Question

我有两个实体一个

@Entity    
public class Job {  

    @Id
    @GeneratedValue
    private Integer id;

    @Size(min = 5,max = 50, message = "Valid title is 5-50 chars")
    private String title;       

    @ManyToMany(cascade = {CascadeType.MERGE})
    @JoinTable(name = "jobs_categories",
                joinColumns = @JoinColumn(name = "jobs_id"),
                inverseJoinColumns = @JoinColumn(name = "categories_id"))
    private List<Category> categories;
    // omitting setters/getters
}

和其他

@Entity
public class Category {    

    @Id
    @GeneratedValue
    private Integer id;

    @Size(min = 5,max = 15, message = "Valid name is 5-15 chars")
    private String name;

    @ManyToMany(mappedBy = "categories", cascade = {CascadeType.MERGE}) 
    private List<Job> jobs; 
    // omitting setters/getters
    }

我想对这两个人实施 CRUD 操作，我用一些类别保存了一份工作

Job title - Fullstack JavaScript CSS3 / HTML5 / Developer
Categories - AngularJS, Backbone.js, CSS, CSS3, Graphic design, HTML, HTML5,
             JavaScript, MongoDB Node.js, twitter bootstrap, Web design.

然后，如果我想通过添加或删除上面保存的作业中的类别来更新作业，则永远不会更新（例如，添加/删除）类别。

用于更新Job我在JobService中有方法

@Service
public class JobService{

    @Autowired
    private JobRepository jobRepository;

    @Autowired
    private CategoryRepository categoryRepository;

    @Autowired
    private LocalContainerEntityManagerFactoryBean entityManagerFactory;

    private Session session;

    Logger logger = LoggerFactory.getLogger(JobService.class);      

    public void updateJobCategory(Job job) {                
    EntityManager entityManager = entityManagerFactory.getObject().createEntityManager();
    session= entityManager.unwrap(org.hibernate.Session.class);
    logger.info("got Job ID as  ==> " + String.valueOf(job.getId()));
    Job jobObj = (Job) session.get(Job.class, job.getId());
    jobObj.getCategories().clear();     
    logger.info("got Job ID as  ==> " + String.valueOf(jobObj.getId()));

    if (!job.getCategories().isEmpty()) {
        logger.info("got job.getCategories() as not Null");
        List<Category> categories = job.getCategories();
        for (Category category : categories) {              
            logger.info("Good job.getCategories() to update ==> " + category.getName());
        }
        logger.info("adding job.getCategories() to update ==> ");
        jobObj.setCategories(job.getCategories());      

    }else {
        logger.info("got job.getCategories() as Null");
    }
    session.update(jobObj); 

    }
    public void update(Job job) {
        jobRepository.update(job.getId(), job.getTitle());
        updateJobCategory(job);
    }
}

我得到了日志

logger.info("Got job.getCategories() to update" + category.getName());

我正在更新（新添加/旧删除）所有类别的列表，

Hibernate: update job set title=? where id=?
INFO : com.rhcloud.jobsnetwork.service.JobService - got Job ID as  ==> 1
Hibernate: select job0_.id as id1_1_0_, job0_.title as title7_1_0_ from job job0_ where job0_.id=?
Hibernate: select categories0_.jobs_id as jobs_id1_1_0_, categories0_.categories_id as categori2_2_0_, category1_.id as id1_0_1_, category1_.name as name2_0_1_ from jobs_categories categories0_ inner join category category1_ on categories0_.categories_id=category1_.id where categories0_.jobs_id=?
INFO : com.rhcloud.jobsnetwork.service.JobService - got Job ID as  ==> 1
INFO : com.rhcloud.jobsnetwork.service.JobService - got job.getCategories() as not Null
INFO : com.rhcloud.jobsnetwork.service.JobService - Good job.getCategories() to update ==> iOS App Dev
INFO : com.rhcloud.jobsnetwork.service.JobService - Good job.getCategories() to update ==> Android App Dev
INFO : com.rhcloud.jobsnetwork.service.JobService - adding job.getCategories() to update

但是当我看到Job的详细信息时，我会列出在创建job而不是更新的作业时添加的类别，我想它不会更新联结表jobs_categories中的类别id值。不知道更新与工作相关的类别？

更新

当我使用

时

public void persistJob(Job newJob) {
         em.persist(newJob);
       }

       public void saveJob(Job job) {
          em.merge(job);
       }
       public void persistCategory(Category newcat) {
         em.persist(newcat);
       }

