Question

I’ve encountered a problem while establishing new table (UserMessage) for many to many relation (User and Message tables). When I try to access a row from the mapping table I get an exception: org.hibernate.PropertyAccessException: could not get a field value by reflection getter of com.package.model.User.userid

UserMessage entity is necessary for further addition of properties to the relation table.

Data is accessed via:

    Session session = (Session) entityManager.getDelegate();
    String hql = "FROM Message M, UserMessage UM WHERE M.messageid = UM.pk.message and UM.pk.user = :id";
    Query query = session.createQuery(hql);
    query.setParameter("id", id);
    query.list();

My classes:

User.java

@Entity
@Table(name = "USER")
public class User {
    @Id @GeneratedValue(generator="system-uuid")
    @GenericGenerator(name="system-uuid", strategy = "uuid")
    @Column(nullable = false)
    private Long userid;

    @Column(unique = true, nullable = false)
    private String username;

    @OneToMany(fetch = FetchType.EAGER, mappedBy = "pk.user", cascade = {CascadeType.PERSIST})
    private Set<UserMessage> inbox = new HashSet<UserMessage>();

    public User() {
    }

    public Long getUserid() {
        return userid;
    }

    public void setUserid(Long id) {
        this.userid = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public Set<UserMessage> getInbox() {
        return inbox;
    }

    public void setInbox(Set<UserMessage> inbox) {
        this.inbox = inbox;
    }

    public void addMessageToUser(Message message){
        UserMessage userMessage = new UserMessage();
        userMessage.setUser(this);
        userMessage.setMessage(message);
        inbox.add(userMessage);
    }
}

Message.java

@Entity
@Table(name = "MESSAGE")
public class Message {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Long messageid;
    private String subject;
    private String body;

    @OneToMany(fetch = FetchType.EAGER, mappedBy = "pk.message",cascade = {CascadeType.PERSIST})
    private Set<UserMessage> toUser = new HashSet<UserMessage>();

    public Set<UserMessage> getToUser() {
        return toUser;
    }

    public void setToUser(Set<UserMessage> toUser) {
        this.toUser = toUser;
    }

    public void addUserToMessage(User user){
        UserMessage userMessage = new UserMessage();
        userMessage.setUser(user);
        userMessage.setMessage(this);
        toUser.add(userMessage);
    }

    public Message() {
    }

    public Long getMessageid() {
        return messageid;
    }

    public void setMessageid(Long id) {
        this.messageid = id;
    }

    public String getSubject() {
        return subject;
    }

    public void setSubject(String subject) {
        this.subject = subject;
    }

    public String getBody() {
        return body;
    }

    public void setBody(String body) {
        this.body = body;
    }
}

UserMessage.java

@Entity
@Table(name = "USER_MESSAGE")
@AssociationOverrides({
        @AssociationOverride(name = "pk.user", joinColumns = @JoinColumn(name = "userid")),
        @AssociationOverride(name = "pk.message", joinColumns = @JoinColumn(name = "messageid"))
})
public class UserMessage{

    @EmbeddedId
    private UserMessagePK pk = new UserMessagePK();


    public UserMessagePK getPk(){
        return pk;
    }

    public void setPk(UserMessagePK pk){
        this.pk = pk;
    }

    public UserMessage(){
    }

    @Transient
    public User getUser(){
        return this.pk.getUser();
    }

    @Transient
    public Message getMessage(){
        return this.pk.getMessage();
    }

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

    public void setMessage(Message message){
        this.pk.setMessage(message);
    }
}

UserMessagePK.java

@Embeddable
public class UserMessagePK implements Serializable {

    private static final long serialVersionUID = 1L;

    @ManyToOne
    private User user;

    @ManyToOne(cascade = CascadeType.REFRESH)
    private Message message;

    public User getUser() {
        return user;
    }

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


    public Message getMessage() {
        return message;
    }

    public void setMessage(Message message) {
        this.message = message;
    }

    public UserMessagePK(User user, Message message){
        this.user = user;
        this.message = message;
    }

    public UserMessagePK(){
    }
}

What is wrong?

Answer 1

The problem was in query.

select distinct M from Message M join M.toUser t where t.pk.user = :user works perfectly.