org.springframework.webflow.expression.el.SpringBeanWebFlowELResolver.java Source code

Introduction

Here is the source code for org.springframework.webflow.expression.el.SpringBeanWebFlowELResolver.java

Source

/*
 * 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
 *
 *      https://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.webflow.expression.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;
import org.springframework.beans.factory.support.StaticListableBeanFactory;
import org.springframework.webflow.execution.RequestContext;
import org.springframework.webflow.execution.RequestContextHolder;

/**
 * EL resolver for resolving Spring Beans accessible by a flow's bean factory.
 * @author Jeremy Grelle
 */
public class SpringBeanWebFlowELResolver extends ELResolver {

    private static final Log logger = LogFactory.getLog(SpringBeanWebFlowELResolver.class);

    private static final BeanFactory EMPTY_BEAN_FACTORY = new StaticListableBeanFactory();

    private RequestContext requestContext;

    public SpringBeanWebFlowELResolver() {
    }

    public SpringBeanWebFlowELResolver(RequestContext context) {
        this.requestContext = context;
    }

    protected BeanFactory getBeanFactory(ELContext elContext) {
        RequestContext requestContext = getRequestContext();
        if (requestContext == null) {
            return EMPTY_BEAN_FACTORY;
        }
        BeanFactory beanFactory = requestContext.getActiveFlow().getApplicationContext();
        return beanFactory != null ? beanFactory : EMPTY_BEAN_FACTORY;
    }

    protected RequestContext getRequestContext() {
        return requestContext != null ? requestContext : RequestContextHolder.getRequestContext();
    }

    // ELResolver implementatio...

    @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;
    }

}