BeanCreationException Using Vaadin and CRUD findAll() Service to Fill ComboBox

Question

I am using Vaadin8 with SpringBoot using vaadin-spring-boot-starter 2.0.0 to fill a ComboBox. I tried the same with NativeSelect, still got the same error message by the way, when I use the setItem() method of the ComboBox.

Repo:

public interface UserCategoryRepo extends CrudRepository<UserCategory, Long> {
}

Service:

@Service
@Transactional
public class UserCategoryServiceImpl implements UserCategoryService {
    @Autowired
    UserCategoryRepo userCategoryRepo;

    @Override
    public void saveCategory(UserCategory userCategory) {
        userCategoryRepo.save(userCategory);
    }

    @Override
    public List<UserCategory> lisUserCategories() {
        List<UserCategory> categoryList = new ArrayList<>();
        for(UserCategory userCategory : userCategoryRepo.findAll())
            categoryList.add(userCategory);
        return categoryList;
    }
}

Form Class:

ppublic class TryVaadin extends FormLayout {

private TryVaadinUI tryVaadinUI;

@Autowired
UserCategoryServiceImpl service;

public TryVaadin(TryVaadinUI tryVaadinUI) {
    this.tryVaadinUI = tryVaadinUI;

    ComboBox<UserCategory> userCategoryCombox = new ComboBox<>("Choose Category");
    userCategoryCombox.setItems(service.lisUserCategories());

    Button saveButton = new Button("Save");
    HorizontalLayout components = new HorizontalLayout(saveButton);
    TextField name = new TextField("Enter Name:");
    addComponents(name, userCategoryCombox, components);
 }
}

UI Class:

 @SpringUI(path = "/try")
public class TryVaadinUI extends UI {

    @Autowired
    TryVaadin form = new TryVaadin(this);

    @Override
    protected void init(VaadinRequest vaadinRequest) {
        final VerticalLayout layout = new VerticalLayout();
        layout.addComponents(form);

            setContent(layout);
        }
    }

Why Am I getting this error?! Can someone explain please... By the way, service.lisUserCategories() works everywhere else!

    org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'tryVaadinUI' defined in file [C:\Users\consc\Desktop\Advanced Software Engineering\gs-accessing-data-jpa-master\gs-accessing-data-jpa-master\TryPLMA\target\classes\com\pringwa\controller\TryVaadinUI.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.pringwa.controller.TryVaadinUI]: Constructor threw exception; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1155) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1099) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:513) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory$2.getObject(AbstractBeanFactory.java:345) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at com.vaadin.spring.internal.BeanStore.create(BeanStore.java:71) ~[vaadin-spring-2.0.0.jar:2.0.0]
    at com.vaadin.spring.internal.UIScopeImpl$UIBeanStore.create(UIScopeImpl.java:282) ~[vaadin-spring-2.0.0.jar:2.0.0]
    at com.vaadin.spring.internal.BeanStore.get(BeanStore.java:62) ~[vaadin-spring-2.0.0.jar:2.0.0]
    at com.vaadin.spring.internal.SessionLockingBeanStore.get(SessionLockingBeanStore.java:46) ~[vaadin-spring-2.0.0.jar:2.0.0]
    at com.vaadin.spring.internal.UIScopeImpl.get(UIScopeImpl.java:79) ~[vaadin-spring-2.0.0.jar:2.0.0]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:340) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:220) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveNamedBean(DefaultListableBeanFactory.java:1018) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:345) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:340) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1093) ~[spring-context-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at com.vaadin.spring.server.SpringUIProvider.createInstance(SpringUIProvider.java:203) ~[vaadin-spring-2.0.0.jar:2.0.0]
    at com.vaadin.server.communication.UIInitHandler.getBrowserDetailsUI(UIInitHandler.java:191) ~[vaadin-server-8.0-20170527.000245-173.jar:8.0-SNAPSHOT]
    at com.vaadin.server.communication.UIInitHandler.synchronizedHandleRequest(UIInitHandler.java:74) ~[vaadin-server-8.0-20170527.000245-173.jar:8.0-SNAPSHOT]
    at com.vaadin.server.SynchronizedRequestHandler.handleRequest(SynchronizedRequestHandler.java:41) ~[vaadin-server-8.0-20170527.000245-173.jar:8.0-SNAPSHOT]
    at com.vaadin.server.VaadinService.handleRequest(VaadinService.java:1464) ~[vaadin-server-8.0-20170527.000245-173.jar:8.0-SNAPSHOT]
    at com.vaadin.server.VaadinServlet.service(VaadinServlet.java:381) [vaadin-server-8.0-20170527.000245-173.jar:8.0-SNAPSHOT]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) [tomcat-embed-websocket-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.springframework.boot.web.filter.ApplicationContextHeaderFilter.doFilterInternal(ApplicationContextHeaderFilter.java:55) [spring-boot-1.5.2.RELEASE.jar:1.5.2.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.springframework.boot.actuate.trace.WebRequestTraceFilter.doFilterInternal(WebRequestTraceFilter.java:108) [spring-boot-actuator-1.5.2.RELEASE.jar:1.5.2.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) [spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:105) [spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81) [spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) [spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.springframework.boot.actuate.autoconfigure.MetricsFilter.doFilterInternal(MetricsFilter.java:106) [spring-boot-actuator-1.5.2.RELEASE.jar:1.5.2.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:474) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:783) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:798) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1434) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_66]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_66]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at java.lang.Thread.run(Thread.java:745) [na:1.8.0_66]
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.pringwa.controller.TryVaadinUI]: Constructor threw exception; nested exception is java.lang.NullPointerException
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:154) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:89) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1147) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    ... 71 common frames omitted
Caused by: java.lang.NullPointerException: null
    at com.pringwa.controller.TryVaadin.<init>(TryVaadin.java:30) ~[classes/:na]
    at com.pringwa.controller.TryVaadinUI.<init>(TryVaadinUI.java:15) ~[classes/:na]
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_66]
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_66]
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_66]
    at java.lang.reflect.Constructor.newInstance(Constructor.java:422) ~[na:1.8.0_66]
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:142) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    ... 73 common frames omitted

