Web开发

• 官方文档 (opens new window)

SpringMVC自动配置概览

Spring Boot provides auto-configuration for Spring MVC that works well with most applications.(大多场景我们都无需自定义配置)

The auto-configuration adds the following features on top of Spring’s defaults:

• Inclusion of ContentNegotiatingViewResolver and BeanNameViewResolver beans.
  • 内容协商视图解析器和BeanName视图解析器
• Support for serving static resources, including support for WebJars (covered later in this document (opens new window))).
  • 静态资源（包括webjars）
• Automatic registration of Converter, GenericConverter, and Formatter beans.
  • 自动注册 Converter，GenericConverter，Formatter
• Support for HttpMessageConverters (covered later in this document (opens new window)).
  • 支持 HttpMessageConverters （后来我们配合内容协商理解原理）
• Automatic registration of MessageCodesResolver (covered later in this document (opens new window)).
  • 自动注册 MessageCodesResolver （国际化用）
• Static index.html support.
  • 静态index.html 页支持
• Custom Favicon support (covered later in this document (opens new window)).
  • 自定义 Favicon
• Automatic use of a ConfigurableWebBindingInitializer bean (covered later in this document (opens new window)).
  • 自动使用 ConfigurableWebBindingInitializer ，（DataBinder负责将请求数据绑定到JavaBean上）

If you want to keep those Spring Boot MVC customizations and make more MVC customizations (opens new window) (interceptors, formatters, view controllers, and other features), you can add your own @Configuration class of type WebMvcConfigurer but without @EnableWebMvc.

不用@EnableWebMvc注解。使用@Configuration + WebMvcConfigurer 自定义规则

If you want to provide custom instances of RequestMappingHandlerMapping, RequestMappingHandlerAdapter, or ExceptionHandlerExceptionResolver, and still keep the Spring Boot MVC customizations, you can declare a bean of type WebMvcRegistrations and use it to provide custom instances of those components.

声明 WebMvcRegistrations 改变默认底层组件

If you want to take complete control of Spring MVC, you can add your own @Configuration annotated with @EnableWebMvc, or alternatively add your own @Configuration-annotated DelegatingWebMvcConfiguration as described in the Javadoc of @EnableWebMvc.

使用 @EnableWebMvc+@Configuration+DelegatingWebMvcConfiguration全面接管SpringMVC

简单功能分析

静态资源访问

只要静态资源放在类路径下： called /static (or /public or /resources or /META-INF/resources

访问 ： 当前项目根路径/ + 静态资源名

原理： 静态映射/**。

请求进来，先去找Controller看能不能处理。不能处理的所有请求又都交给静态资源处理器。静态资源也找不到则响应404页面

改变默认的静态资源路径

spring:
  mvc:
    static-path-pattern: /res/**
  web:
  resources:
    static-locations: [classpath:/haha/]

静态资源访问前缀

默认不前缀

spring:
  mvc:
    static-path-pattern: /res/**

当前项目 + static-path-pattern + 静态资源名 = 静态资源文件夹下找

webjar

自动映射 /webjars (opens new window)/**

https://www.webjars.org/

	    <dependency>
            <groupId>org.webjars</groupId>
            <artifactId>jquery</artifactId>
            <version>3.5.1</version>
        </dependency>

访问地址：http://localhost:8888/webjars/jquery/3.5.1/jquery.js (opens new window) 后面地址要按照依赖里面的包路径

欢迎页支持

• 静态资源路径下 index.html

  • 可以配置静态资源路径
  • 但是不可以配置静态资源的访问前缀。否则导致 index.html不能被默认访问

spring:
#  mvc:
#    static-path-pattern: /res/**   这个会导致welcome page功能失效

  resources:
    static-locations: [classpath:/haha/]

• controller能处理/index

自定义 Favicon

favicon.ico 放在静态资源目录下即可。

spring:
#  mvc:
#    static-path-pattern: /res/**   这个会导致 Favicon 功能失效

了解

静态资源配置原理

• SpringBoot启动默认加载 xxxxAutoConfiguration 类(自动配置类)
• SpringMVC功能的自动配置类 WebMvcAutoConfiguration，生效

@Configuration(
    proxyBeanMethods = false
)
@ConditionalOnWebApplication(
    type = Type.SERVLET
)
@ConditionalOnClass({Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class})
@ConditionalOnMissingBean({WebMvcConfigurationSupport.class})
@AutoConfigureOrder(-2147483638)
@AutoConfigureAfter({DispatcherServletAutoConfiguration.class, TaskExecutionAutoConfiguration.class, ValidationAutoConfiguration.class})
public class WebMvcAutoConfiguration {}

