5、SpringBoot之WEB开发和thymeleaf模板引擎

待我称王封你为后i 2022-01-11 06:33 372阅读 0赞

#### 项目地址：[https://github.com/Chakid/SpringBoot-example][https_github.com_Chakid_SpringBoot-example] ####

## 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/][http_www.webjars.org]  
![image.png][]  
`pom`文件里面引入：

<dependency>
         <groupId>org.webjars</groupId>
         <artifactId>jquery</artifactId>
         <version>3.2.1</version>
    </dependency>

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 ##

JSP、Velocity、Freemarker、Thymeleaf  
![image.png][image.png 1]

SpringBoot推荐的Thymeleaf；

语法更简单，功能更强大；

### 1、引入thymeleaf； ###

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

### 2、Thymeleaf使用 ###

@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；  
例如我写一个测试类：

/** * 该处返回 "success"返回的是 resources/templates目录下面的页面 * 该出要返回的是页面，所以不能配置@ResponseBody注解，如果配置了该注解会以字符串直接输出"success" * @return success.html */
        @RequestMapping("/success")
        public String success(){ 
            return "success";
        }

然后 `resources/templates`目录下新建`success.html`

<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>Title</title>
    </head>
    <body>
    <h1>跳转成功页面</h1>
    </body>
    </html>

![image.png][image.png 2]

使用：

1、导入thymeleaf的名称空间

2、使用thymeleaf语法；  
后端代码改写成：

<!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>
        
        <div th:text="${hello}">这是显示欢迎信息</div>
    </body>
    </html>

![image.png][image.png 3]

### 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

![image.png][image.png 4]

2）、表达式？

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: _

#### 数据渲染到页面相关用法： ####

html页面：

<!DOCTYPE html>
    <html lang="en" xmlns:th="http://www.thymeleaf.org">
    <head>
        <meta charset="UTF-8">
        <title>Title</title>
    </head>
    <body>
    <h1>跳转成功页面</h1>
    
    <div th:text="${hello}"></div>
    
    <hr/>
    <div th:text="${hello}"></div>
    <div th:utext="${hello}"></div>
    
    <hr/>
    <h4 th:text="${user}" th:each="user:${users}"></h4>
    <hr/>
    
    <h4>
        <span th:each="user:${users}" > [[${user}]] </span>
    </h4>
    </body>
    </html>

后端代码：

@RequestMapping("/success")
        public String success(Map<String,Object> map){ 
            map.put("hello","你好");
            map.put("users", Arrays.asList("张三","李四","王五"));
            return "success";
        }

效果图：  
![image.png][image.png 5]

[https_github.com_Chakid_SpringBoot-example]: https://github.com/Chakid/SpringBoot-example
[http_www.webjars.org]: http://www.webjars.org/
[image.png]: /images/20220111/12b53b89e4074b558efcc7c0825f0b8c.png
[image.png 1]: /images/20220111/1a93e456962741ceaeff243469d2ad47.png
[image.png 2]: /images/20220111/6280aea546234437b986bdf8bcac1174.png
[image.png 3]: /images/20220111/3022a92909b845b8b4207531ac4ee106.png
[image.png 4]: /images/20220111/a722e330c8934477a85b8f5a801cea02.png
[image.png 5]: /images/20220111/d3210624aa894c4699a55e57fafd4c47.png