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    <p>If you add extra fields on a linked table (STUDENT_COURSE), you have to choose an approach according to skaffman's answer or another as shown bellow.</p> <p>There is an approach where the linked table (STUDENT_COURSE) behaves like a @Embeddable according to:</p> <pre><code>@Embeddable public class JoinedStudentCourse { // Lets suppose you have added this field @Column(updatable=false) private Date joinedDate; @ManyToOne(fetch=FetchType.LAZY) @JoinColumn(name="STUDENT_ID", insertable=false, updatable=false) private Student student; @ManyToOne(fetch=FetchType.LAZY) @JoinColumn(name="COURSE_ID", insertable=false, updatable=false) private Course course; // getter's and setter's public boolean equals(Object instance) { if(instance == null) return false; if(!(instance instanceof JoinedStudentCourse)) return false; JoinedStudentCourse other = (JoinedStudentCourse) instance; if(!(student.getId().equals(other.getStudent().getId())) return false; if(!(course.getId().equals(other.getCourse().getId())) return false; // ATT: use immutable fields like joinedDate in equals() implementation if(!(joinedDate.equals(other.getJoinedDate())) return false; return true; } public int hashcode() { // hashcode implementation } } </code></pre> <p>So you will have in both Student and Course classes</p> <pre><code>public class Student { @CollectionOfElements @JoinTable( table=@Table(name="STUDENT_COURSE"), joinColumns=@JoinColumn(name="STUDENT_ID") ) private Set&lt;JoinedStudentCourse&gt; joined = new HashSet&lt;JoinedStudentCourse&gt;(); } public class Course { @CollectionOfElements @JoinTable( table=@Table(name="STUDENT_COURSE"), joinColumns=@JoinColumn(name="COURSE_ID") ) private Set&lt;JoinedStudentCourse&gt; joined = new HashSet&lt;JoinedStudentCourse&gt;(); } </code></pre> <p>remember: @Embeddable class has its lifecycle bound to the owning entity class (Both Student and Course), so take care of it.</p> <p>advice: Hibernate team suppports these two approachs (@OneToMany (skaffman's answer) or @CollectionsOfElements) due some limitations in @ManyToMany mapping - cascade operation.</p> <p>regards,</p>
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    1. POCan add extra field(s) to @ManyToMany Hibernate extra table?
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    1. USArthur Ronald
    1. USArthur Ronald
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    1. POCan add extra field(s) to @ManyToMany Hibernate extra table?
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    1. COgreat answer. if one only needs an index-column for mapping to a List one can just add @OrderColumn though
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      1. UScproinger
    2. COWhen i tried above solution i got `Repeated column in mapping for collection` error. Any idea ?
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      1. USAnkur Raiyani
 

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