• 给容器中配置了什么

 	@Import({WebMvcAutoConfiguration.EnableWebMvcConfiguration.class})
    @EnableConfigurationProperties({WebMvcProperties.class, ResourceProperties.class})
    @Order(0)
    public static class WebMvcAutoConfigurationAdapter implements WebMvcConfigurer {}

• 配置文件的相关属性和xxx进行了绑定。WebMvcProperties==spring.mvc、ResourceProperties==spring.resources

配置类只有一个有参构造器

		//有参构造器所有参数的值 都会从容器中确定
        public WebMvcAutoConfigurationAdapter(ResourceProperties resourceProperties, WebMvcProperties mvcProperties, ListableBeanFactory beanFactory, ObjectProvider<HttpMessageConverters> messageConvertersProvider, ObjectProvider<WebMvcAutoConfiguration.ResourceHandlerRegistrationCustomizer> resourceHandlerRegistrationCustomizerProvider, ObjectProvider<DispatcherServletPath> dispatcherServletPath, ObjectProvider<ServletRegistrationBean<?>> servletRegistrations) {
            this.resourceProperties = resourceProperties;
            this.mvcProperties = mvcProperties;
            this.beanFactory = beanFactory;
            this.messageConvertersProvider = messageConvertersProvider;
            this.resourceHandlerRegistrationCustomizer = (WebMvcAutoConfiguration.ResourceHandlerRegistrationCustomizer)resourceHandlerRegistrationCustomizerProvider.getIfAvailable();
            this.dispatcherServletPath = dispatcherServletPath;
            this.servletRegistrations = servletRegistrations;
        }

• resourceProperties:获取和spring.resources绑定的所有的值的对象

• WebMvcProperties mvcProperties:获取和spring.mvc绑定的所有的值的对象

• ListableBeanFactory beanFactory:Spring的beanFactory

• ObjectProvider<HttpMessageConverters> messageConvertersProvider:找到所有的HttpMessageConverters

• ResourceHandlerRegistrationCustomizer:找到资源处理器的自定义器

• DispatcherServletPath

• ServletRegistrationBean:给应用注册原生的Servlet、Filter

资源处理的默认规则

        public void addResourceHandlers(ResourceHandlerRegistry registry) {
            if (!this.resourceProperties.isAddMappings()) {
                logger.debug("Default resource handling disabled");
            } else {
                Duration cachePeriod = this.resourceProperties.getCache().getPeriod();
                CacheControl cacheControl = this.resourceProperties.getCache().getCachecontrol().toHttpCacheControl();
                //webjars的规则
                if (!registry.hasMappingForPattern("/webjars/**")) {
                    this.customizeResourceHandlerRegistration(registry.addResourceHandler(new String[]{"/webjars/**"}).addResourceLocations(new String[]{"classpath:/META-INF/resources/webjars/"}).setCachePeriod(this.getSeconds(cachePeriod)).setCacheControl(cacheControl));
                }

                String staticPathPattern = this.mvcProperties.getStaticPathPattern();
                if (!registry.hasMappingForPattern(staticPathPattern)) {
                    this.customizeResourceHandlerRegistration(registry.addResourceHandler(new String[]{staticPathPattern}).addResourceLocations(WebMvcAutoConfiguration.getResourceLocations(this.resourceProperties.getStaticLocations())).setCachePeriod(this.getSeconds(cachePeriod)).setCacheControl(cacheControl));
                }

            }
        }

• this.resourceProperties.isAddMappings():如果配成false,静态资源被禁用

spring:
  resources:
    add-mappings: false #禁用所有静态资源

@ConfigurationProperties(
    prefix = "spring.resources",
    ignoreUnknownFields = false
)
public class ResourceProperties {
    private static final String[] CLASSPATH_RESOURCE_LOCATIONS = new String[]{"classpath:/META-INF/resources/", "classpath:/resources/", "classpath:/static/", "classpath:/public/"};
    private String[] staticLocations;
    private boolean addMappings;
    private final ResourceProperties.Chain chain;
    private final ResourceProperties.Cache cache;

    public ResourceProperties() {
        this.staticLocations = CLASSPATH_RESOURCE_LOCATIONS;
        this.addMappings = true;
        this.chain = new ResourceProperties.Chain();
        this.cache = new ResourceProperties.Cache();
    }

    public String[] getStaticLocations() {
        return this.staticLocations;
    }

