RequestScopedAttributeParam.java

/*****************************************************************************
 * Copyright 2012 Zdenko Vrabel
 *
 * 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.zdevra.guice.mvc.parameters;

import org.zdevra.guice.mvc.InvokeData;
import org.zdevra.guice.mvc.Utils;
import org.zdevra.guice.mvc.annotations.RequestScopedAttribute;

/**
 * Processor for {@link org.zdevra.guice.mvc.annotations.RequestScopedAttribute} annotation. This class
 * gets the value and fill-in the method's parameter.
 *
 * @see org.zdevra.guice.mvc.annotations.RequestScopedAttribute
 */
public class RequestScopedAttributeParam implements ParamProcessor {

    private final String attributeName;
    private final Class<?> methodParamType;

    /**
     * Class construct and initialize parameter processor
     */
    public static class Factory implements ParamProcessorFactory {

        @Override
        public ParamProcessor buildParamProcessor(ParamMetadata metadata) {
            RequestScopedAttribute annotation = Utils.getAnnotation(RequestScopedAttribute.class, metadata.getAnnotations());
            if (annotation == null) {
                return null;
            }
            return new RequestScopedAttributeParam(annotation.value(), metadata.getType());

        }
    }

    /**
     * Constructor
     * @param attributeName
     */
    private RequestScopedAttributeParam(String attributeName, Class<?> methodParamType) {
        super();
        this.attributeName = attributeName;
        this.methodParamType = methodParamType;
    }

    /**
     * {@inheritDoc}
     *
     * @param data
     * @return
     */
    @Override
    public Object getValue(InvokeData data) {
        Object value = data.getRequest().getAttribute(attributeName);
        if (value != null) {
            if (methodParamType.isInstance(value)) {
                return value;
            } else {
                throw new IllegalStateException("the object in the request is not " + methodParamType.getName() + " but is " + value.getClass().getName());
            }
        }
        return null;
    }
}