/*
* Copyright 2002-2008 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.web.jsf;
import javax.faces.context.FacesContext;
import javax.faces.el.EvaluationException;
import javax.faces.el.VariableResolver;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.util.Assert;
import org.springframework.web.context.WebApplicationContext;
/**
* JSF 1.1 <code>VariableResolver</code> that first delegates to the
* original resolver of the underlying JSF implementation (for resolving
* managed-bean objects as defined in <code>faces-config.xml</code>
* as well as well-known implicit EL attributes), then to the Spring
* root <code>WebApplicationContext</code> (for resolving Spring beans).
*
* <p>Configure this resolver in your <code>faces-config.xml</code> file as follows:
*
* <pre>
* <application>
* ...
* <variable-resolver>org.springframework.web.jsf.DelegatingVariableResolver</variable-resolver>
* </application></pre>
*
* All your JSF expressions can then implicitly refer to the names of
* Spring-managed service layer beans, for example in property values of
* JSF-managed beans:
*
* <pre>
* <managed-bean>
* <managed-bean-name>myJsfManagedBean</managed-bean-name>
* <managed-bean-class>example.MyJsfManagedBean</managed-bean-class>
* <managed-bean-scope>session</managed-bean-scope>
* <managed-property>
* <property-name>mySpringManagedBusinessObject</property-name>
* <value>#{mySpringManagedBusinessObject}</value>
* </managed-property>
* </managed-bean></pre>
*
* with "mySpringManagedBusinessObject" defined as Spring bean in
* applicationContext.xml:
*
* <pre>
* <bean id="mySpringManagedBusinessObject" class="example.MySpringManagedBusinessObject">
* ...
* </bean></pre>
*
* @author Juergen Hoeller
* @since 1.1
* @see WebApplicationContextVariableResolver
* @see FacesContextUtils#getRequiredWebApplicationContext
*/
public class DelegatingVariableResolver extends VariableResolver {
/** Logger available to subclasses */
protected final Log logger = LogFactory.getLog(getClass());
protected final VariableResolver originalVariableResolver;
/**
* Create a new DelegatingVariableResolver, using the given original VariableResolver.
* <p>A JSF implementation will automatically pass its original resolver into the
* constructor of a configured resolver, provided that there is a corresponding
* constructor argument.
* @param originalVariableResolver the original VariableResolver
*/
public DelegatingVariableResolver(VariableResolver originalVariableResolver) {
Assert.notNull(originalVariableResolver, "Original JSF VariableResolver must not be null");
this.originalVariableResolver = originalVariableResolver;
}
/**
* Return the original JSF VariableResolver that this resolver delegates to.
* Used to resolve standard JSF-managed beans.
*/
protected final VariableResolver getOriginalVariableResolver() {
return this.originalVariableResolver;
}
/**
* Delegate to the original VariableResolver first, then try to
* resolve the variable as Spring bean in the root WebApplicationContext.
*/
@Override
public Object resolveVariable(FacesContext facesContext, String name) throws EvaluationException {
Object value = resolveOriginal(facesContext, name);
if (value != null) {
return value;
}
Object bean = resolveSpringBean(facesContext, name);
if (bean != null) {
return bean;
}
return null;
}
/**
* Resolve the attribute via the original JSF VariableResolver.
*/
protected Object resolveOriginal(FacesContext facesContext, String name) {
Object value = getOriginalVariableResolver().resolveVariable(facesContext, name);
if (value != null && logger.isTraceEnabled()) {
logger.trace("Successfully resolved variable '" + name + "' via original VariableResolver");
}
return value;
}
/**
* Resolve the attribute as a Spring bean in the ApplicationContext.
*/
protected Object resolveSpringBean(FacesContext facesContext, String name) {
BeanFactory bf = getBeanFactory(facesContext);
if (bf.containsBean(name)) {
if (logger.isTraceEnabled()) {
logger.trace("Successfully resolved variable '" + name + "' in Spring BeanFactory");
}
return bf.getBean(name);
}
else {
return null;
}
}
/**
* Retrieve the Spring BeanFactory to delegate bean name resolution to.
* <p>The default implementation delegates to <code>getWebApplicationContext</code>.
* Can be overridden to provide an arbitrary BeanFactory reference to resolve
* against; usually, this will be a full Spring ApplicationContext.
* @param facesContext the current JSF context
* @return the Spring BeanFactory (never <code>null</code>)
* @see #getWebApplicationContext
*/
protected BeanFactory getBeanFactory(FacesContext facesContext) {
return getWebApplicationContext(facesContext);
}
/**
* Retrieve the web application context to delegate bean name resolution to.
* <p>The default implementation delegates to FacesContextUtils.
* @param facesContext the current JSF context
* @return the Spring web application context (never <code>null</code>)
* @see FacesContextUtils#getRequiredWebApplicationContext
*/
protected WebApplicationContext getWebApplicationContext(FacesContext facesContext) {
return FacesContextUtils.getRequiredWebApplicationContext(facesContext);
}
}
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