欢迎页的规则

      	@Bean
        public WelcomePageHandlerMapping welcomePageHandlerMapping(ApplicationContext applicationContext, FormattingConversionService mvcConversionService, ResourceUrlProvider mvcResourceUrlProvider) {
            WelcomePageHandlerMapping welcomePageHandlerMapping = new WelcomePageHandlerMapping(new TemplateAvailabilityProviders(applicationContext), applicationContext, this.getWelcomePage(), this.mvcProperties.getStaticPathPattern());
            welcomePageHandlerMapping.setInterceptors(this.getInterceptors(mvcConversionService, mvcResourceUrlProvider));
            welcomePageHandlerMapping.setCorsConfigurations(this.getCorsConfigurations());
            return welcomePageHandlerMapping;
        }

• HandlerMapping:处理器映射。保存了每一个Handler能处理哪些请求

	WelcomePageHandlerMapping(TemplateAvailabilityProviders templateAvailabilityProviders, ApplicationContext applicationContext, Optional<Resource> welcomePage, String staticPathPattern) {
        if (welcomePage.isPresent() && "/**".equals(staticPathPattern)) {
            //要用欢迎页，必须是/**
            logger.info("Adding welcome page: " + welcomePage.get());
            this.setRootViewName("forward:index.html");
        } else if (this.welcomeTemplateExists(templateAvailabilityProviders, applicationContext)) {
            //调用Controller /index
            logger.info("Adding welcome page template: index");
            this.setRootViewName("index");
        }

    }

请求参数处理

请求映射

rest使用与原理

• @xxxMapping；

• Rest风格支持（使用HTTP请求方式动词来表示对资源的操作）

  • 以前：/getUser 获取用户 /deleteUser 删除用户 /editUser 修改用户 /saveUser 保存用户

  • 现在： /user GET-获取用户 DELETE-删除用户 PUT-修改用户 POST-保存用户

  • 核心Filter；HiddenHttpMethodFilter

    • 用法： 表单method=post，隐藏域 _method=put
    • SpringBoot中手动开启

  • 扩展：如何把_method 这个名字换成我们自己喜欢的

    @RequestMapping(value = "/user",method = RequestMethod.GET)
    public String getUser(){
        return "GET-张三";
    }

    @RequestMapping(value = "/user",method = RequestMethod.POST)
    public String saveUser(){
        return "POST-张三";
    }


    @RequestMapping(value = "/user",method = RequestMethod.PUT)
    public String putUser(){
        return "PUT-张三";
    }

    @RequestMapping(value = "/user",method = RequestMethod.DELETE)
    public String deleteUser(){
        return "DELETE-张三";
    }


	@Bean
	@ConditionalOnMissingBean(HiddenHttpMethodFilter.class)
	@ConditionalOnProperty(prefix = "spring.mvc.hiddenmethod.filter", name = "enabled", matchIfMissing = false)//默认false
	public OrderedHiddenHttpMethodFilter hiddenHttpMethodFilter() {
		return new OrderedHiddenHttpMethodFilter();
	}

Rest原理(表单提交要使用REST风格)

• 表单提交会带上_method=PUT
• 请求过来被HiddenHttpMethodFilter拦截
  • 请求是否正常，并且是POST
    • 获取到_method的值
    • 兼容以下请求；PUT.DELETE.PATCH
    • 原生request（post），包装模式requesWrapper重写了getMethod方法，返回的是传入的值。
    • 过滤器链放行的时候用wrapper。以后的方法调用getMethod是调用requestWrapper的。

    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
        HttpServletRequest requestToUse = request;
        if ("POST".equals(request.getMethod()) && request.getAttribute("javax.servlet.error.exception") == null) {
            String paramValue = request.getParameter(this.methodParam);
            if (StringUtils.hasLength(paramValue)) {
                String method = paramValue.toUpperCase(Locale.ENGLISH);
                if (ALLOWED_METHODS.contains(method)) {
                    requestToUse = new HiddenHttpMethodFilter.HttpMethodRequestWrapper(request, method);
                }
            }
        }

        filterChain.doFilter((ServletRequest)requestToUse, response);
    }

Rest使用客户端工具

• 如PostMan直接发送Put、delete等方式请求，无需Filter。

spring:
  mvc:
    hiddenmethod:
      filter:
        enabled: true   #开启页面表单的Rest功能

@GetMapping相当于@RequestMapping(method=RequestMethod.GET)

• 自定义filter

@Configuration
public class WebConfig {

    @Bean
    public HiddenHttpMethodFilter hiddenHttpMethodFilter(){
        HiddenHttpMethodFilter methodFilter=new HiddenHttpMethodFilter();
        methodFilter.setMethodParam("_m");
        return methodFilter;
    }
}

