我在Netbeans中创建的Java Servlet是否添加了一些奇怪的东西？

时间：2010-10-25 12:05:28

标签： java exception servlets netbeans applet

这是我第二次尝试解决这个问题。我的第一次尝试是here，但也许我对我的问题的解释是不够的，我的问题是applet收到了例外：

java.io.StreamCorruptedException: invalid stream header: 0A0A0A3C at 
java.io.ObjectInputStream.readStreamHeader(ObjectInputStream.java:783) at  
java.io.ObjectInputStream.<init>(ObjectInputStream.java:280)

抱歉，如果我听起来像是破纪录的话:)：

我正在尝试在同一台机器上的Applet和Servlet之间进行通信，我通过创建一个新项目 - Java Web - Web应用程序并选择Glassfish Server 3作为服务器，在Netbeans中创建了servlet。它确实创建了一个index.jsp，但我并不需要一个网页界面。

我从NetBeans运行servlet（按f6），它在我的浏览器中部署并打开servlet的index.jsp。然后我运行applet（来自Netbeans中的另一个项目）并尝试连接。我仍然收到好的“无效的流标题”，所以我猜测错误在于我在Netbeans中所做的事情。

我粘贴了一些我认为正在运行的代码（旧代码但未找到更新的完整示例）代码被公然从Link

中窃取

所以最后，我想做的是当applet请求发送数组时，从servlet向applet发送一个二维Object数组。代码示例只是为了显示我收到的无效流标题。

我认为/猜测applet正在接收来自服务器的基于文本的响应，但我希望响应是序列化对象（在代码示例中只是一个字符串），稍后它将是一个Object [] []，如果我得到了一个线索。

感谢您的耐心，大师。 ：）

Applet代码（随意忽略带有所有布局代码的init（））：

package se.iot.recallapplet;

import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;

public class RecallApplet extends Applet {
private TextField inputField = new TextField();
private TextField outputField = new TextField();
private TextArea exceptionArea = new TextArea();

public void init() {
    // set new layout
    setLayout(new GridBagLayout());

    // add title
    Label title = new Label("Echo Applet", Label.CENTER);
    title.setFont(new Font("SansSerif", Font.BOLD, 14));
    GridBagConstraints c = new GridBagConstraints();
    c.gridwidth = GridBagConstraints.REMAINDER;
    c.weightx = 1.0;
    c.fill = GridBagConstraints.HORIZONTAL;
    c.insets = new Insets(5, 5, 5, 5);
    add(title, c);

    // add input label, field and send button
    c = new GridBagConstraints();
    c.anchor = GridBagConstraints.EAST;
    add(new Label("Input:", Label.RIGHT), c);
    c = new GridBagConstraints();
    c.fill = GridBagConstraints.HORIZONTAL;
    c.weightx = 1.0;
    add(inputField, c);
    Button sendButton = new Button("Send");
    c = new GridBagConstraints();
    c.gridwidth = GridBagConstraints.REMAINDER;
    add(sendButton, c);
    sendButton.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            onSendData();
        }
    });

    // add output label and non-editable field
    c = new GridBagConstraints();
    c.anchor = GridBagConstraints.EAST;
    add(new Label("Output:", Label.RIGHT), c);
    c = new GridBagConstraints();
    c.gridwidth = GridBagConstraints.REMAINDER;
    c.fill = GridBagConstraints.HORIZONTAL;
    c.weightx = 1.0;
    add(outputField, c);
    outputField.setEditable(false);

    // add exception label and non-editable textarea
    c = new GridBagConstraints();
    c.anchor = GridBagConstraints.EAST;
    add(new Label("Exception:", Label.RIGHT), c);
    c = new GridBagConstraints();
    c.gridwidth = GridBagConstraints.REMAINDER;
    c.weighty = 1;
    c.fill = GridBagConstraints.BOTH;
    add(exceptionArea, c);
    exceptionArea.setEditable(false);
}

/**
 * Get a connection to the servlet.
 */
private URLConnection getServletConnection()
    throws MalformedURLException, IOException {

    // Connection zum Servlet ˆffnen
            URL urlServlet = new URL("http://localhost:8080/Event_Servlet/");
    URLConnection con = urlServlet.openConnection();

    // konfigurieren
    con.setDoInput(true);
    con.setDoOutput(true);
    con.setUseCaches(false);
    con.setRequestProperty(
        "Content-Type",
        "application/x-java-serialized-object");

    return con;
}

/**
 * Send the inputField data to the servlet and show the result in the outputField.
 */
private void onSendData() {
    try {
        // get input data for sending
        String input = inputField.getText();

        // send data to the servlet
        URLConnection con = getServletConnection();
        OutputStream outstream = con.getOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(outstream);
        oos.writeObject(input);
        oos.flush();
        oos.close();

        // receive result from servlet
        InputStream instr = con.getInputStream();
        ObjectInputStream inputFromServlet = new ObjectInputStream(instr);
        String result = (String) inputFromServlet.readObject();
        inputFromServlet.close();
        instr.close();

        // show result
        outputField.setText(result);

    } catch (Exception ex) {
        ex.printStackTrace();
        exceptionArea.setText(ex.toString());
    }
}
}

Servlet代码：

package se.iot.eventservlet;

import java.io.*;

import javax.servlet.ServletException;
import javax.servlet.http.*;

public class Event_Servlet extends HttpServlet {

public void doPost(
    HttpServletRequest request,
    HttpServletResponse response)
    throws ServletException, IOException {
    try {
        response.setContentType("application/x-java-serialized-object");

        // read a String-object from applet
        // instead of a String-object, you can transmit any object, which
        // is known to the servlet and to the applet
        InputStream in = request.getInputStream();
        ObjectInputStream inputFromApplet = new ObjectInputStream(in);
        String echo = (String) inputFromApplet.readObject();

        // echo it to the applet
        OutputStream outstr = response.getOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(outstr);
        oos.writeObject(echo);
        oos.flush();
        oos.close();

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

堆栈跟踪：

java.io.StreamCorruptedException: invalid stream header: 0A0A0A3C
    at java.io.ObjectInputStream.readStreamHeader(ObjectInputStream.java:783)
    at java.io.ObjectInputStream.<init>(ObjectInputStream.java:280)
    at se.iot.recallapplet.RecallApplet.onSendData(RecallApplet.java:114)
    at se.iot.recallapplet.RecallApplet.access$000(RecallApplet.java:12)
    at se.iot.recallapplet.RecallApplet$1.actionPerformed(RecallApplet.java:48)
    at java.awt.Button.processActionEvent(Button.java:392)
    at java.awt.Button.processEvent(Button.java:360)
    at java.awt.Component.dispatchEventImpl(Component.java:4714)
    at java.awt.Component.dispatchEvent(Component.java:4544)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:635)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

1 个答案:

答案 0 :(得分：1)

问题是applet无法连接到servlet，因此可以忽略servlet中的代码。

我需要使用以下命令配置server.xml：

<Context path="/servletName" docBase="servletName" debug="0" reloadable="true"
   crossContext="true">
   </Context>
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