Thymeleaf 3学习

Thymeleaf学习

1.介绍

Thymeleaf (麝香草叶子), /ˈtaɪmˌlɪːf/ 是一个服务端java模板引擎框架,它能够处理多种数据格式，包括HTML, XML, JavaScript, CSS以及普通文本。

2.简单的示例

<!DOCTYPE html>
<!--声明 th 名称空间-->
<html xmlns:th="http://www.thymeleaf.org">
  <head>
    <title>Good Thymes Virtual Grocery</title>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <link rel="stylesheet" type="text/css" media="all" 
          href="../../css/gtvg.css" th:href="@{/css/gtvg.css}" />
  </head>
  <body>
    <!-- 引用文本-->
    <p th:text="#{home.welcome}">Welcome to our grocery store!</p>
  </body>
</html>

Thymeleaf使用th:* 给现有HTML标签增加属性,因此直接打开模板也能预览效果,很方便。使用时首先需要像在jsp中一样，在html标签内声明th名称空间，然后就可以使用了。

3.Standard Expression Syntax(标准表达式语法)

Variable Expressions(变量表达式): ${...}
Selection Variable Expressions(选择变量表达式): *{...}
Message Expressions(消息表达式): #{...}
Link URL Expressions(链接url表达式): @{...}
Fragment Expressions(代码片段表达式): ~{...}

(1).Messages (信息)

该表达书主要为了实现i18n国际化，需要将多语言的文本放在/WEB-INF/templates目录下，如下

/WEB-INF/templates/home_en.properties 英文的翻译.
/WEB-INF/templates/home.properties 默认的文本

<!--常用使用方法-->
<p th:text="#{home.welcome}">Hello World</p> 

<!--unescaped text 不转义文本-->
<p th:utext="#{home.welcome}">

也可以传参给文本

#home.properties文件
home.welcome=hello, {0}!

<!-- Thymeleaf解析后会将p标签中的Welcome User!替换为th:text指定的文本 -->
<p th:text="#{home.welcome(${session.user.name})}">
  Welcome User!
</p>
<!--消息的key也可以通过动态去获取  -->
<p th:utext="#{${welcomeMsgKey}(${session.user.name})}">
  Welcome User!
</p>

(2).Variables(变量)

Thymeleaf的 ${...}是OGNL (Object-Graph Navigation Language) expressions 语法格式，跟jsp中使用方法差不多,使用示例

/*
 * Access to properties using the point (.). Equivalent to calling property getters.
 */
${person.father.name}

/*
 * Access to properties can also be made by using brackets ([]) and writing 
 * the name of the property as a variable or between single quotes.
 */
${person['father']['name']}

/*
 * If the object is a map, both dot and bracket syntax will be equivalent to 
 * executing a call on its get(...) method.
 */
${countriesByCode.ES}
${personsByName['Stephen Zucchini'].age}

/*
 * Indexed access to arrays or collections is also performed with brackets, 
 * writing the index without quotes.
 */
${personsArray[0].name}

/*
 * Methods can be called, even with arguments.
 */
${person.createCompleteName()}
${person.createCompleteNameWithSeparator('-')}

表达式基本对象(Expression Basic Objects)，#开始

#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.

表达式工具对象

#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).

<!--表达式工具对象的使用-->
<p>
  Today is: <span th:text="${#calendars.format(today,'dd MMMM yyyy')}">13 May 2011
</p>

(3).Expressions on selections (asterisk syntax)(选择表达式 - 星号语法)

<div th:object="${session.user}">
    <p>Name: <span th:text="*{firstName}">Sebastian.</p>
    <p>Surname: <span th:text="*{lastName}">Pepper.</p>
    <p>Nationality: <span th:text="*{nationality}">Saturn.</p>
  </div>

<!-- 等价于 -->
<div>
  <p>Name: <span th:text="${session.user.firstName}">Sebastian.</p>
  <p>Surname: <span th:text="${session.user.lastName}">Pepper.</p>
  <p>Nationality: <span th:text="${session.user.nationality}">Saturn.</p>
</div>

