任何一种语言，都有其语法约束，前端模板引擎也不例外。本文将介绍Thymeleaf方言中最重要的部分之一：标准表达式语法。

标准表达式语法的基本内容如下。

• 简单表达式

• 变量表达式：${...}
• 选择变量表达式：*{...}
• 信息表达式：#{...}
• 链接URL表达式：@{...}
• 片段表达式：~{...}

• 常量

• 文本常量：'example'，'other example'，...
• 号码常量：1，12， 5.0，12.56，...
• 布尔常量：true，false
• 空常量：null
• 常量标记：one，sometext，other，...

• 文本操作

• 字符串串联：+
• 文字替换：|hello，my name is ${name}|

• 算术运算

• 二元运算符：+，-，*，/，%
• 减号（一元运算符）：-

• 布尔运算

• 二元运算符：and，or
• 布尔否定（一元运算符）：!，not

• 比较和相等

• 比较运算：>，<，>=，<=，（gt，lt，ge，le）
• 相等运算（一元运算符）：==，!=，（eq，ne）

• 条件运算符

• If-then：(if) ? (then)
• If-then-else：(if) ? (then) : (else)
• Default：(value) ?: (defaultvalue)

• 特殊令牌

• 无操作：_

所有这些特性均可进行组合和嵌套：

'User is of type ' + (${user.isAdmin()} ? 'Administrator' : (${user.type} ?: 'Unknown'))

信息

信息表达式 #{} 用于展示静态资源的内容，比如i18n属性配置文件。

<p th:utext="#{home.welcome}">Welcome to our grocery store!</p>

新建/static/templates/home.properties，其中home.welcome=this messages is from home.properties!。那么，信息表达式解析后为：

<p>this messages is from home.properties!</p>

如果信息文本不完全是静态的怎么办？例如，如果我们的应用程序知道谁是随时访问该网站的用户并且我们想要通过名字问候他们怎么办？

<p>?Bienvenido a nuestra tienda de comestibles, John Apricot!</p>

我们可以在信息中添加一个参数：

home.welcome=?Bienvenido a nuestra tienda de comestibles, {0}!

参数是根据java.text.MessageFormat标准语法指定的，这意味着可以格式化为java.text.*包中的类的API文档中指定的数字和日期。

假定给定HTTP会话属性user：

<p th:utext="#{home.welcome(${session.user.name})}">
  Welcome to our grocery store, Sebastian Pepper!
</p>

请注意，使用th:utext此处意味着格式化的消息不会被转义。此示例假定user.name已经转义。

也可以指定几个参数，以逗号分隔。

信息键值也可以来自于变量：

<p th:utext="#{${welcomeMsgKey}(${session.user.name})}">
  Welcome to our grocery store, Sebastian Pepper!
</p>

更复杂的例子（预处理）

此例结合了信息表达式、变量表达式、预处理表达式，如看不懂，可选择跳过，待后续表达式语法学习完毕后，可回过来头再看。

#{home.__${sel.code}__}

该表达式解析，实际上可以分解为3步：

1. 先计算变量${sel.code}，假如值是welcome
2. __的含义是需要预处理的变量值，那么就变成#{home.welcome}
3. 计算最终结果

变量

变量表达式 ${...} 实际上是把上下文中包含的变量映射到OGNL表达式，即在SpringMVC中的模型属性，如：${user.name}。可直接使用 th:xx = "${...}" 获取对象属性，如定义在属性中：<span th:text="${book.author.name}">、遍历：<li th:each="book : ${books}">。

从ognl的语法，表达式：

<p>Today is: <span th:text="${today}">13 february 2011</span>.</p>

实际上相当于：

ctx.getVariable("today");

但是OGNL允许我们创建功能更强大的表达式，即这种方式：

<p th:utext="#{home.welcome(${session.user.name})}">
  Welcome to our grocery store, Sebastian Pepper!
</p>

等价于：

((User) ctx.getVariable("session").get("user")).getName();

但是，getter方法导航只是OGNL的功能之一。还有更多：

/*
 * 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

在上下文变量中评估OGNL表达式时，某些对象可用于表达式，以提高灵活性。这些对象（OGNL标准）将以 # 符号开头进行引用：

• #ctx：上下文对象。
• #vars： 上下文变量。
• #locale：上下文语言环境。
• #request：（仅在Web上下文中）HttpServletRequest 对象。
• #response：（仅在Web上下文中）HttpServletResponse 对象。
• #session：（仅在Web上下文中）HttpSession 对象。
• #servletContext：（仅在Web上下文中）ServletContext 对象。

因此，我们可以这样做：

Established locale country: <span th:text="${#locale.country}">US</span>.

