/*
* Copyright (c) 2012-2013, Jan Bernitt
*
* Licensed under the Apache License, Version 2.0, http://www.apache.org/licenses/LICENSE-2.0
*/
package se.jbee.inject.util;
import java.util.HashMap;
import java.util.Map;
import se.jbee.inject.Demand;
import se.jbee.inject.Dependency;
import se.jbee.inject.Injectable;
import se.jbee.inject.Repository;
import se.jbee.inject.Scope;
/**
* Utility as a factory to create/use {@link Scope}s.
*
* @author Jan Bernitt (jan@jbee.se)
*/
public class Scoped {
public interface KeyDeduction {
<T> String deduceKey( Demand<T> demand );
}
public static final KeyDeduction DEPENDENCY_TYPE_KEY = new DependencyTypeAsKey();
public static final KeyDeduction DEPENDENCY_INSTANCE_KEY = new DependencyInstanceAsKey();
public static final KeyDeduction TARGET_INSTANCE_KEY = new TargetInstanceAsKey();
public static final KeyDeduction TARGETED_DEPENDENCY_TYPE_KEY = new ConcatKeysDeduction(
DEPENDENCY_INSTANCE_KEY, TARGET_INSTANCE_KEY );
/**
* Often called the 'default' or 'prototype'-scope. Asks the {@link Injectable} once per
* injection.
*/
public static final Scope INJECTION = new InjectionScope();
/**
* Asks the {@link Injectable} once per binding. Thereby instances become singletons local to
* the application.
*/
public static final Scope APPLICATION = new ApplicationScope();
/**
* Asks the {@link Injectable} once per thread per binding which is understand commonly as a
* usual 'per-thread' singleton.
*/
public static final Scope THREAD = new ThreadScope( new ThreadLocal<Repository>(), APPLICATION );
public static final Scope DEPENDENCY_TYPE = uniqueBy( DEPENDENCY_TYPE_KEY );
public static final Scope DEPENDENCY_INSTANCE = uniqueBy( DEPENDENCY_INSTANCE_KEY );
public static final Scope TARGET_INSTANCE = uniqueBy( TARGET_INSTANCE_KEY );
public static final Scope DEPENDENCY = uniqueBy( TARGETED_DEPENDENCY_TYPE_KEY );
public static Scope uniqueBy( KeyDeduction keyDeduction ) {
return new KeyDeductionScope( keyDeduction );
}
public static Repository asSnapshot( Repository src, Repository dest ) {
return new SnapshotRepository( src, dest );
}
/**
* What is usually called a 'default'-{@link Scope} will ask the {@link Injectable} passed each
* time the {@link Repository#serve(Dependency, Injectable)}-method is invoked.
*
* The {@link Scope} is also used as {@link Repository} instance since both don#t have any
* state.
*
* @see Scoped#INJECTION
*
* @author Jan Bernitt (jan@jbee.se)
*/
private static final class InjectionScope
implements Scope, Repository {
InjectionScope() {
// make visible
}
@Override
public Repository init() {
return this;
}
@Override
public <T> T serve( Demand<T> demand, Injectable<T> injectable ) {
return injectable.instanceFor( demand );
}
@Override
public String toString() {
return "(default)";
}
}
private static final class ThreadScope
implements Scope, Repository {
private final ThreadLocal<Repository> threadRepository;
private final Scope repositoryScope;
ThreadScope( ThreadLocal<Repository> threadRepository, Scope repositoryScope ) {
super();
this.threadRepository = threadRepository;
this.repositoryScope = repositoryScope;
}
@Override
public <T> T serve( Demand<T> demand, Injectable<T> injectable ) {
Repository repository = threadRepository.get();
if ( repository == null ) {
// since each thread is just accessing its own repo there cannot be a repo set for the running thread after we checked for null
repository = repositoryScope.init();
threadRepository.set( repository );
}
return repository.serve( demand, injectable );
}
@Override
public Repository init() {
return this;
}
@Override
public String toString() {
return "(per-thread)";
}
}
/**
* The 'synchronous'-{@link Repository} will be asked first passing a special resolver that will
* ask the 'asynchronous' repository when invoked. Thereby the repository originally bound will
* be asked once. Thereafter the result is stored in the synchronous repository.
*
* Both repositories will remember the resolved instance whereby the repository considered as
* the synchronous-repository will deliver a consistent image of the world as long as it exists.
