BaseServlet优化Servlet，实现类似struts2的一些简单效果

package cn.itcast.web.servlet;

import java.io.IOException;

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

public class AServlet extends BaseServlet {

    private static final long serialVersionUID = 1L;

    /*@Override
    public void service(HttpServletRequest req, HttpServletResponse res)
            throws ServletException, IOException {

         * 1、获取参数，用来说明要调用的方法
         * 2、然后判断是哪个方法执行

        String methodName=req.getParameter("method");

        if(methodName == null || methodName.trim().isEmpty()){
            throw new RuntimeException("您没有传递method参数，无法确定要调用的方法");
        }
//        if(methodName.equals("addUser")){
//            addUser(req,res);
//        }else if(methodName.equals("eidtUser")){
//            editUser(req,res);
//        }else if(methodName.equals("deleteUser")){
//            deleteUser(req,res);
//        }

         * 我们发现这样的代码不好复用
         * 1、我们可以通过方法名称，使用反射调用呢？
         *         需要得到class，然后调用它的方法进行查询
         *         我们查询的是当前类的方法

        Class c=this.getClass();
        Method method=null;
        try{
            method=c.getMethod(methodName,HttpServletRequest.class,HttpServletResponse.class);
        }catch(Exception e){
            throw new RuntimeException("您要调用的方法"+methodName+"(HttpServletRequest,HttpServletResponse) 不存在");
        }

         * 调用method

        try {
            method.invoke(this, req,res);
        } catch (Exception e) {
            System.out.println("您调用的方法"+methodName+"(HttpServletRequest,HttpServletResponse) 内部抛出了异常");
            throw new RuntimeException(e);
        }

    }*/
    public void addUser(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        System.out.println("addUser()...");
        throw new IOException("测试一下");
    }

    public void editUser(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        System.out.println("editUser()...");
    }

    public void findAll(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        System.out.println("findAllUser()...");
    }

    public void deleteUser(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        System.out.println("deleteUser()...");
    }

}
/**
 * 我们发现这样复用性还是不够理想，我们可以抽象出一个弗雷给别人继承
 */

package cn.itcast.web.servlet;

import java.io.IOException;
import java.lang.reflect.Method;

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

@SuppressWarnings({"rawtypes","unchecked"})
public class BaseServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    @Override
    public void service(HttpServletRequest req, HttpServletResponse res)
            throws ServletException, IOException {

        String methodName=req.getParameter("method");
        if(methodName == null || methodName.trim().isEmpty()){
            throw new RuntimeException("您没有传递method参数，无法确定要调用的方法");
        }
        Class c=this.getClass();
        Method method=null;
        try{
            method=c.getMethod(methodName,HttpServletRequest.class,HttpServletResponse.class);
        }catch(Exception e){
            throw new RuntimeException("您要调用的方法"+methodName+"(HttpServletRequest,HttpServletResponse) 不存在");
        }
        String text=null;//获取返回值
        try {
            text=(String) method.invoke(this, req,res);
            /*
             *获取请求处理方法后返回的字符串，它表示转发或者重定向的路径
             *如果返回值中不包含“:”，表示使用默认方式：转发
             *如果返回值中包含“：”，将字符串通过“：”截取为两部分，前一部分表示标识，f代表转发，r代表重定向
             *如果返回的字符串是null或者""，我们什么也不干
             */
        } catch (Exception e) {
            System.out.println("您调用的方法"+methodName+"(HttpServletRequest,HttpServletResponse) 内部抛出了异常");
            throw new RuntimeException(e);
        }
        if(text==null || text.trim().isEmpty()) return;
        if(!text.contains(":")){
            req.getRequestDispatcher(text).forward(req, res);
        }else{
            int index=text.indexOf(":");
            String bz=text.substring(0, index);
            String path=text.substring(index+1);
            if(bz.equalsIgnoreCase("r")){
                res.sendRedirect(path);
            }else if(bz.equalsIgnoreCase("f")){
                req.getRequestDispatcher(path).forward(req, res);
            }else{
                throw new RuntimeException("您的指定："+bz+"暂时没有开通此业务");
            }
        }

    }
    /**
     * 我们在Servlet中实现重定向和转发感觉有点麻烦，我们希望抽象出来再BaseServlet中处理
     * request.getRequestDispatcher("xxx").forward(request,response)
     * response.sendRedirect("xxx")
     */

}

package cn.itcast.web.servlet;

import java.io.IOException;

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

public class BServlet extends BaseServlet {

    private static final long serialVersionUID = 1L;

    public String fun1(HttpServletRequest req,HttpServletResponse res) throws IOException,ServletException{
        //return "forward:/index.jsp";
        System.out.println("fun1()...");
        return "f:/index.jsp";
    }
    public String fun2(HttpServletRequest req,HttpServletResponse res) throws IOException,ServletException{
        //return "redirect:/index.jsp";
        System.out.println("fun2()...");
        return "r:"+req.getContextPath()+"/index.jsp";
    }
    public String fun3(HttpServletRequest req,HttpServletResponse res) throws IOException,ServletException{
        System.out.println("fun3()...");
        return "/index.jsp";
    }
    public String fun4(HttpServletRequest req,HttpServletResponse res) throws IOException,ServletException{
        System.out.println("fun4()...");
        return null;
    }
    public String fun5(HttpServletRequest req,HttpServletResponse res) throws IOException,ServletException{
        System.out.println("fun3()...");
        return "d:/index.jsp";
    }
}

BaseServlet
1.我们希望在一个Servlet中可以有多个请求处理方法
2、客户端发送请求时，必须多给出一个参数，用来说明要调用的方法
3、参数名遵守约定
4、希望帮助简化重定向和转发，利用返回值
domain：User
dao：UserDao
service：UserService
servlet：UserServlet

void init(ServletConfig config)
void destory()
void service(ServletRequest,ServletResponse)throws IOException,ServletException{
在这里让它去调用其他方法！
要求：用户发出请求时，必须给出一个参数