I am confused to using auto-generated endpoint class. I want to use generated endpoint to insert new object into datastore. But, an exception is throwing.
fooEndpoint.insertFoo(foo); // throws null pointer exception
My entity class is similar with the given example at this source: https://developers.google.com/appengine/docs/java/datastore/jpa/overview.
Here is my entity:
@Entity
public class Foo {
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private Key ID;
Here is the stack trace:
java.lang.NullPointerException
at org.datanucleus.api.jpa.JPAEntityManager.find(JPAEntityManager.java:318)
at org.datanucleus.api.jpa.JPAEntityManager.find(JPAEntityManager.java:256)
at com.FooEndpoint.containsFoo(FooEndpoint.java:150)
at com.FooEndpoint.insertFoo(FooEndpoint.java:96)
On the other side, I can insert new object when I use the EntityManager persist method. Because, this does not check exist or not on the datastore.
I expect that, classEndpoint insert method should save the object and assing auto key to ID field.
Or I need to initialize the ID field.
Here is auto-generated endpoint class insertFoo method.
/**
* This inserts a new entity into App Engine datastore. If the entity already
* exists in the datastore, an exception is thrown.
* It uses HTTP POST method.
*
* @param foo the entity to be inserted.
* @return The inserted entity.
*/
public Foo insertFoo(Foo foo) {
EntityManager mgr = getEntityManager();
try {
if (containsFoo(foo)) {
throw new EntityExistsException("Object already exists");
}
mgr.persist(foo);
} finally {
mgr.close();
}
return foo;
}
Here is the containsFoo method
private boolean containsFoo(Foo foo) {
EntityManager mgr = getEntityManager();
boolean contains = true;
try {
Foo item = mgr.find(Foo.class, foo.getID()); // exception occurs here
if (item == null) {
contains = false;
}
} finally {
mgr.close();
}
return contains;
}
foo.getID() is null. Because, it is new object. I am expecting that, app engine creates a key for it. Or I need to explicitly create a key for it?
Other fields in Foo class are simple types such as String and booleans.
Thanks for your time.
I had exactly the same problem. I will present the way I worked around it.
Original auto-generated Endpoints class relevant code:
private boolean containsFoo(Foo foo) {
EntityManager mgr = getEntityManager();
boolean contains = true;
try {
Foo item = mgr.find(Foo.class, foo.getID());
if (item == null) {
contains = false;
}
} finally {
mgr.close();
}
return contains;
}
Changed relevant code to include a null check for the entity object that is passed as an argument.
private boolean containsFoo(Foo foo) {
EntityManager mgr = getEntityManager();
boolean contains = true;
try {
// If no ID was set, the entity doesn't exist yet.
if(foo.getID() == null)
return false;
Foo item = mgr.find(Foo.class, foo.getID());
if (item == null) {
contains = false;
}
} finally {
mgr.close();
}
return contains;
}
This way it will work as supposed, although I'm confident that more experienced answers and explanations will appear.
I was having the same exact problem after using the Eclipse Plugin to autogenerate the cloud endpoints (by selecting "Google > Generate Cloud Endpoint Class").
Following your advice, I added:
if(foo.getID() == null) // replace foo with the name of your own object return false;
The problem was solved.
How is that Google hasn't updated the autogenerated code yet as this must be a highly recurring issue?
Thanks for the solution.
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