请求映射原理

SpringMVC功能分析都从 org.springframework.web.servlet.DispatcherServlet->doDispatch()

    protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
        HttpServletRequest processedRequest = request;
        HandlerExecutionChain mappedHandler = null;
        boolean multipartRequestParsed = false;
        WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);

        try {
            try {
                ModelAndView mv = null;
                Object dispatchException = null;

                try {
                    processedRequest = this.checkMultipart(request);
                    multipartRequestParsed = processedRequest != request;
                    //找到当前请求使用哪个Handler(Controller的方法)处理
                    mappedHandler = this.getHandler(processedRequest);
                	//HandlerMapping:处理器映射/***->xxx

    @Nullable
    protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
        if (this.handlerMappings != null) {
            Iterator var2 = this.handlerMappings.iterator();

            while(var2.hasNext()) {
                HandlerMapping mapping = (HandlerMapping)var2.next();
                HandlerExecutionChain handler = mapping.getHandler(request);
                if (handler != null) {
                    return handler;
                }
            }
        }

        return null;
    }

RequestMappingHandlerMapping:保存了所有@RequestMapping和handler的映射规则。

所有的请求映射都保存在HandlerMapping中

• SpringBoot自动配置欢迎页的WelcomePageHandlerMaping。访问/能访问到index.html
• SpringBoot自动配置了默认的RequestMappingHandlerMapping
• 请求进来，挨个尝试所有的HandlerMapping看是否有请求信息。
  • 如果有就找到这个请求对应的handler
  • 如果没有就是下一个HandlerMapping
• 我们需要一些自定义的映射处理，我们也可以自己给容器中放HandlerMapping。自定义HandlerMapping

普通参数与基本注解

• 注解:

@PathVariable、@RequestHeader、@ModelAttribute、@RequestParam、@MatrixVariable、@CookieValue、@RequestBody

/**
 * @author frx
 * @version 1.0
 * @date 2022/3/31  16:25
 */
@RestController
public class ParameterTestController {

    // /car/2/owner/zhangsan
    @GetMapping("/car/{id}/owner/{username}")
    public Map<String,Object> getCar(@PathVariable("id") Integer id,
                                     @PathVariable("username") String name,
                                     @PathVariable Map<String,String> pv,
                                     @RequestHeader("User-Agent") String userAgent,
                                     @RequestHeader Map<String,String> header,
                                     @RequestParam("age") Integer age,
                                     @RequestParam("inters") List<String> inters,
                                     @RequestParam Map<String,String> params,
                                     @CookieValue("_ga") String _ga,
                                     @CookieValue("_ga") Cookie cookie){
        HashMap<String, Object> map= new HashMap<>();
//        map.put("id",id);
//        map.put("name",name);
//        map.put("pv",pv);
//        map.put("userAgent",userAgent);
//        map.put("headers",header);
        map.put("age",age);
        map.put("inters",inters);
        map.put("params",params);
        map.put("_ga",_ga);
        System.out.println(cookie.getName()+"-->"+cookie.getValue());
        return map;

    }
    @PostMapping("/save")
    public Map postMethod(@RequestBody String content){
        HashMap<String, Object> map = new HashMap<>();
        map.put("content",content);
        return map;
    }
}

/**
 * @author frx
 * @version 1.0
 * @date 2022/3/31  21:17
 */
@Controller
public class RequestController {

    @GetMapping("/goto")
    public String goToPage(HttpServletRequest request){
        request.setAttribute("msg","成功了...");
        request.setAttribute("code",200);
        return "forward:/success";  //转发到 /success请求
    }

    @ResponseBody
    @GetMapping("/success")
    public Map success(@RequestAttribute("msg") String msg,
                       @RequestAttribute("code") Integer code,
                       HttpServletRequest request){
        Object msg1 = request.getAttribute("msg");
        HashMap<String, Object> map = new HashMap<>();
        map.put("reqMethod_msg",msg1);
        map.put("annotation_msg",msg);
        return map;
    }
}

矩阵变量

1. 语法： 请求路径：/cars/sell;low=34;brand=byd,audi,yd
2. SpringBoot默认是禁用了矩阵变量的功能
   • 手动开启：原理。对于路径的处理。UrlPathHelper进行解析。
     • removeSemicolonContent（移除分号内容）支持矩阵变量的
3. 矩阵变量必须有url路径变量才能被解析

/cars/{path}?xxx=xxx&aaa=ccc queryString 查询字符串。@RequestParam；

/cars/sell;low=34;brand=byd,audi,yd ；矩阵变量

页面开发，cookie禁用了，session里面的内容怎么使用；

session.set(a,b)----> jsessionid ----> cookie ----> 每次发请求携带。

url重写：/abc;jsesssionid=xxxx 把cookie的值使用矩阵变量的方式进行传递.

