@JoinColumn，如何初始化它？答案

【问题标题】：@JoinColumn, how to initialise it?@JoinColumn，如何初始化它？
【发布时间】：2019-10-25 14:46:12
【问题描述】：

我正在编写一个 spring-boot、spring-mvc 应用程序。其中有两个实体：用户和任务。该任务必须属于用户。我正在尝试使用外键执行此操作，使用 @OneToMany、@ManyToOne 和 @JoinColumn。

用户.java：

package ru.chausov.to_do_list.data_base.entities;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import ru.chausov.to_do_list.data_base.types.Gender;

import javax.persistence.*;
import java.time.LocalDate;
import java.util.HashSet;
import java.util.Set;


@Data
@Builder
@Entity
@Table(name="users")
@NoArgsConstructor
@AllArgsConstructor
public class User {
    @Id
    @GeneratedValue
    private Long id; 
    private String name;
    private String lastName;
    private LocalDate birthDate;
    private Gender gender;
    private String address;
    private String company;
    @OneToMany(mappedBy = "id", cascade = CascadeType.ALL, orphanRemoval = true)
    private final Set<Task> tasks = new HashSet<>();

}

Task.java：

package ru.chausov.to_do_list.data_base.entities;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

import javax.persistence.*;
import java.time.LocalDateTime;


@Data
@Builder
@Entity
@Table(name="tasks")
@NoArgsConstructor
@AllArgsConstructor
public class Task {
    @Id
    @GeneratedValue
    private Long id; 
    private String name;
    private String description;
    private LocalDateTime receivedDate;
    private LocalDateTime toBeDone;
    private boolean done;
    @ManyToOne
    @JoinColumn(name = "user_id")
    private User user;
}

从 CrudRepository 扩展了标准存储库。

UsersRepositpry.java:

package ru.chausov.to_do_list.data_base.repositories;

import org.springframework.data.repository.CrudRepository;
import ru.chausov.to_do_list.data_base.entities.User;


public interface UsersRepository extends CrudRepository<User, Long> {
}

TasksRepository.java：

package ru.chausov.to_do_list.data_base.repositories;

import org.springframework.data.repository.CrudRepository;
import ru.chausov.to_do_list.data_base.entities.Task;


public interface TasksRepository extends CrudRepository<Task, Long> {
}

编写了 junit/spring-boot 测试。

UserRepositoryTest.java:

package ru.chausov.to_do_list.data_base.repositories;

import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import ru.chausov.to_do_list.data_base.entities.Task;
import ru.chausov.to_do_list.data_base.entities.User;


@RunWith(SpringRunner.class)
@SpringBootTest
public class TasksRepositoryTests {
    @Autowired
    private TasksRepository tasksRepository;
    @Autowired
    private UsersRepository usersRepository;

    @Test
    public void saveTest() {
        User user = new User();

        usersRepository.save(user);

        Task taskToSave = Task.builder().user(user).build();

        Task savedTask = tasksRepository.save(taskToSave);

        Assert.assertEquals(savedTask, taskToSave);
    }

当我启动测试时，我收到一个错误：

org.springframework.dao.DataIntegrityViolationException: could not execute statement; SQL [n/a]; constraint ["FKO4W1P8Y0P6E0GSR7VHBDG76KO: PUBLIC.TASKS FOREIGN KEY(ID) REFERENCES PUBLIC.USERS(ID) (2)"; SQL statement:
insert into tasks (description, done, name, received_date, to_be_done, user_id, id) values (?, ?, ?, ?, ?, ?, ?) [23506-197]]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement

