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    Spring Boot thymeleaf模板引擎的使用详解

    作者:shunshunshun18 栏目:未分类 时间:2021-03-08 14:44:00

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    在早期开发的时候,我们完成的都是静态页面也就是html页面,随着时间轴的发展,慢慢的引入了jsp页面,当在后端服务查询到数据之后可以转发到jsp页面,可以轻松的使用jsp页面来实现数据的显示及交互,jsp有非常强大的功能,但是,在使用springboot的时候,整个项目是以jar包的方式运行而不是war包,而且还嵌入了tomcat容器,因此,在默认情况下是不支持jsp页面的。如果直接以纯静态页面的方式会给我们的开发带来很大的麻烦,springboot推荐使用模板引擎。

    模板引擎有很多种,jsp,freemarker,thymeleaf,模板引擎的作用就是我们来写一个页面模板,比如有些值呢,是动态的,我们写一些表达式。而这些值,从哪来呢,我们来组装一些数据,我们把这些数据找到。然后把这个模板和这个数据交给我们模板引擎,模板引擎按照我们这个数据帮你把这表达式解析、填充到我们指定的位置,然后把这个数据最终生成一个我们想要的内容给我们写出去,这就是我们这个模板引擎,不管是jsp还是其他模板引擎,都是这个思想。只不过不同的模板引擎语法不同而已,下面重点学习下springboot推荐使用的thymeleaf模板引擎,语法简单且功能强大

    1、thymeleaf的介绍

    官网地址:https://www.thymeleaf.org/

    thymeleaf在github的地址:https://github.com/thymeleaf/thymeleaf

    中文网站:https://raledong.gitbooks.io/using-thymeleaf/content/

    导入依赖:

     <!--thymeleaf模板-->
      <dependency>
       <groupId>org.thymeleaf</groupId>
       <artifactId>thymeleaf-spring5</artifactId>
      </dependency>
      <dependency>
       <groupId>org.thymeleaf.extras</groupId>
       <artifactId>thymeleaf-extras-java8time</artifactId>
      </dependency>

    在springboot中有专门的thymeleaf配置类:ThymeleafProperties

    @ConfigurationProperties(prefix = "spring.thymeleaf")
    public class ThymeleafProperties {
    	private static final Charset DEFAULT_ENCODING = StandardCharsets.UTF_8;
    	public static final String DEFAULT_PREFIX = "classpath:/templates/";
    	public static final String DEFAULT_SUFFIX = ".html";
    	/**
    	 * Whether to check that the template exists before rendering it.
    	 */
    	private boolean checkTemplate = true;
    	/**
    	 * Whether to check that the templates location exists.
    	 */
    	private boolean checkTemplateLocation = true;
    	/**
    	 * Prefix that gets prepended to view names when building a URL.
    	 */
    	private String prefix = DEFAULT_PREFIX;
    	/**
    	 * Suffix that gets appended to view names when building a URL.
    	 */
    	private String suffix = DEFAULT_SUFFIX;
    	/**
    	 * Template mode to be applied to templates. See also Thymeleaf's TemplateMode enum.
    	 */
    	private String mode = "HTML";
    	/**
    	 * Template files encoding.
    	 */
    	private Charset encoding = DEFAULT_ENCODING;
    	/**
    	 * Whether to enable template caching.
    	 */
    	private boolean cache = true;

    2、thymeleaf使用模板

    在java代码中写入如下代码:

    @RequestMapping("/hello")
     public String hello(Model model){
      model.addAttribute("msg","Hello");
      //classpath:/templates/hello.html
      return "hello";
     }

    html页面中写入如下代码:

    <!DOCTYPE html>
    <html lang="en" xmlns:th="http://www.thymeleaf.org">
    <body>
    <h1>Hello</h1>
    <div th:text="${msg}"></div>
    </body>
    </html>

    3、thymeleaf的表达式语法

    Simple expressions:
    	Variable Expressions: ${...}
    	Selection Variable Expressions: *{...}
    	Message Expressions: #{...}
    	Link URL Expressions: @{...}
    	Fragment Expressions: ~{...}
    Literals
    	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:
    	String concatenation: +
    	Literal substitutions: |The name is ${name}|
    Arithmetic operations:
    	Binary operators: +, -, *, /, %
    	Minus sign (unary operator): -
    	Boolean operations:
    	Binary operators: and, or
    	Boolean negation (unary operator): !, not
    Comparisons and equality:
    	Comparators: >, <, >=, <= (gt, lt, ge, le)
    	Equality operators: ==, != (eq, ne)
    	Conditional operators:
    	If-then: (if) ? (then)
    	If-then-else: (if) ? (then) : (else)
    	Default: (value) ?: (defaultvalue)
    Special tokens:
    	No-Operation: _