• 开启矩阵变量功能-方法一:

@Configuration
public class WebConfig{
	@Bean
    public WebMvcConfigurer webMvcConfigurer(){
        return new WebMvcConfigurer() {
            @Override
            public void configurePathMatch(PathMatchConfigurer configurer) {
                UrlPathHelper urlPathHelper = new UrlPathHelper();
                urlPathHelper.setRemoveSemicolonContent(false);
                configurer.setUrlPathHelper(urlPathHelper);
            }
        };
    }
}

• 开启矩阵变量功能-方法二:

@Configuration
public class WebConfig implements WebMvcConfigurer {
 	@Override
    public void configurePathMatch(PathMatchConfigurer configurer) {
        UrlPathHelper urlPathHelper = new UrlPathHelper();
        //不移除;后面的内容
        urlPathHelper.setRemoveSemicolonContent(false);
        configurer.setUrlPathHelper(urlPathHelper);
    }
}

• 测试

@RestController
public class ParameterTestController { 	
	//1.语法: /cars/sell;low=34;brand=byd,audi,yd
    //2.SpringBoot默认是禁用了矩阵变量的功能
    //     手动开启:原理.对于路径的处理。
    //3.矩阵变量必须有url路径变量才能被解析
    @GetMapping("/cars/{path}")
    public Map carsSell(@MatrixVariable("low") Integer low,
                        @MatrixVariable("brand") List<String> brand,
                        @PathVariable("path") String path){
        HashMap<String, Object> map = new HashMap<>();
        map.put("low",low);
        map.put("brand",brand);
        map.put("path",path);
        return map;

    }

    // /boss/1;age=20/2;age=10
    @GetMapping("/boss/{bossId}/{empId}")
    public Map boss(@MatrixVariable(value ="age",pathVar = "bossId") Integer bossAge,
                    @MatrixVariable(value = "age",pathVar = "empId") Integer empAge){
        HashMap<String, Object> map = new HashMap<>();
        map.put("bossAge",bossAge);
        map.put("empAge",empAge);
        return map;
    }
}

视图解析与模板引擎

视图解析:SpringBoot默认不支持 JSP，需要引入第三方模板引擎技术实现页面渲染。

视图解析

• 视图处理方式
  • 转发
  • 重定向
  • 自定义视图

模板引擎-Thymeleaf

thymeleaf简介

• 官方文档 (opens new window)

Thymeleaf is a modern server-side Java template engine for both web and standalone environments, capable of processing HTML, XML, JavaScript, CSS and even plain text.

现代化、服务端Java模板引擎

基本语法

表达式

表达式名字	语法	用途
变量取值	${...}	获取请求域、session域、对象等值
选择变量	*{...}	获取上下文对象值
消息	#{...}	获取国际化等值
链接	@{...}	生成链接
片段表达式	~{...}	jsp:include 作用，引入公共

字面量

文本值: 'one text' , 'Another one!' **,…**数字: 0 , 34 , 3.0 , 12.3 **,…**布尔值: true , false

空值: null

变量： one，two，.... 变量不能有空格

文本操作

字符串拼接: +

变量替换: |The name is ${name}|

数学运算

运算符: + , - , * , / , %

布尔运算

运算符: and , or

一元运算: ! , not

比较运算

比较: > , < , >= , <= ( gt , lt , ge , le **)**等式: == , != ( eq , ne )

条件运算

If-then: (if) ? (then)

If-then-else: (if) ? (then) : (else)

Default: (value) ?: (defaultvalue)

特殊操作

无操作： _

设置属性值-th:attr

设置单个值

<form action="subscribe.html" th:attr="action=@{/subscribe}">
  <fieldset>
    <input type="text" name="email" />
    <input type="submit" value="Subscribe!" th:attr="value=#{subscribe.submit}"/>
  </fieldset>
</form>

设置多个值

<img src="../../images/gtvglogo.png"  th:attr="src=@{/images/gtvglogo.png},title=#{logo},alt=#{logo}" />

以上两个的代替写法 th:xxxx

<input type="submit" value="Subscribe!" th:value="#{subscribe.submit}"/>
<form action="subscribe.html" th:action="@{/subscribe}">

所有h5兼容的标签写法

https://www.thymeleaf.org/doc/tutorials/3.0/usingthymeleaf.html#setting-value-to-specific-attributes

迭代

<tr th:each="prod : ${prods}">
        <td th:text="${prod.name}">Onions</td>
        <td th:text="${prod.price}">2.41</td>
        <td th:text="${prod.inStock}? #{true} : #{false}">yes</td>
</tr>

