如何部分更新Google App Engine数据存储中的实体

Question

I am using Objectify in Google App Engine for Data Store. I am having an Entity with 6 Properties. For Example,

• Key (id)
• FirstName
• LastName
• Age
• mobile_Number

• Email

  I need to write an Update Endpoint for the Entity. I want that update Endpoint should be able to update the Entity with the specified fields Not the Entire Entity. For Example If I want to update the mobile_number , it should update the mobile number alone. or If i want to update the firstName it should update that only.

For that I need to write a common method to update the Entity based on the fields.

Many thanks in Advance!

Answer 1

You load and save the entity in a transaction.

ofy().transact(() -> {
    Thing thing = ofy().load().key(key).now();
    thing.setWhatever();
    ofy().save().entity(thing);
});

Transactions guarantee that all units of work are effectively executed in serial. Not actually executed in serial, but the data will be consistent as if all units of work were serialized.

Answer 2

Yes i fixed this update in the following way.

Got the input parameter as Hashmap where i can get the user's properties that to be updated. The hashmap's key should be same as Entity's property value.

public Response update(HashMap<String, String> ProfileEntity) {
 //update logic
}

and updated the value based on the following if condition:

        ProfileEntity existingEntity = getById(ProfileEntity.get("key"));

        if(existingEntity == null)
            System.out.println("Invalid Profile Key");

        if(ProfileEntity.containsKey("firstName"))
            existingEntity.setFirstName(ProfileEntity.get("firstName"));

        if(ProfileEntity.containsKey("lastName"))
            existingEntity.setLastName(ProfileEntity.get("lastName"));

        if(ProfileEntity.containsKey("age"))
            existingEntity.setAge(ProfileEntity.get("age")));

        if(ProfileEntity.containsKey("mobile_Number"))
            existingEntity.setMobileNumber(ProfileEntity.get("mobile_Number"));

        super.save(existingEntity);

Answer 3

I used spring BeanUtils for this.

 public static String[] getNullPropertyNames(Object source) {
        final BeanWrapper src = new BeanWrapperImpl(source);
        java.beans.PropertyDescriptor[] pds = src.getPropertyDescriptors();

        Set<String> emptyNames = new HashSet<String>();
        for (java.beans.PropertyDescriptor pd : pds) {
            Object srcValue = src.getPropertyValue(pd.getName());
            if (srcValue == null) emptyNames.add(pd.getName());
        }
        String[] result = new String[emptyNames.size()];
        return emptyNames.toArray(result);
    }

    public static void copyProperties(Object src, Object target) {
        BeanUtils.copyProperties(src, target, getNullPropertyNames(src));
    }

Then use your update like this

 public Publisher update(@Named("id") Long id, Publisher publisher) throws Exception {
        checkExists(id);
        Publisher destination = get(id);
        copyProperties(publisher, destination);
        return insert(destination);
    }

NOTE: This method will not overide null and list properties.