从 Java 应用程序调用 Servlet

Question

我想从 Java 应用程序调用 Servlet。问题是，该调用似乎没有到达 Servlet。我没有收到任何错误，但没有到达 Servlet 中的第一个输出“doPost”。如果我在网络浏览器中打开 URL，我当然会得到不支持 GET 等错误，但至少我看到，发生了一些事情。

我使用以下代码（ActionPackage 类仅包含参数向量并且是可序列化的）：

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);       
}

}

有什么想法出了什么问题吗？

谢谢。

Answer 1

仅当您调用任何 get 方法时，URLConnection 才会延迟执行。

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

InputStream response = servletConnection.getInputStream();

另请参阅：

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

Answer 2

尝试将 doPost 的整个主体包装在 try/catch 块中：

public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    try {
        System.out.println("doPost");
        ObjectInputStream objIn = new ObjectInputStream(request.getInputStream());
        ActionPackage p = null;
        p = (ActionPackage) objIn.readObject();
        System.out.println("Servlet received p: "+p);       
    } catch (Throwable e) {
        e.printStackTrace(System.out);
    }
}

然后再次查看 Servlet 输出日志文件或窗口以查找可能有帮助的新异常。

Answer 3

public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    try {
        System.out.println("doPost");
        ObjectInputStream objIn = new ObjectInputStream(request.getInputStream());
        ActionPackage p = null;
        p = (ActionPackage) objIn.readObject();
        System.out.println("Servlet rece p: "+p);       
    } catch (Throwable e) {
        e.printStackTrace(System.out);
    }
}