Spring MVC的架構模式

2020-04-18 19:01:00 肥貓三千問

MVC 架構模式

在 UI 相關的開發領域，通過控制實現模型與視圖解耦

M 模型：實體、業務邏輯

V 視圖：用戶接口（Web、桌面、移動端）

C 控制器：Servlet、Action、Controller

MVC 架構模式相關的：MVVM（移動端、Vue、React）

問題域（通用的，與語言無關，都需要面對的）

MVC / MVVM ：模型與視圖的解耦

ORM - OOP ：語言 & RDBMS 之間的映射

IoC / DI ：依賴注入

Java EE 技術規範中 Web 相關技術

Servlet ：通過繼承 HttpServlet定義大量的 Servlet

JSP/JSTL

Filter：對特定路徑的請求執行前置或後置的過濾（加入功能）

Listener：對應用程序（全局）、用戶會話、HTTP 請求的生命週期或特定時刻進行監聽，註冊回調函數

啟動順序:

Filter 早於 Servlet

關於 Filter 和Listener的具體作用：（接下來用代碼演示）

工程目錄：

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 創建");

}

/**

* @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("鑑權"+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;

/**

* 過濾器

@WebFilter("/*")

public class EncodingFilter implements Filter {

/**

* Default constructor.

public EncodingFilter() {

System.out.println("創建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 {

//執行前

//應用場景：編碼設置，鑑權，圖片加水印。。。

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")) {

//鑑權

System.out.println("需要鑑權");

}

//執行後續的正常流程

chain.doFilter(request, response);

//執行後

//如果是圖片

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;

/**

* 監聽器

* 不是你去調用的

* 該監聽器關注的事件發生時，回調特定的方法

* @author Admin

@WebListener

public class AppContextListener implements ServletContextListener {

/**

* Default constructor.

public AppContextListener() {

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

}

/**

* @see ServletContextListener#contextDestroyed(ServletContextEvent)

public void contextDestroyed(ServletContextEvent sce) {

System.out.println("ServletContextListener 準備銷燬。。。");

System.out.println("ServletContextListener 釋放資源，如關閉數據庫的連接池，");

System.out.println("ServletContextListener 銷燬完畢。。。");

}

/**

* @see ServletContextListener#contextInitialized(ServletContextEvent)

public void contextInitialized(ServletContextEvent sce) {

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

System.out.println("ServletContextListener 加載資源，如創建數據庫的連接池，裝配依賴的資源");

}

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;

/**

*監聽一個Http請求的生命週期

@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:銷燬為%s使用過的數據庫連接\\n",req.getRequestURI());

}

/**

* @see ServletRequestListener#requestInitialized(ServletRequestEvent)

public void requestInitialized(ServletRequestEvent sre) {

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

System.out.printf("RequestListener:為%s從數據庫連接池創建一個數據庫連接\\n",req.getRequestURI());

}

程序運行後，控制檯輸出為：