Hibernate 无法延迟初始化集合答案

【问题标题】：Hibernate failed to lazily initialize a collectionHibernate 无法延迟初始化集合
【发布时间】：2020-05-23 18:49:06
【问题描述】：

我在 Spring Boot 中设置了两个数据源。在控制器中，我想在两者上都保留几个父子实体。它们几乎是相同的双向关系，但第一个有效，而第二个发出提交消息但实际上并没有持久化子实体。来自工作数据源的实体

@Entity
public class Brand {

private Integer id;

private Set<Line> lines = new HashSet<Line>(); 

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@JsonIgnore
public Integer getId() {
    return id;
}

@JsonIgnore
@OneToMany(mappedBy = "brand", cascade = CascadeType.ALL, orphanRemoval = true)
public Set<Line> getLines() {
    return lines;
}

@Entity
public class Line {

private Integer id;

private Brand brand;

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
public Integer getId() {
    return id;
}

@ManyToOne
@JoinColumn(name = "brand")
public Brand getBrand() {
    return brand;
}

虽然这些来自第二个数据源，但它保留了父级而不是子级

@Entity
public class User {

private String id;

private List<UserCommit> userCommitList = new ArrayList<UserCommit>();

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
public Integer getId() {
    return id;
}
}

@OneToMany(mappedBy = "user", cascade = CascadeType.ALL, orphanRemoval = true)
public List<UserCommit> getUserCommitList() {
    return userCommitList;
}

@Entity
public class UserCommit {

private Integer id;

private User user;

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
public Integer getId() {
    return id;
}

@ManyToOne
@JoinColumn(name = "user")
public User getUser() {
    return user;
}

这是控制器的有趣部分

    Brand brand = brandService.createFrom(fsDto.getBrand());
    Line line = lineService.createFrom(fsDto.getLine(), brand);
    AccessToken accToken = token.getAccount().getKeycloakSecurityContext().getToken();

    try {

        prodService.updateFrom(id, line, fsDto);

        User user = userService.createFrom(accToken);
        ucService.createFrom(user, id, "EDIT", "FIRST");

这些是服务方法

public Brand createFrom(String name) {

    Brand foundBrand = findByName(name);
    Brand brand = new Brand();
    if (foundBrand == null) {
        brand = brandRepo.save(brand);
        brand.setName(name);
    } else
        brand = foundBrand;

    return brand;

public Line createFrom(String name, Brand brand) {

    Line foundLine = findByNameAndBrand(name, brand);
    Line line = new Line();
    if (foundLine == null) {
        line.setName(name);
        line.setBrand(brand);
        line.getBrand().addLine(line);

    } else
        line = foundLine;

    return line;
}

public User createFrom(AccessToken accToken) {

    User user = findByKcId(accToken.getSubject());

    if(user == null) {
        user = new User();
        user.setKcId(accToken.getSubject());
        user.setName(accToken.getPreferredUsername());
        userRepo.save(user);
    }

    return user;

}

public UserCommit createFrom(User user, Integer prodId, String ucType, String stage) {

    UserCommit uc = new UserCommit();
    uc.setUser(user);
    uc.getUser().addUserCommit(uc);
    uc.setProdId(prodId);
    uc.setUCType(UserCommit.UCType.valueOf(ucType));
    uc.setStage(UserCommit.Stage.valueOf(stage));
    uc.setTime(LocalDateTime.now());

    return uc;
}

品牌持续存在。
线路保持不变。
用户被持久化。
UserCommit 不要被持久化。
如果我明确表示一切正常调用 UserCommitService.save()，但我认为不需要。

编辑我更新了我的代码以使两对事务更加相似，现在对于第二个事务，我在延迟初始化时遇到了这个经典错误。

org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: petmenu.entities.users.User.userCommitList, could not initialize proxy - no Session

真正让我抓狂的是 Brand→Line 有效，而 User→UserCommit 无效。即使跟踪 JPA，我也无法理解为什么 User 实体未包含在 UserCommit 提交时的会话中。

