尚硅谷【SpringBoot】web(源码讲解太多不建议阅读)

四、Web开发

1、简介

使用SpringBoot；

1）、创建SpringBoot应用，选中我们需要的模块；

2）、SpringBoot已经默认将这些场景配置好了，只需要在配置文件中指定少量配置就可以运行起来

3）、自己编写业务代码；

自动配置原理？

这个场景SpringBoot帮我们配置了什么？能不能修改？能修改哪些配置？能不能扩展？xxx

xxxxAutoConfiguration：帮我们给容器中自动配置组件；
xxxxProperties:配置类来封装配置文件的内容；

2、SpringBoot对静态资源的映射规则；

@ConfigurationProperties(prefix = "spring.resources", ignoreUnknownFields = false)
public class ResourceProperties implements ResourceLoaderAware {
  //可以设置和静态资源有关的参数，缓存时间等

    WebMvcAuotConfiguration：
        @Override
        public void addResourceHandlers(ResourceHandlerRegistry registry) {
            if (!this.resourceProperties.isAddMappings()) {
                logger.debug("Default resource handling disabled");
                return;
            }
            Integer cachePeriod = this.resourceProperties.getCachePeriod();
            if (!registry.hasMappingForPattern("/webjars/**")) {
                customizeResourceHandlerRegistration(
                        registry.addResourceHandler("/webjars/**")
                                .addResourceLocations(
                                        "classpath:/META-INF/resources/webjars/")
                        .setCachePeriod(cachePeriod));
            }
            String staticPathPattern = this.mvcProperties.getStaticPathPattern();
            //静态资源文件夹映射
            if (!registry.hasMappingForPattern(staticPathPattern)) {
                customizeResourceHandlerRegistration(
                        registry.addResourceHandler(staticPathPattern)
                                .addResourceLocations(
                                        this.resourceProperties.getStaticLocations())
                        .setCachePeriod(cachePeriod));
            }
        }
​
        //配置欢迎页映射
        @Bean
        public WelcomePageHandlerMapping welcomePageHandlerMapping(
                ResourceProperties resourceProperties) {
            return new WelcomePageHandlerMapping(resourceProperties.getWelcomePage(),
                    this.mvcProperties.getStaticPathPattern());
        }
​
       //配置喜欢的图标
        @Configuration
        @ConditionalOnProperty(value = "spring.mvc.favicon.enabled", matchIfMissing = true)
        public static class FaviconConfiguration {
​
            private final ResourceProperties resourceProperties;
​
            public FaviconConfiguration(ResourceProperties resourceProperties) {
                this.resourceProperties = resourceProperties;
            }
​
            @Bean
            public SimpleUrlHandlerMapping faviconHandlerMapping() {
                SimpleUrlHandlerMapping mapping = new SimpleUrlHandlerMapping();
                mapping.setOrder(Ordered.HIGHEST_PRECEDENCE + 1);
                //所有  **/favicon.ico 
                mapping.setUrlMap(Collections.singletonMap("**/favicon.ico",
                        faviconRequestHandler()));
                return mapping;
            }
​
            @Bean
            public ResourceHttpRequestHandler faviconRequestHandler() {
                ResourceHttpRequestHandler requestHandler = new ResourceHttpRequestHandler();
                requestHandler
                        .setLocations(this.resourceProperties.getFaviconLocations());
                return requestHandler;
            }
​
        }
​

==1）、所有 /webjars/** ，都去 classpath:/META-INF/resources/webjars/ 找资源；==

​ webjars：以jar包的方式引入静态资源；

http://www.webjars.org/

==2）、"/**" 访问当前项目的任何资源，都去（静态资源的文件夹）找映射==

"classpath:/META-INF/resources/",
"classpath:/resources/",
"classpath:/static/",
"classpath:/public/"
"/"：当前项目的根路径

localhost:8080/abc === 去静态资源文件夹里面找abc

==3）、欢迎页； 静态资源文件夹下的所有index.html页面；被"/**"映射；==

​ localhost:8080/ 找index页面

==4）、所有的 **/favicon.ico 都是在静态资源文件下找；==

3、模板引擎

SpringBoot推荐的Thymeleaf；

语法更简单，功能更强大；

1、引入thymeleaf；个人使用

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

全部引入最新版本，git.com查看最新版本

<thymeleaf.version>3.0.11.RELEASE</thymeleaf.version>
   <!-- 布局功能的支持程序  thymeleaf3主程序  layout2以上版本 -->
   <!-- thymeleaf2   layout1-->
   <thymeleaf-layout-dialect.version>2.3.0</thymeleaf-layout-dialect.version>
</properties>