2017-07-18 01:44:34.866 ERROR 29140 --- [nio-8080-exec-6] o.a.c.c.C.[.[.[/].[springVaadinServlet]  : Servlet.service() for servlet [springVaadinServlet] in context with path [] threw exception [com.vaadin.server.ServiceException: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'tryVaadinUI' defined in file [C:\Users\consc\Desktop\Advanced Software Engineering\gs-accessing-data-jpa-master\gs-accessing-data-jpa-master\TryPLMA\target\classes\com\pringwa\controller\TryVaadinUI.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.pringwa.controller.TryVaadinUI]: Constructor threw exception; nested exception is java.lang.NullPointerException] with root cause

java.lang.NullPointerException: null
    at com.pringwa.controller.TryVaadin.<init>(TryVaadin.java:30) ~[classes/:na]
    at com.pringwa.controller.TryVaadinUI.<init>(TryVaadinUI.java:15) ~[classes/:na]
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_66]
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_66]
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_66]
    at java.lang.reflect.Constructor.newInstance(Constructor.java:422) ~[na:1.8.0_66]
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:142) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:89) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1147) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1099) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:513) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory$2.getObject(AbstractBeanFactory.java:345) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at com.vaadin.spring.internal.BeanStore.create(BeanStore.java:71) ~[vaadin-spring-2.0.0.jar:2.0.0]
    at com.vaadin.spring.internal.UIScopeImpl$UIBeanStore.create(UIScopeImpl.java:282) ~[vaadin-spring-2.0.0.jar:2.0.0]
    at com.vaadin.spring.internal.BeanStore.get(BeanStore.java:62) ~[vaadin-spring-2.0.0.jar:2.0.0]
    at com.vaadin.spring.internal.SessionLockingBeanStore.get(SessionLockingBeanStore.java:46) ~[vaadin-spring-2.0.0.jar:2.0.0]
    at com.vaadin.spring.internal.UIScopeImpl.get(UIScopeImpl.java:79) ~[vaadin-spring-2.0.0.jar:2.0.0]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:340) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:220) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveNamedBean(DefaultListableBeanFactory.java:1018) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:345) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:340) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1093) ~[spring-context-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at com.vaadin.spring.server.SpringUIProvider.createInstance(SpringUIProvider.java:203) ~[vaadin-spring-2.0.0.jar:2.0.0]
    at com.vaadin.server.communication.UIInitHandler.getBrowserDetailsUI(UIInitHandler.java:191) ~[vaadin-server-8.0-20170527.000245-173.jar:8.0-SNAPSHOT]
    at com.vaadin.server.communication.UIInitHandler.synchronizedHandleRequest(UIInitHandler.java:74) ~[vaadin-server-8.0-20170527.000245-173.jar:8.0-SNAPSHOT]
    at com.vaadin.server.SynchronizedRequestHandler.handleRequest(SynchronizedRequestHandler.java:41) ~[vaadin-server-8.0-20170527.000245-173.jar:8.0-SNAPSHOT]
    at com.vaadin.server.VaadinService.handleRequest(VaadinService.java:1464) ~[vaadin-server-8.0-20170527.000245-173.jar:8.0-SNAPSHOT]
    at com.vaadin.server.VaadinServlet.service(VaadinServlet.java:381) ~[vaadin-server-8.0-20170527.000245-173.jar:8.0-SNAPSHOT]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) ~[tomcat-embed-websocket-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.springframework.boot.web.filter.ApplicationContextHeaderFilter.doFilterInternal(ApplicationContextHeaderFilter.java:55) ~[spring-boot-1.5.2.RELEASE.jar:1.5.2.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.springframework.boot.actuate.trace.WebRequestTraceFilter.doFilterInternal(WebRequestTraceFilter.java:108) ~[spring-boot-actuator-1.5.2.RELEASE.jar:1.5.2.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:105) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.springframework.boot.actuate.autoconfigure.MetricsFilter.doFilterInternal(MetricsFilter.java:106) ~[spring-boot-actuator-1.5.2.RELEASE.jar:1.5.2.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:474) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:783) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:798) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1434) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_66]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_66]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at java.lang.Thread.run(Thread.java:745) [na:1.8.0_66]

