Question

When I run the following class:

@Entity
public class SurveyResponse {

    @Id
    private String assignmentId;

    public String getAssignmentId() {
        return assignmentId;
    }

    public void setAssignmentId(String assignmentId) {
        this.assignmentId = assignmentId;
    }

    @ElementCollection
    @MapKeyColumn(name="topic")
    @Column(name="relevance")
    @CollectionTable(name="RelevanceScore", joinColumns=@JoinColumn(name="assignmentId"))
    Map<Topic, Relevance> topicRelevance = new HashMap<Topic, Relevance>(); // maps from attribute name to value    

    public static void main( String[] args ) {
        Configuration config = new Configuration();
        config.addAnnotatedClass(SurveyResponse.class);
        config.configure( "hibernate.cfg.xml" );        
        new SchemaExport(config).create( true, true );      
    }

}

it creates the tables SurveyResponse and RelevanceScore as expected. However, when I place the @Id annotation above the getter for the primary key…

@Entity
public class SurveyResponse {

    private String assignmentId;

    @Id 
    public String getAssignmentId() {
        return assignmentId;
    }

    ...

}

… it fails to produce table RelevanceScore. Why?

Answer 1

Short answer : you have to choose whether you put your annotations on fields or on getters, you cannot mix them.

Long answer : Hibernate looks for the @Id annotation ; if it is on a field, it looks for all other annotations on fields, and doesn’t even bother to look on getters. The opposite also holds true : if the @Id annotation is on a getter, the annotations you put on other fields won’t be taken into account.

This is why your tables aren’t generated if you only move your @Id annotation on the getAssignment method ; you should also put all the annotations that describe the topicRelevance field on its related getter.