spring JPA - 如何从加入的 table 中读取？

Question

我正在尝试在 spring-boot 中使用具有复合键的 table。
（在我的例子中是整数和整数）

我用这个答案来了解如何使用复合键将写入table：

但我无法理解如何从中读取。

因为 CrudRepository 的函数 "findOne()" 只能获取一个参数（在我的例子中是 Integer），但是 EntityManager 会抛出一个异常，因为它希望得到一个 "Composite-Key-Bean"（比如 "TimePK" 在上面的答案中）而不是整数。

我所要求的实体：

CustomersCouponsPK.class :

package beans;

import java.io.Serializable;

import javax.persistence.Embeddable;

@Embeddable
public class CustomersCuoponsPK implements Serializable {

 private Integer cust_id;
 private Integer coupon_id;

 public CustomersCuoponsPK() {
 }
 
 public CustomersCuoponsPK(int cust_id, int coupon_id) {
  super();
  this.cust_id = cust_id;
  this.coupon_id = coupon_id;
 }

 public int getCust_id() {
  return cust_id;
 }

 public void setCust_id(int cust_id) {
  this.cust_id = cust_id;
 }

 public int getCoupon_id() {
  return coupon_id;
 }

 public void setCoupon_id(int coupon_id) {
  this.coupon_id = coupon_id;
 }

 @Override
 public int hashCode() {
  final int prime = 31;
  int result = 1;
  result = prime * result + ((coupon_id == null) ? 0 : coupon_id.hashCode());
  result = prime * result + ((cust_id == null) ? 0 : cust_id.hashCode());
  return result;
 }

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

}

CustomersCoupons.class:

package beans;

import javax.persistence.EmbeddedId;
import javax.persistence.Entity;

@Entity
public class CustomersCoupons {

 @EmbeddedId
 private CustomersCuoponsPK customersCuoponsPK;

 public CustomersCoupons() {

 }

 public CustomersCoupons(CustomersCuoponsPK customersCuoponsPK) {
  super();
  this.customersCuoponsPK = customersCuoponsPK;
 }

 public CustomersCuoponsPK getCustomersCuoponsPK() {
  return customersCuoponsPK;
 }

 public void setCustomersCuoponsPK(CustomersCuoponsPK customersCuoponsPK) {
  this.customersCuoponsPK = customersCuoponsPK;
 }

}

CustomersCouponsRepo：

package repos;

import org.springframework.data.jpa.repository.JpaRepository;

import beans.CustomersCoupons;
import beans.CustomersCuoponsPK;

public interface CustomersCouponsRepo extends JpaRepository<CustomersCoupons, Integer> {

 public default CustomersCoupons findOne(int cust_id, int coupon_id){
  if(this.getOne(cust_id).equals(this.getOne(coupon_id))){
   CustomersCuoponsPK pk = new CustomersCuoponsPK();
   pk.setCoupon_id(coupon_id);
   pk.setCust_id(cust_id);
   CustomersCoupons cc = new CustomersCoupons();
   cc.setCustomersCuoponsPK(pk);
   return cc;
  }
  return null;
 }

}

CustomerCouponsDAO：

package DAOs;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;

import beans.CustomersCoupons;
import beans.CustomersCuoponsPK;
import repos.CustomersCouponsRepo;

@Repository
public class CustomersCouponsDAO {

 @Autowired
 private CustomersCouponsRepo repo;

 public void createCustomerCoupon(int cust_id, int coupon_id) {
  CustomersCoupons customersCoupons = new CustomersCoupons(new CustomersCuoponsPK(cust_id, coupon_id));
  repo.save(customersCoupons);
 }

 public List<CustomersCoupons> getAllCustomersCoupons() {
  return (List<CustomersCoupons>) repo.findAll();
 }

 public CustomersCoupons readCustomersCoupons(int cust_id, int coupon_id) {
  return repo.findOne(cust_id, coupon_id);
 }

 public void updateCustomersCoupons(CustomersCoupons customersCoupons) {
  repo.save(customersCoupons);
 }

