5、SpringBoot之WEB开发和thymeleaf模板引擎

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/

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

SpringBoot推荐的Thymeleaf;

语法更简单,功能更强大;

1、引入thymeleaf;

  <!--引入thymeleaf模板引擎-->
 <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

使用:

1、导入thymeleaf的名称空间

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

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>
    <!--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>
image.png

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

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

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