從Java應用程序調用Servlet

Question

我想從Java應用程序調用Servlet。 問題是，調用似乎沒有到達Servlet。 我沒有得到任何錯誤，但沒有到達Servlet中的第一個輸出“doPost”。 如果我在網絡瀏覽器中打開URL，我當然得到了GET不支持的錯誤等，但至少我看到，有些事情發生了。

我使用以下代碼（ActionPackage類只包含參數Vector並且是Serializable）：

Java應用程序：

    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的：

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);       
}

}

出了什么問題？

謝謝。

Answer 1

只要你調用任何get方法， URLConnection就會被懶惰地執行。

將以下內容添加到代碼中以實際執行HTTP請求並獲取servlet響應主體。

InputStream response = servletConnection.getInputStream();

也可以看看：

• 如何使用java.net.URLConnection來觸發和處理HTTP請求？

Answer 2

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);
    }
}

Answer 3

嘗試在try / catch塊中包裝doPost的整個主體：

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輸出日志文件或窗口以獲取可能有用的新異常。