    4、thymeleaf实例演示

    1、th的常用属性值

    ​一、th:text :设置当前元素的文本内容,相同功能的还有th:utext,两者的区别在于前者不会转义html标签,后者会。优先级不高:order=7

    ​二、th:value:设置当前元素的value值,类似修改指定属性的还有th:src,th:href。优先级不高:order=6

    ​三、th:each:遍历循环元素,和th:text或th:value一起使用。注意该属性修饰的标签位置,详细往后看。优先级很高:order=2

    ​四、th:if:条件判断,类似的还有th:unless,th:switch,th:case。优先级较高:order=3

    ​五、th:insert:代码块引入,类似的还有th:replace,th:include,三者的区别较大,若使用不恰当会破坏html结构,常用于公共代码块提取的场景。优先级最高:order=1

    ​六、th:fragment:定义代码块,方便被th:insert引用。优先级最低:order=8

    ​七、th:object:声明变量,一般和*{}一起配合使用,达到偷懒的效果。优先级一般:order=4

    ​八、th:attr:修改任意属性,实际开发中用的较少,因为有丰富的其他th属性帮忙,类似的还有th:attrappend,th:attrprepend。优先级一般:order=5

    thymeleaf.html

    <!DOCTYPE html>
    <html lang="en" xmlns:th="http://www.thymeleaf.org">
    <head>
     <meta charset="UTF-8">
     <title>Title</title>
    </head>
    <body>
     <p th:text="${thText}"></p>
     <p th:utext="${thUText}"></p>
     <input type="text" th:value="${thValue}">
     <div th:each="message:${thEach}">
      <p th:text="${message}"></p>
     </div>
     <div>
      <p th:text="${message}" th:each="message:${thEach}"></p>
     </div>
     <p th:text="${thIf}" th:if="${not #strings.isEmpty(thIf)}"></p>
     <div th:object="${thObject}">
      <p>name:<span th:text="*{name}"/></p>
      <p>age:<span th:text="*{age}"/></p>
      <p>gender:<span th:text="*{gender}"/></p>
     </div>
    
    </body>
    </html>

    ThymeleafController.java

    import org.springframework.stereotype.Controller;
    import org.springframework.ui.ModelMap;
    import org.springframework.web.bind.annotation.RequestMapping;
    
    @Controller
    public class ThymeleafController {
    
     @RequestMapping("thymeleaf")
     public String thymeleaf(ModelMap map){
    
      map.put("thText","th:text设置文本内容 <b>加粗</b>");
      map.put("thUText","th:utext 设置文本内容 <b>加粗</b>");
      map.put("thValue","thValue 设置当前元素的value值");
      map.put("thEach","Arrays.asList(\"th:each\", \"遍历列表\")");
      map.put("thIf","msg is not null");
      map.put("thObject",new Person("zhangsan",12,"男"));
      return "thymeleaf";
     }
    }

    2、标准表达式语法

    ​${...} 变量表达式,Variable Expressions

    ​*{...} 选择变量表达式,Selection Variable Expressions

    ​一、可以获取对象的属性和方法

    ​二、可以使用ctx,vars,locale,request,response,session,servletContext内置对象

    session.setAttribute("user","zhangsan");
    th:text="${session.user}"

    ​三、可以使用dates,numbers,strings,objects,arrays,lists,sets,maps等内置方法

    standardExpression.html

    <!--
    一、strings:字符串格式化方法,常用的Java方法它都有。比如:equals,equalsIgnoreCase,length,trim,toUpperCase,toLowerCase,indexOf,substring,replace,startsWith,endsWith,contains,containsIgnoreCase等
    
