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Primefaces JSF空从RequestContext.getCurrentInstance返

2019-09-17 13:46发布

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我正在开发使用Primefaces标签库的应用程序。

到目前为止，我从他们的官方网站上复制了一些例子，一切似乎除了使用该RequestContext.getCurrentInstance（）方法，任何工作。 它要么返回null每一次，造成的Tomcat抛出一个空指针异常或挂起永远，永远不会返回任何东西。

这里是我的代码（如果它挂起的情况下）：

GlobalCounterBean.java 

package org.primefaces.examples.view;

import java.io.Serializable;
import org.primefaces.context.RequestContext;

public class GlobalCounterBean implements Serializable{

    private int count;

    public int getCount() {
    return count;
    }

    public void setCount(int count) {
    this.count = count;
    }

    public synchronized void increment() {
    count++;
    System.out.println("aaaa");
        RequestContext.getCurrentInstance().push("counter", count);
    }
}

test.xhtml： 

<html xmlns="http://www.w3.org/1999/xhtml"
    xmlns:h="http://java.sun.com/jsf/html"
        xmlns:f="http://java.sun.com/jsf/core"
        xmlns:p="http://primefaces.org/ui">
    <h:head>
    </h:head>   
    <h:body>    

        <p:spinner />   

        <h:form>
    <h:outputText value="#{globalCounter.count}" styleClass="ui-widget display" />

    <br />

    <p:commandButton value="Click" actionListener="#{globalCounter.increment}" />
</h:form>

<p:push onmessage="handleMessage" channel="counter" />

<script type="text/javascript">
    function handleMessage(evt, data) {
            $('.display').html(data);
    }
</script>


    </h:body>
</html>

这里是为当它返回空的情况下，代码（所有文件都在同一个项目）：

ChatController.java： 

    package org.primefaces.examples.view;

    import java.io.Serializable;
    import java.util.HashSet;
    import java.util.Set;

    import javax.faces.application.FacesMessage;
    import javax.faces.bean.ApplicationScoped;
    import javax.faces.bean.ManagedBean;
    import javax.faces.context.FacesContext;
    import javax.faces.event.ActionEvent;

    import org.primefaces.context.RequestContext;


    public class ChatController implements Serializable {

        private final static String CHANNEL = "chat";

        private String message;

        private String username;

        private boolean loggedIn;

        private Set<String> users = new HashSet<String>();

        public String getMessage() {
            return message;
        }
        public void setMessage(String message) {
            this.message = message;
        }

        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 send() {
            RequestContext.getCurrentInstance().push(CHANNEL, username + ": "+  message);

            message = 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.addPartialUpdateTarget("growl");
            }
            else {
                users.add(username);
                loggedIn = true;

                requestContext.push(CHANNEL, username + " joined the channel.");
            }
        }

        public void disconnect() {
            RequestContext.getCurrentInstance().push(CHANNEL, username + " has left the channel.");
            loggedIn = false;
            username = null;
        }
    }

chat.xhtml 

        <html xmlns="http://www.w3.org/1999/xhtml"
            xmlns:h="http://java.sun.com/jsf/html"
            xmlns:f="http://java.sun.com/jsf/core"
            xmlns:p="http://primefaces.org/ui">

        <head>
        <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" />
        <title>Insert title here</title>
        </head>
        <body>
        <f:view>
        <p:growl id="growl" showDetail="true" />

        <h:form>

            <p:fieldset id="container" legend="PrimeChat">

                <h:panelGroup rendered="#{chatController.loggedIn}" >
                    <p:outputPanel layout="block" style="width:600px;height:200px;overflow:auto" 
                               styleClass="chatroom" />
                    <p:spinner />
                    <p:separator />

                    <p:inputText value="#{chatController.message}" styleClass="messageInput" />
                    <p:spacer width="5" />
                    <p:commandButton value="Send" actionListener="#{chatController.send}" global="false" oncomplete="$('.messageInput').val('').focus()"/>
                    <p:spacer width="5" />
                    <p:commandButton value="Disconnect" actionListener="#{chatController.disconnect}" global="false" 
                                        oncomplete="chatAgent.close()" update="container" />
                </h:panelGroup>

                <h:panelGroup rendered="#{not chatController.loggedIn}" >
                    Username: <p:inputText value="#{chatController.username}" />

                    <p:spacer width="5" />
                    <p:commandButton value="Login" actionListener="#{chatController.login}" update="container" 
                                     icon="ui-icon-person"/>
                </h:panelGroup>

            </p:fieldset>

        </h:form>

        <p:push onmessage="handleMessage" channel="chat" widgetVar="chatAgent" />

        <script type="text/javascript">
            function handleMessage(evt, data) {
                var chatContent = $('.chatContent');
                chatContent.append(data + '<br />');

