spring boot 学习3 web MVC核心与视图

旧城等待， 2022-02-05 01:34 235阅读 0赞

内容：理解、认识、简化

servlet

特点：请求响应式（Request/Response）、屏蔽网络通讯细节、有完整的生命周期

职责：处理请求（handler等）、资源管理（连接数据库、redis）、视图渲染（html等）

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## 核心组件： ##

处理器管理

*  映射：HandlerMapping
 *  适配器：HandlerAdapter
 *  执行：HandlerExecutionChain
 *  视图解析：ViewResolver
 *  国际化：LocaleResolver、LocaleContextResolver
 *  个性化：ThemeResolver
 *  异常处理：HandlerExceptionResolver

** 核心主键bean**

<table> 
 <thead> 
  <tr> 
   <th style="width:301px;">组件 Bean 类型</th> 
   <th style="width:565px;">说明</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td style="width:301px;">HandlerMapping</td> 
   <td style="width:565px;">映射请求（Request）到处理器（Handler）加上其关联的拦截（HandlerInterceptor）列表。(就是url映射目录和拦截器)</td> 
  </tr> 
  <tr> 
   <td style="width:301px;">HandlerAdapter</td> 
   <td style="width:565px;">调用请求处理器（Handler）无需关注其中实际的调用细节。调用注解实现的 Controller 。（适配器）</td> 
  </tr> 
  <tr> 
   <td style="width:301px;">HandlerExceptionResolver</td> 
   <td style="width:565px;">解析异常，可能策略是将异常处理映射到其他处理（Handlers） 、或到某个 HTML错误页面</td> 
  </tr> 
  <tr> 
   <td style="width:301px;">ViewResolver&nbsp;</td> 
   <td style="width:565px;">从处理器（Handler）返回字符类型的逻辑视图名称解析出实际的 View 对象</td> 
  </tr> 
  <tr> 
   <td style="width:301px;">LocaleResolver,LocaleContextResolver</td> 
   <td style="width:565px;">实现国际化视图</td> 
  </tr> 
  <tr> 
   <td style="width:301px;">MultipartResolver&nbsp;</td> 
   <td style="width:565px;">解析多部分请求（如 Web 浏览器文件上传）的抽象实现</td> 
  </tr> 
 </tbody> 
</table>

## **xml方式实现mvc** ##

**web.xml(webapp.WEB-INF.web.xml) 配置DispatcherServlet，指定xml扫描路径**

<web-app>
        <servlet>
            <servlet-name>app</servlet-name>
            <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
            <load-on-startup>1</load-on-startup>
            <init-param>
                <param-name>contextConfigLocation</param-name>
                <param-value>/WEB-INF/app-context.xml</param-value>
            </init-param>
        </servlet>
    
        <servlet-mapping>
            <servlet-name>app</servlet-name>
            <url-pattern>/</url-pattern>
        </servlet-mapping>
    </web-app>

** 配置 Web MVC 组件（指定扫描范围，设置：**HandlerMapping，HandlerAdapter，ViewResolver **）**

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xmlns:context="http://www.springframework.org/schema/context"
           xsi:schemaLocation="
            http://www.springframework.org/schema/beans
            http://www.springframework.org/schema/beans/spring-beans.xsd
            http://www.springframework.org/schema/context
            http://www.springframework.org/schema/context/spring-context.xsd">
    
        <context:component-scan base-package="com.imooc.web"/>
    
        <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping"/>
    
        <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter"/>
    
        <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
            <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
            <property name="prefix" value="/WEB-INF/jsp/"/>
            <property name="suffix" value=".jsp"/>
        </bean>
    
    </beans>

**添加controller**

@Controller
    public class HelloWorldController {
    
        @RequestMapping("")
        public String index(@RequestParam int value, Model model) {
            return "index";
        }
    
    }

## **Web MVC 注解驱动** ##

<dependency>
                <groupId>javax.servlet</groupId>
                <artifactId>javax.servlet-api</artifactId>
                <scope>provided</scope>
            </dependency>
    
            <dependency>
                <groupId>javax.servlet</groupId>
                <artifactId>jstl</artifactId>
            </dependency>
    