    二、numbers:数值格式化方法,常用的方法有:formatDecimal等
    
    三、bools:布尔方法,常用的方法有:isTrue,isFalse等
    
    四、arrays:数组方法,常用的方法有:toArray,length,isEmpty,contains,containsAll等
    
    五、lists,sets:集合方法,常用的方法有:toList,size,isEmpty,contains,containsAll,sort等
    
    六、maps:对象方法,常用的方法有:size,isEmpty,containsKey,containsValue等
    
    七、dates:日期方法,常用的方法有:format,year,month,hour,createNow等
    -->
    <!DOCTYPE html>
    <html lang="en" xmlns:th="http://www.thymeleaf.org">
    <head>
     <meta charset="UTF-8">
     <title>thymeleaf内置方法</title>
    </head>
    <body>
     <h3>#strings </h3>
     <div th:if="${not #strings.isEmpty(Str)}" >
      <p>Old Str : <span th:text="${Str}"/></p>
      <p>toUpperCase : <span th:text="${#strings.toUpperCase(Str)}"/></p>
      <p>toLowerCase : <span th:text="${#strings.toLowerCase(Str)}"/></p>
      <p>equals : <span th:text="${#strings.equals(Str, 'blog')}"/></p>
      <p>equalsIgnoreCase : <span th:text="${#strings.equalsIgnoreCase(Str, 'blog')}"/></p>
      <p>indexOf : <span th:text="${#strings.indexOf(Str, 'r')}"/></p>
      <p>substring : <span th:text="${#strings.substring(Str, 2, 4)}"/></p>
      <p>replace : <span th:text="${#strings.replace(Str, 'it', 'IT')}"/></p>
      <p>startsWith : <span th:text="${#strings.startsWith(Str, 'it')}"/></p>
      <p>contains : <span th:text="${#strings.contains(Str, 'IT')}"/></p>
     </div>
     <h3>#numbers </h3>
     <div>
      <p>formatDecimal 整数部分随意,小数点后保留两位,四舍五入: <span th:text="${#numbers.formatDecimal(Num, 0, 2)}"/></p>
      <p>formatDecimal 整数部分保留五位数,小数点后保留两位,四舍五入: <span th:text="${#numbers.formatDecimal(Num, 5, 2)}"/></p>
     </div>
    
     <h3>#bools </h3>
     <div th:if="${#bools.isTrue(Bool)}">
      <p th:text="${Bool}"></p>
     </div>
    
     <h3>#arrays </h3>
     <div th:if="${not #arrays.isEmpty(Array)}">
      <p>length : <span th:text="${#arrays.length(Array)}"/></p>
      <p>contains : <span th:text="${#arrays.contains(Array,2)}"/></p>
      <p>containsAll : <span th:text="${#arrays.containsAll(Array, Array)}"/></p>
     </div>
     <h3>#lists </h3>
     <div th:if="${not #lists.isEmpty(List)}">
      <p>size : <span th:text="${#lists.size(List)}"/></p>
      <p>contains : <span th:text="${#lists.contains(List, 0)}"/></p>
      <p>sort : <span th:text="${#lists.sort(List)}"/></p>
     </div>
     <h3>#maps </h3>
     <div th:if="${not #maps.isEmpty(hashMap)}">
      <p>size : <span th:text="${#maps.size(hashMap)}"/></p>
      <p>containsKey : <span th:text="${#maps.containsKey(hashMap, 'thName')}"/></p>
      <p>containsValue : <span th:text="${#maps.containsValue(hashMap, '#maps')}"/></p>
     </div>
     <h3>#dates </h3>
     <div>
      <p>format : <span th:text="${#dates.format(Date)}"/></p>
      <p>custom format : <span th:text="${#dates.format(Date, 'yyyy-MM-dd HH:mm:ss')}"/></p>
      <p>day : <span th:text="${#dates.day(Date)}"/></p>
      <p>month : <span th:text="${#dates.month(Date)}"/></p>
      <p>monthName : <span th:text="${#dates.monthName(Date)}"/></p>
      <p>year : <span th:text="${#dates.year(Date)}"/></p>
      <p>dayOfWeekName : <span th:text="${#dates.dayOfWeekName(Date)}"/></p>
      <p>hour : <span th:text="${#dates.hour(Date)}"/></p>
      <p>minute : <span th:text="${#dates.minute(Date)}"/></p>
      <p>second : <span th:text="${#dates.second(Date)}"/></p>
      <p>createNow : <span th:text="${#dates.createNow()}"/></p>
     </div>
    </body>
    </html>

    ThymeleafController.java

    @RequestMapping("standardExpression")
     public String standardExpression(ModelMap map){
      map.put("Str", "Blog");
      map.put("Bool", true);
      map.put("Array", new Integer[]{1,2,3,4});
      map.put("List", Arrays.asList(1,3,2,4,0));
      Map hashMap = new HashMap();
      hashMap.put("thName", "${#...}");
      hashMap.put("desc", "变量表达式内置方法");
      map.put("Map", hashMap);
      map.put("Date", new Date());
      map.put("Num", 888.888D);
      return "standardExpression";
     }

