Springboot之Web开发：模板引擎

╰半夏微凉° 2022-05-16 12:21 279阅读 0赞

### 1、模板引擎 ###

JSP、Velocity、Freemarker、Thymeleaf  
模板引擎原理图：

![70][]

Springboot推荐使用 Thymeleaf模板引擎：语法简单，功能强大

### 2、引入Thymeleaf ###

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

将Thymeleaf切换版本，在maven的properties中进入如下配置

<thymeleaf.version>3.0.9.RELEASE</thymeleaf.version>
    
    
    <thymeleaf-layout-dialect.version>2.2.2</thymeleaf-layout-dialect.version>

### 3、Thymeleaf的使用 ###

@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/下，Thymeleaf就可以帮我们自动渲染。

如：

@RequestMapping(value = "/Thymeleaf")
        public String thymeleaf(){
            //classpath:/templates/thymeleaf.html
            return "thymeleaf";
        }

1、在html页面中导入Thymeleaf的名称空间

2、使用Thymeleaf的语法

@RequestMapping(value = "/Thymeleaf")
        public String thymeleaf(Map<String ,Object> map){
            //classpath:/templates/thymeleaf.html
            map.put("hello","you are so excellent" );
            return "thymeleaf";
        }

### 4、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

![70 1][]

2）表达式

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.
            #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 aresult 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>

其他的一些

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: _

实例：

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

@RequestMapping(value = "/Thymeleaf")
        public String thymeleaf(Map<String ,Object> map){
            //classpath:/templates/thymeleaf.html
            map.put("hello","<h4>you are so excellent</h4>" );
            map.put("users", Arrays.asList("张三","李四","王五"));
            return "thymeleaf";
        }

[70]: /images/20220516/e131f4d53bce4a88aa9298ec04c629a0.png
[70 1]: /images/20220516/743e817cb87444c986b68c1d7b718e7a.png