CODEWITHSUNDEEP
javagoogle-app-enginejpajpql
Michael
Michael

Reputation: 2128

ClassCastException when executing SELECT query

Currently I upload a CSV file which contains the following columns to the Google App Engine datastore:

id, roleName, eggName, highestAllTimePrice, lowestAllTimePrice, averagePrice

And the result of the table when I go to localhost:8888/_ah/admin/datastore are as follows:

Key, Write Ops, ID/Name, averagePrice, eggName, eggNumber, highestAllTimePrice, lowestAllTimePrice, roleName

I get all of the data from the table as follows:

public String GetData(final ModelMap model)
{
    EntityManager em = EMF.get().createEntityManager();
    Query q = em.createQuery("SELECT s FROM Egg s");
    List<Egg> eggs = new ArrayList<Egg>(q.getResultList());

    model.addAttribute("eggs", eggs);
    return "index";
}

Entity

@Entity
public class Egg {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Key key;

    private int eggNumber;
    private String roleName;
    private String eggName;
    private double highestPrice;
    private double lowestPrice;
    private double averagePrice;

    // getters setters
}

But when I run that query, I get this error:

java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Double
    at com.google.appengine.datanucleus.FetchFieldManager.fetchDoubleField(FetchFieldManager.java:140)
    at org.datanucleus.state.AbstractStateManager.replacingDoubleField(AbstractStateManager.java:2256)
    at Entity.Egg.jdoReplaceField(Egg.java)
    at Entity.Egg.jdoReplaceFields(Egg.java)

The problem is I don't know why it's converting types? Have I mapped my entity class wrong?

Upvotes: 0

Views: 136

Answers (1)

mpierce
mpierce

Reputation: 468

Perhaps your double fields (highestPrice, etc) are considered to be strings in the datastore, and thus cannot be mapped to your entity.

Upvotes: 1

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