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问题描述
我正在尝试持久化一个新的‘UserTopics’对象,并在与多个UserID对应的‘Theme’表中映射新的UserTheme。
我不知道我做错了什么。下面是我的代码和例外情况。
我的用户主题实体:
@Entity
@Table(name="USERS_TOPICS")
public class UserTopics {
@Id
@GeneratedValue(strategy= GenerationType.IDENTITY)
@Column(name="TOPICUSER_ID")
private Integer id;
@Column(name="USER_ID")
private Integer userId;
@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "TOPICS_TOPICS_ID")
private Topics topics;
// Getters and setters
和主题实体:
@Entity
@Table(name="TOPICS")
public class Topics {
@Id
@GeneratedValue(strategy= GenerationType.IDENTITY)
@Column(name="TOPICS_ID")
private Integer id;
@Column(name="TOPICNAME")
private String topicName;
@OneToMany(mappedBy = "topics", cascade= {CascadeType.ALL,CascadeType.PERSIST})
private Set<UserTopics> userTopics;
//Getter and setters
在我的服务类中,我尝试按如下方式保存用户主题:
@Service("userTopicsService")
@Transactional
public class UserTopicsServiceImpl implements UserTopicsService {
@Autowired
TopicsDao topicsDao;
@Override
public void createTopicc(int UserIdOne, int UserIdTwo) {
Set<UserTopics> userTopics = new HashSet<>();
Topics topic = new Topics();
topic.setTopicName(String.valueOf(UserIdOne+UserIdTwo));
UserTopics userTopicOne = new UserTopics();
userTopicOne.setUserId(UserIdOne);
userTopics.add(userTopicOne);
UserTopics userTopicTwo = new UserTopics();
userTopicTwo.setUserId(UserIdTwo);
userTopics.add(userTopicTwo);
topic.setUserTopics(userTopics);
topicsDao.saveTopic(topic);
}
//Other methods...
下面的异常
18:58:54.434 [http-apr-8080-exec-9] WARN org.hibernate.engine.jdbc.spi.SqlExceptionHelper - SQL Error: 1048, SQLState: 23000
18:58:54.434 [http-apr-8080-exec-9] ERROR org.hibernate.engine.jdbc.spi.SqlExceptionHelper - Column 'TOPICS_TOPICS_ID' cannot be null
18:58:54.442 [http-apr-8080-exec-9] DEBUG org.hibernate.engine.jdbc.spi.SqlExceptionHelper - SQL Warning
java.sql.SQLWarning: Column 'TOPICS_TOPICS_ID' cannot be null
at com.mysql.jdbc.SQLError.convertShowWarningsToSQLWarnings(SQLError.java:779)
at com.mysql.jdbc.SQLError.convertShowWarningsToSQLWarnings(SQLError.java:707)
推荐答案
所以解决方案是:
将级联类型添加到UserTopics实体中的Topics对象,如下所示:
@ManyToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
@JoinColumn(name = "TOPICS_TOPICS_ID")
private Topics topics;
而My Service类中保存新主题及其子UserTopics的代码如下。
Topics topic = new Topics();
topic.setTopicName(String.valueOf(UserIdOne+UserIdTwo));
Set<UserTopics> userTopics = new HashSet<>();
UserTopics userTopicOne = new UserTopics();
userTopicOne.setUserId(UserIdOne);
userTopicOne.setTopics(topic);
UserTopics userTopicTwo = new UserTopics();
userTopicTwo.setUserId(UserIdTwo);
userTopicOne.setTopics(topic);
userTopics.add(userTopicOne);
userTopics.add(userTopicTwo);
List<UserTopics> userTopicsList = new ArrayList<>();
userTopics.add(userTopicOne);
userTopics.add(userTopicTwo);
for(UserTopics next : userTopics) {
userTopicsDao.save(next);
}
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