    ​@{...} 链接表达式,Link URL Expressions

    <!--
    不管是静态资源的引用,form表单的请求,凡是链接都可以用@{...} 。这样可以动态获取项目路径,即便项目名变了,依然可以正常访问
    链接表达式结构
    无参:@{/xxx}
    有参:@{/xxx(k1=v1,k2=v2)} 对应url结构:xxx?k1=v1&k2=v2
    引入本地资源:@{/项目本地的资源路径}
    引入外部资源:@{/webjars/资源在jar包中的路径}
    -->
    <link th:href="@{/webjars/bootstrap/4.0.0/css/bootstrap.css}" rel="external nofollow" rel="stylesheet">
    <link th:href="@{/main/css/123.css}" rel="external nofollow" rel="stylesheet">
    <form class="form-login" th:action="@{/user/login}" th:method="post" >
    <a class="btn btn-sm" th:href="@{/login.html(l='zh_CN')}" rel="external nofollow" >中文</a>
    <a class="btn btn-sm" th:href="@{/login.html(l='en_US')}" rel="external nofollow" >English</a>

    ​#{...} 消息表达式,Message Expressions

    <!-- 
    消息表达式一般用于国际化的场景。结构:th:text="#{msg}"
    -->

    ​~{...} 代码块表达式,Fragment Expressions

    fragment.html

    <!--
    支持两种语法结构
    
    

    1、在idea中设置统一的编码格式,file->settings->Editors->File Encoding,选择编码格式为utf-8

    2、在resources资源文件下创建一个i8n的目录,创建一个login.properties的文件,还有login_zh_CN.properties,idea会自动识别国际化操作

    3、创建三个不同的文件,名称分别是:login.properties,login_en_US.properties,login_zh_CN.properties

    内容如下:

    #login.properties
    login.password=密码1
    login.remmber=记住我1
    login.sign=登录1
    login.username=用户名1
    #login_en_US.properties
    login.password=Password
    login.remmber=Remember Me
    login.sign=Sign In
    login.username=Username
    #login_zh_CN.properties
    login.password=密码~
    login.remmber=记住我~
    login.sign=登录~
    login.username=用户名~

    4、配置国际化的资源路径

    spring:
     messages:
     basename: i18n/login

    5、编写html页面

    初始html页面
    <!DOCTYPE html>
    <html lang="en" xmlns:th="http://www.thymeleaf.org">
     <head>
      <meta charset="UTF-8"/>
      <title>Title</title>
     </head>
     <body>
      <form action="" method="post">
    
       <label >Username</label>
       <input type="text" name="username" placeholder="Username" >
       <label >Password</label>
       <input type="password" name="password" placeholder="Password" >
       <br> <br>
       <div>
        <label>
         <input type="checkbox" value="remember-me"/> Remember Me
        </label>
       </div>
       <br>
       <button type="submit">Sign in</button>
       <br> <br>
       <a>中文</a>
       <a>English</a>
      </form>
     </body>
    </html>
    
    修改后的页面
    <!DOCTYPE html>
    <html lang="en" xmlns:th="http://www.thymeleaf.org">
     <head>
      <meta charset="UTF-8"/>
      <title>Title</title>
     </head>
     <body>
      <form action="" method="post">
       <label th:text="#{login.username}">Username</label>
       <input type="text" name="username" placeholder="Username" th:placeholder="#{login.username}">
       <label th:text="#{login.password}">Password</label>
       <input type="password" name="password" placeholder="Password" th:placeholder="#{login.password}">
       <br> <br>
       <div>
        <label>
         <input type="checkbox" value="remember-me"/> [[#{login.remmber}]]
        </label>
       </div>
       <br>
       <button type="submit" th:text="#{login.sign}">Sign in</button>
       <br> <br>
       <a>中文</a>
       <a>English</a>
      </form>
     </body>
    </html>

    可以看到通过浏览器的切换语言已经能够实现,想要通过超链接实现的话,如下所示:

    添加WebMVCConfig.java代码

    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.util.StringUtils;
    import org.springframework.web.servlet.LocaleResolver;
    import org.springframework.web.servlet.config.annotation.ViewControllerRegistry;
    import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
    
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.util.Locale;
    
    @Configuration
    public class WebMVCConfig implements WebMvcConfigurer {
    
     @Override
     public void addViewControllers(ViewControllerRegistry registry) {
      registry.addViewController("/").setViewName("login");
      registry.addViewController("/login.html").setViewName("login");
     }
    
