org.springframework.beans.factory.access.el.SpringBeanELResolver.java Source code

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Here is the source code for org.springframework.beans.factory.access.el.SpringBeanELResolver.java

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/*
 * Copyright 2002-2014 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.beans.factory.access.el;

import java.beans.FeatureDescriptor;
import java.util.Iterator;
import javax.el.ELContext;
import javax.el.ELException;
import javax.el.ELResolver;
import javax.el.PropertyNotWritableException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.factory.BeanFactory;

/**
 * Unified EL {@code ELResolver} that delegates to a Spring BeanFactory,
 * resolving name references to Spring-defined beans.
 *
 * @author Juergen Hoeller
 * @since 2.5.2
 * @see org.springframework.web.jsf.el.SpringBeanFacesELResolver
 */
public abstract class SpringBeanELResolver extends ELResolver {

    /** Logger available to subclasses */
    protected final Log logger = LogFactory.getLog(getClass());

    @Override
    public Object getValue(ELContext elContext, Object base, Object property) throws ELException {
        if (base == null) {
            String beanName = property.toString();
            BeanFactory bf = getBeanFactory(elContext);
            if (bf.containsBean(beanName)) {
                if (logger.isTraceEnabled()) {
                    logger.trace("Successfully resolved variable '" + beanName + "' in Spring BeanFactory");
                }
                elContext.setPropertyResolved(true);
                return bf.getBean(beanName);
            }
        }
        return null;
    }

    @Override
    public Class<?> getType(ELContext elContext, Object base, Object property) throws ELException {
        if (base == null) {
            String beanName = property.toString();
            BeanFactory bf = getBeanFactory(elContext);
            if (bf.containsBean(beanName)) {
                elContext.setPropertyResolved(true);
                return bf.getType(beanName);
            }
        }
        return null;
    }

    @Override
    public void setValue(ELContext elContext, Object base, Object property, Object value) throws ELException {
        if (base == null) {
            String beanName = property.toString();
            BeanFactory bf = getBeanFactory(elContext);
            if (bf.containsBean(beanName)) {
                if (value == bf.getBean(beanName)) {
                    // Setting the bean reference to the same value is alright - can simply be ignored...
                    elContext.setPropertyResolved(true);
                } else {
                    throw new PropertyNotWritableException("Variable '" + beanName
                            + "' refers to a Spring bean which by definition is not writable");
                }
            }
        }
    }

    @Override
    public boolean isReadOnly(ELContext elContext, Object base, Object property) throws ELException {
        if (base == null) {
            String beanName = property.toString();
            BeanFactory bf = getBeanFactory(elContext);
            if (bf.containsBean(beanName)) {
                return true;
            }
        }
        return false;
    }

    @Override
    public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext elContext, Object base) {
        return null;
    }

    @Override
    public Class<?> getCommonPropertyType(ELContext elContext, Object base) {
        return Object.class;
    }

    /**
     * Retrieve the Spring BeanFactory to delegate bean name resolution to.
     * @param elContext the current ELContext
     * @return the Spring BeanFactory (never {@code null})
     */
    protected abstract BeanFactory getBeanFactory(ELContext elContext);

}