com.wesley_acheson.spring.BackingBeanUrlHandlerMapper.java Source code

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Here is the source code for com.wesley_acheson.spring.BackingBeanUrlHandlerMapper.java

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//   Copyright 2012 Wesley Acheson
//
//   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 com.wesley_acheson.spring;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.core.PriorityOrdered;
import org.springframework.web.servlet.HandlerExecutionChain;
import org.springframework.web.servlet.handler.AbstractUrlHandlerMapping;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

/**
 * A Handler mapper that delegates to a {@link UrlBackingBeanMapper} to know
 * whether it should match a url. If it does match a url then it adds the bean
 * which matches the url to the request.
 * 
 * @author Wesley Acheson
 * 
 */
public class BackingBeanUrlHandlerMapper extends AbstractUrlHandlerMapping implements PriorityOrdered {

    private UrlBackingBeanMapper<?> urlMapper;

    /**
     * 
     * @param urlMapper
     *            The bean which matches urls with other beans.
     */
    public void setUrlMapper(UrlBackingBeanMapper<?> urlMapper) {
        this.urlMapper = urlMapper;
    }

    protected UrlBackingBeanMapper<?> getUrlMapper() {
        return urlMapper;
    }

    public static final String BACKING_BEAN_ATTRIBUTE = BackingBeanUrlHandlerMapper.class.getName()
            + ".backingBean";

    /**
     * The controller which control will be passed to if there is any beans
     * matching in @{link {@link #setUrlMapper(UrlBackingBeanMapper)}.
     */
    public Object controller;

    /**
     * @param controller
     *            <p>
     *            The controller which control will be passed to if there is any
     *            beans matching in @{link
     *            {@link #setUrlMapper(UrlBackingBeanMapper)}.
     */
    public void setController(Object controller) {
        this.controller = controller;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.springframework.web.servlet.handler.AbstractUrlHandlerMapping#
     * lookupHandler(java.lang.String, javax.servlet.http.HttpServletRequest)
     */
    @Override
    protected Object lookupHandler(String urlPath, HttpServletRequest request) throws Exception {

        if (urlMapper.isPathMapped(urlPath)) {
            Object bean = urlMapper.retrieveBackingBean(urlPath);
            return buildChain(bean, urlPath);
        }

        return super.lookupHandler(urlPath, request);
    }

    /**
     * Builds a handler execution chain that contains both a path exposing
     * handler and a backing bean exposing handler.
     * 
     * @param bean
     *            The object to be wrapped in the handler execution chain.
     * @param urlPath
     *            The path which matched. In this case the full path.
     * @return The handler execution chain that contains the backing bean.
     * 
     * @see {@link AbstractUrlHandlerMapping#buildPathExposingHandler(Object, String, String, java.util.Map)}
     *    
     */
    protected HandlerExecutionChain buildChain(Object bean, String urlPath) {
        // I don't know why but the super class declares object but actually
        // returns handlerExecution chain.
        HandlerExecutionChain chain = (HandlerExecutionChain) buildPathExposingHandler(controller, urlPath, urlPath,
                null);
        addBackingBeanInteceptor(chain, bean);
        return chain;
    }

    /**
     * Adds an inteceptor which adds the backing bean into the request to an
     * existing HandlerExecutionChain.
     * 
     * @param chain
     *            The chain which the backing bean is being added to.
     * @param bean
     *            The object to pass through to the controller.
     */
    protected void addBackingBeanInteceptor(HandlerExecutionChain chain, Object bean) {
        chain.addInterceptor(new BackingBeanExposingInteceptor(bean));

    }

    /**
     * An Interceptor which adds a bean to a request for later consumption by a
     * controller.
     * 
     * @author Wesley Acheson
     * 
     */
    protected class BackingBeanExposingInteceptor extends HandlerInterceptorAdapter {
        private Object backingBean;

        /**
         * @param backingBean
         *            the bean which is passed through to the controller.
         */
        public BackingBeanExposingInteceptor(Object backingBean) {
            this.backingBean = backingBean;
        }

        @Override
        public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
                throws Exception {
            request.setAttribute(BACKING_BEAN_ATTRIBUTE, backingBean);
            return true;
        }
    }

}