Java 我能'；t在Vaadin组件中调用JpaReposistory api_Java_Spring_Vaadin

Java 我能'；t在Vaadin组件中调用JpaReposistory api

java spring vaadin

Java 我能'；t在Vaadin组件中调用JpaReposistory api,java,spring,vaadin,Java,Spring,Vaadin,我对Vaadin和Spring Boot还不熟悉，我正在尝试制作一个能够处理所有CRUD方法的小应用程序。我正在制作这个表单，它将接收字段中的所有数据，将其保存到一个模型对象，并将其保存到我的数据库中，但它不允许我这样做 StudentRepo package com.vinh.vaadin.allinone.repo; import org.springframework.data.jpa.repository.JpaRepository; import org.springframework

我对Vaadin和Spring Boot还不熟悉，我正在尝试制作一个能够处理所有CRUD方法的小应用程序。我正在制作这个表单，它将接收字段中的所有数据，将其保存到一个模型对象，并将其保存到我的数据库中，但它不允许我这样做

StudentRepo

package com.vinh.vaadin.allinone.repo;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;
import com.vinh.vaadin.allinone.entity.Student;
@Repository
public interface StudentRepo extends JpaRepository<Student, Long>{
}

但是，如果我将

repo.save（）

放入

MainContent

中的

saveStudent（）

方法中，将该

MainContent

传递到

StudentForm

中，然后从那里调用

saveStudent（）

方法，它就会工作。为什么?

我的另一个问题是在主要内容中，我必须在

@PostConstruct

中添加

repo.findAll（）

，这样它才能工作，如果我把它放在其他任何不是@PostConstruct的地方，那么它就不会工作，这是为什么？

您的StudentRepo类应该用@Component注释，因为您正在StudentForm类中创建它的bean

当创建StudentForm的bean时，它需要StudentRepo类的bean，而该类没有创建，因为您没有将其标记为@Component。因此，当您尝试访问StudentRepo的方法时，会引发空指针异常

@Component
public interface StudentRepo extends JpaRepository<Student, Long> {
}

@组件
公共接口StudentRepo扩展了JpaRepository{
}

您还可以使用@Repository注释来指定这是一个dao层类。 @存储库从@Component扩展而来，仅用于保持命名一致。

因此，这两种注释都可以使用

您正在调用bindInstanceFields，但您尚未使用@PropertyId（..）注释对字段进行注释。因此，它可能什么也不做，并且您的编辑永远不会绑定到您的学生bean。参见JavaDoc

添加了@Repository，仍然无法工作。当它到达try-catch-finally博客时，我尝试了sysout，student不是空的。请发布全文exception@JohnJoe编辑默认情况下的bindInstanceFields将所有字段绑定到实体的属性基于命名约定，我的实体有一个名为lastName的属性，其中一个textField名为lastName，这两个将被捆绑在一起@PropertyId允许绑定具有不同名称的字段和属性。

package com.vinh.vaadin.allinone.vaadin;

import java.util.ArrayList;
import java.util.List;

import javax.annotation.PostConstruct;

import org.assertj.core.util.Lists;
import org.springframework.beans.factory.annotation.Autowired;

import com.vaadin.icons.VaadinIcons;
import com.vaadin.spring.annotation.SpringComponent;
import com.vaadin.ui.Alignment;
import com.vaadin.ui.Button;
import com.vaadin.ui.CssLayout;
import com.vaadin.ui.Grid;
import com.vaadin.ui.HorizontalLayout;
import com.vaadin.ui.TextField;
import com.vaadin.ui.VerticalLayout;
import com.vaadin.ui.themes.ValoTheme;
import com.vinh.vaadin.allinone.entity.Student;
import com.vinh.vaadin.allinone.repo.StudentRepo;

import javassist.expr.NewArray;

@SpringComponent
public class MainContent extends VerticalLayout {
    @Autowired
    private Student student;
    @Autowired
    StudentRepo repo;

    private StudentForm studentForm = new StudentForm();



    private CssLayout filterLayout;
    private TextField filterText;
    private Button filterBtn;
    private HomeUI homeUI;
    private Grid<Student> studentGrid;

