nullpointerexception

-3

我的问题是一个简单的nullpointerexception，但是，我不明白我怎么弄出来的。这里是代码。nullpointerexception

我想运行primefaces的聊天工具。我正在使用tomcat 7 ..只要我能到达这里，但现在我得到了这个问题。

public class ChatView { 

private final PushContext pushContext = PushContextFactory.getDefault().getPushContext(); 

private ChatUsers users; 

    private String privateMessage; 

private String globalMessage; 

    private String username; 

    private boolean loggedIn; 

private String privateUser; 

private final static String CHANNEL = "/chat/"; 

public void setUsers(ChatUsers users) { 
    this.users = users; 
} 

public String getPrivateUser() { 
    return privateUser; 
} 

public void setPrivateUser(String privateUser) { 
    this.privateUser = privateUser; 
} 

public String getGlobalMessage() { 
    return globalMessage; 
} 

public void setGlobalMessage(String globalMessage) { 
    this.globalMessage = globalMessage; 
} 

public String getPrivateMessage() { 
    return privateMessage; 
} 

public void setPrivateMessage(String privateMessage) { 
    this.privateMessage = privateMessage; 
} 

    public String getUsername() { 
      return username; 
    } 
    public void setUsername(String username) { 
      this.username = username; 
    } 

    public boolean isLoggedIn() { 
      return loggedIn; 
    } 
    public void setLoggedIn(boolean loggedIn) { 
      this.loggedIn = loggedIn; 
    } 

    public void sendGlobal() { 
    pushContext.push(CHANNEL + "*", username + ": " + globalMessage); 

      globalMessage = null; 
    } 

public void sendPrivate() { 
    pushContext.push(CHANNEL + privateUser, "[PM] " + username + ": " + privateMessage); 

    privateMessage = null; 
} 

    public void login() { 
    RequestContext requestContext = RequestContext.getCurrentInstance(); 

      if(users.contains(username)) { 
     loggedIn = false; 
     FacesContext.getCurrentInstance().addMessage(null, new FacesMessage(FacesMessage.SEVERITY_ERROR, "Username taken", "Try with another username.")); 

     requestContext.update("growl"); 
    } 
    else { 
     users.addUser(username); 
     pushContext.push(CHANNEL, username + " joined the channel."); 
     requestContext.execute("subscriber.connect('/" + username + "')"); 
     loggedIn = true; 
    } 
    } 

public void disconnect() { 
    //remove user and update ui 
    users.removeUser(username); 
    RequestContext.getCurrentInstance().update("form:users"); 

    //push leave information 
    pushContext.push(CHANNEL, username + " left the channel."); 

    //reset state 
    loggedIn = false; 
    username = null; 
} 
}

....

public class User implements Serializable { 


private static final long serialVersionUID = 1L; 
    private String firstname; 
    private String lastname; 
    private Integer age; 
    private String street; 
    private String city; 
    private String postalCode; 
    private String info; 
    private String email; 
    private String phone; 

    public String getFirstname() { 
      return firstname; 
    } 

    public void setFirstname(String firstname) { 
      this.firstname = firstname; 
    } 

    public String getLastname() { 
      return lastname; 
    } 

    public void setLastname(String lastname) { 
      this.lastname = lastname; 
    } 

    public Integer getAge() { 
      return age; 
    } 

    public void setAge(Integer age) { 
      this.age = age; 
    } 

    public String getStreet() { 
      return street; 
    } 

    public void setStreet(String street) { 
      this.street = street; 
    } 

    public String getCity() { 
      return city; 
    } 

    public void setCity(String city) { 
      this.city = city; 
    } 

    public String getPostalCode() { 
      return postalCode; 
    } 

    public void setPostalCode(String postalCode) { 
      this.postalCode = postalCode; 
    } 

    public String getInfo() { 
      return info; 
    } 

    public void setInfo(String info) { 
      this.info = info; 
    } 

    public String getEmail() { 
      return email; 
    } 

    public void setEmail(String email) { 
      this.email = email; 
    } 

    public String getPhone() { 
      return phone; 
    } 

    public void setPhone(String phone) { 
      this.phone = phone; 
    } 
}

....

public class ChatUsers { 

private List<String> users = Arrays.asList("fatih"); 


@PostConstruct 
public void init() { 
    this.users = new ArrayList<String>(); 
} 

public List<String> getUsers() { 
    return users; 
} 

public void setUsers(List<String> users) { 
    this.users = users; 
} 

public void addUser(String user) { 
    this.users.add(user); 
} 

public void removeUser(String user) { 
    this.users.remove(user); 
} 

public boolean contains(String user) { 
    return this.users.contains(user); 
} 
}

我收到例外ChatView类和此行if(users.contains(username))

任何建议将是非常很有帮助。谢谢..