You did not post the entire stack trace, but I'm going to take a shot in the dark. Inside the ui you have a `new TryVaadin(this)` which in turn has a `new UserServiceCategoryImpl()` which finally has an autowired `UserCategoryRepo`. The thing is, except in a few special cases such as methods annotated with `@Bean` from `@Configuration` classes, when you instantiate an object yourself instead of requesting it from the context, spring has no way of knowing, and dependency injection does not take place, so your repo field remains null. — Morfic, Jul 11 '17 at 23:11
I see you've made some changes since last night, and the NPE is now different, but I don't see any code updates, so please add them if there are any. From the stack trace it now seems that you've defined your `TryVaadin` as a spring managed bean and maybe annotated your service field with `@Autowired`. If that's the case, then probably `TryVaadin:32` where the NPE originates, is `userCategoryCombox.setItems(service.lisUserCategories());`. This is because, spring has to instantiate an object before injecting autowired fields, so when the constructor is called, the service will still be `null`. — Morfic, Jul 12 '17 at 08:00
You can use [constructor injection](https://docs.spring.io/spring/docs/current/spring-framework-reference/htmlsingle/#beans-autowired-annotation) (as of Spring 4.3 `@Autowired` is no longer required if you only have one constructor) or a [`@PostConstruct` annotated method](https://docs.spring.io/spring/docs/current/spring-framework-reference/htmlsingle/#beans-postconstruct-and-predestroy-annotations) which is called after a bean is created and all injections performed. Nonetheless, this is a _guess_ so it would really be helpful if we could see the new code changes. — Morfic, Jul 12 '17 at 08:51
@Morfic I have have the question edited with the latest stack trace and most stable build — Marcellinus, Jul 17 '17 at 23:50

score 0 · Answer 1 · answered Jul 12 '17 at 06:16

0

You should not pass the UI to a Component.

In the TryVaadinUI class the line

private TryVaadin form = new TryVaadin(this);

should be

private TryVaadin form = new TryVaadin();

and the TryVaadin Constructor should not take parameters. You can access the UI by using the getUI() function which is provided and accessible in the TryVaadin Class.

answered Jul 12 '17 at 06:16

Manuel Kollegger

238
1
9

1

While it is true that you can use `getUI()`, I don't see wow this is relevant to the problem described in your question. What am I missing? – Morfic Jul 12 '17 at 07:50
I do believe that `new TryVaadin(this)` is called too early (while initializing TryVaadinUI) resulting in `this` being null. – Manuel Kollegger Jul 12 '17 at 08:08
As I'm sure you're aware, `this` is a reference to the current object, so [there's no way this would be `null`](https://stackoverflow.com/questions/3789528/can-this-ever-be-null-in-java). And even if it were, why would it be producing a NPE since inside the TryVaadin constructor, it doesn't do anything else besides this.tryVaadinUI = tryVaadinUI. At least in this version of the code that we have... – Morfic Jul 12 '17 at 10:40

score 0 · Accepted Answer · answered Jul 20 '17 at 00:35

The solution I got was, first move the contents in the constructor of TryVaadin to some new method! The Class will now look like this:

public class TryVaadin extends FormLayout {

    private static final long serialVersionUID = -4812112027634726927L;
    private TryVaadinUI tryVaadinUI;

    public TryVaadin() {
    }

    public void creat(List<UserCategory> list){
        ComboBox<UserCategory> userCategoryCombox = new ComboBox<>("Choose Category");
        userCategoryCombox.setItems(list);

        Button saveButton = new Button("Save");
        HorizontalLayout components = new HorizontalLayout(saveButton);
        TextField name = new TextField("Enter Name:");
        addComponents(name, userCategoryCombox, components);
    }
}

Now the UI class TryVaadinUI will now look like this:

@SpringUI(path = "/try")
public class TryVaadinUI extends UI {

    private static final long serialVersionUID = -1301392602647903109L;

    @Autowired
    UserCategoryServiceImpl service;

    TryVaadin form = new TryVaadin();

    @Override
    protected void init(VaadinRequest vaadinRequest) {
        final VerticalLayout layout = new VerticalLayout();
        form.creat(service.lisUserCategories());
        layout.addComponents(form);

        setContent(layout);
    }
}

BeanCreationException Using Vaadin and CRUD findAll() Service to Fill ComboBox

2 Answers2