<tr th:each="prod,iterStat : ${prods}" th:class="${iterStat.odd}? 'odd'">
  <td th:text="${prod.name}">Onions</td>
  <td th:text="${prod.price}">2.41</td>
  <td th:text="${prod.inStock}? #{true} : #{false}">yes</td>
</tr>

条件运算

<a href="comments.html"
th:href="@{/product/comments(prodId=${prod.id})}"
th:if="${not #lists.isEmpty(prod.comments)}">view</a>

<div th:switch="${user.role}">
  <p th:case="'admin'">User is an administrator</p>
  <p th:case="#{roles.manager}">User is a manager</p>
  <p th:case="*">User is some other thing</p>
</div>

属性优先级

thymeleaf使用

引入Starter

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>

自动配置好了thymeleaf

@Configuration(proxyBeanMethods = false)
@EnableConfigurationProperties(ThymeleafProperties.class)
@ConditionalOnClass({ TemplateMode.class, SpringTemplateEngine.class })
@AutoConfigureAfter({ WebMvcAutoConfiguration.class, WebFluxAutoConfiguration.class })
public class ThymeleafAutoConfiguration { }

自动配好的策略

• 所有thymeleaf的配置值都在 ThymeleafProperties
• 配置好了 SpringTemplateEngine
• 配好了 ThymeleafViewResolver
• 我们只需要直接开发页面

    public static final String DEFAULT_PREFIX = "classpath:/templates/";
    public static final String DEFAULT_SUFFIX = ".html"; //xxx.html

页面开发

• View层

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1 th:text="${msg}">哈哈</h1>
<h2>
    <a href="www.atguigu.com" th:href="${link}">去百度</a>  <br/>
    <a href="www.atguigu.com" th:href="@{link}">去百度2</a>
</h2>
</body>
</html>

• 控制层

/**
 * @author frx
 * @version 1.0
 * @date 2022/4/2  0:17
 */
@Controller
public class ViewTestController {

    @GetMapping("/atSchool")
    public String atSchool(Model model){
        //model中的数据会被放到请求域中 request.setAttribute("a",aa)
        model.addAttribute("msg","你好 atSchool");
        model.addAttribute("link","http://www.baidu.com");
        return "success";
    }
}

• View层

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1 th:text="${msg}">哈哈</h1>
<h2>
    <a href="www.atguigu.com" th:href="${link}">去百度</a>  <br/>
    <a href="www.atguigu.com" th:href="@{link}">去百度2</a>
</h2>
</body>
</html>

• 测试结果

构建后台管理项目

项目创建

thymeleaf、web-starter、devtools、lombok

静态资源处理

自动配置好，我们只需要把所有静态资源放到 static 文件夹下

路径构建

th:action="@{/login}"

页面跳转

/**
 * @author frx
 * @version 1.0
 * @date 2022/4/3  17:27
 */
@Controller
public class IndexController {

    /**
     * 来登录页
     * @return
     */
    @GetMapping(value = {"/","/login"})
    public String loginPage(){
        return "login";
    }

    @PostMapping("/login")
    public String main(User user, HttpSession session, Model model){

        if(!StringUtils.isEmpty(user.getUserName())&&"123456".equals(user.getPassword())){
            //把登陆成功的用户保存起来
            session.setAttribute("loginUser",user);
            //登陆成功重定向到main.html;重定向防止表单重复提交
            return "redirect:/main.html";
        }else {
            model.addAttribute("msg","账号密码错误");
            //回到登录页
            return "login";
        }
    }

    /**
     * 去main页面
     * @return
     */
    @GetMapping("/main.html")
    public String mainPage(HttpSession session,Model model){
        //是否登录 拦截器，过滤器
        Object loginUser = session.getAttribute("loginUser");
        if(loginUser!=null){
            return "main";
        }else {
            //回到登录页
            model.addAttribute("msg","请重新登录");
            return "login";
        }
    }
}

数据渲染

  @GetMapping("/dynamic_table")
    public String dynamic_table(Model model){
        //表格内容的遍历
        List<User> users = Arrays.asList(new User("zhangsan", "123456"),
                new User("lisi", "123444"),
                new User("haha", "aaaaa"),
                new User("hehe ", "aaddd"));
        model.addAttribute("users",users);

        return "table/dynamic_table";
    }

<table class="display table table-bordered" id="hidden-table-info">
        <thead>
        <tr>
            <th>#</th>
            <th>用户名</th>
            <th>密码</th>
        </tr>
        </thead>
        <tbody>
        <tr class="gradeX" th:each="user,stats:${users}">
            <td th:text="${stats.count}">Trident</td>
            <td th:text="${user.userName}">Internet</td>
            <td >[[${user.password}]]</td>
        </tr>
        </tbody>
        </table>

