/*
* Copyright 2006-2013 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.batch.core.scope;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.batch.core.scope.context.StepContext;
import org.springframework.batch.core.scope.context.StepSynchronizationManager;
import org.springframework.beans.BeanWrapper;
import org.springframework.beans.BeanWrapperImpl;
import org.springframework.beans.factory.ObjectFactory;
import org.springframework.beans.factory.config.Scope;
/**
* Scope for step context. Objects in this scope use the Spring container as an
* object factory, so there is only one instance of such a bean per executing
* step. All objects in this scope are <aop:scoped-proxy/> (no need to
* decorate the bean definitions).<br>
* <br>
*
* In addition, support is provided for late binding of references accessible
* from the {@link StepContext} using #{..} placeholders. Using this feature,
* bean properties can be pulled from the step or job execution context and the
* job parameters. E.g.
*
* <pre>
* <bean id="..." class="..." scope="step">
* <property name="parent" ref="#{stepExecutionContext[helper]}" />
* </bean>
*
* <bean id="..." class="..." scope="step">
* <property name="name" value="#{stepExecutionContext['input.name']}" />
* </bean>
*
* <bean id="..." class="..." scope="step">
* <property name="name" value="#{jobParameters[input]}" />
* </bean>
*
* <bean id="..." class="..." scope="step">
* <property name="name" value="#{jobExecutionContext['input.stem']}.txt" />
* </bean>
* </pre>
*
* The {@link StepContext} is referenced using standard bean property paths (as
* per {@link BeanWrapper}). The examples above all show the use of the Map
* accessors provided as a convenience for step and job attributes.
*
* @author Dave Syer
* @author Michael Minella
* @since 2.0
*/
public class StepScope extends BatchScopeSupport {
private static final String TARGET_NAME_PREFIX = "stepScopedTarget.";
private Log logger = LogFactory.getLog(getClass());
private final Object mutex = new Object();
/**
* Context key for clients to use for conversation identifier.
*/
public static final String ID_KEY = "STEP_IDENTIFIER";
public StepScope() {
super();
setName("step");
}
/**
* This will be used to resolve expressions in step-scoped beans.
*/
@Override
public Object resolveContextualObject(String key) {
StepContext context = getContext();
// TODO: support for attributes as well maybe (setters not exposed yet
// so not urgent).
return new BeanWrapperImpl(context).getPropertyValue(key);
}
/**
* @see Scope#get(String, ObjectFactory)
*/
@Override
public Object get(String name, ObjectFactory<?> objectFactory) {
StepContext context = getContext();
Object scopedObject = context.getAttribute(name);
if (scopedObject == null) {
synchronized (mutex) {
scopedObject = context.getAttribute(name);
if (scopedObject == null) {
logger.debug(String.format("Creating object in scope=%s, name=%s", this.getName(), name));
scopedObject = objectFactory.getObject();
context.setAttribute(name, scopedObject);
}
}
}
return scopedObject;
}
/**
* @see Scope#getConversationId()
*/
@Override
public String getConversationId() {
StepContext context = getContext();
return context.getId();
}
/**
* @see Scope#registerDestructionCallback(String, Runnable)
*/
@Override
public void registerDestructionCallback(String name, Runnable callback) {
StepContext context = getContext();
logger.debug(String.format("Registered destruction callback in scope=%s, name=%s", this.getName(), name));
context.registerDestructionCallback(name, callback);
}
/**
* @see Scope#remove(String)
*/
@Override
public Object remove(String name) {
StepContext context = getContext();
logger.debug(String.format("Removing from scope=%s, name=%s", this.getName(), name));
return context.removeAttribute(name);
}
/**
* Get an attribute accessor in the form of a {@link StepContext} that can
* be used to store scoped bean instances.
*
* @return the current step context which we can use as a scope storage
* medium
*/
private StepContext getContext() {
StepContext context = StepSynchronizationManager.getContext();
if (context == null) {
throw new IllegalStateException("No context holder available for step scope");
}
return context;
}
@Override
public String getTargetNamePrefix() {
return TARGET_NAME_PREFIX;
}
}