无法调用“com.vaadin.flow.server.RequestHandler.handleRequest

问题描述 投票：0回答：1

我正在尝试将 Vaadin 24.4.0.beta1 与 Java 17 和 Intellij IDEA 结合使用。我从 start.vaadin.com 下载了一个示例项目，它是一个具有多个频道的聊天视图 - Flow 元素。

我尝试稍微编辑一下这段代码。我没有 Vaadin 工具，因此我检查了浏览器中的更改。因此，当我更改代码时，我按下运行“应用程序”，当我结束时，只是停止“应用程序”。

我不知道，但当我添加

// todo
时，我不断开始收到下一个异常。

ERROR 48164 --- [nio-8080-exec-2] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [com.vaadin.flow.server.ServiceException: java.lang.NullPointerException: Cannot invoke "com.vaadin.flow.server.RequestHandler.handleRequest(com.vaadin.flow.server.Vaadin session, 
com.vaadin.flow.server.VaadinRequest, com.vaadin.flow.server.VaadinResponse)" 
because "handler" is null] with root cause

java.lang.NullPointerException: Cannot invoke "com.vaadin.flow.server.RequestHandler.handleRequest(com.vaadin.flow.server.VaadinSession, com.vaadin.flow.server.VaadinRequest, com.vaadin.flow.server.VaadinResponse)" because "handler" is null
    at com.vaadin.flow.server.communication.SessionRequestHandler.handleRequest(SessionRequestHandler.java:64) ~[flow-server-24.4.0.beta1.jar:24.4.0.beta1]
    at com.vaadin.flow.server.VaadinService.handleRequest(VaadinService.java:1577) ~[flow-server-24.4.0.beta1.jar:24.4.0.beta1]
    at com.vaadin.flow.server.VaadinServlet.service(VaadinServlet.java:398) ~[flow-server-24.4.0.beta1.jar:24.4.0.beta1]
    at com.vaadin.flow.spring.SpringServlet.service(SpringServlet.java:106) ~[vaadin-spring-24.4.0.beta1.jar:na]
    at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:658) ~[tomcat-embed-core-10.1.20.jar:6.0]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:206) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:150) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:653) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:419) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:313) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:277) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.springframework.web.servlet.mvc.ServletForwardingController.handleRequestInternal(ServletForwardingController.java:142) ~[spring-webmvc-6.1.6.jar:6.1.6]
    at org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:178) ~[spring-webmvc-6.1.6.jar:6.1.6]
    at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:51) ~[spring-webmvc-6.1.6.jar:6.1.6]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1089) ~[spring-webmvc-6.1.6.jar:6.1.6]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:979) ~[spring-webmvc-6.1.6.jar:6.1.6]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1014) ~[spring-webmvc-6.1.6.jar:6.1.6]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:903) ~[spring-webmvc-6.1.6.jar:6.1.6]
    at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:564) ~[tomcat-embed-core-10.1.20.jar:6.0]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:885) ~[spring-webmvc-6.1.6.jar:6.1.6]
    at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:658) ~[tomcat-embed-core-10.1.20.jar:6.0]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:206) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:150) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) ~[tomcat-embed-websocket-10.1.20.jar:10.1.20]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:175) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:150) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-6.1.6.jar:6.1.6]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.1.6.jar:6.1.6]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:175) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:150) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-6.1.6.jar:6.1.6]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.1.6.jar:6.1.6]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:175) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:150) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-6.1.6.jar:6.1.6]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.1.6.jar:6.1.6]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:175) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:150) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:167) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:482) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:115) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:344) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:391) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:896) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1736) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) ~[tomcat-embed-core-10.1.20.jar:10.1.20]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:63) ~[tomcat-embed-core-10.1.20.jar:10.1.20]

除了创建新项目并重新开始直到再次获得相同的异常之外，我不知道该怎么办？

当我清除项目中所有生成的文件和文件夹并使用另一个 vaadin.version 构建应用程序时，它会有所帮助。终端中的

./mvnw
不起作用，我一直收到下一个异常：

[ERROR] Failed to execute goal com.vaadin:vaadin-maven-plugin:24.3.11:prepare-frontend (default) on project chat-app: Execution default of goal com.vaadin:vaadin-maven-plugin:24.3.11:prepare-frontend failed: U
nable to load the mojo 'prepare-frontend' in the plugin 'com.vaadin:vaadin-maven-plugin:24.3.11' due to an API incompatibility: org.codehaus.plexus.component.repository.exception.ComponentLookupException: com/
vaadin/flow/plugin/maven/PrepareFrontendMojo has been compiled by a more recent version of the Java Runtime (class file version 61.0), this version of the Java Runtime only recognizes class file versions up to 55.0

虽然我检查了我的Java项目sdk，用ctrl+shift+alt+s，它是liberica 17。

java vaadin
1个回答
0
投票

回答我的问题。该问题是由于应用程序运行后未执行 

maven clean
引起的。据我了解，从 Maven 切换到 gradle 也有帮助。

为了消除

./mvnw
问题，请仔细检查
JAVA_HOME
环境变量。可能是这样，您的项目使用 SDK 17，但您的 
JAVA_HOME
导致 
JDK
/
JRE
{another_version}。

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