Question

我在Spring Boot应用程序中更新实体时遇到此错误。

我有这两个对象

@Entity
public class User {
...
@ManyToMany
    @JoinColumn(name="locationId")
    @JsonIgnore
    private List<Location> locations;
...
//getters and setters
}

然后

 @Entity
    public class Coupon {

    .....
    @ManyToMany(cascade = {CascadeType.PERSIST, CascadeType.REMOVE, CascadeType.DETACH, CascadeType.REFRESH}, fetch = FetchType.LAZY)
        private List<Location> locations;
    ....
    //getters and setters
    }

在调度程序中，我需要与用户和优惠券进行交互

List<Location> locations = new ArrayList<>();
locations.addAll(user.getLocations());
Coupon coupon = couponService.generateCoupons(CouponType.TIME   , contract.getType().getTimeCredit(), locations, couponName);
    userService updateUser(user);

generateCoupons位于@Service和@Transactional类;

@Override
    public Coupon generateCoupons(CouponType type, int value, List<Location> locations, String couponName) {
        Coupon coupon = new Coupon();
        coupon.setActive(true);
        coupon.setCode(generateRandomCouponCode());
        coupon.setCouponCount(0);
        coupon.setCouponLimit(1);
        coupon.setCouponName(couponName);
        LocalDateTime limit = LocalDateTime.now().plusYears(1);
        coupon.setDateLimit(Date.from(limit.atZone(ZoneId.systemDefault()).toInstant()));
        coupon.setLocations(locations);
        coupon.setStartDate(new Date());
        coupon.setType(type);
        coupon.setUserLimit(1);
        coupon.setValue(value);

        return saveCoupon(coupon);
    }

当试图保留优惠券时我得到了异常，我不知道为什么，一切都发生在交易中......

这是完整的堆栈跟踪

aused by: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: it.besmart.eshare.persistence.model.User.locations, could not initialize proxy - no Session
    at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:587)
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:204)
    at org.hibernate.collection.internal.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:148)
    at org.hibernate.collection.internal.PersistentBag.size(PersistentBag.java:261)
    at org.hibernate.collection.internal.PersistentBag.addAll(PersistentBag.java:328)
    at it.besmart.eshare.service.CouponService.generateCoupons(CouponService.java:248)
    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:498)
    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:333)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
    at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:282)
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213)
    at com.sun.proxy.$Proxy171.generateCoupons(Unknown Source)
    at it.besmart.eshare.scheduler.cronjobs.CheckContract.executeInternal(CheckContract.java:102)
    at org.springframework.scheduling.quartz.QuartzJobBean.execute(QuartzJobBean.java:75)
    at org.quartz.core.JobRunShell.run(JobRunShell.java:202)
    ... 1 common frames omitted

Answer 1

先生，在这里你没有指定获取类型渴望。默认情况下，它是懒惰的提取。但是你试图热切地获取它。所以一个例外发生在这里。

         user. getLocation();//Failed to lazy initialize User. 
         // locations the Exception what we seen in console

只需像这样修改用户模型类

       @ManytoMany(fetch=FetchType.EAGER)
       @JoinColumn(name="locationId")
        @JsonIgnore
        private List<Location> locations;

Answer 2

默认情况下，会话管理配置设置为在提交事务时关闭会话。如果您要使用惰性实体，立即获取延迟实体是一种很好的做法。就像在这个JPQL查询中一样：

select User u from User join fetch u.locations

否则，获取用户然后获取位置应该包含在事务方法中。在你的情况下，hibernate尝试获取位置，但看到已经没有他附加的会话。你需要定义@Transaction方法将从你获得用户的地方开始，正如我在调度程序中所理解的那样。但要小心，最重要的是不要延迟事务的持续时间，因此对于纯数据处理，你应该创建一个单独的@Transactional方法。

Hibernate - 懒得初始化角色集合：无法初始化代理 - 没有会话

2 个答案: