服务器端Java错误
我制作了一个程序,从手机(JavaME)向服务器发送消息“test”。但是我在尝试调用服务器端的服务器端Java错误,java,mobile,Java,Mobile,我制作了一个程序,从手机(JavaME)向服务器发送消息“test”。但是我在尝试调用服务器端的closeCrap()方法时出错 错误日志: 线程“main”java.lang.NullPointerException中出现异常 在server.closeCrap(server.java:106) 在server.startRunning(server.java:55) 在pagr.main(pagr.java:7) server.java import java.io.*; import ja
closeCrap()
方法时出错
错误日志:
线程“main”java.lang.NullPointerException中出现异常在server.closeCrap(server.java:106)
在server.startRunning(server.java:55)
在pagr.main(pagr.java:7)
server.java
import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class server extends JFrame{
private static final long serialVersionUID = 1L;
private JTextField userText;
private JTextArea chatWindow;
private ObjectOutputStream output;
private ObjectInputStream input;
private ServerSocket server;
private Socket connection;
// constructor
public server(){
super("CP Chat");
userText = new JTextField();
userText.setEditable(false);
userText.addActionListener(
new ActionListener(){
public void actionPerformed(ActionEvent event){
sendMessage(event.getActionCommand());
// nusius teksta ivesta
userText.setText("");
}
}
);
add(userText,BorderLayout.NORTH);
chatWindow = new JTextArea();
chatWindow.setEditable(false);
add(new JScrollPane(chatWindow));
setSize(300,150);
setVisible(true);
}
// set up and run a server
public void startRunning(){
try{
// 1 arg - jungiasi prie port (gali buti betkoks)
//2 - backLog (kiek zmoniu gali prisijungti prie port)
server = new ServerSocket(6789,100);
while(true){
try{
waitForConnection();
setupStreams();
whileChatting();
}catch(EOFException exc){ // end of stream
showMessage("\n Server ended the connection!");
}finally{
closeCrap();
}
}
}catch(IOException ex){
ex.printStackTrace();
}
}
// wait for connection, then display connection info
private void waitForConnection() throws IOException{
showMessage("Waiting for someone to connect... \n");
connection = server.accept();
showMessage("Now connected to " + connection.getInetAddress().getHostName());
}
// get stream to send and receive data
private void setupStreams() throws IOException{
//creating path way to connect to another computer.
output = new ObjectOutputStream(connection.getOutputStream());
// flushes any left overs to the other pc while sending messages
output.flush();
input = new ObjectInputStream(connection.getInputStream());
showMessage("\n Streams are now setup!\n");
}
//during the chat conversation
private void whileChatting() throws IOException{
String message = "You are now connected!";
sendMessage(message);
ableToType(true);
do{
try{
// gauna atsiunciama zinute
message = (String) input.readObject();
showMessage("\n" + message);
}catch(ClassNotFoundException notFound){
showMessage("\n idk wtf that user send!");
}
}while(!message.equals("CLIENT - END"));
}
//close Streams and Sockets after youre done chatting
private void closeCrap(){
showMessage("\n Closing connection... \n");
ableToType(false);
try{
output.close();
input.close();
connection.close();
}catch(IOException except){
except.printStackTrace();
}
}
private void sendMessage(String message){
try{
// sends a message to client
output.writeObject("SERVER - " + message);
// if something is left - flush those bytes to the client.
output.flush();
showMessage("\n SERVER - " + message);
}catch(IOException e){
chatWindow.append("\n ERROR: dude i cant send that message");
}
}
// updates chat window
private void showMessage(final String text){
// creates a thread that will update a part of GUI
SwingUtilities.invokeLater(
new Runnable(){
public void run(){
//add message to the end of the document
//and it updates the chat window
chatWindow.append(text);
}
}
);
}
// let the user type something in the text field
// final type - cant be modified
private void ableToType(final boolean tof){
SwingUtilities.invokeLater(
new Runnable(){
public void run(){
userText.setEditable(tof);
}
}
);
}
}
play.java(在手机上)
编辑:我已更改了用户Endox告诉我的内容,但出现了一个错误:
java.net.SocketException: Connection reset by peer: socket write error
at java.net.SocketOutputStream.socketWrite0(Native Method)
at java.net.SocketOutputStream.socketWrite(Unknown Source)
at java.net.SocketOutputStream.write(Unknown Source)
at java.io.ObjectOutputStream$BlockDataOutputStream.drain(Unknown Source)
at java.io.ObjectOutputStream$BlockDataOutputStream.setBlockDataMode(Unknown Source)
at java.io.ObjectOutputStream.<init>(Unknown Source)
at server.setupStreams(server.java:75)
at server.startRunning(server.java:50)
at pagr.main(pagr.java:7)