                //keep scroll
                chatContent.scrollTop(chatContent.height());
            }
        </script>
        <script type="text/javascript">
        function handleComplete(xhr, status, args) {
            if(args.validationFailed) {
                PrimeFaces.debug("Validation Failed");
            } 
            else {
                PrimeFaces.debug("Save:" + args.saved);
                PrimeFaces.debug("FirstName: " + args.user.firstname + ", Lastname: " + args.user.lastname); 
            }
        }
        </script>

        </f:view>
        </body>
        </html>

faces-config.xml中： 

    <?xml version="1.0" encoding="utf-8"?>
    <faces-config version="2.0" xmlns="http://java.sun.com/xml/ns/javaee"
     xmlns:xi="http://www.w3.org/2001/XInclude"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-facesconfig_2_0.xsd">
     <managed-bean eager="true">
      <managed-bean-name>chatController</managed-bean-name>
      <managed-bean-class>org.primefaces.examples.view.ChatController</managed-bean-class>
      <managed-bean-scope>request</managed-bean-scope>
     </managed-bean>
     <managed-bean>
      <managed-bean-name>globalCounter</managed-bean-name>
      <managed-bean-class>org.primefaces.examples.view.GlobalCounterBean</managed-bean-class>
      <managed-bean-scope>application</managed-bean-scope>
     </managed-bean>
     <!--
        No ManagedBean declarations here as we are using @ManagedBean Annotations.
        -->
    </faces-config>

web.xml中： 

        <?xml version="1.0" encoding="UTF-8"?>
        <web-app version="2.5"
            xmlns="http://java.sun.com/xml/ns/javaee"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" >

            <welcome-file-list>
                <welcome-file>index.jsp</welcome-file>
            </welcome-file-list>

            <servlet>
                <servlet-name>Faces Servlet</servlet-name>
                <servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
                <load-on-startup>1</load-on-startup>
            </servlet>

            <servlet-mapping>
                <servlet-name>Faces Servlet</servlet-name>
                <url-pattern>*.xhtml</url-pattern>
            </servlet-mapping>

        </web-app>

而这里的tomcat中控制台抛出的异常： 

                        2012-05-27 19:16:25 com.sun.faces.context.ExceptionHandlerImpl log
            SEVERE: JSF1073: javax.faces.event.AbortProcessingException caught during processing of INVOKE_APPLICATION 5 : UIComponent-ClientId=j_idt2:j_idt16, Message=java.lang.NullPointerException
            2012-05-27 19:16:25 com.sun.faces.context.ExceptionHandlerImpl log
            SEVERE: java.lang.NullPointerException
            javax.faces.event.AbortProcessingException: java.lang.NullPointerException
                at javax.faces.event.MethodExpressionActionListener.processAction(MethodExpressionActionListener.java:178)
                at javax.faces.event.ActionEvent.processListener(ActionEvent.java:84)
                at javax.faces.component.UIComponentBase.broadcast(UIComponentBase.java:773)
                at javax.faces.component.UICommand.broadcast(UICommand.java:296)
                at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:781)
                at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1246)
                at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:77)
                at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:97)
                at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:114)
                at javax.faces.webapp.FacesServlet.service(FacesServlet.java:308)
                at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
                at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
                at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
                at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
                at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
                at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
                at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
                at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
                at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
                at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)
                at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
                at java.lang.Thread.run(Thread.java:680)
            Caused by: java.lang.NullPointerException
                at org.primefaces.examples.view.ChatController.login(ChatController.java:69)
                at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
                at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
                at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
                at java.lang.reflect.Method.invoke(Method.java:597)
                at org.apache.el.parser.AstValue.invoke(AstValue.java:191)
                at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:276)
                at javax.faces.event.MethodExpressionActionListener.processAction(MethodExpressionActionListener.java:149)
                ... 21 more

Answer 1:

你的web.xml缺少PrimeFaces的“URL配置”部分按设置。

正如我的回答对你提到的前一个问题 ，PrimeFaces推的安装细节PrimeFaces第6章概述用户指南 。 下面是你错过步骤相关的摘录：

6.1安装

推送服务器

PrimeFaces推使用servlet作为调度员。 这个servlet应该在不同的应用程序比JSF应用程序，目前只能在码头服务器上部署。 

 <servlet> <servlet-name>Push Servlet</servlet-name> <servlet-class>org.primefaces.push.PushServlet</servlet-class> <load-on-startup>1</load-on-startup> <init-param> <param-name>channels</param-name> <param-value>chat,counter</param-value> </init-param> </servlet> <servlet-mapping> <servlet-name>Push Servlet</servlet-name> <url-pattern>/prime-push/*</url-pattern> </servlet-mapping>

渠道配置定义推送服务器可以发布到主题名称。

网址配置

JSF应用程序需要定义推送服务器的URL发送消息。 

 <context-param> <param-name>primefaces.PUSH_SERVER_URL</param-name> <param-value>ws://url_to_push_server</param-value> </context-param>


文章来源: Primefaces JSF null returned from RequestContext.getCurrentInstance()
标签： jsf primefaces nullpointerexception RequestContext
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