拦截器

HandlerInterceptor 接口

/**
 * @author frx
 * @version 1.0
 * @date 2022/4/5  0:30
 * 登陆检查
 * 1.配置好拦截器要拦截哪些请求
 * 2.把这些配置放在容器中
 */
@Slf4j
public class LoginInterceptor implements HandlerInterceptor {

    /**
     * 目标方法执行之前
     * @param request
     * @param response
     * @param handler
     * @return
     * @throws Exception
     */
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {

        String requestURI = request.getRequestURI();
        log.info("拦截的请求路径是{}",requestURI);

        //登陆检查逻辑
        HttpSession session = request.getSession();
        Object loginUser = session.getAttribute("loginUser");
        if(loginUser!=null){
            //放行
            return true;
        }
        //拦截住,未登录，跳转到登录页
        request.setAttribute("msg","请先登录");
//        response.sendRedirect("/");
        request.getRequestDispatcher("/").forward(request,response);
        return false;
    }

    /**
     * 目标方法执行完成以后
     * @param request
     * @param response
     * @param handler
     * @param modelAndView
     * @throws Exception
     */
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        log.info("postHandle执行{}",modelAndView);
    }

    /**
     * 页面渲染以后
     * @param request
     * @param response
     * @param handler
     * @param ex
     * @throws Exception
     */
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        log.info("afterCompletion执行异常{}",ex);
    }
}

配置拦截器

/**
 * @author frx
 * @version 1.0
 * @date 2022/4/5  1:04
 * 1.编写一个拦截器，实现HandlerInterceptor 接口
 * 2.拦截器注册到容器中  实现WebMvcConfigurer的addInterceptors方法
 * 3.指定拦截规则【如果是拦截所有，静态资源也会被拦截】
 */
@Configuration
public class AdminWebConfig implements WebMvcConfigurer {

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new LoginInterceptor())
                .addPathPatterns("/**")  //所有请求都被拦截 //静态资源也会拦截
                .excludePathPatterns("/","/login","/css/**","/fonts/**","/images/**","/js/**"); //放行的请求
    }
}

• 结果

preHandle拦截的请求路径是/main.html
当前方法是:mainPage
postHandle执行ModelAndView [view="main";model={}]
afterComletion执行异常{}

文件上传

页面表单

<form method="post" action="/upload" enctype="multipart/form-data">
    <input type="file" name="file"><br>
    <input type="submit" value="提交">
</form>

文件上传代码

/**
 * @author frx
 * @version 1.0
 * @date 2022/4/6  17:01
 * 文件上传测试
 */
@Slf4j
@Controller
public class FormTestController {

    @GetMapping("/form_layouts")
    public String form_layouts(){
        return "form/form_layouts";
    }

    /**
     * MultipartFile自动封装上传过来的文件
     * @param email
     * @param username
     * @param headerImg
     * @param photos
     * @return
     */
    @PostMapping("/upload")
    public String upload(@RequestParam("email") String email,
                         @RequestParam("username") String username,
                         @RequestPart("headerImg")MultipartFile headerImg,
                         @RequestPart("photos") MultipartFile[] photos) throws IOException {

        log.info("上传的信息:emails={},username={},headerImg={},photos={}",
                email,username,headerImg.getSize(),photos.length);
        
        if(!headerImg.isEmpty()){
            //保存到文件服务器，OOS服务器
            String filename = headerImg.getOriginalFilename();
            headerImg.transferTo(new File("D:\\cache\\"+filename));
        }

        if(photos.length>0){
            for (MultipartFile photo : photos) {
                if(!photo.isEmpty()){
                    String filename = photo.getOriginalFilename();
                    photo.transferTo(new File("D:\\cache\\"+filename));
                }
            }
        }
        return "main";
    }
}

异常处理

错误处理

默认规则

• 默认情况下，Spring Boot提供/error处理所有错误的映射
• 对于机器客户端，它将生成JSON响应，其中包含错误，HTTP状态和异常消息的详细信息。对于浏览器客户端，响应一个“ whitelabel”错误视图，以HTML格式呈现相同的数据

• 要对其进行自定义，添加View解析为error
• 要完全替换默认行为，可以实现 ErrorController并注册该类型的Bean定义，或添加ErrorAttributes类型的组件以使用现有机制但替换其内容。
• error/下的4xx，5xx页面会被自动解析

Web原生组件注入(Servlet、Filter、Listener)