    at org.springframework.orm.jpa.vendor.HibernateJpaDialect.convertHibernateAccessException(HibernateJpaDialect.java:296)
    at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:253)
    at org.springframework.orm.jpa.JpaTransactionManager.doCommit(JpaTransactionManager.java:536)
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:746)
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:714)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.commitTransactionAfterReturning(TransactionAspectSupport.java:533)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:304)
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:98)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:139)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:138)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:93)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.data.repository.core.support.SurroundingTransactionDetectorMethodInterceptor.invoke(SurroundingTransactionDetectorMethodInterceptor.java:61)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212)
    at com.sun.proxy.$Proxy97.save(Unknown Source)
    at ru.chausov.to_do_list.data_base.repositories.TasksRepositoryTests.saveTest(TasksRepositoryTests.java:29)
    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.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.springframework.test.context.junit4.statements.RunBeforeTestExecutionCallbacks.evaluate(RunBeforeTestExecutionCallbacks.java:74)
    at org.springframework.test.context.junit4.statements.RunAfterTestExecutionCallbacks.evaluate(RunAfterTestExecutionCallbacks.java:84)
    at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:251)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190)
    at org.junit.runners.Suite.runChild(Suite.java:128)
    at org.junit.runners.Suite.runChild(Suite.java:27)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: org.hibernate.exception.ConstraintViolationException: could not execute statement
    at org.hibernate.exception.internal.SQLStateConversionDelegate.convert(SQLStateConversionDelegate.java:112)
    at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:42)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:113)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:99)
    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:178)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3174)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3688)
    at org.hibernate.action.internal.EntityInsertAction.execute(EntityInsertAction.java:90)
    at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:604)
    at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:478)
    at org.hibernate.event.internal.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:356)
    at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:39)
    at org.hibernate.internal.SessionImpl.doFlush(SessionImpl.java:1453)
    at org.hibernate.internal.SessionImpl.managedFlush(SessionImpl.java:510)
    at org.hibernate.internal.SessionImpl.flushBeforeTransactionCompletion(SessionImpl.java:3282)
    at org.hibernate.internal.SessionImpl.beforeTransactionCompletion(SessionImpl.java:2478)
    at org.hibernate.engine.jdbc.internal.JdbcCoordinatorImpl.beforeTransactionCompletion(JdbcCoordinatorImpl.java:473)
    at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.beforeCompletionCallback(JdbcResourceLocalTransactionCoordinatorImpl.java:178)
    at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.access$300(JdbcResourceLocalTransactionCoordinatorImpl.java:39)
    at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl$TransactionDriverControlImpl.commit(JdbcResourceLocalTransactionCoordinatorImpl.java:271)
    at org.hibernate.engine.transaction.internal.TransactionImpl.commit(TransactionImpl.java:104)
    at org.springframework.orm.jpa.JpaTransactionManager.doCommit(JpaTransactionManager.java:532)
    ... 55 more
Caused by: org.h2.jdbc.JdbcSQLException: Нарушение ссылочной целостности: "FKO4W1P8Y0P6E0GSR7VHBDG76KO: PUBLIC.TASKS FOREIGN KEY(ID) REFERENCES PUBLIC.USERS(ID) (2)"
Referential integrity constraint violation: "FKO4W1P8Y0P6E0GSR7VHBDG76KO: PUBLIC.TASKS FOREIGN KEY(ID) REFERENCES PUBLIC.USERS(ID) (2)"; SQL statement:
insert into tasks (description, done, name, received_date, to_be_done, user_id, id) values (?, ?, ?, ?, ?, ?, ?) [23506-197]
    at org.h2.message.DbException.getJdbcSQLException(DbException.java:357)
    at org.h2.message.DbException.get(DbException.java:179)
    at org.h2.message.DbException.get(DbException.java:155)
    at org.h2.constraint.ConstraintReferential.checkRowOwnTable(ConstraintReferential.java:332)
    at org.h2.constraint.ConstraintReferential.checkRow(ConstraintReferential.java:274)
    at org.h2.table.Table.fireConstraints(Table.java:995)
    at org.h2.table.Table.fireAfterRow(Table.java:1013)
    at org.h2.command.dml.Insert.insertRows(Insert.java:192)
    at org.h2.command.dml.Insert.update(Insert.java:134)
    at org.h2.command.CommandContainer.update(CommandContainer.java:102)
    at org.h2.command.Command.executeUpdate(Command.java:261)
    at org.h2.jdbc.JdbcPreparedStatement.executeUpdateInternal(JdbcPreparedStatement.java:199)
    at org.h2.jdbc.JdbcPreparedStatement.executeUpdate(JdbcPreparedStatement.java:153)
    at com.zaxxer.hikari.pool.ProxyPreparedStatement.executeUpdate(ProxyPreparedStatement.java:61)
    at com.zaxxer.hikari.pool.HikariProxyPreparedStatement.executeUpdate(HikariProxyPreparedStatement.java)
    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:175)
    ... 72 more

据我了解，该错误是由于外键 user_id 为空而引起的。

我应该如何初始化 user_id？

【问题讨论】：

标签： java spring-boot spring-mvc jpa

【解决方案1】：

我犯的错误是在 mappedBy 中。我应该使用“user”而不是“id”

用户.java：

package ru.chausov.to_do_list.data_base.entities;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import ru.chausov.to_do_list.data_base.types.Gender;

import javax.persistence.*;
import java.time.LocalDate;
import java.util.HashSet;
import java.util.Set;


@Data
@Builder
@Entity
@Table(name="users")
@NoArgsConstructor
@AllArgsConstructor
public class User {
    @Id
    @GeneratedValue
    private Long id; //how to make final to get through might be uninitialised?
    private String name;
    private String lastName;
    private LocalDate birthDate;
    private Gender gender;
    private String address;
    private String company;
    @OneToMany(mappedBy = "user", cascade = CascadeType.ALL, orphanRemoval = true, fetch = FetchType.EAGER)
    private final Set<Task> tasks = new HashSet<>();

}

我添加了 fetch = FetchType.EAGER 以防止延迟初始化 HashSet 任务的错误。

现在测试可以正常工作了。

【讨论】：

【解决方案2】：

尝试通过用户实体保存任务和用户

@Test
public void saveTest() {
    User user = new User();
    Task taskToSave = Task.builder().user(user).build();
    user.getTasks().add(task);
    usersRepository.save(user);
}

然后检查db，应该填写与Tasks相关的表。

【讨论】：

获取 StackOverflowError
java.lang.StackOverflowError at ru.chausov.to_do_list.data_base.entities.Task.hashCode(Task.java:12) at java.util.AbstractSet.hashCode(AbstractSet.java:126) at ru.chausov.to_do_list.data_base.entities.User.hashCode(User.java:15) 在 ru.chausov.to_do_list.data_base.entities.Task.hashCode(Task.java:12)
那是因为Data注解，尝试打开目标类，你会看到生成的hashCode方法包含循环方法调用（用户hashcode触发任务hashcode，反之亦然）。解决这个错误：去掉Data注解，给User和Task添加Getter Setter注解，自己实现hashcode和toString（也要注意toString的实现，会导致同样的错误）

【解决方案3】：

您需要在User 上填写@OneToMany 设置，并使用您还保存的Task：

@Test
public void saveTest() {
    User user = new User();

    usersRepository.save(user);

    Task taskToSave = Task.builder().user(user).build();

    user.getTasks().add(task); // -> Add this 

    Task savedTask = tasksRepository.save(taskToSave);

    Assert.assertEquals(savedTask, taskToSave);
}

这是因为它们处于双向映射中。

【讨论】：

不幸的是，它并没有解决问题。得到同样的错误。