如何使用 java 和 dwr 更新 ajax 网络聊天中的用户列表

Question

我正在使用 java 和 dwr ajax 反向开发网络聊天。我有两个关于如何在用户离线时删除用户的问题

1.当用户关闭浏览器

时服务器端代码java

import java.util.HashMap;
import java.util.Map;

import org.directwebremoting.Browser;
import org.directwebremoting.ScriptSessions;

public class Chat{
    private int id = 0;
    private final Map<String,String> users = new HashMap<String, String>();

    /**
     * @param idOrName when type=0 is id when type=1 is name
     * @param type type=0 remove a user type=1 add a user
     */
    public void addOrRemoveUser(String idOrName,int type){
        if(type == 0){  
            users.remove(idOrName);
        }
        if(type == 1){
            users.put(String.valueOf(id++),idOrName);
        }
        Browser.withCurrentPage(new Runnable() {
            public void run() {
                ScriptSessions.addFunctionCall("updateUserList", users);
            }
        });
    }
}

客户端代码javascript

function removeUser(){
     Chat.addOrRemoveUser(chat.userid,0);
}

当用户关闭浏览器时我将removeUser()与onunload事件绑定。在firefox和chrome上没问题，但在ie8上失败，服务器日志如下：

2010-8-10 22:34:58 org.directwebremoting.dwrp.BaseCallHandler marshallException
警告: Exception while processing batch
org.directwebremoting.extend.ServerException: Failed to read input
    at org.directwebremoting.dwrp.Batch.parseBasicPost(Batch.java:224)
    at org.directwebremoting.dwrp.Batch.parsePost(Batch.java:116)
    at org.directwebremoting.dwrp.Batch.<init>(Batch.java:56)
    at org.directwebremoting.dwrp.CallBatch.<init>(CallBatch.java:46)
    at org.directwebremoting.dwrp.BaseCallHandler.handle(BaseCallHandler.java:72)
    at org.directwebremoting.servlet.UrlProcessor.handle(UrlProcessor.java:120)
    at org.directwebremoting.servlet.DwrServlet.doPost(DwrServlet.java:141)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:243)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:201)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:163)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:108)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:556)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:402)
    at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:310)
    at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:575)
    at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1555)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
    at java.lang.Thread.run(Thread.java:619)
Caused by: java.io.IOException
    at org.apache.coyote.http11.InternalAprInputBuffer.fill(InternalAprInputBuffer.java:798)
    at org.apache.coyote.http11.InternalAprInputBuffer$SocketInputBuffer.doRead(InternalAprInputBuffer.java:827)
    at org.apache.coyote.http11.filters.IdentityInputFilter.doRead(IdentityInputFilter.java:116)
    at org.apache.coyote.http11.InternalAprInputBuffer.doRead(InternalAprInputBuffer.java:738)
    at org.apache.coyote.Request.doRead(Request.java:427)
    at org.apache.catalina.connector.InputBuffer.realReadBytes(InputBuffer.java:286)
    at org.apache.tomcat.util.buf.ByteChunk.substract(ByteChunk.java:407)
    at org.apache.catalina.connector.InputBuffer.read(InputBuffer.java:309)
    at org.apache.catalina.connector.CoyoteInputStream.read(CoyoteInputStream.java:198)
    at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:264)
    at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:306)
    at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:158)
    at java.io.InputStreamReader.read(InputStreamReader.java:167)
    at java.io.BufferedReader.fill(BufferedReader.java:136)
    at java.io.BufferedReader.readLine(BufferedReader.java:299)
    at java.io.BufferedReader.readLine(BufferedReader.java:362)
    at org.directwebremoting.dwrp.Batch.parseBasicPost(Batch.java:181)
    ... 23 more

2.有什么方法可以删除服务器无法向其推送消息的用户吗？

Answer 1

我认为这里发生的情况是，您正在启动 POST（执行远程方法），但由于它是 onunload，因此浏览器窗口在完成之前就消失了。

我建议尝试 onbeforeunload 而不是 onunload。

关于#2，请查看 DefaultScriptSessionManager。它具有获取所有活动会话的方法，以及更改超时以检查死会话的方法。