Spring Boot数据插入包含已持久化到数据库的数据的行

Question

我正在使用Hibernate/JPA完成我的第一个Spring Boot应用程序。我已经创建了两个@Entity，带有@ManyToMore映射：Team和Game。

目前，数据库有一个包含团队的表，我想插入一个游戏，它引用两个团队。

问题是我得到了错误：

`org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataLoader': Invocation of init method failed; nested exception is org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.example.data.entities.FootballTeam.homeGames, could not initialize proxy - no Session
    at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor.postProcessBeforeInitialization(InitDestroyAnnotationBeanPostProcessor.java:136) ~[spring-beans-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInitialization(AbstractAutowireCapableBeanFactory.java:408) ~[spring-beans-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1570) ~[spring-beans-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:545) ~[spring-beans-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482) ~[spring-beans-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:772) ~[spring-beans-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:838) ~[spring-context-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:537) ~[spring-context-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:118) ~[spring-boot-1.3.0.RELEASE.jar:1.3.0.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:752) [spring-boot-1.3.0.RELEASE.jar:1.3.0.RELEASE]
    at org.springframework.boot.SpringApplication.doRun(SpringApplication.java:347) [spring-boot-1.3.0.RELEASE.jar:1.3.0.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:295) [spring-boot-1.3.0.RELEASE.jar:1.3.0.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1112) [spring-boot-1.3.0.RELEASE.jar:1.3.0.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1101) [spring-boot-1.3.0.RELEASE.jar:1.3.0.RELEASE]
    at com.example.FootballPoolSpringSpringBoot.main(FootballPoolSpringSpringBoot.java:11) [classes/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_65]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_65]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_65]
    at java.lang.reflect.Method.invoke(Method.java:497) ~[na:1.8.0_65]
    at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) [spring-boot-devtools-1.3.0.RELEASE.jar:1.3.0.RELEASE]
Caused by: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.example.data.entities.FootballTeam.homeGames, could not initialize proxy - no Session
    at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:576) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:215) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:555) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.write(AbstractPersistentCollection.java:400) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at org.hibernate.collection.internal.PersistentBag.add(PersistentBag.java:314) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
    at com.example.service.DataLoader.loadData(DataLoader.java:106) ~[classes/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_65]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_65]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_65]
    at java.lang.reflect.Method.invoke(Method.java:497) ~[na:1.8.0_65]
    at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleElement.invoke(InitDestroyAnnotationBeanPostProcessor.java:354) ~[spring-beans-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleMetadata.invokeInitMethods(InitDestroyAnnotationBeanPostProcessor.java:305) ~[spring-beans-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor.postProcessBeforeInitialization(InitDestroyAnnotationBeanPostProcessor.java:133) ~[spring-beans-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    ... 23 common frames omitted`. 

我做错了什么？

@Entity
public class FootballTeam {

private FootballTeam(){/**/}

public FootballTeam(String teamName) {
    this.teamName = teamName;
}



@Id
@GeneratedValue
private Long teamId;

@Column(name = "team_name", unique = true)
private String teamName;

@Column(name = "short_name", unique = true)
private String teamShortName;

private String teamLeague;
private String teamDivision;

@Embedded
private Location teamLocation;

@ManyToMany(cascade = CascadeType.ALL, mappedBy = "favoriteTeams")
private List<Users> fans = new ArrayList<>();

@OneToMany(mappedBy = "homeTeam")
List<FootballGame> homeGames = new ArrayList<>();

@OneToMany(mappedBy = "visitingTeam")
List<FootballGame> awayGames = new ArrayList<>();

/* getters and setters omitted for brevity */
}

Game.java

@Entity
@Table(name = "football_game",
    uniqueConstraints= @UniqueConstraint(
            columnNames={"played_on", "home_team", "visiting_team"}))
public class FootballGame {

private FootballGame(){/**/}

public FootballGame(Date playedOn, FootballTeam homeTeam, FootballTeam visitingTeam) {
    this.homeTeam = homeTeam;
    this.playedOn = playedOn;
    this.visitingTeam = visitingTeam;
}

@Id
@GeneratedValue
private Long gameId;

@Column(name = "played_on", nullable = false)
private Date playedOn;

@ManyToOne(cascade = CascadeType.MERGE)
@JoinColumn(name = "home_team", nullable = false)
private FootballTeam homeTeam;

@ManyToOne(cascade = CascadeType.MERGE)
@JoinColumn(name = "visiting_team", nullable = false)
private FootballTeam visitingTeam;

private int homeTeamScore;
private int visitingTeamScore;

@OneToOne(mappedBy = "footballGame")
private FootballPool footballPool;

/* getters and setters omitted for brevity */
}

数据oader.class

  @Service
public class DataLoader {

    private FootballTeamRepository teamRepository;
    private FootballGameRepository gameRepository;

    @Autowired
    public DataLoader(FootballGameRepository gameRepository,
                      FootballTeamRepository teamRepository) {
        this.gameRepository = gameRepository;
        this.teamRepository = teamRepository;
}

@PostConstruct
private void loadData(){
    FootballTeam f4 = new FootballTeam("lil Shin-Kickers");
    f4.setTeamLocation(new Location("California"));
    teamRepository.save(f4);

    FootballTeam f1 = new FootballTeam("Tumble Tots");
    f1.setTeamLocation(new Location("Colorado"));
    teamRepository.save(f1);

    FootballTeam homeTeam = teamRepository.findTeamByTeamNameIgnoreCase("lil Shin-Kickers");

    System.out.println(homeTeam.getTeamName());
    FootballTeam visitingTeam = teamRepository.findTeamByTeamNameIgnoreCase("Tumble Tots");

    FootballGame footballGame = new FootballGame(new Date(), homeTeam, visitingTeam);
    footballGame.setHomeTeamScore(7);
    footballGame.setVisitingTeamScore(21);

    gameRepository.save(footballGame);

}

Answer 1

因此，如果您得到“分离实体错误”，这意味着您的子对象没有任何要跟踪的标志。所以，只要你保存，它就会把孩子当作新的对象。所以只需将“版本”字段放在带有注释@version的实体上，并将版本字段放在相关表中。另外，在保存新的子对象时，请确保在子对象上设置父对象。

Answer 2

在JPA多对多关系中，如果在CascadeType中设置了级联类型。Persist（或CascadeType.ALL，其中包括CascadeType。PERSIST），然后在保存父级并用子级的引用更新它的同时，它将再次尝试保存子级。

由于您正在使用Hibernate，请尝试：

@ManyToOne(cascade = CascadeType.MERGE)

Answer 3

这指向您的错误：

Caused by: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.example.data.entities.FootballTeam.homeGames, could not initialize proxy - no Session

############################################################################################################################

如果映射不会太大，您可以将映射上的获取策略指定为：

@OneToMany(mappedBy = "homeTeam", fetch = FetchType.EAGER)

这将立即将实例加载到内存中。请注意，您可能需要在所有映射中使用此选项。

UDPATE：下面的选项不适用于@PostContruct方法。见下面的David Lizrraga评论。将适用于更一般的情况，例如从Controller调用Service类，并用@Transactional注释Service方法

如果不能立即将所有内容加载到内存中，则在引用映射对象时，必须确保您的会话仍在范围内。对于您当前的情况，这可以通过使用@Transactional注释对您的方法进行注释来实现。通常，您需要确保访问延迟加载对象的方法是在@Transaction方法中完成的。