基于前后端实现第一阶段的一个MVC框架

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <servlet>
        <servlet-name>DispatcherServlet</servlet-name>
        <servlet-class>com.Express.mvc.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contentConfigLocation</param-name>
            <param-value>application.properties</param-value>
        </init-param>
        <load-on-startup>0</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>DispatcherServlet</servlet-name>
        <url-pattern>*.do</url-pattern>
    </servlet-mapping>
</web-app>

<%--
  Created by IntelliJ IDEA.
  User: ly
  Date: 2021/2/3
  Time: 13:12
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>
  $END$
  </body>
</html>

<%--
  Created by IntelliJ IDEA.
  User: ly
  Date: 2021/2/3
  Time: 11:58
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>注册成功<></h1>
</body>
</html>

package com.Expres.test;

import com.Express.mvc.ResponseBody;
import com.Express.mvc.ResponseView;

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

public class UserController {
    @ResponseBody("/login.do")
    public String login(HttpServletRequest request, HttpServletResponse response){
        return  "success login";
    }
    @ResponseView("/reg.do")
    public  String reg(HttpServletRequest request, HttpServletResponse response){
        return "success.jsp";
    }
}

package com.Express.mvc;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;


@WebServlet(name = "DispatcherServlet")
public class DispatcherServlet extends javax.servlet.http.HttpServlet {
    @Override
    public void init(ServletConfig config) throws ServletException {
        String path= config.getInitParameter("contentConfigLocation");
       InputStream is=DispatcherServlet.class.getClassLoader().getResourceAsStream(path);
       HandlerMapping.load(is);
        //通过反射获取注解
    }

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1 获取用户请求的URI
        String uri = req.getRequestURI();
        HandlerMapping.MVCMapping mapping = HandlerMapping.get(uri);
        if (mapping==null)
        {
            resp.sendError(404,"您的MVC请求地址有误"+uri);
            return;
        }
        Object obj = mapping.getObj();
        Method method = mapping.getMethod();
        Object result=null;
        try {
            result = method.invoke(obj, req, resp);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
        switch (mapping.getType()){
            case TEXT:
                resp.getWriter().write((String)result);
                break;
            case VIEW:
                resp.sendRedirect((String)result);
                break;
        }

    }
}

package com.Express.mvc;

import java.io.IOException;
import java.io.InputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;

/**
 * 映射器（包含大量网址与方法的对应关系）
 */
public class HandlerMapping {
    private  static Map<String,MVCMapping> data= new HashMap<>();
    //从装有一大堆集合的方法里面获取网址所对应的方法
    public static MVCMapping get(String uri){
        return  data.get(uri);
    }
    //加载配置文件的方法
    public  static  void load(InputStream is){
        Properties ppt =new Properties();
        try {
            ppt.load(is);
        } catch (IOException e) {
            e.printStackTrace();
        }
        //获取配置文件中的一个个类
        Collection<Object> values = ppt.values();
        for (Object cla:values) {
            String className=(String) cla;
            Class c= null;
            try {
                //加载配置文件中描述的每一个类
                c = Class.forName(className);
                //创建这个类的对象
                Object obj =c.getConstructor().newInstance();
                //获取这个类的所有方法
                Method [] methods=c.getMethods();
                for (Method m:methods
                     ) {
                    Annotation [] as=m.getAnnotations();
                    if(as!=null)
                    {
                        for (Annotation anno:as
                             ) {
                            if (anno instanceof ResponseBody){
                                //此方法是用于返回字符串给客户端
                                MVCMapping map=new MVCMapping(obj,m,ResponseType.TEXT);
                                //没有处理重复的情况
                                //data.put(((ResponseBody) anno).value(), map);
                               //处理重复的情况
                                Object o=data.put(((ResponseBody) anno).value(), map);
                                if (o!=null){
                                    //存在了重复的 请求地址
                                    throw new RuntimeException("请求地址重复"+((ResponseBody) anno).value());
                                }
                            }
                            else if (anno instanceof ResponseView){
                                //此方法适用于返回界面给客户端
                                MVCMapping map=new MVCMapping(obj,m,ResponseType.VIEW);
                                Object o=  data.put(((ResponseView) anno).value(), map);
                                if (o!=null){
                                    //存在了重复的 请求地址
                                    throw new RuntimeException("请求地址重复"+((ResponseView) anno).value());
                                }
                            }
                        }
                    }
                }
            } catch (Exception e) {
                e.printStackTrace();
            }

        }
    }
    /**
     * 映射对象，每一个对象封装了一个方法用于处理请求
     */
    public static class MVCMapping{
        private Object obj;
        private Method method;
        private  ResponseType type;

        public MVCMapping(Object obj, Method method, ResponseType type) {
            this.obj = obj;
            this.method = method;
            this.type = type;
        }

        public MVCMapping() {
        }

        public Object getObj() {
            return obj;
        }

        public void setObj(Object obj) {
            this.obj = obj;
        }

        public Method getMethod() {
            return method;
        }

        public void setMethod(Method method) {
            this.method = method;
        }

        public ResponseType getType() {
            return type;
        }

        public void setType(ResponseType type) {
            this.type = type;
        }
    }
}

package com.Express.mvc;
import java.lang.annotation.*;

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
/**
 * 被此注解添加的方法会被用于处理请求
 * 方法返回的内容会以文字形式返回到客户端
 */
public @interface ResponseBody {
    String value();
}

package com.Express.mvc;

public enum ResponseType {
    TEXT,VIEW;
}

package com.Express.mvc;
import java.lang.annotation.*;

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
/**
 * 被此注解添加的方法会被用于处理请求
 * 方法返回的内容会直接重定向
 */
public @interface ResponseView {
    String value();
}

配置文件

#配置每一个用于处理请求的类每一个类中包含可能用到的n个方法
a=com.Expres.test.UserController