gw.config.ServiceKernel Maven / Gradle / Ivy
/*
* Copyright 2014 Guidewire Software, Inc.
*/
package gw.config;
import gw.lang.parser.ILanguageLevel;
import gw.util.Stack;
import manifold.util.ReflectUtil;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.util.HashMap;
import java.util.Map;
public abstract class ServiceKernel
{
private Map, IService> _services;
private Stack _initingServices = new Stack<>();
private boolean _definingServices = false;
protected ServiceKernel()
{
resetKernel();
}
protected void resetKernel()
{
_services = new HashMap, IService>();
_definingServices = true;
try
{
defineServices();
}
finally
{
_definingServices = false;
}
redefineServices();
}
/**
* Contains all the definitions of the services provided by this kernel
*/
protected abstract void defineServices();
/**
* Contains the redefinition logic for this kernel
*/
protected abstract void redefineServices();
/**
* @param service
* @return
*/
public T getService( Class service )
{
if( _definingServices )
{
throw new IllegalStateException( "Service definition in progress, access to " + service.getName() + " is not " +
"allowed. Move this access to the init() method of the offending service." );
}
IService serviceImpl = _services.get( service );
if( serviceImpl == null )
{
throw new IllegalStateException( "The service " + service.getName() + " is not provided by this ServiceKernel." );
}
return (T)serviceImpl;
}
/**
* Overrides the default implemenation of the service with a different provider. Note that the current
* provider cannot have been accessed (all services must be consistent during runtime.)
*
* @param service - the service to provide
* @param newProvider - the new provider of this service
*/
public void redefineService(Class service, Q newProvider)
{
if( _definingServices )
{
throw new IllegalStateException( "Service definition in progress, so service redefinition is not allowed. Please " +
"move redefinitions to the redefineServices method." );
}
IService existingServiceImpl = _services.get( service );
if( existingServiceImpl == null )
{
throw new IllegalArgumentException( "Service " + service.getName() + " is not defined in this ServiceKernel.");
}
if( existingServiceImpl.isInited() )
{
throw new IllegalStateException( "Service " + service.getName() + " has already been " +
"initialized with the " + existingServiceImpl.getClass().getName() +
" implementation");
}
_services.put( service, newProvider );
}
public void redefineService_Privileged(Class service, Q newProvider)
{
IService existingServiceImpl = _services.get( service );
if( existingServiceImpl == null )
{
throw new IllegalArgumentException( "Service " + service.getName() + " is not defined in this ServiceKernel.");
}
_services.put( service, newProvider );
}
protected void defineService(Class serviceClass, Class implClass ) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException, InstantiationException
{
T serviceImpl = (T)ReflectUtil.constructor( implClass ).newInstance();
defineService( serviceClass, serviceImpl );
}
/**
* Defines a service provided by this ServiceKernel
*
* @param service - the service to provide
* @param defaultImplementation - the default implementation of this service
*/
protected void defineService(Class service, Q defaultImplementation)
{
if( !_definingServices )
{
throw new IllegalStateException( "Service definition must be done only in the defineServices() method." );
}
if( !service.isInterface() )
{
throw new IllegalArgumentException( "Services may only be defined as interfaces, and " +
service.getName() +
" is not an interface" );
}
IService existingServiceImpl = _services.get( service );
if( existingServiceImpl != null )
{
throw new IllegalStateException( "Service " + service.getName() + " has already been " +
"defined with the " + existingServiceImpl.getClass().getName() +
" default implementation");
}
_services.put( service, defaultImplementation );
}
/**
* @param initClassName a class name of a class that implements {@link ServiceKernelInit) and that will be created
* and given a chance to redefine the service implementations in this kernel.
*/
protected void redefineServicesWithClass( String initClassName )
{
try
{
Class aClass = getClass().forName( initClassName );
ServiceKernelInit init = (ServiceKernelInit)aClass.newInstance();
init.init( this );
}
catch( ClassNotFoundException e )
{
try {
Class aClass = Thread.currentThread().getContextClassLoader().loadClass( initClassName );
ServiceKernelInit init = (ServiceKernelInit)aClass.newInstance();
init.init( this );
} catch (Exception e1) {
e1.printStackTrace();
throw new RuntimeException( e1 );
}
}
catch (Exception e1) {
throw new RuntimeException( e1 );
} finally {
ILanguageLevel.Util.reset();
}
}
private void detectCircularInitializationDependencies( IService service )
{
if( _initingServices.contains( service ) )
{
StringBuilder sb = new StringBuilder( "Circular service initialization dependency detected : " );
for( IService initingService : _initingServices )
{
sb.append( "\n\t" ).append( initingService );
}
throw new IllegalStateException( sb.toString() );
}
}
}