每个方法没有@Transactional我得到了expception

javax.persistence.TransactionRequiredException: No transactional EntityManager available
    at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:275)
    at com.sun.proxy.$Proxy167.persist(Unknown Source)
    at com.rhcloud.jobsnetwork.service.JobService.persistJob(JobService.java:29)
    at com.rhcloud.jobsnetwork.service.JobService$$FastClassBySpringCGLIB$$53974ce3.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:649)
    at com.rhcloud.jobsnetwork.service.JobService$$EnhancerBySpringCGLIB$$c08e8d16.persistJob(<generated>)
    at com.rhcloud.jobsnetwork.controllers.JobController.addJobDetail(JobController.java:86)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:776)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:705)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:868)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:650)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:957)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:423)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1079)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:620)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:318)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)

添加@Transactional后，它可以摆脱上述异常，我使用

保存新作业

@RequestMapping(value = "/add-job", method = RequestMethod.POST)
    public String addJobDetail(@ModelAttribute("job") Job job) {            
        jobService.persistJob(job); 
        return "redirect:/";
    }

我让所有的事情都很完美，但当我在JobController中使用saveJob作为

时

@RequestMapping(value = "/updated", method = RequestMethod.POST)
    public String updateJob(@ModelAttribute("job") Job job) {           
        jobService.saveJob(job);
        return "redirect:/";
    }

在更新的作业中没有保存任何类别（之前没有添加任何更新的类别），在这种情况下有任何建议。

更新 - 2

根据您的建议，我将记录器添加到

 @Transactional
   public void saveJob(Job job) {
       logger.error("got job.getCategories() of " + job.getCategories().size());
      em.merge(job);         
   }

此时我在

处得到NullPointerException

 logger.error("got job.getCategories() of " + job.getCategories().size() + " size");

log / trace是

java.lang.NullPointerException
    at com.rhcloud.jobsnetwork.service.JobService.saveJob(JobService.java:37)
    at com.rhcloud.jobsnetwork.service.JobService$$FastClassBySpringCGLIB$$53974ce3.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:717)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
    at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:98)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:262)
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:95)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:653)
    at com.rhcloud.jobsnetwork.service.JobService$$EnhancerBySpringCGLIB$$41dc2ac2.saveJob(<generated>)
    at com.rhcloud.jobsnetwork.controllers.JobController.updateJob(JobController.java:109)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:776)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:705)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:868)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:650)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:957)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:423)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1079)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:620)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:318)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)

Answer 1

在您的情况下，您有两个实体，每个实体可以独立存在 - 类别没有工作就可以了，而且工作不能分配任何类别。 orphanRemoval用于OnetoMany或OneToOne，如果您想对不再从父实体引用的相关实体执行删除操作（想想组合），那就是'这里的情况。我相信你只想删除工作和特定类别（思考关联）之间的联系。

您的映射是正确的（双向很多，以Job作为关系所有者），我建议只做一些小修改：使用java.util.Set（通过删除连接表来提高性能，防止“无法获取多个包”例外）为您的集合和覆盖equals方法（使集合操作更容易）。

我们走了：

@Entity    
public class Job { 
@Id
@GeneratedValue
private Integer id;

private String title;

@ManyToMany(fetch=FetchType.EAGER,cascade = { CascadeType.MERGE })
@JoinTable(name = "jobs_categories", joinColumns = @JoinColumn(name = "jobs_id") , inverseJoinColumns = @JoinColumn(name = "categories_id") )
private Set<Category> categories = new HashSet<Category>();

和类别

@Entity
public class Category {

@Id
@GeneratedValue
private Integer id;

private String name;

@ManyToMany(mappedBy = "categories", cascade = { CascadeType.MERGE })
private List<Job> jobs;

@Override
public boolean equals(Object obj) {
    if (this == obj)
        return true;
    if (obj == null)
        return false;
    if (getClass() != obj.getClass())
        return false;
    Category other = (Category) obj;
    if (id == null) {
        if (other.id != null)
            return false;
    } else if (!id.equals(other.id))
        return false;
    return true;
}

更新功能中的一个问题是您在作业实体中覆盖对集合的引用。

jobObj.setCategories(job.getCategories());

您应该始终修改原始集合，永远不要分配新集合。

您还可以考虑从Merge中完全删除ManyToMany级联，因为它会使代码工作流程更易于理解 - 类别将单独管理，您只需将已保存的类别添加到新作业实例（但这只是一个建议，我们将使其工作，甚至与级联:)）。