2、Thymeleaf使用

```java
@ConfigurationProperties(prefix = "spring.thymeleaf")
public class ThymeleafProperties {

private static final Charset DEFAULT_ENCODING = Charset.forName("UTF-8");

private static final MimeType DEFAULT_CONTENT_TYPE = MimeType.valueOf("text/html");

public static final String DEFAULT_PREFIX = "classpath:/templates/";

public static final String DEFAULT_SUFFIX = ".html";
//
```

只要我们把HTML页面放在classpath:/templates/，thymeleaf就能自动渲染；

使用：

1、导入thymeleaf的名称空间

```xml
<html lang="en" xmlns:th="http://www.thymeleaf.org">
```

2、使用thymeleaf语法；

```html
<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<h1>成功！</h1>
<!--th:text 将div里面的文本内容设置为 -->
<div th:text="${hello}">这是显示欢迎信息</div>
</body>
</html>
```

### 3、语法规则

1）、th:text；改变当前元素里面的文本内容；

​ th：任意html属性；来替换原生属性的值

2）、表达式？

```properties
Simple expressions:（表达式语法）

Variable Expressions: ${...}：获取变量值；OGNL；
1）、获取对象的属性、调用方法
2）、使用内置的基本对象：
#ctx : the context object.
#vars: the context variables.
#locale : the context locale.
#request : (only in Web Contexts) the HttpServletRequest object.
#response : (only in Web Contexts) the HttpServletResponse object.
#session : (only in Web Contexts) the HttpSession object.
#servletContext : (only in Web Contexts) the ServletContext object.

${session.foo}
3）、内置的一些工具对象：
#execInfo : information about the template being processed.
#messages : methods for obtaining externalized messages inside variables expressions, in the same way as they would be obtained using #{…} syntax.
#uris : methods for escaping parts of URLs/URIs
#conversions : methods for executing the configured conversion service (if any).
#dates : methods for java.util.Date objects: formatting, component extraction, etc.
#calendars : analogous to #dates , but for java.util.Calendar objects.
#numbers : methods for formatting numeric objects.
#strings : methods for String objects: contains, startsWith, prepending/appending, etc.
#objects : methods for objects in general.
#bools : methods for boolean evaluation.
#arrays : methods for arrays.
#lists : methods for lists.
#sets : methods for sets.
#maps : methods for maps.
#aggregates : methods for creating aggregates on arrays or collections.
#ids : methods for dealing with id attributes that might be repeated (for example, as a result of an iteration).

Selection Variable Expressions: *{...}：选择表达式：和${}在功能上是一样；
补充：配合 th:object="${session.user}：
<div th:object="${session.user}">
<p>Name: <span th:text="*{firstName}">Sebastian</span>.</p>
<p>Surname: <span th:text="*{lastName}">Pepper</span>.</p>
<p>Nationality: <span th:text="*{nationality}">Saturn</span>.</p>
</div>

Message Expressions: #{...}：获取国际化内容
Link URL Expressions: @{...}：定义URL；
@{/order/process(execId=${execId},execType='FAST')}
Fragment Expressions: ~{...}：片段引用表达式
<div th:insert="~{commons :: main}">...</div>

Literals（字面量）
Text literals: 'one text' , 'Another one!' ,…
Number literals: 0 , 34 , 3.0 , 12.3 ,…
Boolean literals: true , false
Null literal: null
Literal tokens: one , sometext , main ,…
Text operations:（文本操作）
String concatenation: +
Literal substitutions: |The name is ${name}|
Arithmetic operations:（数学运算）
Binary operators: + , - , * , / , %
Minus sign (unary operator): -
Boolean operations:（布尔运算）
Binary operators: and , or
Boolean negation (unary operator): ! , not
Comparisons and equality:（比较运算）
Comparators: > , < , >= , <= ( gt , lt , ge , le )
Equality operators: == , != ( eq , ne )
Conditional operators:条件运算（三元运算符）
If-then: (if) ? (then)
If-then-else: (if) ? (then) : (else)
Default: (value) ?: (defaultvalue)
Special tokens:
No-Operation: _
```

```java
@ConfigurationProperties(prefix = "spring.thymeleaf")
public class ThymeleafProperties {

private static final Charset DEFAULT_ENCODING = Charset.forName("UTF-8");

private static final MimeType DEFAULT_CONTENT_TYPE = MimeType.valueOf("text/html");

public static final String DEFAULT_PREFIX = "classpath:/templates/";

public static final String DEFAULT_SUFFIX = ".html";
//
```