     @Bean
     public LocaleResolver localeResolver(){
      return new NativeLocaleResolver();
     }
    
     protected static class NativeLocaleResolver implements LocaleResolver{
    
      @Override
      public Locale resolveLocale(HttpServletRequest request) {
       String language = request.getParameter("language");
       Locale locale = Locale.getDefault();
       if(!StringUtils.isEmpty(language)){
        String[] split = language.split("_");
        locale = new Locale(split[0],split[1]);
       }
       return locale;
      }
    
      @Override
      public void setLocale(HttpServletRequest request, HttpServletResponse response, Locale locale) {
    
      }
     }
    }

    login.html页面修改为:

    <!DOCTYPE html>
    <html lang="en" xmlns:th="http://www.thymeleaf.org">
    <head>
     <meta charset="UTF-8"/>
     <title>Title</title>
    </head>
    <body>
    <form action="" method="post">
     <label th:text="#{login.username}">Username</label>
     <input type="text" name="username" placeholder="Username" th:placeholder="#{login.username}">
     <label th:text="#{login.password}">Password</label>
     <input type="password" name="password" placeholder="Password" th:placeholder="#{login.password}">
     <br> <br>
     <div>
      <label>
       <input type="checkbox" value="remember-me"/> [[#{login.remmber}]]
      </label>
     </div>
     <br>
     <button type="submit" th:text="#{login.sign}">Sign in</button>
     <br> <br>
     <a th:href="@{/login.html(language='zh_CN')}" rel="external nofollow" >中文</a>
     <a th:href="@{/login.html(language='en_US')}" rel="external nofollow" >English</a>
    </form>
    </body>
    </html>

    国际化的源码解释:

    //MessageSourceAutoConfiguration 
    public class MessageSourceAutoConfiguration {
     private static final Resource[] NO_RESOURCES = new Resource[0];
    
     public MessageSourceAutoConfiguration() {
     }
    
     @Bean
     @ConfigurationProperties(prefix = "spring.messages") //我们的配置文件可以直接放在类路径下叫: messages.properties, 就可以进行国际化操作了
     public MessageSourceProperties messageSourceProperties() {
      return new MessageSourceProperties();
     }
    
     @Bean
     public MessageSource messageSource(MessageSourceProperties properties) {
      ResourceBundleMessageSource messageSource = new ResourceBundleMessageSource();
      if (StringUtils.hasText(properties.getBasename())) {
            //设置国际化文件的基础名(去掉语言国家代码的)
       messageSource.setBasenames(StringUtils.commaDelimitedListToStringArray(StringUtils.trimAllWhitespace(properties.getBasename())));
      }
    
      if (properties.getEncoding() != null) {
       messageSource.setDefaultEncoding(properties.getEncoding().name());
      }
    
      messageSource.setFallbackToSystemLocale(properties.isFallbackToSystemLocale());
      Duration cacheDuration = properties.getCacheDuration();
      if (cacheDuration != null) {
       messageSource.setCacheMillis(cacheDuration.toMillis());
      }
    
      messageSource.setAlwaysUseMessageFormat(properties.isAlwaysUseMessageFormat());
      messageSource.setUseCodeAsDefaultMessage(properties.isUseCodeAsDefaultMessage());
      return messageSource;
     }
    }
    
    
    //WebMvcAutoConfiguration
    		@Bean
    		@ConditionalOnMissingBean
    		@ConditionalOnProperty(prefix = "spring.mvc", name = "locale")
    		public LocaleResolver localeResolver() {
    			if (this.mvcProperties.getLocaleResolver() == WebMvcProperties.LocaleResolver.FIXED) {
    				return new FixedLocaleResolver(this.mvcProperties.getLocale());
    			}
    			AcceptHeaderLocaleResolver localeResolver = new AcceptHeaderLocaleResolver();
    			localeResolver.setDefaultLocale(this.mvcProperties.getLocale());
    			return localeResolver;
    		}
    
    //AcceptHeaderLocaleResolver
    	@Override
    	public Locale resolveLocale(HttpServletRequest request) {
    		Locale defaultLocale = getDefaultLocale();
    		if (defaultLocale != null && request.getHeader("Accept-Language") == null) {
    			return defaultLocale;
    		}
    		Locale requestLocale = request.getLocale();
    		List<Locale> supportedLocales = getSupportedLocales();
    		if (supportedLocales.isEmpty() || supportedLocales.contains(requestLocale)) {
    			return requestLocale;
    		}
    		Locale supportedLocale = findSupportedLocale(request, supportedLocales);
    		if (supportedLocale != null) {
    			return supportedLocale;
    		}
    		return (defaultLocale != null ? defaultLocale : requestLocale);
    	}