从Java应用程序调用Servlet [英] Calling a Servlet from a Java application

问题描述

我想从Java应用程序调用Servlet。问题是，调用似乎没有到达Servlet。我没有收到任何错误，但是没有到达Servlet中的第一个输出doPost。如果我在网络浏览器中打开URL，我当然得到了GET不支持的错误等，但至少我看到，有些事情发生了。

I want to call a Servlet from a Java application. The problem is, that the call seems not to reach the Servlet. I do not get any error, but do not reach the first output "doPost" in the Servlet. If I open the URL in a web browser, I got - of course - the error that GET is not supported etc., but at least I see, that something happens.

我使用以下代码（ActionPackage类只包含参数Vector并且可以序列化）：

I use the following code (the ActionPackage class only holds a Vector of parameters and is Serializable):

Java应用程序：

    ActionPackage p = new ActionPackage();
    p.addParameter("TEST", "VALUE");

    System.out.println(p);

    URL gwtServlet = null;
    try {
        gwtServlet = new URL("http://localhost:8888/app/PushServlet");
        HttpURLConnection servletConnection = (HttpURLConnection) gwtServlet.openConnection();
        servletConnection.setRequestMethod("POST");
        servletConnection.setDoOutput(true);

        ObjectOutputStream objOut = new ObjectOutputStream(servletConnection.getOutputStream());
        objOut.writeObject(p);
        objOut.flush();
        objOut.close();

    } catch (MalformedURLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

Servlet：

public class PushServlet extends HttpServlet {

public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    System.out.println("doPost");
    ObjectInputStream objIn = new ObjectInputStream(request.getInputStream());

    ActionPackage p = null;
    try {
        p = (ActionPackage) objIn.readObject();

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

    System.out.println("Servlet received p: "+p);       
}

}

出了什么问题？

谢谢。

推荐答案

URLConnection 只有在你调用任何 get 方法时才会延迟执行。

URLConnection is only lazily executed whenever you call any of the get methods.

将以下内容添加到您的代码中实际执行HTTP请求并获取servlet响应正文。

Add the following to your code to actually execute the HTTP request and obtain the servlet response body.

InputStream response = servletConnection.getInputStream();

参见：

• 如何使用 java.net.URLConnection 来触发和处理HTTP请求？



See also:

• How to use java.net.URLConnection to fire and handle HTTP requests?

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