.execute(httppost);

          ans = (EntityUtils.toString(response.getEntity()));

        } catch (IOException e) {
          e.printStackTrace();
        }

        return ans;
    }

当我在Tomcat服务器上部署此代码时，它会在终端中打印about to make postCall，这意味着它会在POST调用之前成功执行。但是，它不打印Within postCall method这意味着调用本身出了问题？

我看到的错误消息是NullPointerException，会导致ServletException

修改

但是，当我使用POSTMAN Rest Client Chrome应用程序进行POST调用时，它会成功完成。

第二次修改

我在浏览器中看到的堆栈跟踪是

exception

javax.servlet.ServletException: Servlet execution threw an exception
root cause

java.lang.ExceptionInInitializerError
    com.bl.apps.MemoLocalRecorder.App.doGet(App.java:121)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
root cause

java.lang.NullPointerException
    java.io.Reader.<init>(Reader.java:78)
    java.io.InputStreamReader.<init>(InputStreamReader.java:72)
    com.bl.util.Commons.setURL(Commons.java:221)
    com.bl.util.Commons.<clinit>(Commons.java:150)
    com.bl.apps.MemoLocalRecorder.App.doGet(App.java:121)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

Answer 1

根据您发布的堆栈跟踪。错误基本上是因为静态块中的静态变量初始化

中的任何异常

下面是一些信息和一些链接，以便更多地了解这个

在看到异常的名称时，您可能会猜到这一点异常与变量的初始化有关。当然是这个错误与静态变量的初始化有关变量可以是基本类型或用户定义类型。您可能都是已经了解了类的静态初始化器。

http://examples.javacodegeeks.com/java-basics/exceptions/java-lang-exceptionininitializererror-how-to-handle-exception-initializer-error/

http://craftingjava.blogspot.in/2012/06/javalangexceptionininitializererror.html

POST调用失败

1 个答案: