com.persistit.encoding

Interface ValueRenderer

All Superinterfaces:

ValueCoder

All Known Subinterfaces:

ObjectCoder

All Known Implementing Classes:

CollectionValueCoder, DefaultObjectCoder, DefaultValueCoder

public interface ValueRenderer
extends ValueCoder

An extended ValueCoder that can populate a supplied Object with data that was formerly written to a Value by the ValueCoder.

A ValueRenderer implements an additional method called render(com.persistit.Value, java.lang.Object, java.lang.Class<?>, com.persistit.encoding.CoderContext) that populates a supplied target object rather than creating a new object instance. The application provides the mutable target object to Value.get(Object).

A ValueRenderer can implement an application-level contract to recover a limited set of fields from an encoded Value or to populate a generic target object that might be suitable for utility display purposes. For example, suppose there is a complex Person class with many fields that refer to other objects. Deserializing and populating all the fields of such a Person object might not be appropriate in an area of the application that merely needs to display a list of names. To avoid completely deserializing numerous Person objects, the application could register a ValueRenderer implementation that knows how to decode a serialized Person into a PersonListData object. To do so it would Value.get() the desired interior fields of the encoded Person and Value.skip() the other fields.

Version:

1.0

Method Summary

Modifier and Type	Method and Description
void	render(Value value, Object target, Class<?> clazz, CoderContext context) Populates the state of the supplied (mutable) target Object by decoding the supplied Value.

Methods inherited from interface com.persistit.encoding.ValueCoder

get, put

Method Detail

render

void render(Value value,
            Object target,
            Class<?> clazz,
            CoderContext context)
     throws ConversionException

Populates the state of the supplied (mutable) target Object by decoding the supplied Value. This method will be called only if this ValueRenderer has been registered with the current CoderManager to encode objects having the supplied Class value. Persistit will never call this method to decode a value that was null when written because null values are handled by built-in encoding logic.

Parameters:

value - The Value from which interior fields of the object are to be retrieved

target - The object into which the decoded value is to be written

clazz - The class of the object that was originally encoded into Value.

context - An arbitrary object that can optionally be supplied by the application to convey an application-specific context for the operation. (See CoderContext.) The default value is null.

Throws:

ConversionException