org.neo4j.kernel
Class KernelExtension<S>

java.lang.Object
  org.neo4j.helpers.Service
      org.neo4j.kernel.KernelExtension<S>

Type Parameters:

S - the Extension state type

public abstract class KernelExtension<S>
extends Service

Hook for providing extended functionality to the Neo4j Graph Database kernel. Implementations of KernelExtension must fulfill the following contract:

• Must have a public no-arg constructor.
• The same instance must be able to load with multiple GraphDatabase kernels.
• Different instances should be able to access the same state from the same kernel.
  To achieve this, different instances of the same class should have the same hashCode() and be equals(Object). This is enforced by this base class by delegating hashCode() and equals(Object) to the same methods on the class object.

The simplest way to implement an extension that fulfills this contract is if the extension implementation is stateless, and all state is kept in the state object returned by the load method. Note that for an extension to be considered loaded by the kernel, the load method may not return null. The unload method will only be invoked if the kernel considers the extension loaded.

Author:

Tobias Ivarsson

Nested Class Summary

Nested classes/interfaces inherited from class org.neo4j.helpers.Service

Service.CaseInsensitiveService, Service.Implementation

Constructor Summary

KernelExtension(String key)

Method Summary

protected Object	agentArgument(String agentArg)
protected S	agentLoad(KernelData kernel, Object param)
protected void	agentVisit(KernelData kernel, S state, Object param)
boolean	equals(Object obj)
protected S	getState(KernelData kernel)
int	hashCode()
protected boolean	isLoaded(KernelData kernel)
protected abstract S	load(KernelData kernel) Load this extension for a particular Neo4j Kernel.
protected void	loadAgent(KernelData kernel, Object param)
void	loadAgent(String agentArgs)
protected void	loadConfiguration(KernelData kernel) Takes place before any data sources has been registered and is there to let extensions affect the configuration of other things starting up.
protected void	unload(S state)

Methods inherited from class org.neo4j.helpers.Service

load, load, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

KernelExtension

public KernelExtension(String key)

Method Detail

hashCode

public final int hashCode()

Overrides:

hashCode in class Object

equals

public final boolean equals(Object obj)

Overrides:

equals in class Object

loadAgent

public final void loadAgent(String agentArgs)

loadAgent

protected final void loadAgent(KernelData kernel,
                               Object param)

agentArgument

protected Object agentArgument(String agentArg)

load

protected abstract S load(KernelData kernel)

Load this extension for a particular Neo4j Kernel.

agentLoad

protected S agentLoad(KernelData kernel,
                      Object param)

agentVisit

protected void agentVisit(KernelData kernel,
                          S state,
                          Object param)

loadConfiguration

protected void loadConfiguration(KernelData kernel)

Takes place before any data sources has been registered and is there to let extensions affect the configuration of other things starting up.

unload

protected void unload(S state)

getState

protected final S getState(KernelData kernel)

isLoaded

protected boolean isLoaded(KernelData kernel)