            
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-webmvc</artifactId>
            </dependency>

老式非 spring boot 没有内嵌tomcat 需要放入tomcat才能使用。

## 注解驱动： ##

@EnableWebMvc 默认配置了HandlerMapping，HandlerAdapter的bean

实现WebMvcConfigurer 自定义url拦截器

@Configuration
    @EnableWebMvc
    public class WebMvcConfig implements WebMvcConfigurer {
    
        @Bean
        public ViewResolver viewResolver(){
            InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
            viewResolver.setViewClass(JstlView.class);
            viewResolver.setPrefix("/WEB-INF/jsp/");
            viewResolver.setSuffix(".jsp");
            return viewResolver;
        }
    
        @Override
        public void addInterceptors(InterceptorRegistry registry) {
            registry.addInterceptor(new HandlerInterceptor() {
                @Override
                public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
                    System.out.println("拦截中...");
                    return true;
                }
            });
        }
    }

**常用注解**

<table style="width:500px;"> 
 <tbody> 
  <tr> 
   <td>@ModelAttribute</td> 
   <td>注册模型属性（可以在jsp页面读取这些属性）</td> 
  </tr> 
  <tr> 
   <td>@RequestHeader</td> 
   <td>读取请求头</td> 
  </tr> 
  <tr> 
   <td>@CookieValue</td> 
   <td>读取 Cookie</td> 
  </tr> 
  <tr> 
   <td>@Valid 、 @Validated</td> 
   <td>校验参数</td> 
  </tr> 
  <tr> 
   <td>@ExceptionHandler</td> 
   <td>注解处理，异常时处理</td> 
  </tr> 
  <tr> 
   <td>&nbsp;@ControllerAdvice</td> 
   <td>切面通知（通过代理模式添加通知数据）</td> 
  </tr> 
 </tbody> 
</table>

//代理的HelloWorldController这个类里的通知
    @ControllerAdvice(assignableTypes = HelloWorldController.class)
    public class HelloWorldControllerAdvice {
    
        @ModelAttribute("acceptLanguage")
        public String acceptLanguage(@RequestHeader("Accept-Language") String acceptLanguage){
            return acceptLanguage;
        }
    
        @ModelAttribute("jsessionId")
        public String jsessionId(@CookieValue("JSESSIONID") String jsessionId){
            return jsessionId;
        }
    
        @ModelAttribute("message")
        public String message(){
            return "Hello,World";
        }
    
        @ExceptionHandler(Throwable.class)
        public ResponseEntity<String> onException(Throwable throwable) {
            return ResponseEntity.ok(throwable.getMessage());
        }
    
    }

@Controller
    public class HelloWorldController {
        
        @RequestMapping("")
        public String index(@RequestParam int value, Model model) {
    //        model.addAttribute("acceptLanguage",acceptLanguage);
    //        model.addAttribute("jsessionId",jsessionId);
    //        model.addAttribute("message","Hello,World");
            return "index";
        }
    }

<jsp:root xmlns:jsp="http://java.sun.com/JSP/Page" version="2.0">
        <body>
            <message>${message}</message>
            <language>${acceptLanguage}</language>
            <jsessionId>${jsessionId}</jsessionId>
        </body>
    </jsp:root>

## **spring boot 自动装配** ##

Spring Boot JSP 依赖

<dependency>
                <groupId>org.apache.tomcat.embed</groupId>
                <artifactId>tomcat-embed-jasper</artifactId>
            </dependency>

application.properties

spring.mvc.view.prefix = /WEB-INF/jsp/
    spring.mvc.view.suffix = .jsp

@Configuration
    public class WebMvcConfig implements WebMvcConfigurer {
    
        @Override
        public void addInterceptors(InterceptorRegistry registry) {
            registry.addInterceptor(new HandlerInterceptor() {
                @Override
                public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
                    System.out.println("拦截中...");
                    return true;
                }
            });
        }
    }

启动类

@SpringBootApplication(scanBasePackages = "com.imooc.web")
    public class SpringBootWebMvcBootstrap {
    
        public static void main(String[] args) {
            SpringApplication.run(SpringBootWebMvcBootstrap.class, args);
        }
    
    }

# #

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