使用Spring CrudRepository进行Hibernate LazyInitializationException

问题描述

我总是得到异常：

  org.hibernate.LazyInitializationException：未能懒惰地初始化一个角色集合：com。 knapp.vk.domain.Business.businessCategorySet，无法初始化代理 - 无会话
  

我不能想要设置获取渴望。什么是其他好的解决方案？

业务实体类：

  @Entity 
 public class Business 
 {
 @Id 
 @GeneratedValue 
 private int pk; 
 
 @ManyToMany 
私人套餐< BusinessCategory> businessCategorySet = new HashSet< BusinessCategory>（）; 
 
 
} 
  

BusinessRepository接口： p>

  import org.springframework.data.repository.CrudRepository; 
 import org.springframework.transaction.annotation.Transactional; 
 
 @Transactional 
 public interface BusinessRepository扩展CrudRepository< Business，Integer> 
 {
 
} 
  

配置：

  import javax.persistence.EntityManager; 
 import javax.persistence.EntityManagerFactory; 
 import javax.persistence.Persistence; 
 
 import org.springframework.context.annotation.Bean; 
 import org.springframework.context.annotation.Configuration; 
 import org.springframework.data.jpa.repository.config.EnableJpaRepositories; 
 import org.springframework.orm.hibernate4.HibernateExceptionTranslator; 
 import org.springframework.orm.jpa.JpaTransactionManager; 
 import org.springframework.transaction.PlatformTransactionManager; 
 import org.springframework.transaction.annotation.EnableTransactionManagement; 
 
 @Configuration 
 @EnableJpaRepositories（basePackages =com.knapp.vk.repositorynew）
 @EnableTransactionManagement 
 public class JPAConfiguration 
 {
 @Bean 
 public EntityManagerFactory entityManagerFactory（）抛出SQLException 
 {
返回Persistence.createEntityManagerFactory（standardManager）; 
 
 $ b $Bean 
 public EntManagerManager entityManager（EntityManagerFactory entityManagerFactory）
 {
 return entityManagerFactory.createEntityManager（）; 
 
 $ b @Bean 
 public PlatformTransactionManager transactionManager（）throws SQLException 
 {
 JpaTransactionManager txManager = new JpaTransactionManager（）; 
 txManager.setEntityManagerFactory（entityManagerFactory（））; 
返回txManager; 
 
 
 @Bean 
 public HibernateExceptionTranslator hibernateExceptionTranslator（）
 {
 return new HibernateExceptionTranslator（）; 
 
 
 $ / code $ / pre 
 
解决方案
您可以通过在Service中初始化businessCategoruSet来完成此操作，而不是在存储库中使用 @Transactional 在服务中使用它。 
让我们写一些方法，比如通过id或业务列表在仓库中获取业务，并从服务中访问该方法。
  @Transactional 
 public Class BusinessService {
 
 @resource 
 BusinessRepository businessRepository; 
 
 public Business getBusiness（）{
 Business business = businessRepository.getBusiness（）; 
 //这里您应该初始化BusinessCategorySet 
 Object object = business.getBusinessCategoriesSet（）。size（）; 
 
 
  
有关的详细信息@交易  
 
I always get the exception: 
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.knapp.vk.domain.Business.businessCategorySet, could not initialize proxy - no Session
I don´t want to set fetch to eager. What would be other good solutions?
Business Entity class:
@Entity
public class Business
{
    @Id
    @GeneratedValue
    private int pk;

    @ManyToMany
    private Set<BusinessCategory> businessCategorySet = new HashSet<BusinessCategory>();

...
}
BusinessRepository interface:
import org.springframework.data.repository.CrudRepository;
import org.springframework.transaction.annotation.Transactional;

@Transactional
public interface BusinessRepository extends CrudRepository<Business, Integer>
{

}
Config:
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.orm.hibernate4.HibernateExceptionTranslator;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;

@Configuration
@EnableJpaRepositories(basePackages = "com.knapp.vk.repositorynew")
@EnableTransactionManagement
public class JPAConfiguration
{
    @Bean
    public EntityManagerFactory entityManagerFactory() throws SQLException
    {
        return Persistence.createEntityManagerFactory("standardManager");
    }

    @Bean
    public EntityManager entityManager(EntityManagerFactory entityManagerFactory)
    {
        return entityManagerFactory.createEntityManager();
    }

    @Bean
    public PlatformTransactionManager transactionManager() throws SQLException
    {
        JpaTransactionManager txManager = new JpaTransactionManager();
        txManager.setEntityManagerFactory(entityManagerFactory());
        return txManager;
    }

    @Bean
    public HibernateExceptionTranslator hibernateExceptionTranslator()
    {
        return new HibernateExceptionTranslator();
    }
}
 解决方案 
So you can do it by initializing businessCategoruSet in Service so instead of using @Transactional in Repository use it in Service.Let write some method like get business by id or list of business in repository and access that method from service.
@Transactional
public Class BusinessService{

@resource
BusinessRepository businessRepository;

public Business getBusiness(){
  Business business = businessRepository.getBusiness();
  //Here you should initialize BusinessCategorySet
  Object object = business.getBusinessCategoriesSet().size();
  }
}
For more details about @Transactional Refer this link
                        
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