编辑

'SEVERE: Received 'java.lang.UnsupportedOperationException' when invoking action listener '#{chatView.login}' for component 'j_idt21' 
Dec 25, 2012 10:01:18 PM javax.faces.event.MethodExpressionActionListener processAction 
SEVERE: java.lang.UnsupportedOperationException 
at java.util.AbstractList.add(Unknown Source) 
at java.util.AbstractList.add(Unknown Source) 
at org.primefaces.examples.view.ChatUsers.addUser(ChatUsers.java:43) 
at org.primefaces.examples.view.ChatView.login(ChatView.java:109) 
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
at java.lang.reflect.Method.invoke(Unknown Source) 
at org.apache.el.parser.AstValue.invoke(AstValue.java:278) 
at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:274) 
at javax.faces.event.MethodExpressionActionListener.processAction(MethodExpressionActionListener.java:153) 
at javax.faces.event.ActionEvent.processListener(ActionEvent.java:88) 
at javax.faces.component.UIComponentBase.broadcast(UIComponentBase.java:769) 
at javax.faces.component.UICommand.broadcast(UICommand.java:300) 
at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:794) 
at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1259) 
at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81) 
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) 
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118) 
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593) 
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) 
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) 
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222) 
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123) 
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) 
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168) 
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99) 
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929) 
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) 
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407) 
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1002) 
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:585) 
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312) 
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) 
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) 
at java.lang.Thread.run(Unknown Source) 

Dec 25, 2012 10:01:18 PM com.sun.faces.context.AjaxExceptionHandlerImpl log 
SEVERE: JSF1073: javax.faces.event.AbortProcessingException caught during processing of INVOKE_APPLICATION 5 : UIComponent-ClientId=form:j_idt21, Message=java.lang.UnsupportedOperationException 
Dec 25, 2012 10:01:18 PM com.sun.faces.context.AjaxExceptionHandlerImpl log 
SEVERE: java.lang.UnsupportedOperationException 
javax.faces.event.AbortProcessingException: java.lang.UnsupportedOperationException 
at javax.faces.event.MethodExpressionActionListener.processAction(MethodExpressionActionListener.java:182) 
at javax.faces.event.ActionEvent.processListener(ActionEvent.java:88) 
at javax.faces.component.UIComponentBase.broadcast(UIComponentBase.java:769) 
at javax.faces.component.UICommand.broadcast(UICommand.java:300) 
at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:794) 
at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1259) 
at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81) 
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) 
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118) 
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593) 
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) 
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) 
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222) 
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123) 
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) 
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168) 
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99) 
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929) 
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) 
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407) 
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1002) 
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:585) 
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312) 
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) 
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) 
at java.lang.Thread.run(Unknown Source) 
Caused by: java.lang.UnsupportedOperationException 
at java.util.AbstractList.add(Unknown Source) 
at java.util.AbstractList.add(Unknown Source) 
at org.primefaces.examples.view.ChatUsers.addUser(ChatUsers.java:43) 
at org.primefaces.examples.view.ChatView.login(ChatView.java:109) 
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
at java.lang.reflect.Method.invoke(Unknown Source) 
at org.apache.el.parser.AstValue.invoke(AstValue.java:278) 
at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:274) 
at javax.faces.event.MethodExpressionActionListener.processAction(MethodExpressionActionListen er.java:153) 
... 25 more

来源

2012-12-25 mft

我真的没有经过entore类，但是从你的最后一条语句我可以得到'users'标识符的值为空 – iDroid

如果你发布异常堆栈跟踪将会很有帮助。 –

你有没有在那里初始化在CharView类ChatUsers参考。所以，当你使用它时你会得到一个NPE。或者你可能没有在login方法之前调用setUsers方法，所以你的users保持未初始化。

你的宣言： -

private ChatUsers users;

应改为： -

private ChatUsers users = new ChatUsers();

更新： -

在你CharView类，当你创建一个列表如： -

private List<String> users = Arrays.asList("fatih");

您将得到一个固定大小的列表，您不能修改它。因此，在ChatView类的addUsers方法中，当您尝试向其添加用户时，将获得UnsupportedOperationException。

您应该创建列表如下： -

private List<String> users = new ArrayList<String>();

如果你想初始化列表中声明的时候，你可以这样做： -

private List<String> users = new ArrayList<String>() {{ 
    add("fatih"); 
}};

这就是所谓的double braces initialization

来源

2012-12-25 19:54:08

根据托管bean的范围，这可能是真的。也许它被注入代码中的其他地方。 –

@LuiggiMendoza。很可能，但我没有看到任何可能会在那里显示注入的注释。 –

@LuiggiMendoza我同意你的观点，因为涉及到getter制定者，所以我猜可能有一些独立于这个类别的注入 – iDroid

请注意

private ChatUsers users;

而且

private ChatUsers users = null;

是同一类的变量。

所以你必须在使用它之前将它初始化为非null对象。

来源

2012-12-25 20:00:09 Suranga

nullpointerexception

回答

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