JPA, How to find an object that has composite id? - jpa

Question

Based on second approach answered here I designed my JPA class.
#Entity(name = "SearchKeywordJPA")
#IdClass(SearchKeywordJPA.SearchKeyId.class)
public class SearchKeywordJPA implements Comparable<SearchKeywordJPA> {
#Id
private String keyword;
#Id
private long date;
private String userUUID;
#Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
SearchKeywordJPA that = (SearchKeywordJPA) o;
if (date != that.date) return false;
if (!keyword.equals(that.keyword)) return false;
if (!userUUID.equals(that.userUUID)) return false;
return true;
}
#Override
public int hashCode() {
int result = keyword.hashCode();
result = 31 * result + (int) (date ^ (date >>> 32));
result = 31 * result + userUUID.hashCode();
return result;
}
#Override
public String toString() {
return "SearchKeywordJPA{" +
"keyword='" + keyword + '\'' +
", date=" + date +
", userUUID='" + userUUID + '\'' +
'}';
}
public String getKeyword() {
return keyword;
}
public void setKeyword(String keyword) {
this.keyword = keyword;
}
public long getDate() {
return date;
}
public void setDate(long date) {
this.date = date;
}
public String getUserUUID() {
return userUUID;
}
public void setUserUUID(String userUUID) {
this.userUUID = userUUID;
}
#Override
public int compareTo(SearchKeywordJPA searchRecord) {
long comparedDate = searchRecord.date;
if (this.date > comparedDate) {
return 1;
} else if (this.date == comparedDate) {
return 0;
} else {
return -1;
}
}
/**********************
* Key class
**********************/
public class SearchKeyId {
private int id;
private int version;
}
}
In my servlet I want to check datastore and store my object if is not exist.
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
...
for(SearchKeywordJPA item: applicationList) {
if(!isRecorded(item))
storeRecord(item);
}
}
private boolean isRecorded(SearchKeywordJPA record) {
EntityManager em = EMF.get().createEntityManager();
SearchKeywordJPA item = em.find(SearchKeywordJPA.class, record);
return item != null;
}
private void storeRecord(SearchKeywordJPA record) {
EntityManager em = EMF.get().createEntityManager();
em.persist(record);
}
However when I run, application crashes and log says
javax.persistence.PersistenceException: org.datanucleus.store.appengine.FatalNucleusUserException: Received a request to find an object of type com.twitterjaya.model.SearchKeywordJPA identified by SearchKeywordJPA{keyword='airasia', date=1335680686149, userUUID='FFFF0000'}. This is not a valid representation of a primary key for an instance of com.twitterjaya.model.SearchKeywordJPA.
What is the reason? any suggestion would be appreciated. Thanks

Answer 1

You pass an instance of the IdClass into em.find ... i.e SearchKeyId. Obviously if you really have an IdClass that has no equals/hashCode/toString/constructor then you will likely get many problems. Those problems will only be increased by using an ancient plugin for GAE/Datastore.

Answer 2

If your Key is
#Entity(name = "SearchKeywordJPA")
#IdClass(SearchKeywordJPA.SearchKeyId.class)
public class SearchKeywordJPA implements Comparable<SearchKeywordJPA> {
you are doing it wrong.
IdClass does not need any annotation of #IdClass just the #Id
annotation.
Key can not be an entity.
Need to implements Serializable , comparable is not needed
Need to override equals and hascode and have no arg constructor
Class key need to be as follows.
public class SearchKeyId implements Serializable {
private String keyword;
private long date;
And your entity I assume something like this.
#Entity(name = "SearchKeywordJPA")
#IdClass(SearchKeyId.class)
public class SearchKeywordJPA {
#Id
private String keyword;
#Id
private long date;
private String userUUID;
Just consider that find method will use the SearchKey.class to find
the entities.
Fields that are in the IdClass need to have #Id annotation in the entity.
Key can not be an entity on its own.
Comparable is not really needed as all the comparison are placed in the IdClass