在SpringMVC返回json格式数据时，如果handler返回值是自己封装实体类，一定要提供set和get方法，否则会抛出如下异常

2022-03-11 22:32:58.707  WARN 33648 --- [  XNIO-1 task-8] .m.m.a.ExceptionHandlerExceptionResolver : Failure in @ExceptionHandler com.wdadmin.webstarter.advice.BaseControllerAdvice#handlerException(Exception)

org.springframework.http.converter.HttpMessageNotWritableException: No converter for [class com.wdadmin.common.model.R] with preset Content-Type 'application/json;charset=UTF-8'
	at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:312) ~[spring-webmvc-5.3.10.jar:5.3.10]
	at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:183) ~[spring-webmvc-5.3.10.jar:5.3.10]
	at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:78) ~[spring-web-5.3.10.jar:5.3.10]
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:135) ~[spring-webmvc-5.3.10.jar:5.3.10]
	at org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver.doResolveHandlerMethodException(ExceptionHandlerExceptionResolver.java:428) ~[spring-webmvc-5.3.10.jar:5.3.10]
	at org.springframework.web.servlet.handler.AbstractHandlerMethodExceptionResolver.doResolveException(AbstractHandlerMethodExceptionResolver.java:75) [spring-webmvc-5.3.10.jar:5.3.10]
	at org.springframework.web.servlet.handler.AbstractHandlerExceptionResolver.resolveException(AbstractHandlerExceptionResolver.java:141) [spring-webmvc-5.3.10.jar:5.3.10]
	at org.springframework.web.servlet.handler.HandlerExceptionResolverComposite.resolveException(HandlerExceptionResolverComposite.java:80) [spring-webmvc-5.3.10.jar:5.3.10]
	at org.springframework.web.servlet.DispatcherServlet.processHandlerException(DispatcherServlet.java:1327) [spring-webmvc-5.3.10.jar:5.3.10]
	at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1138) [spring-webmvc-5.3.10.jar:5.3.10]
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1084) [spring-webmvc-5.3.10.jar:5.3.10]
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963) [spring-webmvc-5.3.10.jar:5.3.10]
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) [spring-webmvc-5.3.10.jar:5.3.10]
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) [spring-webmvc-5.3.10.jar:5.3.10]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:497) [jakarta.servlet-api-4.0.4.jar:4.0.4]
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) [spring-webmvc-5.3.10.jar:5.3.10]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:584) [jakarta.servlet-api-4.0.4.jar:4.0.4]
	at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:74) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:129) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) [spring-web-5.3.10.jar:5.3.10]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.3.10.jar:5.3.10]
	at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:61) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:131) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:103) [spring-web-5.3.10.jar:5.3.10]
	at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:61) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:131) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:103) [spring-web-5.3.10.jar:5.3.10]
	at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:61) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:131) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.handlers.FilterHandler.handleRequest(FilterHandler.java:84) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.handlers.ServletChain$1.handleRequest(ServletChain.java:68) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.handlers.RedirectDirHandler.handleRequest(RedirectDirHandler.java:68) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43) [undertow-core-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43) [undertow-core-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:262) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.handlers.ServletInitialHandler.dispatchToPath(ServletInitialHandler.java:187) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.spec.RequestDispatcherImpl.error(RequestDispatcherImpl.java:506) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.spec.RequestDispatcherImpl.error(RequestDispatcherImpl.java:419) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.spec.HttpServletResponseImpl.doErrorDispatch(HttpServletResponseImpl.java:165) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:287) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.handlers.ServletInitialHandler.access$100(ServletInitialHandler.java:79) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:134) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:131) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:48) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:260) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:79) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:100) [undertow-servlet-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.server.Connectors.executeRootHandler(Connectors.java:387) [undertow-core-2.2.10.Final.jar:2.2.10.Final]
	at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:852) [undertow-core-2.2.10.Final.jar:2.2.10.Final]
	at org.jboss.threads.ContextClassLoaderSavingRunnable.run(ContextClassLoaderSavingRunnable.java:35) [jboss-threads-3.1.0.Final.jar:3.1.0.Final]
	at org.jboss.threads.EnhancedQueueExecutor.safeRun(EnhancedQueueExecutor.java:2019) [jboss-threads-3.1.0.Final.jar:3.1.0.Final]
	at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.doRunTask(EnhancedQueueExecutor.java:1558) [jboss-threads-3.1.0.Final.jar:3.1.0.Final]
	at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1433) [jboss-threads-3.1.0.Final.jar:3.1.0.Final]
	at org.xnio.XnioWorker$WorkerThreadFactory$1$1.run(XnioWorker.java:1280) [xnio-api-3.8.4.Final.jar:3.8.4.Final]
	at java.lang.Thread.run(Thread.java:748) [na:1.8.0_221]

一定要为返回的实体类提供set和get方法