com.googlecode.objectify.impl.translate

Interface Populator<P>

All Known Implementing Classes:

ClassPopulator, NullPopulator, PropertyPopulator

public interface Populator<P>

A populator knows how to copy properties between POJO objects and a PropertiesContainer. Unlike a translator, it doesn't create the POJO or container.

P is the pojo type.

Author:

Jeff Schnitzer

Method Summary

Modifier and Type	Method and Description
void	load(com.google.appengine.api.datastore.PropertyContainer node, LoadContext ctx, Path path, P into) Loads the content of the specified datastore node, returning the pojo equivalent.
void	save(P pojo, boolean index, SaveContext ctx, Path path, com.google.appengine.api.datastore.PropertyContainer into) Translates a pojo (or some component thereof) into a format suitable for storage in the datastore.

Method Detail

load

void load(com.google.appengine.api.datastore.PropertyContainer node,
          LoadContext ctx,
          Path path,
          P into)

Loads the content of the specified datastore node, returning the pojo equivalent.

There is one special value for loading: If a Result is returned from a translator, the content of the Result will be used instead, but delayed until ctx.done() is called. This happens at the end of a "round" of load operations and is the magic trick that makes populating entity references work efficiently.

Parameters:

node - is the part of the native datastore entity tree we are transforming.

ctx - holds state information during an entity load.

path - is the current path to this translator

into - is an optional parameter; sometimes we need to create an object at a higher level and pass it down through a stack of translators. Most translators will ignore this, but some will have special behavior, for example, this allows collections to be recycled.

save

void save(P pojo,
          boolean index,
          SaveContext ctx,
          Path path,
          com.google.appengine.api.datastore.PropertyContainer into)

Translates a pojo (or some component thereof) into a format suitable for storage in the datastore.

Parameters:

pojo - is an object from the pojo entity graph; possibly the whole graph or possibly just a leaf field.

index - is whether the instruction so far is to index or not index property values

path - is the path that we have taken to get here, which could be long due to re-entrant translators (ie, an embedded pojo that also has a reference to the same class).