*
* @author Jan Bernitt (jan@jbee.se)
*/
private static final class SnapshotRepository
implements Repository {
private final Repository dest;
private final Repository src;
SnapshotRepository( Repository src, Repository dest ) {
super();
this.dest = dest;
this.src = src;
}
@Override
public <T> T serve( Demand<T> demand, Injectable<T> injectable ) {
return dest.serve( demand, new SnapshotingInjectable<T>( injectable, src ) );
}
private static final class SnapshotingInjectable<T>
implements Injectable<T> {
private final Injectable<T> supplier;
private final Repository src;
SnapshotingInjectable( Injectable<T> supplier, Repository src ) {
super();
this.supplier = supplier;
this.src = src;
}
@Override
public T instanceFor( Demand<T> demand ) {
return src.serve( demand, supplier );
}
}
}
private static final class KeyDeductionScope
implements Scope {
private final KeyDeduction keyDeduction;
KeyDeductionScope( KeyDeduction keyDeduction ) {
super();
this.keyDeduction = keyDeduction;
}
@Override
public Repository init() {
return new KeyDeductionRepository( keyDeduction );
}
@Override
public String toString() {
return "(per-" + keyDeduction + ")";
}
}
private static final class ConcatKeysDeduction
implements KeyDeduction {
private final KeyDeduction first;
private final KeyDeduction second;
ConcatKeysDeduction( KeyDeduction first, KeyDeduction second ) {
super();
this.first = first;
this.second = second;
}
@Override
public <T> String deduceKey( Demand<T> demand ) {
return first.deduceKey( demand ).concat( second.deduceKey( demand ) );
}
}
private static final class TargetInstanceAsKey
implements KeyDeduction {
TargetInstanceAsKey() {
// make visible
}
@Override
public <T> String deduceKey( Demand<T> demand ) {
Dependency<? super T> dependency = demand.getDependency();
StringBuilder b = new StringBuilder();
for ( int i = dependency.injectionDepth() - 1; i >= 0; i-- ) {
b.append( dependency.target( i ) );
}
return b.toString();
}
@Override
public String toString() {
return "target-instance";
}
}
private static final class DependencyTypeAsKey
implements KeyDeduction {
DependencyTypeAsKey() {
// make visible
}
@Override
public <T> String deduceKey( Demand<T> demand ) {
return demand.getDependency().getType().toString();
}
@Override
public String toString() {
return "dependendy-type";
}
}
private static final class DependencyInstanceAsKey
implements KeyDeduction {
DependencyInstanceAsKey() {
// make visible
}
@Override
public <T> String deduceKey( Demand<T> demand ) {
return demand.getDependency().getName().toString() + "@"
+ demand.getDependency().getType().toString();
}
@Override
public String toString() {
return "dependendy-type";
}
}
// e.g. get receiver class from dependency -to be reusable the provider could offer a identity --> a wrapper class would be needed anyway so maybe best is to have quite similar impl. all using a identity hash-map
private static final class KeyDeductionRepository
implements Repository {
private final Map<String, Object> instances = new HashMap<String, Object>();
private final KeyDeduction injectionKey;
KeyDeductionRepository( KeyDeduction injectionKey ) {
super();
this.injectionKey = injectionKey;
}
@Override
@SuppressWarnings ( "unchecked" )
public <T> T serve( Demand<T> demand, Injectable<T> injectable ) {
final String key = injectionKey.deduceKey( demand );
T instance = (T) instances.get( key );
if ( instance != null ) {
return instance;
}
synchronized ( instances ) {
instance = (T) instances.get( key );
if ( instance == null ) {
instance = injectable.instanceFor( demand );
instances.put( key, instance );
}
}
return instance;
}
}
/**
* Will lead to instances that can be seen as application-wide-singletons.
*
* @author Jan Bernitt (jan@jbee.se)
*
*/
private static final class ApplicationScope
implements Scope {
ApplicationScope() {
//make visible
}
@Override
public Repository init() {
return new ResourceRepository();
}
@Override
public String toString() {
return "(per-app)";
}
}
/**
* Contains once instance per resource. Resources are never updated. This can be used to create
* a thread or request {@link Scope}.
*
* @author Jan Bernitt (jan@jbee.se)
*/
private static final class ResourceRepository
implements Repository {
private Object[] instances;
ResourceRepository() {
super();
}
@Override
@SuppressWarnings ( "unchecked" )
public <T> T serve( Demand<T> demand, Injectable<T> injectable ) {
if ( instances == null ) {
instances = new Object[demand.envCardinality()];
}
T res = (T) instances[demand.envSerialNumber()];
if ( res != null ) {
return res;
}
// just sync the (later) unexpected path that is executed once
synchronized ( instances ) {
res = (T) instances[demand.envSerialNumber()];
if ( res == null ) { // we need to ask again since the instance could have been initialized before we got entrance to the sync block
res = injectable.instanceFor( demand );
instances[demand.envSerialNumber()] = res;
}
}
return res;
}
}
}