Question

我正在使用Hibernate 4.1.0.Final，JPA 2.0和MySQL 5.5。我有以下实体：

@GenericGenerator(name = "uuid-strategy", strategy = "uuid.hex")
@Entity
@Table(name = "cb_organization", uniqueConstraints = {@UniqueConstraint(columnNames={"organization_id"})})
public class Organization implements Serializable
{

    …

    @OneToMany(fetch = FetchType.EAGER, cascade = {CascadeType.PERSIST, CascadeType.MERGE})
    @JoinTable(name = "cb_organization_address",
              joinColumns = @JoinColumn(name = "organization_id"),
              inverseJoinColumns = @JoinColumn(name = "address_id"))
    /* List of addresses associated with this organization */
    private List<Address> addresses;

注意连接表“cb_organization_address”。它的主键是varchar（32）not null字段，我想成为GUID，类似于组织实体的ID。如何为此表自动生成ID？当我尝试使用地址保存组织时，我得到例外......

javax.persistence.PersistenceException: org.hibernate.exception.GenericJDBCException: Field 'ID' doesn't have a default value
    org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1361)
    org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1289)
    org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1295)
    org.hibernate.ejb.AbstractEntityManagerImpl.flush(AbstractEntityManagerImpl.java:976)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    java.lang.reflect.Method.invoke(Method.java:597)
    org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:240)
    $Proxy47.flush(Unknown Source)
    org.mainco.subco.organization.repo.OrganizationDaoImpl.save(OrganizationDaoImpl.java:63)
    org.mainco.subco.organization.service.OrganizationServiceImpl.save(OrganizationServiceImpl.java:64)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    java.lang.reflect.Method.invoke(Method.java:597)
    org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:318)
    org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
    org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:110)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
    org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202)
    $Proxy62.save(Unknown Source)
    org.mainco.subco.sbadmin.controllers.OrganizationController.save(OrganizationController.java:204)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    java.lang.reflect.Method.invoke(Method.java:597)
    org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:213)
    org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:126)
        org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:96)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:617)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:578)
    org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
    org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:789)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:754)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:847)

Answer 1

您不应自动为连接表生成ID。相反，您应该从cb_organization_address删除ID列。

连接表通常没有自己的ID，它们只代表两件事之间的关联。因此，关系本身的“身份”通常是两个相关事物的复合关键。对于您的用例，我会说这是正确的数据模型：每个组织可以有任何地址零次或一次，每个地址可以在任意数量的组织中。

Answer 2

您应该为连接表创建 id 类型，而不是 uuid 类型，而是类似于 bigserial （在 postgres 中）。这个解决方案对我有帮助。我认为连接表实体的 id 不应该像 uuid 那样困难。通常，这个 id 是隐藏的

如何为连接表自动生成GUID？

2 个答案: