Question

当我想将学生添加到另一项运动时，我有一个问题，而不是保存额外的运动，它会覆盖现有的运动。

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column(name="STUDENT_ID")
private int studentId;

@Column(name="\"ACTIVE\"")
private boolean active;

@OneToMany(cascade = CascadeType.ALL)
@JoinTable(name = "STUDENT_SPORTS", 
    joinColumns = { @JoinColumn(name = "STUDENT_ID") }, 
    inverseJoinColumns = { @JoinColumn(name = "SPORTS_ID") })
private List<Sports> sports= new ArrayList<Sports>();

public Student () {
}

public int getStudentId() {
    return studentId;
}

public void setStudentId(int studentId) {
    this.studentId= studentId;
}

我的输出应该是Student_sports中的以下内容：

Student_id sports_id

5 5

5 6

但是在Student_sports表中输出是这样的：

Student_id sports_id

5 6

Answer 1

此处有unique = true：

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column(name="STUDENT_ID", unique = true, nullable = false, length = 5) // <= You can also add some details more like this 
private int studentId;

@Column(name="\"ACTIVE\"")
private boolean active;

@OneToMany(cascade = CascadeType.ALL)
@JoinTable(name = "STUDENT_SPORTS", 
    joinColumns = { @JoinColumn(name = "STUDENT_ID") }, 
    inverseJoinColumns = { @JoinColumn(name = "SPORTS_ID") })
private List<Sports> sports= new ArrayList<Sports>();

public Student () {
}

public int getStudentId() {
    return studentId;
}

public void setStudentId(int studentId) {
    this.studentId= studentId;
}

请你试试吗？

使用复合主键进行Hibernate单向映射

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