    @PostConstruct
    void init() {
        setStudents(repo.findAll());
    }

    private void setStudents(List<Student> findAll) {
        studentGrid.setItems(findAll);
    }

    public MainContent() {
        addFilter();
        addMainContent();
    }

    private void addMainContent() {
        HorizontalLayout main = new HorizontalLayout();
        studentGrid = new Grid<>(Student.class);
        studentGrid.setColumns("firstName", "lastName", "email");
        main.addComponentsAndExpand(studentGrid);
        main.addComponents(studentForm);
        studentGrid.setSizeFull();
        addComponents(main);
    }

    private void addFilter() {
        filterLayout = new CssLayout();
        filterLayout.addStyleName(ValoTheme.LAYOUT_COMPONENT_GROUP);

        filterText = new TextField();
        filterText.setPlaceholder("filter by name...");

        filterBtn = new Button(VaadinIcons.CLOSE);

        filterLayout.addComponents(filterText, filterBtn);

        HorizontalLayout toolbar = new HorizontalLayout(filterLayout);
        addComponent(toolbar);
    }
}

java.lang.NullPointerException: null
    at com.vinh.vaadin.allinone.vaadin.StudentForm.lambda$0(StudentForm.java:44) ~[classes/:na]
    at sun.reflect.GeneratedMethodAccessor309.invoke(Unknown Source) ~[na:na]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_171]
    at java.lang.reflect.Method.invoke(Unknown Source) ~[na:1.8.0_171]
    at com.vaadin.event.ListenerMethod.receiveEvent(ListenerMethod.java:499) ~[vaadin-server-8.4.1.jar:8.4.1]
    at com.vaadin.event.EventRouter.fireEvent(EventRouter.java:273) ~[vaadin-server-8.4.1.jar:8.4.1]
    at com.vaadin.event.EventRouter.fireEvent(EventRouter.java:237) ~[vaadin-server-8.4.1.jar:8.4.1]
    at com.vaadin.server.AbstractClientConnector.fireEvent(AbstractClientConnector.java:1014) ~[vaadin-server-8.4.1.jar:8.4.1]
    at com.vaadin.ui.Button.fireClick(Button.java:384) ~[vaadin-server-8.4.1.jar:8.4.1]
    at com.vaadin.ui.Button$1.click(Button.java:57) ~[vaadin-server-8.4.1.jar:8.4.1]
    at sun.reflect.GeneratedMethodAccessor308.invoke(Unknown Source) ~[na:na]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_171]
    at java.lang.reflect.Method.invoke(Unknown Source) ~[na:1.8.0_171]
    at com.vaadin.server.ServerRpcManager.applyInvocation(ServerRpcManager.java:155) ~[vaadin-server-8.4.1.jar:8.4.1]
    at com.vaadin.server.ServerRpcManager.applyInvocation(ServerRpcManager.java:116) ~[vaadin-server-8.4.1.jar:8.4.1]
    at com.vaadin.server.communication.ServerRpcHandler.handleInvocation(ServerRpcHandler.java:445) [vaadin-server-8.4.1.jar:8.4.1]
    at com.vaadin.server.communication.ServerRpcHandler.handleInvocations(ServerRpcHandler.java:410) [vaadin-server-8.4.1.jar:8.4.1]
    at com.vaadin.server.communication.ServerRpcHandler.handleRpc(ServerRpcHandler.java:274) [vaadin-server-8.4.1.jar:8.4.1]
    at com.vaadin.server.communication.UidlRequestHandler.synchronizedHandleRequest(UidlRequestHandler.java:90) [vaadin-server-8.4.1.jar:8.4.1]
    at com.vaadin.server.SynchronizedRequestHandler.handleRequest(SynchronizedRequestHandler.java:40) [vaadin-server-8.4.1.jar:8.4.1]
    at com.vaadin.server.VaadinService.handleRequest(VaadinService.java:1601) [vaadin-server-8.4.1.jar:8.4.1]
    at com.vaadin.server.VaadinServlet.service(VaadinServlet.java:445) [vaadin-server-8.4.1.jar:8.4.1]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) [tomcat-embed-websocket-8.5.31.jar:8.5.31]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) [spring-web-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109) [spring-web-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) [spring-web-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) [spring-web-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:496) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1468) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [na:1.8.0_171]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [na:1.8.0_171]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.31.jar:8.5.31]
    at java.lang.Thread.run(Unknown Source) [na:1.8.0_171]

@Component
public interface StudentRepo extends JpaRepository<Student, Long> {
}