一、模板引擎
常用的模板引擎：JSP、Velocity、Freemarker、Thymeleaf
Thymeleaf是一款用于渲染XML/XHTML/HTML5内容的模板引擎。类似JSP，Velocity， FreeMaker等，它也可以轻易的与Spring MVC等Web框架进行集成
作为Web应用的模板引擎。与其它模板引擎相比， Thymeleaf最大的特点是能够直接在浏览器中打开并正确显示模板页面，而不需要启动整个Web应用
SpringBoot 推荐的 ThymeLeaf：语法更简单，功能更强大；
Spring Boot推荐使用Thymeleaf、 Freemarker等后现代的模板引擎技术；一但导入相关依赖，会自动配置ThymeleafAutoConfiguration、 FreeMarkerAutoConfiguration。
二、引入 Thymeleaf
<!--默认版本为2.1.6-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
<properties>
<!-- 切换thymeleaf版本 -->
<!-- 布局功能的支持程序： thymeleaf3主程序 layout2以上版本 如果使用 thymeleaf2 layout1以上版本-->
<thymeleaf.version>3.0.9.RELEASE</thymeleaf.version>
<thymeleaf-layout-dialect.version>2.2.2</thymeleaf-layout-dialect.version>
</properties>
三、Thymeleaf 使用
Thymeleaf 的配置信息都在 ThymeleafProperties 文件中：
@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；
示例：
//测试
@RequestMapping(value = "/success", method = RequestMethod.GET)
public String success(Map<String,Object> map){
map.put("hello","<h1>你好</h1>");
//classpath:/templates/success.html
return "success";
}
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：
<!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>
四、语法规则
1、th：任意 html 属性，来替换原生属性的值；
th:text 改变当前元素里面的文本内容；
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 ${name}| Arithmetic operations:（数学运算） Binary operators: + , - , * , / , % Minus sign (unary operator): - Boolean operations:（布尔运算） Binary operators: and , or Boolean negation (unary operator): ! , not Comparisons and equality:（比较运算） Comparators: > , < , >= , <= ( gt , lt , ge , le ) Equality operators: == , != ( eq , ne ) Conditional operators:条件运算（三元运算符） If-then: (if) ? (then) If-then-else: (if) ? (then) : (else) Default: (value) ?: (defaultvalue) Special tokens: No-Operation: _
3、示例代码
控制器方法：
//查出用户数据，在页面展示
@RequestMapping(value = "/success", method = RequestMethod.GET)
public String success(Map<String,Object> map){
map.put("hello","<h1>你好</h1>");
map.put("users", Arrays.asList("zhangsan","lisi","wangwu"));
return "success";
}
页面：
<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<h1>成功！</h1>
<!--th:text 将div里面的文本内容设置为 -->
<div id="div01" class="myDiv" th:id="${hello}" th:class="${hello}" th:text="${hello}">这是显示欢迎信息</div>
<hr/>
<div th:text="${hello}"></div>
<div th:utext="${hello}"></div>
<hr/>
<!-- th:each每次遍历都会生成当前这个标签： 3个h4 -->
<h4 th:text="${user}" th:each="user:${users}"></h4>
<hr/>
<h4>
<span th:each="user:${users}"> [[${user}]] </span>
</h4>
</body>
</html>
展示效果：