<!-- 还可以混合使用-->
<div th:object="${session.user}">
  <p>Name: <span th:text="*{firstName}">Sebastian.</p>
  <p>Surname: <span th:text="${session.user.lastName}">Pepper.</p>
  <p>Nationality: <span th:text="*{nationality}">Saturn.</p>
</div>
<!-- #object 引用表达式的对象 -->
<div th:object="${session.user}">
  <p>Name: <span th:text="${#object.firstName}">Sebastian.</p>
  <p>Surname: <span th:text="${session.user.lastName}">Pepper.</p>
  <p>Nationality: <span th:text="*{nationality}">Saturn.</p>
</div>

th:object定义选择的对象,在标签内使用*{...}来取出对象中相应的数据，如果没有选择的对象直接使用*{...}等价于#{...}

(4).Link URLs(链接URL)

<!-- Will produce 'http://localhost:8080/gtvg/order/details?orderId=3' (plus rewriting) -->
<a href="details.html" 
   th:href="@{http://localhost:8080/gtvg/order/details(orderId=${o.id})}">view</a>

<!-- Will produce '/gtvg/order/details?orderId=3' (plus rewriting) -->
<a href="details.html" th:href="@{/order/details(orderId=${o.id})}">view</a>

<!-- Will produce '/gtvg/order/3/details' (plus rewriting) -->
<a href="details.html" th:href="@{/order/{orderId}/details(orderId=${o.id})}">view</a>

(5).Literals(文本)

<!-- 基本的使用-->
<p>
  Now you are looking at a <span th:text="'working web application'">template file.
</p>

<p>The year is <span th:text="2013">1492.</p> 

<!-- ==false 需要写在{}外面才交由thymeleaf处理，写在里面时交由 OGNL/SpringEL处理 -->
<div th:if="${user.isAdmin()} == false"> </div>
<div th:if="${user.isAdmin() == false}"></div>
<!--判空-->
<div th:if="${variable.something} == null">
<!-- 文本链接 -->
<span th:text="'The name of the user is ' + ${user.name}">
  
  
  <!-- 文本替换,(免去+号链接字符串),需要写在 || 之间
        仅变量，信息表达式可以使用${...}, *{...}, #{...}
-->
  <span th:text="|Welcome to our application, ${user.name}!|">

(6).Arithmetic operations(算术操作)

<!-- 也可以使用文本 div (/), mod (%).-->
<div th:with="isEven=(${prodStat.count} % 2 == 0)">

(7).Comparators and Equality(比较)

html起止标签的缘故，大于，小于等需要使用转义

gt (>), lt (<), ge (>=), le (<=), not (!) eq (==), neq/ne (!=).

<div th:if="${prodStat.count} &gt; 1">
<span th:text="'Execution mode is ' + ( (${execMode} == 'dev')? 'Development' : 'Production')"

(8).Conditional expressions(条件表达式)

<!--C中的三元运算符 -->
<tr th:class="${row.even}? 'even' : 'odd'">
</tr>
<!-- 省略-->
<tr th:class="${row.even}? 'alt'">
  ...
</tr>

(9). Default expressions (Elvis operator) 默认表达式

<div th:object="${session.user}">
  <p>Age: <span th:text="*{age}?: '(no age specified)'">27.</p>
</div>
<!-- 等价于,省略表达式为true时的语句 -->
<p>Age: <span th:text="*{age != null}? *{age} : '(no age specified)'">27.</p>

(10). The No-Operation token(空操作符)

空操作符( No-Operation token)使用下划线表示_，它允许原生页面定义的文本为默认值,便于模板的设计

<span th:text="${user.name} ?: 'no user authenticated'">...
<span th:text="${user.name} ?: _">no user authenticated

(11). Data Conversion / Formatting (数据转换/格式化)

Thymeleaf 定义了双花括号语法用于变量${...}和选择表达式*{...}

<td th:text="${{user.lastAccessDate}}">...</td>

4.Iteration(遍历)

<table>
  <tr>
    <th>NAME</th>
    <th>PRICE</th>
    <th>IN STOCK</th>
  </tr>
  <tr th:each="prod,iterStat : ${prods}" th:class="${iterStat.odd}? 'odd'">
    <td th:text="${prod.name}">Onions</td>
    <td th:text="${prod.price}">2.41</td>
    <td th:text="${prod.inStock}? #{true} : #{false}">yes</td>
  </tr>
</table>

th:each说明

prod保存每次遍历的对象，iterStat保存遍历的相关信息

The current iteration index, starting with 0. This is the index property. 遍历索引，从0开始
The current iteration index, starting with 1. This is the count property. 遍历计数，从1开始
The total amount of elements in the iterated variable. This is the size property. 被遍历对象的大小
The iter variable for each iteration. This is the current property. 当前遍历的对象
Whether the current iteration is even or odd. These are the even/odd boolean properties. 奇偶布尔值
Whether the current iteration is the first one. This is the first boolean property. 是否是遍历第一个
Whether the current iteration is the last one. This is the last boolean property. 是否是遍历最后一个