只要我们把HTML页面放在classpath:/templates/，thymeleaf就能自动渲染

4、SpringMVC自动配置

https://docs.spring.io/spring-boot/docs/1.5.10.RELEASE/reference/htmlsingle/#boot-features-developing-web-applications

1. Spring MVC auto-configuration

Spring Boot 自动配置好了SpringMVC

以下是SpringBoot对SpringMVC的默认配置:==（WebMvcAutoConfiguration）==

• Inclusion of ContentNegotiatingViewResolver and BeanNameViewResolver beans.

  • 自动配置了ViewResolver（视图解析器：根据方法的返回值得到视图对象（View），视图对象决定如何渲染（转发？重定向？））

  • ContentNegotiatingViewResolver：组合所有的视图解析器的；

  • ==如何定制：我们可以自己给容器中添加一个视图解析器；自动的将其组合进来；==

• Support for serving static resources, including support for WebJars (see below).静态资源文件夹路径,webjars

• Static index.html support. 静态首页访问

• Custom Favicon support (see below). favicon.ico

  ​

• 自动注册了 of Converter, GenericConverter, Formatter beans.

  • Converter：转换器； public String hello(User user)：类型转换使用Converter

  • Formatter 格式化器； 2017.12.17===Date；

        @Bean
        @ConditionalOnProperty(prefix = "spring.mvc", name = "date-format")//在文件中配置日期格式化的规则
        public Formatter<Date> dateFormatter() {
            return new DateFormatter(this.mvcProperties.getDateFormat());//日期格式化组件
        }

​ ==自己添加的格式化器转换器，我们只需要放在容器中即可==

• Support for HttpMessageConverters (see below).

  • HttpMessageConverter：SpringMVC用来转换Http请求和响应的；User---Json；

  • HttpMessageConverters 是从容器中确定；获取所有的HttpMessageConverter；

    ==自己给容器中添加HttpMessageConverter，只需要将自己的组件注册容器中（@Bean,@Component）==

    ​

• Automatic registration of MessageCodesResolver (see below).定义错误代码生成规则

• Automatic use of a ConfigurableWebBindingInitializer bean (see below).

  ==我们可以配置一个ConfigurableWebBindingInitializer来替换默认的；（添加到容器）==

  初始化WebDataBinder；
  请求数据=====JavaBean；
  

org.springframework.boot.autoconfigure.web：web的所有自动场景；

If you want to keep Spring Boot MVC features, and you just want to add additional MVC configuration (interceptors, formatters, view controllers etc.) you can add your own @Configuration class of type WebMvcConfigurerAdapter, but without @EnableWebMvc. If you wish to provide custom instances of RequestMappingHandlerMapping, RequestMappingHandlerAdapter or ExceptionHandlerExceptionResolver you can declare a WebMvcRegistrationsAdapter instance providing such components.

If you want to take complete control of Spring MVC, you can add your own @Configuration annotated with @EnableWebMvc.

2、扩展SpringMVC