Exception in thread "main" java.lang.NullPointerException
at server.closeCrap(server.java:107)
at server.startRunning(server.java:56)
at pagr.main(pagr.java:7)
java.net.SocketException:peer重置连接:套接字写入错误
位于java.net.SocketOutputStream.socketWrite0(本机方法)
位于java.net.SocketOutputStream.socketWrite(未知源)
位于java.net.SocketOutputStream.write(未知源)
位于java.io.ObjectOutputStream$BlockDataOutputStream.drain(未知源)
位于java.io.ObjectOutputStream$BlockDataOutputStream.setBlockDataMode(未知源)
位于java.io.ObjectOutputStream。(未知源)
在server.setupStreams上(server.java:75)
startRunning(server.java:50)
在pagr.main(pagr.java:7)
线程“main”java.lang.NullPointerException中出现异常
在server.closeCrap(server.java:107)
startRunning(server.java:56)
在pagr.main(pagr.java:7)
EDIT2我在close crap方法中添加了if语句:在关闭输出之前,它会检查该对象是否为NOTNULL。新错误:
java.net.SocketException: Software caused connection abort: recv failed
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(Unknown Source)
at java.net.SocketInputStream.read(Unknown Source)
at java.io.ObjectInputStream$PeekInputStream.read(Unknown Source)
at java.io.ObjectInputStream$PeekInputStream.readFully(Unknown Source)
at java.io.ObjectInputStream$BlockDataInputStream.readShort(Unknown Source)
at java.io.ObjectInputStream.readStreamHeader(Unknown Source)
at java.io.ObjectInputStream.<init>(Unknown Source)
at server.setupStreams(server.java:77)
at server.startRunning(server.java:50)
at pagr.main(pagr.java:7)
java.net.SocketException:软件导致的连接中止:recv失败
位于java.net.SocketInputStream.socketRead0(本机方法)
位于java.net.SocketInputStream.read(未知源)
位于java.net.SocketInputStream.read(未知源)
位于java.io.ObjectInputStream$PeekInputStream.read(未知源)
在java.io.ObjectInputStream$PeekInputStream.readFully处(未知源)
位于java.io.ObjectInputStream$BlockDataInputStream.readShort(未知源)
位于java.io.ObjectInputStream.readStreamHeader(未知源)
位于java.io.ObjectInputStream。(未知源)
在server.setupStreams上(server.java:77)
startRunning(server.java:50)
在pagr.main(pagr.java:7)
在此循环中:
while(true){
try{
waitForConnection();
setupStreams();
whileChatting();
}catch(EOFException exc){ // end of stream
showMessage("\n Server ended the connection!");
}finally{
closeCrap();
}
}
如果waitForConnection()
抛出EOFException
您将直接进入最终
块(显示消息后)setupStreams()
没有要调用的更改,因此导致此行出现NullPointerException
(在closeCrap()
内):
问题可能是由
Server.java
中的setUpStreams
方法引起的。线路
output = new ObjectOutputStream(connection.getOutputStream());
根据java规范ObjectOutputStream
可能引发异常
public ObjectOutputStream(OutputStream out)
throws IOException
这可能导致您的
输出为空。EDIT3:
output = new ObjectOutputStream(connection.getOutputStream());
从跟踪中可以看出,该行抛出了一个套接字异常
,但我不知道为什么。所以你应该对这部分做些什么。NullPointerException
是由SocketException
引起的
EDIT2:在server.java中更改此部分:
try{
waitForConnection();
setupStreams();
whileChatting();
}catch(EOFException exc){ // end of stream
showMessage("\n Server ended the connection!");
}finally{
closeCrap();
}
致:
然后将stacktrace粘贴到这里,也许我们可以进行更好的调试。:)
编辑:这与play.java
有关,但仍然是一个问题
引发了NullPointer异常
,因为您在这些方法中定义了两个局部变量(连接、输出):
private void connection() throws IOException{
StreamConnection connection = (StreamConnection)Connector.open("socket://127.0.0.1:6789");
in = connection.openInputStream();
}
private void setupStreams() throws IOException{
PrintStream output = new PrintStream(connection.openOutputStream());
output.println("Test");
output.flush();
}
在closeCrapi()
方法中,您使用了两个仍然为空引用的类成员:
public class play extends GameCanvas {
StreamConnection connection;
PrintStream output;
InputStream in;
...
private void closeCrapi(){
try{
output.close();
in.close();
connection.close();
}catch(IOException ex){}
}
因此,无论在connection()
和setupStreams()
方法中发生了什么,在closeCrapi()
方法中,您尝试调用两个null
引用(连接、输出)上的方法.server.java中的第106行是什么?似乎在初始化时应该调用setupStreams
当我运行它抛出的服务器时:连接到本地主机,然后立即在closeCrap()方法中“关闭连接”。我在主要问题上发布了它。我像你说的那样改变了输出和连接
try{
waitForConnection();
setupStreams();
whileChatting();
}catch(IOException exc){ // end of stream
exc.printStackTrace();
showMessage("\n Server ended the connection!");
}finally{
closeCrap();
}
private void connection() throws IOException{
StreamConnection connection = (StreamConnection)Connector.open("socket://127.0.0.1:6789");
in = connection.openInputStream();
}
private void setupStreams() throws IOException{
PrintStream output = new PrintStream(connection.openOutputStream());
output.println("Test");
output.flush();
}
public class play extends GameCanvas {
StreamConnection connection;
PrintStream output;
InputStream in;
...
private void closeCrapi(){
try{
output.close();
in.close();
connection.close();
}catch(IOException ex){}
}