被遍历的对象类型

Any object implementing java.util.Iterable
Any object implementing java.util.Enumeration.
Any object implementing java.util.Iterator, whose values will be used as they are returned by the iterator, without the need to cache all values in memory.
Any object implementing java.util.Map. When iterating maps, iter variables will be of class java.util.Map.Entry.
Any array.
Any other object will be treated as if it were a single-valued list containing the object itself.

5.Conditional Evaluation(条件表达式)

if和unless语句

<!-- 如果if表达式成立则显示该标签-->
<a href="comments.html"
   th:href="@{/product/comments(prodId=${prod.id})}" 
   th:if="${not #lists.isEmpty(prod.comments)}">view</a>

<!--还可以使用相反的表达式unless -->
<a href="comments.html"
   th:href="@{/comments(prodId=${prod.id})}" 
   th:unless="${#lists.isEmpty(prod.comments)}">view</a>

if遵循的规则

If value is not null:
If value is a boolean and is true.
If value is a number and is non-zero
If value is a character and is non-zero
If value is a String and is not “false”, “off” or “no”
If value is not a boolean, a number, a character or a String.
(If value is null, th:if will evaluate to false).
switch/case语句

<div th:switch="${user.role}">
  <p th:case="'admin'">User is an administrator</p>
  <p th:case="#{roles.manager}">User is a manager</p>
  <p th:case="*">User is some other thing</p> <!--默认值-->
</div>

6.Template Layout (模板布局)

使用th:fragment定义需要复用的代码片段，th:insert或th:replac引用片段

~{templatename::selector} 引用片段

~{templatename}引用整个文件

~{::selector}或~{this::selector}引用自身的代码片段

<!--定义代码片段 -->
<html xmlns:th="http://www.thymeleaf.org">
  <body>
    <div th:fragment="copy">
      &copy; 2011 The Good Thymes Virtual Grocery
    </div>
  </body>
</html>

<!-- 引用代码片 -->
<body>
  <div th:insert="footer :: copy"></div>
</body>

<!-- 根据条件引用-->
<div th:insert="footer :: (${user.isAdmin}? #{footer.admin} : #{footer.normaluser})"></div>


<!-- 根据id引用 css选择器语法类似-->
<div id="copy-section">
  &copy; 2011 The Good Thymes Virtual Grocery
</div>
<div th:insert="~{footer :: #copy-section}"></div>

`th:insert` , `th:replace` ,`th:include`

th:insert is the simplest: it will simply insert the specified fragment as the body of its host tag. (在定义的标签体内引用代码片段)
th:replace actually replaces its host tag with the specified fragment.(将定义标签替换为引用的代码片段)
th:include is similar to th:insert, but instead of inserting the fragment it only inserts the contents of this fragment.(Thymeleaf 3.0后不推荐使用)

#### 参数化方式引用代码片段(Parameterizable fragment signatures)

html  <div th:fragment="frag (onevar,twovar)"> <p th:text="${onevar} + ' - ' + ${twovar}">...</p> </div>  <div th:replace="::frag (${value1},${value2})">...</div> <div th:replace="::frag (onevar=${value1},twovar=${value2})">...</div> <div th:replace="::frag (twovar=${value2},onevar=${value1})">...</div>

7.Local Variables(局部变量)

<!-- 使用th:with定义,可以再标签体中使用-->
<div th:with="firstPer=${persons[0]}">
  <p>
    The name of the first person is <span th:text="${firstPer.name}">Julius Caesar.
  </p>
</div>

8.参考资料

1.Thymleaf Document(http://www.thymeleaf.org/documentation.html)

2.属性优先级(http://www.thymeleaf.org/doc/tutorials/3.0/usingthymeleaf.html#attribute-precedence)

3.可用属性(http://www.thymeleaf.org/doc/tutorials/3.0/usingthymeleaf.html#setting-value-to-specific-attributes)