java Hibernate如何正确使用关系中的级联

Question

我在SpringMVC应用程序中使用hibernate，对cascade有一个问题。我看到了许多类似的问题，但没有一个能回答我的问题。假设我有User和UserPosition对象User有一个UserPosition集合，还有一个UserPosition作为默认位置。结构如下所示：

用户：

@OneToMany(mappedBy = "user", fetch = FetchType.LAZY)
private Collection<UserPosition> userPositionCollection;

public Collection<UserPosition> getUserPositionCollection() {
    return userPositionCollection;
}

public void setUserPositionCollection(Collection<UserPosition> collection) {
    this.userPositionCollection = collection;
}


 @OneToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
@JoinColumn(name = "default_User_Position_ID", referencedColumnName = "id")
private UserPosition defaultUserPosition;

public UserPosition getDefaultUserPosition() {
    return defaultUserPosition;
}

public void setDefaultUserPosition(UserPosition defaultUserPosition) {
    this.defaultUserPosition = defaultUserPosition;
}

用户位置：

@JoinColumn(name = "user_id", referencedColumnName = "id")
@ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.PERSIST)
private User user;

public User getUser() {
    return user;
}

public void setUser(User user) {
    this.user = user;
}

@OneToOne(fetch = FetchType.LAZY, mappedBy = "defaultUserPosition", cascade = CascadeType.PERSIST)
private User defaultUserPosition;

public User getDefaultUserPosition() {
    return defaultUserPosition;
}

public void setDefaultUserPosition(User defaultUserPosition) {
    this.defaultUserPosition = defaultUserPosition;
}

现在，我的问题是使用cascade保存相关对象的最佳实践是什么。事实上，我混淆了这三种解决方案：

解决方案1:

User user = new User();
//some setters and getters 
UserPosition userPosition = new UserPosition();
//some setters and getters 
List<UserPosition> positionList = new ArrayList<>();
positionList.add(userPosition);
user.setDefaultUserPosition(userPosition);
user.setUserPositionCollection((Collection<UserPosition>) positionList );
session.persist(user)

解决方案2:

User user = new User();
//some setters and getters 
UserPosition userPosition = new UserPosition();
//some setters and getters 
userPosition.setUser(user);
userPosition.setDefaultUserPosition(user);
session.persist(userPosition)

解决方案3（前两种解决方案的组合）：

User user = new User();
//some setters and getters 
UserPosition userPosition = new UserPosition();
//some setters and getters 
List<UserPosition> positionList = new ArrayList<>();
positionList.add(userPosition);
user.setDefaultUserPosition(userPosition);
user.setUserPositionCollection((Collection<UserPosition>) positionList );
userPosition.setUser(user);
userPosition.setDefaultUserPosition(user);
session.persist(user);

这对我很重要，所以请帮助我。哪种解决方案是正确的，在哪里应该是cascade属性？谢谢你抽出时间

Answer 1

User是父实体，级联一个lways propagates from Parent to Child entities

因此，用户关联成为：

@OneToMany(mappedBy = "user", 
    fetch = FetchType.LAZY, 
    cascade = CascadeType.ALL, 
    orphanRemoval = true)
private Collection<UserPosition> userPositionCollection;

但是对于默认位置，用户成为关联的Child：

@OneToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "default_User_Position_ID", referencedColumnName = "id")
private UserPosition defaultUserPosition;

在UserPosition类中，情况正好相反：

@JoinColumn(name = "user_id", referencedColumnName = "id")
@ManyToOne(fetch = FetchType.LAZY)
private User user;

及

@OneToOne(fetch = FetchType.LAZY, 
    mappedBy = "defaultUserPosition", 
    cascade = CascadeType.PERSIST)
private User defaultUserPosition;

然后，您还必须添加以下实用程序方法，这些方法始终同步双方。它们进入User类：

public void addUserPosition(UserPosition userPosition) {
    userPositionCollection.add(userPosition);
    userPosition.setUser(this);
}

public void addDefaultUserPosition(UserPosition userPosition) {
    defaultUserPosition = userPosition;
    userPosition.setDefaultUserPosition(this);
}

持久化逻辑变成：

User user = new User();
//some setters and getters 
UserPosition userPosition = new UserPosition();
//some setters and getters 

user.addUserPosition(userPosition);
user.setDefaultUserPosition(userPosition);

session.persist(user);