requestprocessor.java

《Java网络程序设计.rar》包括三个网络程序的源代码。

/*
 
 */
package org.impact.stars.control.web;

import java.util.Collection;
import java.util.HashMap;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.*;

import java.rmi.RemoteException;
import org.impact.stars.util.Debug;
import org.impact.stars.util.WebKeys;
import org.impact.stars.control.event.StarsEvent;
import org.impact.stars.control.exceptions.StarsEventException;
import org.impact.stars.control.web.ScreenFlowManager;
import org.impact.stars.control.web.checker.CheckerManager;

import org.impact.stars.control.web.handlers.RequestHandler;


/**
 * This is the web tier controller for the sample application.
 *
 * This class is responsible for processing all requests received from
 * the Main.jsp and generating necessary events to modify data which
 * are sent to the UserControllerWebImpl.
 *
 */
public class RequestProcessor implements java.io.Serializable {
    
    private ServletContext context;
    private HashMap urlMappings;
    
    /** Empty constructor for use by the JSP engine. */
    public RequestProcessor() {}
    
    
    public void init(ServletContext context) {
        this.context = context;
        urlMappings = (HashMap)context.getAttribute(WebKeys.URLMappingsKey);
    }
    
    /**
     * The UrlMapping object contains information that will match
     * a url to a mapping object that contains information about
     * the current screen, the RequestHandler that is needed to
     * process a request, and the RequestHandler that is needed
     * to insure that the propper screen is displayed.
     */
    
    private URLMapping getURLMapping(String urlPattern) {
        if ((urlMappings != null) && urlMappings.containsKey(urlPattern)) {
            return (URLMapping)urlMappings.get(urlPattern);
        } else {
            return null;
        }
    }
    
    
    /**
     * This method is the core of the RequestProcessor. It receives all requests
     *  and generates the necessary events.
     */
    public void processRequest(HttpServletRequest request, HttpServletResponse response) throws StarsEventException, IOException {
        StarsEvent event = null;
        String client = request.getParameter("client");
        String selectedUrl = request.getPathInfo();
        String checkresult = null; //to check the access control
        PrintWriter out = response.getWriter();
        Debug.println("Getting ModelManager :" );
        ModelManager mm = (ModelManager)request.getSession().getAttribute(WebKeys.ModelManagerKey);
        // application level ModelManager
        AppModelManager apmm = (AppModelManager)context.getAttribute(WebKeys.AppModelManagerKey);
        // application level checkermanager
        Debug.println("Getting CheckerManager :" );
        CheckerManager chm = (CheckerManager)context.getAttribute(WebKeys.CheckerManagerKey);
        UserControllerWebImpl ucrwimpl = (UserControllerWebImpl)request.getSession().getAttribute(WebKeys.WebControllerKey);
        if (ucrwimpl == null) {
            Debug.println("RequestProcessor : new UserControllerWebImpl" );
            ucrwimpl = new UserControllerWebImpl(request.getSession());
            mm.setURC(ucrwimpl);
            request.getSession().setAttribute(WebKeys.WebControllerKey, ucrwimpl);
        }
        RequestHandler handler = getHandler(selectedUrl);
        if (handler != null) {
            handler.setServletContext(context);
            handler.doStart(request);
            event = handler.processRequest(request);
            //check the consistency for this even
            
            if (event != null) {
                
                checkresult = chm.checkEvent(event);
                Debug.println("get Check result" + checkresult);
                if(checkresult.equals("OK")) {
                    chm.doStart(event); //update model state
                    Collection updatedModelList = ucrwimpl.handleEvent(event);
                    mm.notifyListeners(updatedModelList);
                    apmm.notifyListeners(updatedModelList);
                    chm.doEnd(event); //reset model state
                }
                if(client== null) //client is applet not a page
                {
                    out.println(checkresult);
                }
            }
            handler.doEnd(request);
        }
        if(client== null) //client is applet not a page
        {
            out.close();
            
        }
        
    }
    
    /**
     * This method load the necessary RequestHandler class necessary to process a the
     * request for the specified URL.
     */
    
    private RequestHandler getHandler(String selectedUrl) {
        Debug.println("RequestProcessor: inside getHandler " );
        RequestHandler handler = null;
        URLMapping urlMapping = getURLMapping(selectedUrl);
        String requestProcessorString = null;
        if (urlMapping != null) {
            requestProcessorString = urlMapping.getRequestHandler();
            if (urlMapping.useRequestHandler()) {
                try {
                    Debug.println("RequestProcessor: loading handler " + requestProcessorString);
                    handler = (RequestHandler)getClass().getClassLoader().loadClass(requestProcessorString).newInstance();
                } catch (Exception ex) {
                    Debug.println("RequestProcessor caught loading handler: " + ex);
                }
            }
        }
        return handler;
    }
}