2020-05-26 16:51:54.258 DEBUG 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.s.orm.jpa.JpaTransactionManager        : Found thread-bound EntityManager [SessionImpl(1767213597<open>)] for JPA transaction
2020-05-26 16:51:54.258 DEBUG 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.s.orm.jpa.JpaTransactionManager        : Creating new transaction with name [petmenu.services.users.UserService.createFrom]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT
2020-05-26 16:51:54.259 DEBUG 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.s.orm.jpa.JpaTransactionManager        : Exposing JPA transaction as JDBC [org.springframework.orm.jpa.vendor.HibernateJpaDialect$HibernateConnectionHandle@41ca5759]
2020-05-26 16:52:01.687 DEBUG 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.s.orm.jpa.EntityManagerFactoryUtils    : Opening JPA EntityManager
2020-05-26 16:52:01.708 DEBUG 78269 --- [http-nio-192.168.1.10-8080-exec-2] org.hibernate.SQL                        : select user0_.id as id1_0_, user0_.kc_id as kc_id2_0_, user0_.name as name3_0_ from user user0_ where user0_.kc_id=?
2020-05-26 16:52:01.708 TRACE 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.h.type.descriptor.sql.BasicBinder      : binding parameter [1] as [VARCHAR] - [80a3b4b1-00d1-4062-a7e5-1927b938c203]
2020-05-26 16:52:01.709 TRACE 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.h.type.descriptor.sql.BasicExtractor   : extracted value ([id1_0_] : [INTEGER]) - [2005]
2020-05-26 16:52:01.709 TRACE 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.h.type.descriptor.sql.BasicExtractor   : extracted value ([kc_id2_0_] : [VARCHAR]) - [80a3b4b1-00d1-4062-a7e5-1927b938c203]
2020-05-26 16:52:01.709 TRACE 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.h.type.descriptor.sql.BasicExtractor   : extracted value ([name3_0_] : [VARCHAR]) - [user1]
2020-05-26 16:52:01.709 TRACE 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.s.orm.jpa.JpaTransactionManager        : Triggering beforeCommit synchronization
2020-05-26 16:52:01.709 TRACE 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.s.orm.jpa.JpaTransactionManager        : Triggering beforeCompletion synchronization
2020-05-26 16:52:01.709 DEBUG 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.s.orm.jpa.JpaTransactionManager        : Initiating transaction commit
2020-05-26 16:52:01.709 DEBUG 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.s.orm.jpa.JpaTransactionManager        : Committing JPA transaction on EntityManager [SessionImpl(1767213597<open>)]
2020-05-26 16:53:06.630 TRACE 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.s.orm.jpa.JpaTransactionManager        : Triggering afterCommit synchronization
2020-05-26 16:53:06.671 TRACE 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.s.orm.jpa.JpaTransactionManager        : Triggering afterCompletion synchronization
2020-05-26 16:53:06.671 DEBUG 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.s.orm.jpa.JpaTransactionManager        : Not closing pre-bound JPA EntityManager after transaction
2020-05-26 16:53:06.671 DEBUG 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.s.orm.jpa.JpaTransactionManager        : Found thread-bound EntityManager [SessionImpl(1767213597<open>)] for JPA transaction
2020-05-26 16:53:06.671 DEBUG 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.s.orm.jpa.JpaTransactionManager        : Creating new transaction with name [petmenu.services.users.UserCommitService.createFrom]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT
2020-05-26 16:53:06.671 DEBUG 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.s.orm.jpa.JpaTransactionManager        : Exposing JPA transaction as JDBC [org.springframework.orm.jpa.vendor.HibernateJpaDialect$HibernateConnectionHandle@323b85aa]
2020-05-26 16:53:17.438 TRACE 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.s.orm.jpa.JpaTransactionManager        : Triggering beforeCompletion synchronization
2020-05-26 16:53:17.472 DEBUG 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.s.orm.jpa.JpaTransactionManager        : Initiating transaction rollback
2020-05-26 16:53:17.472 DEBUG 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.s.orm.jpa.JpaTransactionManager        : Rolling back JPA transaction on EntityManager [SessionImpl(1767213597<open>)]
2020-05-26 16:53:17.472 TRACE 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.s.orm.jpa.JpaTransactionManager        : Triggering afterCompletion synchronization
2020-05-26 16:53:17.472 DEBUG 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.s.orm.jpa.JpaTransactionManager        : Not closing pre-bound JPA EntityManager after transaction
2020-05-26 16:53:17.473 DEBUG 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.j.s.OpenEntityManagerInViewInterceptor : Closing JPA EntityManager in OpenEntityManagerInViewInterceptor
2020-05-26 16:53:17.496 ERROR 78269 --- [http-nio-192.168.1.10-8080-exec-2] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: petmenu.entities.users.User.userCommitList, could not initialize proxy - no Session] with root cause

【问题讨论】：

从未与实体合作过，但看起来您保存用户而不是添加提交。用户 createFrom(AccessToken accToken) --> 保存用户 UserCommit createFrom --> 创建用户提交您是否尝试添加提交然后再次保存用户以查看是否是这种情况？
是的。我对 Brand 和 Line 做同样的事情，而且效果很好。

标签： hibernate spring-boot jpa persistence mariadb-10.3

【解决方案1】：

我研究了很多关于事务管理等的东西，我（希望）找到了罪魁祸首。 但谢天谢地，每个更正都被接受了。

LSS

似乎 Spring Boot 注册 OpenEntityManagerInViewInterceptor 只是用于主要数据源（我在网上找到了一些关于此的信息，但在官方文档中没有找到）。

TL:DR

将会话绑定到整个视图并加载热切管理实体的集合，当运行LineService.createFrom Brand 的集合时已经持久化，然后新添加的 Line 在事务结束时被刷新。在没有视图会话的对应对象上，我在 UserCommitService.createFrom 事务中没有托管集合，然后在没有显式调用 UserCommitRepo.save 的情况下，UserCommit 将保持暂时状态，并且将在事务提交时从刷新中静默丢弃。

我不知道我是否正确理解了所有内容，如果是这样，我希望有人解释CascadeType.PERSIST（包含在CascadeType.ALL 中）在双向的@OneToMany 一侧的意义何在关系。

【讨论】：