 public void deleteC(int cust_id, int coupon_id) {
 }
}

异常：

Exception in thread "main" org.springframework.dao.InvalidDataAccessApiUsageException: Provided id of the wrong type for class beans.CustomersCoupons. Expected: class beans.CustomersCuoponsPK, got class java.lang.Integer; nested exception is java.lang.IllegalArgumentException: Provided id of the wrong type for class beans.CustomersCoupons. Expected: class beans.CustomersCuoponsPK, got class java.lang.Integer
 at org.springframework.orm.jpa.EntityManagerFactoryUtils.convertJpaAccessExceptionIfPossible(EntityManagerFactoryUtils.java:384)
 at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:246)
 at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(AbstractEntityManagerFactoryBean.java:488)
 at org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:59)
 at org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:213)
 at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:147)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
 at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:133)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
 at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
 at org.springframework.data.repository.core.support.SurroundingTransactionDetectorMethodInterceptor.invoke(SurroundingTransactionDetectorMethodInterceptor.java:57)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
 at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213)
 at com.sun.proxy.$Proxy76.getOne(Unknown Source)
 at repos.CustomersCouponsRepo.findOne(CustomersCouponsRepo.java:11)
 at java.lang.invoke.MethodHandle.invokeWithArguments(Unknown Source)
 at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:62)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
 at org.springframework.transaction.interceptor.TransactionInterceptor.proceedWithInvocation(TransactionInterceptor.java:99)
 at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:282)
 at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
 at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:136)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
 at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:133)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
 at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
 at org.springframework.data.repository.core.support.SurroundingTransactionDetectorMethodInterceptor.invoke(SurroundingTransactionDetectorMethodInterceptor.java:57)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
 at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213)
 at com.sun.proxy.$Proxy76.findOne(Unknown Source)
 at DAOs.CustomersCouponsDAO.readCustomersCoupons(CustomersCouponsDAO.java:28)
 at DAOs.CustomersCouponsDAO$$FastClassBySpringCGLIB$$d50d5f2d.invoke(<generated>)
 at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
 at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:738)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
 at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:136)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
 at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:673)
 at DAOs.CustomersCouponsDAO$$EnhancerBySpringCGLIB$07e960.readCustomersCoupons(<generated>)
 at com.example.CouponSystem.CouponSystemApplication.main(CouponSystemApplication.java:35)
Caused by: java.lang.IllegalArgumentException: Provided id of the wrong type for class beans.CustomersCoupons. Expected: class beans.CustomersCuoponsPK, got class java.lang.Integer
 at org.hibernate.jpa.spi.AbstractEntityManagerImpl.getReference(AbstractEntityManagerImpl.java:1019)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
 at java.lang.reflect.Method.invoke(Unknown Source)
 at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:298)
 at com.sun.proxy.$Proxy69.getReference(Unknown Source)
 at org.springframework.data.jpa.repository.support.SimpleJpaRepository.getOne(SimpleJpaRepository.java:278)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
 at java.lang.reflect.Method.invoke(Unknown Source)
 at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.executeMethodOn(RepositoryFactorySupport.java:504)
 at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:489)
 at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:461)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
 at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:56)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
 at org.springframework.transaction.interceptor.TransactionInterceptor.proceedWithInvocation(TransactionInterceptor.java:99)
 at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:282)
 at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
 at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:136)
 ... 37 more
Caused by: org.hibernate.TypeMismatchException: Provided id of the wrong type for class beans.CustomersCoupons. Expected: class beans.CustomersCuoponsPK, got class java.lang.Integer
 at org.hibernate.event.internal.DefaultLoadEventListener.checkIdClass(DefaultLoadEventListener.java:166)
 at org.hibernate.event.internal.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:86)
 at org.hibernate.internal.SessionImpl.fireLoad(SessionImpl.java:1129)
 at org.hibernate.internal.SessionImpl.access00(SessionImpl.java:164)
 at org.hibernate.internal.SessionImpl$IdentifierLoadAccessImpl.getReference(SessionImpl.java:2669)
 at org.hibernate.internal.SessionImpl.load(SessionImpl.java:965)
 at org.hibernate.jpa.spi.AbstractEntityManagerImpl.getReference(AbstractEntityManagerImpl.java:1013)
 ... 59 more

Answer 1

您实体的 ID 类型为 CustomerCuoponsPK。所以你的 repo 应该实现 JpaRepository，而不是 JpaRepository。这正是异常的错误消息告诉您的内容。根据以下更改实现。

package repos;

import org.springframework.data.jpa.repository.JpaRepository;

import beans.CustomersCoupons;
import beans.CustomersCuoponsPK;

public interface CustomersCouponsRepo extends JpaRepository<CustomersCoupons, CustomersCuoponsPK> {

 public default CustomersCoupons findOne(CustomersCuoponsPK pk){
  return findOne(pk);
 }

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