java - Spring Hibernate getEntity 无法转换为类

Question

我有以下问题:

在我的带有 Hibernate 的 Java Spring Boot 应用程序中，我有 Service 实现类。它看起来像这样:

package eu.barz.familykurse.services;

import eu.barz.familykurse.domain.Course;
import eu.barz.familykurse.domain.Leader;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.query.Query;
import org.springframework.stereotype.Service;
import java.util.List;


@Service
public class CourseServiceImpl implements CourseService {

    private SessionFactory factory = new Configuration().configure().addAnnotatedClass(Course.class).addAnnotatedClass(Leader.class).buildSessionFactory();

    public CourseServiceImpl(){

    }



    @Override
    public Course getCourse(int id) {
        Session session = factory.getCurrentSession();
        session.beginTransaction();
        Course c = session.get(Course.class, id);
        session.getTransaction().commit();
        return c;
        //return courseMap.get(id);
    }


    @Override
    public List<Course> listCourses() {
        Session session = factory.getCurrentSession();
        session.beginTransaction();
        Query<Course> theQuery = session.createQuery("from Course", Course.class);

        List<Course> courses = theQuery.getResultList();
        session.getTransaction().commit();
        return courses;


    }

}

listCourse 方法工作正常，但使用 getCourse(int id) 时出现以下问题:

2017-08-26 10:56:08.103 ERROR 80687 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.ClassCastException: eu.barz.familykurse.domain.Course cannot be cast to eu.barz.familykurse.domain.Course] with root cause

java.lang.ClassCastException: eu.barz.familykurse.domain.Course cannot be cast to eu.barz.familykurse.domain.Course
    at eu.barz.familykurse.services.CourseServiceImpl.getCourse(CourseServiceImpl.java:28) ~[classes/:na]
    at eu.barz.familykurse.controller.CourseController.returnCourseById(CourseController.java:30) ~[classes/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_131]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_131]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_131]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_131]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) ~[spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133) ~[spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97) ~[spring-webmvc-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827) ~[spring-webmvc-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738) ~[spring-webmvc-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) ~[spring-webmvc-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967) ~[spring-webmvc-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901) ~[spring-webmvc-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) ~[spring-webmvc-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) ~[spring-webmvc-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:635) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) ~[spring-webmvc-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) ~[tomcat-embed-websocket-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:105) ~[spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81) ~[spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) ~[spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:799) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1455) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_131]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_131]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.16.jar:8.5.16]
    at java.lang.Thread.run(Thread.java:748) [na:1.8.0_131]

我不明白为什么

eu.barz.familykurse.domain.Course 无法转换为 eu.barz.familykurse.domain.Course

应该是错的吧？

在 Course.java 中，它看起来像这样:

package eu.barz.familykurse.domain;

import javax.persistence.*;

@Entity
@Table(name="course")
public class Course {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="id", unique=true, nullable=false)
    private Integer id;

    @Column(name="name")
    private String courseName;

    @Column(name="description_long")
    private String courseDescription;

    @Column(name="description_short")
    private String courseDescriptionShort;


    @OneToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "LEADER_ID")
    private Leader leader;

    @Column(name="city")
    private String city;

    @Column(name="plz")
    private Integer plz;

    @Column(name="street")
    private String street;

    @Column(name="number")
    private String number;

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public Integer getPlz() {
        return plz;
    }

    public void setPlz(Integer plz) {
        this.plz = plz;
    }

    public String getStreet() {
        return street;
    }

    public void setStreet(String street) {
        this.street = street;
    }

    public String getNumber() {
        return number;
    }

    public void setNumber(String number) {
        this.number = number;
    }

    public Leader getLeader() {
        return leader;
    }

    public void setLeader(Leader leader){
        this.leader = leader;
    }




    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getCourseName() {
        return courseName;
    }

    public void setCourseName(String courseName) {
        this.courseName = courseName;
    }

    public String getCourseDescription() {
        return courseDescription;
    }

    public void setCourseDescription(String courseDescription) {
        this.courseDescription = courseDescription;
    }

    public String getCourseDescriptionShort() {
        return courseDescriptionShort;
    }

    public void setCourseDescriptionShort(String courseDescriptionShort) {
        this.courseDescriptionShort = courseDescriptionShort;
    }

    public String getLink(){

        return ("/course/" + courseName.replaceAll(" ", "-") + "-" + id);
    }
}

pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>eu.barz</groupId>
    <artifactId>baby-kurse</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>baby-kurse</name>
    <description>Webseite für Babykurse</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.6.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>commons-pool</groupId>
            <artifactId>commons-pool</artifactId>
            <version>1.4</version>
            <!-- <version>1.5.6</version> -->
        </dependency>
<!--        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-orm</artifactId>
            <version>4.3.10.RELEASE</version>
        </dependency>
-->
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>


</project>

Answer 1

使用此问题 Spring Boot / Thymeleaf / Hibernate: Sessionfactory Bean with Java Annotations 中的信息我这里也可以解决这个问题。看起来像是一些链式问题。