Package org.apache.jackrabbit.rmi.value

Serializable implementation of the JCR Value interfaces.

See:
Description

Interface Summary

StatefulValue

The StatefullValue interface defines the API used for the state classes used by the SerialValue class.

Class Summary

BaseNonStreamValue	The BaseNonStreamValue class implements the basic committed value state for non-stream values as a part of the State design pattern (Gof) used by this package.
BinaryValue	The BinaryValue class implements the committed value state for Binary values as a part of the State design pattern (Gof) used by this package.
BooleanValue	The BooleanValue class implements the committed value state for Boolean values as a part of the State design pattern (Gof) used by this package.
DateValue	The DateValue class implements the committed value state for Date values as a part of the State design pattern (Gof) used by this package.
DoubleValue	The DoubleValue class implements the committed value state for Double values as a part of the State design pattern (Gof) used by this package.
LongValue	The LongValue class implements the committed value state for Long values as a part of the State design pattern (Gof) used by this package.
NameValue	The NameValue class implements the committed value state for Name values as a part of the State design pattern (Gof) used by this package.
PathValue	The PathValue class implements the committed value state for Path values as a part of the State design pattern (Gof) used by this package.
ReferenceValue	The ReferenceValue class implements the committed value state for Reference values as a part of the State design pattern (Gof) used by this package.
SerialValueFactory	The SerialValueFactory class is used in the RMI infrastructure to create serializable Value instances on the client side.
StringValue	The StringValue class implements the committed value state for String values as a part of the State design pattern (Gof) used by this package.

Package org.apache.jackrabbit.rmi.value Description

Serializable implementation of the JCR Value interfaces.

This package contains a simple implementation of the JCR Value and ValueFactory interfaces. The implementation has no external dependencies and supports serialization of Value instances.

Note that the Value instances created by this package are not thread safe.

Implementation notes

This package uses the State design pattern (GoF) to implement the JCR Value interface. A Value instance is initially in a fresh state that gets committed to a stream or non-stream state once the first value getter method is invoked. After that the Value state is no longer changed. The state diagram below illustrates the Value states.

The GeneralValue implementation class acts as the state context object. It contains a reference to another Value instance that represents the current Value state. The reference is initially set to an InitialValue instance that is used to intercept the first value getter method. When the first method call is made, the InitialValue instance performs the correct state transition by changing the GenericValue state reference to a committed Value instance.

The committed Value states are implemented by the type-specific classes StringValue, LongValue, DoubleValue, BooleanValue, DateValue, and BinaryValue. These classes handle no state transitions, but implement the value conversion rules defined in the JCR specification.

The sequence diagram below illustrates the sequence of actions of creating a string value, committing it to the stream state, and finally using it in that state.

These implementation classes are all package-local and final, and their behaviour can therefore not be modified externally. The Decorator design pattern should be used if changes to Value behaviour are needed.

About Value equality

The current JCR specification (0.16.4) does not define a safe mechanism for implementing the equals method in general. A proper implementation of this method would currently require potential state changes in the compared Value instances. Thus this package only defines equality comparisons between Value instances generated by this package and throws UnsupportedOperationExceptions for more general Value comparisons.