custom struts framework

1. Difference between stucts1 and struts2

    struts1 : Servlet used as Controller , you can visit the Servlet directly, code like if---else if--else

    struts2 : Filter used as Controller , you can only  visit it passively, though setting the condition like "/*"

2. Imitate the core Filter of Struts2 (StrutsPrepareAndExecuterFilter.java)

 version 1.0(like struts1)

package com.cdv.web.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet Filter implementation class StrutsPreparedAndExecuterFilter
 */
public class StrutsPreparedAndExecuterFilter implements Filter {

    /**
     * Default constructor. 
     */
    public StrutsPreparedAndExecuterFilter() {
        // TODO Auto-generated constructor stub
    }

    /**
     * @see Filter#destroy()
     */
    public void destroy() {
        // TODO Auto-generated method stub
    }

    /**
     * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
     */
    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) resp;
        String uri = request.getRequestURI();
        boolean isDo = uri.endsWith(".do");
        if(isDo){
            //get the operation
            String op = uri.substring(uri.lastIndexOf("/"), uri.lastIndexOf("."));
            if(op.equals("login")){
                request.setAttribute("username", "zhangsan");
            }else{
                //to do something
            }
        }else{
            //
            chain.doFilter(request, response);
        }
    }

    /**
     * @see Filter#init(FilterConfig)
     */
    public void init(FilterConfig fConfig) throws ServletException {
        // TODO Auto-generated method stub
    }

}

version 2.0

we need create the interface , for creating different instance aim at different params condition, and use the map  instead of if--else

package com.cdv.web.action;

import javax.servlet.http.HttpServletRequest;

public interface Action {

    String execute(HttpServletRequest request);
}

package com.cdv.web.action;

import javax.servlet.http.HttpServletRequest;

public class LoginAction implements Action {

    @Override
    public String execute(HttpServletRequest request) {
        String username = request.getParameter("username");
        if(username.equals("zhangsan")){
            return "ok";
        }
        return null;
    }

}

package com.cdv.web.filter;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.cdv.web.action.Action;
import com.cdv.web.action.LoginAction;

/**
 * Servlet Filter implementation class StrutsPreparedAndExecuterFilter
 */
public class StrutsPreparedAndExecuterFilter2 implements Filter {

    private Map<String, Action> actionMap = new HashMap<String, Action>();
    /**
     * Default constructor. 
     */
    public StrutsPreparedAndExecuterFilter2() {
        // TODO Auto-generated constructor stub
    }

    /**
     * @see Filter#destroy()
     */
    public void destroy() {
        // TODO Auto-generated method stub
    }

    /**
     * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
     */
    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) resp;
        String uri = request.getRequestURI();
        boolean isDo = uri.endsWith(".do");
        if(isDo){
            String op = uri.substring(uri.lastIndexOf("/"), uri.lastIndexOf("."));
            Action instance = actionMap.get(op);
            String result = instance.execute(request);
            if(result.equals("ok")){
                request.setAttribute("user", "zhangsan");
            }
        }else{
            chain.doFilter(request, response);
        }
    }

    /**
     * @see Filter#init(FilterConfig)
     */
    public void init(FilterConfig fConfig) throws ServletException {
        actionMap.put("login", new LoginAction());
        //actionMap.put("logout", new LogoutAction());
        //...
    }    

}

version 3.0 

put the value of instance into xml file , use dom4j to parse it, and use reflect technology to create instance dynamic.

struts.xml

<?xml version="1.0" encoding="UTF-8"?>
<package name="mypackage">
    <action name="loginAction" class="com.cdv.web.action.LoginAction"></action>
    <action name="logoutAction" class="com.cdv.web.action.LogoutAction"></action>
</package>

package com.cdv.web.filter;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.cdv.web.action.Action;
import com.cdv.web.action.LoginAction;

/**
 * Servlet Filter implementation class StrutsPreparedAndExecuterFilter
 */
public class StrutsPreparedAndExecuterFilter3 implements Filter {

    private Map<String, Action> actionMap = new HashMap<String, Action>();
    /**
     * Default constructor. 
     */
    public StrutsPreparedAndExecuterFilter3() {
        // TODO Auto-generated constructor stub
    }

    /**
     * @see Filter#destroy()
     */
    public void destroy() {
        // TODO Auto-generated method stub
    }

    /**
     * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
     */
    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) resp;
        String uri = request.getRequestURI();
        boolean isDo = uri.endsWith(".do");
        if(isDo){
            String op = uri.substring(uri.lastIndexOf("/"), uri.lastIndexOf("."));
            Action instance = actionMap.get(op);
            String result = instance.execute(request);
            if(result.equals("ok")){
                request.setAttribute("user", "zhangsan");
            }
        }else{
            chain.doFilter(request, response);
        }
    }

    /**
     * @see Filter#init(FilterConfig)
     */
    public void init(FilterConfig fConfig) throws ServletException {
        //进行dom4j解析，将struts.xml中的name 和 value取出，
        //并利用反射将class的值转化为对象
/*        Document document = Dom4jUtil.getDocument();
        List<Node> list = document.selectNodes("//action");
        for(Node node : list){
            //遍历action节点，取出值
            String key = node.valueOf("@name");
            String value = node.valueOf("@class");
            actionMap.put(key, (Action) Class.forName(value).newInstance());
        }*/
    }    

}