现在有一些测试代码。我使用普通的JPA，而不是Spring存储库，以使其易于理解。

JobService（在您的情况下，它将被拆分为多个类，存储库..）：

public class JobService {

   @PersistenceContext
   EntityManager em;

   public void persistJob(Job newJob) {
     em.persist(newJob);
   }

   public Job getJob(Integer jobId) {
     return em.find(Job.class, jobId);
   }

   public void saveJob(Job job) {
      em.merge(job);
   }

   public void persistCategory(Category newcat) {
     em.persist(newcat);
   }

   public List<Category> getAllCategories() {
     return em.createQuery("from Category", Category.class).getResultList();
   }  
}

让我们测试一下：

Job job = new Job();
job.setTitle("Web developer");
Category catJS = new Category();
catJS.setName("javascript");
Category catCSS = new Category();
catCSS.setName("CSS");
Category catNG = new Category();
catNG.setName("AngualrJS");
Category catHTML = new Category();
catHTML.setName("HTML5");
//persist categories separately
jobservice.persistCategory(catNG);
jobservice.persistCategory(catCSS);
jobservice.persistCategory(catHTML);
jobservice.persistCategory(catJS);
//at this point, we have 4 categories as managed entities
//add the saved categories to a new job instance
job.getCategories().add(catHTML);
job.getCategories().add(catJS);

//save job in DB
jobservice.persistJob(job);
//we do not need to set Job references in Category objects, because Job is the relationship owner - it will correctly update the FKs in join table
assertNotNull("job should be saved", job.getId());
Job fromDb = jobservice.getJob(job.getId());//reload from DB
assertNotNull("job should be stored in DB", fromDb);
assertTrue("job should have 2 categories", fromDb.getCategories().size() == 2);
//great si far so good  

//remove one of the assigned categories from Job(this is where you need that **equals** method in Category )
fromDb.getCategories().remove(catHTML);
assertTrue("job should not have only one category in Memory", fromDb.getCategories().size() ==1);
jobservice.saveJob(fromDb);
//we do not want to delete the *HTML* category from DB, just remove it from the particular job
Job fromDbAfterUpdate = jobservice.getJob(job.getId());
assertTrue("job should not have only one category in BD", fromDbAfterUpdate.getCategories().size() ==1);
List<Category> allCategories = jobservice.getAllCategories();
assertTrue("there should still be 4 categories in DB", allCategories.size() == 4);


//now lets test the Merge cascade
Category unsavedCategory = new Category();
unsavedCategory.setName("jquery");
fromDbAfterUpdate.getCategories().add(unsavedCategory );
//we have added an unsaved category to an  existing job. As Job has cascade merge on it categories, the *unsavedCategory* will be saved and then linked to job via job_category join table
jobservice.saveJob(fromDbAfterUpdate);
fromDbAfterUpdate = jobservice.getJob(fromDbAfterUpdate.getId());
assertTrue("job should now have 2 categories", fromDbAfterUpdate.getCategories().size() ==2);


// one more test, add and remove at the same time
fromDbAfterUpdate.getCategories().remove(catJS);
fromDbAfterUpdate.getCategories().add(catHTML);
fromDbAfterUpdate.getCategories().add(catCSS);
jobservice.saveJob(fromDbAfterUpdate);
fromDbAfterUpdate = jobservice.getJob(fromDbAfterUpdate.getId());
assertTrue("job should now have 3 categories", fromDbAfterUpdate.getCategories().size() ==3);
allCategories = jobservice.getAllCategories();
assertTrue("there should be 5 categories in DB", allCategories.size() == 5);

TL; DR

保持您的更新方法简单 - 您不需要从DB获取对象并在托管和分离对象之间移动东西，让JPA合并做它的事情
永远不要更改对托管实体集合的引用 - 直接在集合上执行操作
忽略任何级联，直到你确实需要它们

有关详细信息，请参阅JPA Spec

Answer 2

您的映射错误。试试这个：

@Entity
public class Category {    

@Id
@GeneratedValue
private Integer id;

@Size(min = 5,max = 15, message = "Valid name is 5-15 chars")
private String name;

@ManyToMany(cascade = CascadeType.ALL,orphanRemoval = true) 
@JoinColumn(name = "jobs_id",referencedColumnName = "jobs_id")
private List<Job> jobs; 
// omitting setters/getters
}

和第二个实体：

@Entity    
public class Job {  

@Id
@GeneratedValue
private Integer id;

@Size(min = 5,max = 50, message = "Valid title is 5-50 chars")
private String title;       

@ManyToMany(cascade = CascadeType.ALL,orphanRemoval = true)
@JoinColumn(name = "categories_id",referencedColumnName = "categories_id")
private List<Category> categories;
// omitting setters/getters
}

P.S。按表格编辑列名;

更新联结表中的值是麻烦的弹簧数据JPA

更新 - 2

2 个答案: