Spring JPA多对多懒删除

Question

我正在使用Spring jpa和mysql，在删除实体时遇到问题，如何以最佳方式做到这一点？

我的实体用户：

@ManyToMany(cascade = CascadeType.REMOVE)
@JoinTable(name = "users_tasks",
        joinColumns = {@JoinColumn(name = "user_id")},
        inverseJoinColumns = {@JoinColumn(name = "task_id")})
private List<Task> tasks;

我的实体任务：

@ManyToMany(fetch=FetchType.LAZY, mappedBy = "tasks")
private List<User> users = new ArrayList<>();

在userServiceImpl中删除用户（我不确定这是否正确，但是可以正常工作）：

user.setTasks(Collections.emptyList());
userRepository.save(user);
userRepository.delete(user);

删除taskServiceImpl中的任务（它不起作用）：

task.setUsers(Collections.emptyList());
taskRepository.save(task);
taskRepository.delete(task);

例外：

java.sql.SQLIntegrityConstraintViolationException: Cannot delete or update a parent row: a foreign key constraint fails (`testdb`.`users_tasks`, CONSTRAINT `FK7todmyl52eiddpi6hc2nfgvbs` FOREIGN KEY (`task_id`) REFERENCES `tasks` (`task_id`))

我的jpa配置：

@Bean
public DataSource dataSource() {
BasicDataSource dataSource = new BasicDataSource();    
dataSource.setDriverClassName(
env.getRequiredProperty("database.driver");
dataSource.setUrl(env.getRequiredProperty("database.url"));
dataSource.setUsername(env.getRequiredProperty("database.password"));
dataSource.setPassword(env.getRequiredProperty("database.username"));
return dataSource;
}

@Bean
public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
    JpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
    LocalContainerEntityManagerFactoryBean factory = new LocalContainerEntityManagerFactoryBean();
    factory.setDataSource(dataSource());
    factory.setPackagesToScan("com.taskmanager");
    factory.setJpaVendorAdapter(vendorAdapter);
    factory.setJpaProperties(additionalProperties());
    return factory;
}

@Bean
public JpaTransactionManager transactionManager() {
    JpaTransactionManager transactionManager = new JpaTransactionManager();
    transactionManager.setEntityManagerFactory(entityManagerFactory().getObject());
    return transactionManager;
}

@Bean
public DataSourceInitializer dataSourceInitializer(DataSource dataSource) {
    DataSourceInitializer initializer = new DataSourceInitializer();
    initializer.setDataSource(dataSource);
    initializer.setDatabasePopulator(databasePopulator());
    return initializer;
}

private Properties additionalProperties() {
    Properties properties = new Properties();
    properties.put("hibernate.dialect", env.getRequiredProperty("hibernate.dialect"));
    properties.put("hibernate.show_sql", env.getRequiredProperty("hibernate.show_sql"));
    properties.put("hibernate.hbm2ddl.auto", env.getRequiredProperty("hibernate.hbm2ddl.auto"));
    properties.put("hibernate.enable_lazy_load_no_trans",
            env.getRequiredProperty("hibernate.enable_lazy_load_no_trans"));
    return properties;
}

private DatabasePopulator databasePopulator() {
    ResourceDatabasePopulator populator = new ResourceDatabasePopulator();
    populator.addScript(dataScript);
    return populator;
}

帮助我找到删除的最佳解决方法，我的设置拼写正确吗？ 谢谢

Answer 1

在您的示例中，表User是关系的所有者，这就是为什么在更新用户的任务时Hibernate会删除任务列表的原因。

解决此问题的一种方法是，通过在任务实体上设置联接表，使两个实体都成为关系的所有者：

@ManyToMany(fetch=FetchType.LAZY)
@JoinTable(name = "users_tasks",
    joinColumns = {@JoinColumn(name = "task_id")},
    inverseJoinColumns = {@JoinColumn(name = "user_id")})
private List<User> users = new ArrayList<>();

请注意，反向克隆反转了，映射由删除，表名相同。

另一个值得一提的解决方法是，通过使用ON DELETE CASCADE更改users_tasks fks，直接在数据库上管理级联