JsfManagedBeanResolver.java :  » Workflow-Engines » spring-webflow-2.0.8 » org » springframework » faces » webflow » Java Open Source

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spring webflow 2.0.8 » org » springframework » faces » webflow » JsfManagedBeanResolver.java
/*
 * Copyright 2004-2008 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.faces.webflow;

import java.util.Iterator;

import javax.el.ELContext;
import javax.el.ELResolver;
import javax.faces.context.FacesContext;
import javax.faces.el.ValueBinding;

import org.springframework.util.Assert;
import org.springframework.webflow.execution.RequestContext;
import org.springframework.webflow.execution.RequestContextHolder;

/**
 * ELResolver that checks request, session, and application scopes for existing JSF-managed beans. This allows
 * traditional JSF-managed beans (defined in faces-config.xml) to be resolved through expressions in a flow definition.
 * The preferred approach is to instead use Spring to configure such beans, but this is meant to ease migration for
 * users with existing JSF artifacts. This resolver will delegate to a temporary FacesContext so that JSF managed bean
 * initialization will be triggered if the bean has not already been initialized by JSF.
 * 
 * @author Jeremy Grelle
 */
public class JsfManagedBeanResolver extends ELResolver {

  public Class getCommonPropertyType(ELContext context, Object base) {
    return Object.class;
  }

  public Iterator getFeatureDescriptors(ELContext context, Object base) {
    return null;
  }

  public Class getType(ELContext context, Object base, Object property) {
    if (base == null) {
      Object bean = getFacesBean(property);
      if (bean != null) {
        context.setPropertyResolved(true);
        return bean.getClass();
      }
    }
    return null;
  }

  public Object getValue(ELContext context, Object base, Object property) {
    if (base == null) {
      Object bean = getFacesBean(property);
      if (bean != null) {
        context.setPropertyResolved(true);
        return bean;
      }
    }
    return null;
  }

  public boolean isReadOnly(ELContext context, Object base, Object property) {
    if (base == null) {
      RequestContext requestContext = RequestContextHolder.getRequestContext();
      if (requestContext.getExternalContext().getRequestMap().contains(property.toString())
          || requestContext.getExternalContext().getSessionMap().contains(property.toString())
          || requestContext.getExternalContext().getApplicationMap().contains(property.toString())) {
        context.setPropertyResolved(true);
      }
    }
    return false;
  }

  /**
   * Sets a bean value if a corresponding key is found in one of the ExternalContext scopes.
   */
  public void setValue(ELContext context, Object base, Object property, Object value) {
    if (base == null) {
      RequestContext requestContext = RequestContextHolder.getRequestContext();
      if (requestContext.getExternalContext().getRequestMap().contains(property.toString())) {
        context.setPropertyResolved(true);
        requestContext.getExternalContext().getRequestMap().put(property.toString(), value);
      } else if (requestContext.getExternalContext().getSessionMap().contains(property.toString())) {
        context.setPropertyResolved(true);
        requestContext.getExternalContext().getSessionMap().put(property.toString(), value);
      } else if (requestContext.getExternalContext().getApplicationMap().contains(property.toString())) {
        context.setPropertyResolved(true);
        requestContext.getExternalContext().getApplicationMap().put(property.toString(), value);
      }
    }
  }

  /**
   * This resolver is only meant to be called from the Flow Execution, thus it assumes that the FacesContext will not
   * be available and creates a temporary one on the fly.
   * @return The initialized FacesContext.
   */
  private FacesContext getFacesContext() {
    RequestContext requestContext = RequestContextHolder.getRequestContext();
    Assert.notNull(requestContext, "RequestContext cannot be null - This resolver is only intended to be invoked "
        + "from an active Flow Execution.");
    FacesContext facesContext = FlowFacesContext.newInstance(requestContext, FlowLifecycle.newInstance());
    return facesContext;
  }

  /**
   * Uses a temporary FacesContext to try and resolve a JSF Managed Bean
   * @param beanName - The name of the bean to resolve.
   * @return The JSF Managed Bean instance if found.
   */
  private Object getFacesBean(Object beanName) {
    FacesContext facesContext = getFacesContext();
    Object result = null;
    try {
      ValueBinding vb = facesContext.getApplication().createValueBinding("#{" + beanName + "}");
      result = vb.getValue(facesContext);
    } finally {
      facesContext.release();
    }
    return result;
  }
}
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