SessionAttributeParam.java

/*****************************************************************************
 * Copyright 2011 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 javax.servlet.http.HttpSession;

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

/**
 * The parameter's processor is associated with {@link SessionParameter} annotation
 * and supports building process of arguments with this annotation.
 * <p>
 * 
 * for example:
 * <pre class="prettyprint">
 *  {@literal @}Path(path="/loggeduserinfo") 
 *  public void getInfoAboutLoggedUser({@literal @}SessionParameter("loggeduser") Customer customer) {
 *    ...			
 *	}
 * </pre>
 * 
 * 
 * In this case, processor build the customer's argument and fills it with the value from the 
 * session with the name 'loggeduser'. If this attribute doesn't exist in the session, then is 
 * filled by null. In case when in 'loggeduser' session attribute is object
 * which is not instance of customer, then exception is throwed.
 *  
 */
public class SessionAttributeParam implements ParamProcessor {

    private final String nameInSession;
    private final Class<?> paramType;

    /**
     * Factory class for {@link SessionAttributeParam}
     */
    public static class Factory implements ParamProcessorFactory {

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


    /**
     * Constructor
     */
    private SessionAttributeParam(String nameInSession, Class<?> paramType) {
        this.nameInSession = nameInSession;
        this.paramType = paramType;
    }


    /**
     * {@inheritDoc}
     *
     * @param data
     * @return
     */
    @Override
    public Object getValue(InvokeData data) {
        HttpSession session = data.getRequest().getSession(true);
        Object obj = session.getAttribute(this.nameInSession);
        if (obj != null) {
            if (!paramType.isInstance(obj)) {
                throw new IllegalStateException("the object in the session is not " + paramType.getName() + " but is " + obj.getClass().getName());
            }
        }
        return obj;
    }
}