MvcDispatcherServlet.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;

import java.io.IOException;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;

import javax.inject.Inject;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.zdevra.guice.mvc.exceptions.NoMethodInvoked;

import com.google.inject.Injector;

/**
 * The Core Dispatcher servlet forward a request to the concrete 
 * controller and after that, the produced model is forwarded into
 * view resolver.
 */
class MvcDispatcherServlet extends HttpServlet {

    private static final Logger logger = Logger.getLogger(MvcDispatcherServlet.class.getName());

    @Inject
    private Injector injector;

    @Inject
    private ViewResolver viewResolver;

    @Inject
    private ExceptionResolver exceptionResolver;

    @Inject
    private InterceptorService interceptorService;

    /** collection of all controllers associated to this servlet */
    protected final Collection<Class<?>> controllers;

    /** collection of all interceptors associated tu this servlet */
    protected final Collection<Class<? extends InterceptorHandler>> interceptorHandlerClasses;

    protected Collection<ClassInvoker> classInvokers;

    protected InterceptorChain interceptorChain;

    /**
     * Constructor for testing purpose
     * @param controllerClass
     * @param injector
     */
    public MvcDispatcherServlet(Class<?> controllerClass, Injector injector) {
        this(controllerClass);
        this.injector = injector;
        this.viewResolver = injector.getInstance(ViewResolver.class);
        this.exceptionResolver = injector.getInstance(ExceptionResolver.class);
        this.interceptorService = injector.getInstance(InterceptorService.class);
    }

    /**
     * Constructor for testing purpose
     * @param controllers
     * @param injector
     */
    public MvcDispatcherServlet(Class<?>[] controllers, Injector injector) {
        this(controllers);
        this.injector = injector;
        this.viewResolver = injector.getInstance(ViewResolver.class);
        this.exceptionResolver = injector.getInstance(ExceptionResolver.class);
        this.interceptorService = injector.getInstance(InterceptorService.class);
    }

    /**
     * Constructor used by MvcModule
     * @param controllerClass
     */
    public MvcDispatcherServlet(Class<?> controllerClass) {
        this(Arrays.asList(new Class<?>[]{controllerClass}));
    }

    /**
     * Constructor for testing purpose
     * @param controllers
     */
    public MvcDispatcherServlet(Class<?>[] controllers) {
        this(Arrays.asList(controllers));
    }

    /**
     * Main constructor used by MvcModule
     * @param controllers
     */
    public MvcDispatcherServlet(List<Class<?>> controllers) {
        this(controllers, new LinkedList<Class<? extends InterceptorHandler>>());
    }

    /**
     * Main constructor used by MvcModule
     * @param controllers
     */
    public MvcDispatcherServlet(List<Class<?>> controllers, List<Class<? extends InterceptorHandler>> interceptorHandlerClasses) {
        this.controllers = Collections.unmodifiableCollection(controllers);
        this.interceptorHandlerClasses = Collections.unmodifiableCollection(interceptorHandlerClasses);
    }

    @Override
    protected final void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        processRequest(req, resp, HttpMethodType.GET);
    }

    @Override
    protected final void doDelete(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        processRequest(req, resp, HttpMethodType.DELETE);
    }

    @Override
    protected final void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        processRequest(req, resp, HttpMethodType.POST);
    }

    @Override
    protected final void doPut(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        processRequest(req, resp, HttpMethodType.PUT);
    }

    @Override
    public final void init() throws ServletException {
        //interceptor chain init
        InterceptorChain globalChain = interceptorService.getGlobalInterceptorChain();
        this.interceptorChain = globalChain.putInterceptorHandlers(getInterceptorHandlers());

        //class invokers initialization
        List<ClassInvoker> allInvokers = new LinkedList<ClassInvoker>();
        ClassScanner scanner = new ClassScanner();
        for (Class<?> controller : controllers) {
            ClassInvoker classInvoker = scanner.scan(controller, injector);
            allInvokers.add(classInvoker);
        }

        this.classInvokers = Collections.unmodifiableCollection(allInvokers);

        super.init();
    }

    /**
     * main processing of MVC dispatcher servlet.
     *
     * @param req
     * @param resp
     * @param reqType
     * @throws ServletException
     * @throws IOException
     */
    private void processRequest(HttpServletRequest req, HttpServletResponse resp, HttpMethodType reqType)
            throws ServletException, IOException {
        Throwable throwedException = null;
        InvokeData data = null;

        try {
            if (logger.isLoggable(Level.FINEST)) {
                logger.finest("request '" + req.getRequestURL().toString() + "' is handled by Lime MVC Servler ");
            }

            //prepare invoke data & do preprocessing
            data =
                    new InvokeData(
                    req,
                    resp,
                    null,
                    reqType,
                    injector);

            boolean res = interceptorChain.preHandle(data.getRequest(), data.getResponse());
            if (!res) {
                return;
            }

            //invoke method in controller
            ModelAndView mav = invoke(data);
            if (mav != null) {
                if (logger.isLoggable(Level.FINEST)) {
                    logger.finest("controller produce model " + mav.getModel().toString());
                }

                //postprocessing & resolve view
                interceptorChain.postHandle(data.getRequest(), data.getResponse(), mav);
                viewResolver.resolve(mav.getView(), mav.getModel(), this, req, resp);
                mav = null;
            }

        } catch (Throwable e) {
            throwedException = e;
            exceptionResolver.handleException(e, this, req, resp);
        }

        interceptorChain.afterCompletion(data.getRequest(), data.getResponse(), throwedException);
    }


    /**
     * returns list of all interceptor handlers
     *
     * @return
     */
    private List<InterceptorHandler> getInterceptorHandlers() {
        List<InterceptorHandler> handlers = new LinkedList<InterceptorHandler>();
        for (Class<? extends InterceptorHandler> ihc : this.interceptorHandlerClasses) {
            InterceptorHandler handler = this.injector.getInstance(ihc);
            handlers.add(handler);
        }
        return handlers;
    }


    /**
     * Invoke the controller's method
     *
     * @param data
     * @return
     */
    protected ModelAndView invoke(InvokeData data) {
        ModelAndView mav = new ModelAndView();
        int invokedcount = 0;

        for (ClassInvoker invoker : this.classInvokers) {
            ModelAndView methodMav = invoker.invoke(data);
            if (methodMav != null) {
                mav.mergeModelAndView(methodMav);
                methodMav = null;
                invokedcount++;
            }
        }

        if (invokedcount == 0) {
            throw new NoMethodInvoked(data.getRequest());
        }

        //post-production of model
        for (ClassInvoker classInvoker : this.classInvokers) {
            classInvoker.moveDataToSession(mav.getModel(), data.getRequest());
        }
        mav.getModel().moveObjectsToRequestAttrs(data.getRequest());

        return mav;
    }
}