org.hibernate.QueryException: could not resolve property

Question

This is the first time that I use JPA. I write the code with Java and JPA. My code is below.

 String queryStr = "SELECT m.title, b.isbn, b.authors";
    queryStr += " FROM Book b, Media m";
    queryStr += " WHERE m.MediaID = b.MediaID";
            queryStr += " AND b.isbn = '" + isbn + "' AND m.title = '%" + title +"%'"; 
Query query = em.createQuery(queryStr);

From my code, Class Book extends class Media.

But I got the error which is

org.hibernate.QueryException: could not resolve property: MediaID of: mediaManagement.Media [SELECT m.title, b.isbn, b.authors FROM mediaManagement.Book b, mediaManagement.Media m WHERE m.MediaID = b.MediaID ]

This is the Media class.

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
@Table(name = "Media")
@NamedQuery(name = "findAllMedias", query = "select b from Media b")
public class Media {

@Id
@Column(name = "MediaID")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int mediaID;

/**
 * Getter of the property <tt>mediaID</tt>
 * 
 * @return Returns the mediaID.
 * @uml.property name="mediaID"
 */
public int getMediaID() {
    return mediaID;
}

/**
 * Setter of the property <tt>mediaID</tt>
 * 
 * @param mediaID
 *            The mediaID to set.
 * @uml.property name="mediaID"
 */
public void setMediaID(int mediaID) {
    this.mediaID = mediaID;
}

/**
 * @uml.property name="title"
 */
@Column(name = "title")
private String title;

/**
 * Getter of the property <tt>title</tt>
 * 
 * @return Returns the title.
 * @uml.property name="title"
 */
public String getTitle() {
    return title;
}

/**
 * Setter of the property <tt>title</tt>
 * 
 * @param title
 *            The title to set.
 * @uml.property name="title"
 */
public void setTitle(String title) {
    this.title = title;
}

/**
 * @uml.property name="editionDate"
 */

private Calendar editionDate;

/**
 * Getter of the property <tt>editionDate</tt>
 * 
 * @return Returns the editionDate.
 * @uml.property name="editionDate"
 */
public Calendar getEditionDate() {
    return editionDate;
}

/**
 * Setter of the property <tt>editionDate</tt>
 * 
 * @param editionDate
 *            The editionDate to set.
 * @uml.property name="editionDate"
 */
public void setEditionDate(Calendar editionDate) {
    this.editionDate = editionDate;
}

/*
 * Two medias are equal if their mediaID is the same
 */
@Override
public boolean equals(Object media) {
    if (media == null)
        return false;
    Media b = (Media) media;

    if (b.mediaID == mediaID)
        return true;

    return false;
}

public Media() {
};

/**
 * Creates a media All parameters should be given
 * 
 * @param title
 *            the title of the media
 * 
 * @param editionDate
 *            date of the edition of the media
 * 
 * @throws BadParametersException
 */
public Media(String title, Calendar editionDate)
        throws BadParametersException {
    if ((title == null) || (editionDate == null))
        throw new BadParametersException();

    this.title = title;
    this.editionDate = editionDate;

}

/**
 * Returns a description of the media
 */
public String toString() {
    return this.title + "  " + String.valueOf(this.title);
}

/** 
 * @uml.property name="copies"
 * @uml.associationEnd multiplicity="(0 -1)" inverse="media:copyManagement.Copy"
 */
@OneToMany(mappedBy="mediaRef") protected Set<Copy> copies;

public void addCopy(Copy copy) {
    copies.add(copy);
}

/** 
 * Getter of the property <tt>copies</tt>
 * @return Returns the copies.
 * @uml.property name="copies"
 */
public Set<Copy> getCopies() {
    return copies;
}

/** 
 * Setter of the property <tt>copies</tt>
 * @param editionDate The copies to set.
 * @uml.property  name="copies"
 */
public void setCopies(Set<Copy> copies) {
    this.copies = copies;
}

And this is Book class.

@Entity
@Table(name = "Book")
@NamedQuery(name = "findAllBooks", query = "select b from Book b")
public class Book extends Media {
/**
 * @uml.property name="authors"
 */
@Column(name = "authors")
private ArrayList<String> authors;

/**
 * Getter of the property <tt>authors</tt>
 * 
 * @return Returns the authors.
 * @uml.property name="authors"
 */
public ArrayList<String> getAuthors() {
    return authors;
}

/**
 * Setter of the property <tt>authors</tt>
 * 
 * @param authors
 *            The authors to set.
 * @uml.property name="authors"
 */
public void setAuthors(ArrayList<String> authors) {
    this.authors = authors;
}

/**
 * @uml.property name="isbn"
 */

@Column(name = "isbn")
private String isbn;

/**
 * Getter of the property <tt>isbn</tt>
 * 
 * @return Returns the isbn.
 * @uml.property name="isbn"
 */
public String getisbn() {
    return isbn;
}

/**
 * Setter of the property <tt>isbn</tt>
 * 
 * @param isbn
 *            The isbn to set.
 * @uml.property name="isbn"
 */
public void setisbn(String isbn) {
    this.isbn = isbn;
}

public Book() {
    // TODO Auto-generated constructor stub
}

public Book(String title, Calendar editionDate, ArrayList<String> authors,
        String isbn) throws BadParametersException {
    super(title, editionDate);
    this.authors = authors;
    this.isbn = isbn;
    // TODO Auto-generated constructor stub
}

}

Anyone can help?

Answer 1

If book extends media, why are you joining with the Media table? (though it would be easier with the Book and Media classes and mappings)

Querying the "Book" object should be enough. Also perhaps "MediaId" should be "mediaId". Hibernate is case sensitive on it's property names.