Retrieve GAE Datastore's data types in Java

Question

How to retrieve data types of properties of entities stored in Google App Engine Datastore using Java? I didn't find property.getType() or similar method in Java Datastore API.

Answer 1

There is no direct method provided.

but you can retrieve it by comparing the java Type of Property with the table given at this link

Map<String, Object> properties = entity.getProperties();
    String[] propertyNames = properties.keySet().toArray(
        new String[properties.size()]);

    for(final String propertyName : propertyNames) {
      // propertyNames string contains
      // "com.google.appengine.api.users.User" then its Google Accounts user
      // "java.lang.Integer" then its Integer
      // "int" then premetive integer
    }

Hope this helps

Answer 2

You need to use Property Metadata Queries .

Be aware that, as stated in the documentation, the property representation returned by the queries would be AppEngine representation, and does not have one-to-one mapping with Java classes. But you would be able to get the general data type at least.