Spring MVC的架构模式

2020-04-18 19:01:00 肥貓三千問

MVC 架构模式

在 UI 相关的开发领域，通过控制实现模型与视图解耦

M 模型：实体、业务逻辑

V 视图：用户接口（Web、桌面、移动端）

C 控制器：Servlet、Action、Controller

MVC 架构模式相关的：MVVM（移动端、Vue、React）

问题域（通用的，与语言无关，都需要面对的）

MVC / MVVM ：模型与视图的解耦

ORM - OOP ：语言 & RDBMS 之间的映射

IoC / DI ：依赖注入

Java EE 技术规范中 Web 相关技术

Servlet ：通过继承 HttpServlet定义大量的 Servlet

JSP/JSTL

Filter：对特定路径的请求执行前置或后置的过滤（加入功能）

Listener：对应用程序（全局）、用户会话、HTTP 请求的生命周期或特定时刻进行监听，注册回调函数

启动顺序:

Filter 早于 Servlet

关于 Filter 和Listener的具体作用：（接下来用代码演示）

工程目录：

AuthFilter.java

package com.newer.mvc.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.annotation.WebFilter;

import javax.servlet.http.HttpServletRequest;

/**

* Servlet Filter implementation class AuthListener

@WebFilter(value = {"/admin/*","/api/*","/other"})

public class AuthFilter implements Filter {

/**

* Default constructor.

public AuthFilter() {

System.out.println("AuthListener 创建");

}

/**

* @see Filter#destroy()

public void destroy() {

// TODO Auto-generated method stub

}

/**

* @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {

HttpServletRequest req=(HttpServletRequest) request;

System.out.println("鉴权"+req.getRequestURI());

chain.doFilter(request, response);

}

/**

* @see Filter#init(FilterConfig)

public void init(FilterConfig fConfig) throws ServletException {

// TODO Auto-generated method stub

}

EncodingFilter.java

package com.newer.mvc.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.annotation.WebFilter;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

* 过滤器

@WebFilter("/*")

public class EncodingFilter implements Filter {

/**

* Default constructor.

public EncodingFilter() {

System.out.println("创建EncodingFilter");

}

/**

* @see Filter#destroy()

public void destroy() {

// TODO Auto-generated method stub

}

/**

* @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)

public void doFilter(

ServletRequest request,

ServletResponse response,

FilterChain chain) throws IOException, ServletException {

//执行前

//应用场景：编码设置，鉴权，图片加水印。。。

HttpServletRequest req=(HttpServletRequest) request;

HttpServletResponse res=(HttpServletResponse) response;

req.setCharacterEncoding("UTF-8");

res.setCharacterEncoding("UTF-8");

String path=req.getRequestURI();

System.out.println("EncodingFilter doFilter:"+path);

if(path.equals("/mvc/admin")) {

//鉴权

System.out.println("需要鉴权");

}

//执行后续的正常流程

chain.doFilter(request, response);

//执行后

//如果是图片

if(res.getContentType().equals("image/*")){

System.out.println("加水印");

}

/**

* @see Filter#init(FilterConfig)

public void init(FilterConfig fConfig) throws ServletException {

System.out.println("EncodingFilter 初始化。。。。。。");

}

AppContextListener.java

package com.newer.mvc.web.listener;

import javax.servlet.ServletContextEvent;

import javax.servlet.ServletContextListener;

import javax.servlet.annotation.WebListener;

/**

* 监听器

* 不是你去调用的

* 该监听器关注的事件发生时，回调特定的方法

* @author Admin

@WebListener

public class AppContextListener implements ServletContextListener {

/**

* Default constructor.

public AppContextListener() {

System.out.println("ServletContextListener 创建");

}

/**

* @see ServletContextListener#contextDestroyed(ServletContextEvent)

public void contextDestroyed(ServletContextEvent sce) {

System.out.println("ServletContextListener 准备销毁。。。");

System.out.println("ServletContextListener 释放资源，如关闭数据库的连接池，");

System.out.println("ServletContextListener 销毁完毕。。。");

}

/**

* @see ServletContextListener#contextInitialized(ServletContextEvent)

public void contextInitialized(ServletContextEvent sce) {

System.out.println("ServletContextListener 初始化。。。");

System.out.println("ServletContextListener 加载资源，如创建数据库的连接池，装配依赖的资源");

}

RequestListener.java

package com.newer.mvc.web.listener;

import javax.servlet.ServletRequestEvent;

import javax.servlet.ServletRequestListener;

import javax.servlet.annotation.WebListener;

import javax.servlet.http.HttpServletRequest;

/**

*监听一个Http请求的生命周期

@WebListener

public class RequestListener implements ServletRequestListener {

/**

* Default constructor.

public RequestListener() {

System.out.println("RequestListener");

}

/**

* @see ServletRequestListener#requestDestroyed(ServletRequestEvent)

public void requestDestroyed(ServletRequestEvent sre) {

HttpServletRequest req=(HttpServletRequest) sre.getServletRequest();

System.out.printf("RequestListener:销毁为%s使用过的数据库连接\\n",req.getRequestURI());

}

/**

* @see ServletRequestListener#requestInitialized(ServletRequestEvent)

public void requestInitialized(ServletRequestEvent sre) {

HttpServletRequest req=(HttpServletRequest) sre.getServletRequest();

System.out.printf("RequestListener:为%s从数据库连接池创建一个数据库连接\\n",req.getRequestURI());

}

程序运行后，控制台输出为：