使用Servlet API

@ServletComponentScan(basePackages = "com.frx01.admin")//指定原生Servlet组件都放在那里
@SpringBootApplication
public class Boot05WebAdminApplication {

    public static void main(String[] args) {
        SpringApplication.run(Boot05WebAdminApplication.class, args);
    }
}

/**
 * @author frx
 * @version 1.0
 * @date 2022/4/7  15:54
 */
@WebServlet(urlPatterns = "/my")//效果：直接相应，没有Spring的拦截器
public class MyServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.getWriter().write("666");
    }
}

/**
 * @author frx
 * @version 1.0
 * @date 2022/4/7  16:03
 */
@Slf4j
@WebFilter(urlPatterns = {"/css/*","/images/*"})
public class MyFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        log.info("MyFilter初始化完成");
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        log.info("MyFilter工作");
        chain.doFilter(request,response);
    }

    @Override
    public void destroy() {
        log.info("MyFilter销毁");
    }
}

/**
 * @author frx
 * @version 1.0
 * @date 2022/4/7  16:13
 */
@Slf4j
@WebListener
public class MyServletContextListener implements ServletContextListener {

    @Override
    public void contextInitialized(ServletContextEvent sce) {
        log.info("MyServletContextListener监听到项目初始化完成");

    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        log.info("MyServletContextListener监听到项目销毁");
    }
}

推荐这种方式

扩展：DispatchServlet 如何注册进来

• 容器中自动配置了 DispatcherServlet 属性绑定到 WebMvcProperties；对应的配置文件配置项是 spring.mvc。
• 通过 ServletRegistrationBean<DispatcherServlet> 把 DispatcherServlet 配置进来。
• 默认映射的是 / 路径

Tomcat-Servlet；

多个Servlet都能处理到同一层路径，精确优选原则

A： /my/

B： /my/1

使用RegistrationBean

ServletRegistrationBean, FilterRegistrationBean, and ServletListenerRegistrationBean

/**
 * @author frx
 * @version 1.0
 * @date 2022/4/7  16:22
 */

@Configuration(proxyBeanMethods = true) /*(proxyBeanMethods = true)*/ //保证依赖的组件始终是单实例的
public class MyRegistConfig {

    @Bean
    public ServletRegistrationBean myServlet(){
        MyServlet myServlet = new MyServlet();
        return new ServletRegistrationBean(myServlet,"/my","/my02");
    }

    @Bean
    public FilterRegistrationBean myFilter(){
        MyFilter myFilter = new MyFilter();
//        return new FilterRegistrationBean(myFilter,myServlet());
        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean(myFilter);
        filterRegistrationBean.setUrlPatterns(Arrays.asList("/my","/css/*"));
        return new FilterRegistrationBean(myFilter);
    }

    @Bean
    public ServletListenerRegistrationBean myListener(){
        MyServletContextListener myServletContextListener = new MyServletContextListener();
        return new ServletListenerRegistrationBean(myServletContextListener);
    }
}

定制化原理

定制化的常见方式

• 修改配置文件；
• xxxxxCustomizer；
• 编写自定义的配置类 xxxConfiguration；+ @Bean替换、增加容器中默认组件；视图解析器
• Web应用 编写一个配置类实现 WebMvcConfigurer 即可定制化web功能；+ @Bean给容器中再扩展一些组件

@Configuration
public class AdminWebConfig implements WebMvcConfigurer

• @EnableWebMvc + WebMvcConfigurer —— @Bean 可以全面接管SpringMVC，所有规则全部自己重新配置； 实现定制和扩展功能

• • 原理

    1、WebMvcAutoConfiguration 默认的SpringMVC的自动配置功能类。静态资源、欢迎页.....

    2、一旦使用 @EnableWebMvc 、。会 @Import(DelegatingWebMvcConfiguration.class)

    3、DelegatingWebMvcConfiguration 的 作用，只保证SpringMVC最基本的使用

• • • 把所有系统中的 WebMvcConfigurer 拿过来。所有功能的定制都是这些 WebMvcConfigurer 合起来一起生效
    • 自动配置了一些非常底层的组件。RequestMappingHandlerMapping、这些组件依赖的组件都是从容器中获取
    • public class DelegatingWebMvcConfiguration extends WebMvcConfigurationSupport

• ​ 4、WebMvcAutoConfiguration 里面的配置要能生效 必须 @ConditionalOnMissingBean(WebMvcConfigurationSupport.class)

• ​ 5、@EnableWebMvc 导致了 WebMvcAutoConfiguration 没有生效。

• ... ...

原理分析套路

场景starter - xxxxAutoConfiguration - 导入xxx组件 - 绑定xxxProperties -- 绑定配置文件项