完整的表达式基本对象请参见附录1。

表达式实用对象

除了基本对象之外，Thymeleaf还为我们提供一组实用对象，这些对象将帮助我们在表达式中执行常见任务。

• #execInfo：正在处理的模板的信息。
• #messages：用于获取变量表达式内的外部化消息的方法，与使用＃{…} 语法获得消息的方法相同。
• #uris：用于转义部分 URL / URI 的方法
• #conversions：用于执行已配置的转换服务（如果有）的方法。
• #dates：java.util.Date 对象的方法：格式化，组件提取等。
• #calendars：与 #dates 类似，用于 java.util.Calendar 对象。
• #numbers：格式化数字的方法。
• #strings：String对象的方法：包含，startsWith，prepending/appending等。
• #objects：一般对象的方法。
• #bools：布尔值评估的方法。
• #arrays：数组方法。
• #lists：列表方法。
• #sets：set集合方法。
• #maps：map方法。
• #aggregates：用于在数组或集合上创建聚合的方法。
• #ids：用于处理可能重复的id属性的方法（例如，由于迭代的结果）。

具体每个实用对象的功能，可以参见附录2。

用一下

格式化日期：

<p>
  Today is: <span th:text="${#calendars.format(today,'dd MMMM yyyy')}">13 May 2011</span>
</p>

非空判断：

<div th:fragment="alert (type, message)" th:assert="${!#strings.isEmpty(type) and !#strings.isEmpty(message)}" class="alert alert-dismissable" th:classappend="'alert-' + ${type}">
    <button type="button" class="close" data-dismiss="alert" aria-hidden="true">×</button>
    <span th:text="${message}">Test</span>
</div>

怎么样，方便吧！

附录1：表达式基础对象

基础对象

• #ctx：上下文对象。实现了 org.thymeleaf.context.IContext 或 org.thymeleaf.context.IWebContext 接口，取决于我们的环境（单机或网络）。

注意，与 #vars 和 #root 是同一个对象，但建议使用 #ctx。

/*
 * ======================================================================
 * See javadoc API for class org.thymeleaf.context.IContext
 * ======================================================================
 */

${#ctx.locale}
${#ctx.variableNames}

/*
 * ======================================================================
 * See javadoc API for class org.thymeleaf.context.IWebContext
 * ======================================================================
 */

${#ctx.request}
${#ctx.response}
${#ctx.session}
${#ctx.servletContext}

• #locale：访问 java.util.Locale 与当前请求关联的内容。

${#locale}

请求/会话属性等的Web上下文名称空间

在Web环境中使用Thymeleaf时，我们可以使用一系列快捷方式来访问请求参数，会话属性和应用程序属性：

请注意，这些不是上下文对象，而是作为变量添加到上下文中的映射，因此我们不使用 # 即可访问它们。在某种程度上，它们充当命名空间。

• param：用于检索请求参数。${param.foo} 是 String[] 类型的foo request参数的值数组，因此${param.foo[0]}通常用于获取第一个值。

/*
 * ============================================================================
 * See javadoc API for class org.thymeleaf.context.WebRequestParamsVariablesMap
 * ============================================================================
 */

${param.foo}              // Retrieves a String[] with the values of request parameter 'foo'
${param.size()}
${param.isEmpty()}
${param.containsKey('foo')}
...

• session : 用于检索会话属性。

/*
 * ======================================================================
 * See javadoc API for class org.thymeleaf.context.WebSessionVariablesMap
 * ======================================================================
 */

${session.foo}                 // Retrieves the session atttribute 'foo'
${session.size()}
${session.isEmpty()}
${session.containsKey('foo')}
...

• application 用于检索应用程序/ servlet上下文属性。

/*
 * =============================================================================
 * See javadoc API for class org.thymeleaf.context.WebServletContextVariablesMap
 * =============================================================================
 */

${application.foo}              // Retrieves the ServletContext atttribute 'foo'
${application.size()}
${application.isEmpty()}
${application.containsKey('foo')}
...

请注意，无需指定用于访问请求属性的名称空间（与request参数相对），因为所有请求属性都作为变量自动添加到上下文根目录中：

${myRequestAttribute}

Web上下文对象

在Web环境中，还可以直接访问以下对象（请注意，这些是对象，而不是映射/命名空间）：

• #request：直接访问 javax.servlet.http.HttpServletRequest 与当前请求关联的对象。

${#request.getAttribute('foo')}
${#request.getParameter('foo')}
${#request.getContextPath()}
${#request.getRequestName()}
...

• #session：直接访问 javax.servlet.http.HttpSession 与当前请求关联的对象。

${#session.getAttribute('foo')}
${#session.id}
${#session.lastAccessedTime}
...

• #servletContext：直接访问 javax.servlet.ServletContext 与当前请求关联的对象。

${#servletContext.getAttribute('foo')}
${#servletContext.contextPath}
...

附录2：表达式实用对象

Execution Info

• #execInfo：提供有关Thymeleaf标准表达式中正在处理的模板的有用信息的表达式对象。

/*
 * ======================================================================
 * See javadoc API for class org.thymeleaf.expression.ExecutionInfo
 * ======================================================================
 */

/*
 * Return the name and mode of the 'leaf' template. This means the template
 * from where the events being processed were parsed. So if this piece of
 * code is not in the root template "A" but on a fragment being inserted
 * into "A" from another template called "B", this will return "B" as a
 * name, and B's mode as template mode.
 */
${#execInfo.templateName}
${#execInfo.templateMode}

/*
 * Return the name and mode of the 'root' template. This means the template
 * that the template engine was originally asked to process. So if this
 * piece of code is not in the root template "A" but on a fragment being
 * inserted into "A" from another template called "B", this will still 
 * return "A" and A's template mode.
 */
${#execInfo.processedTemplateName}
${#execInfo.processedTemplateMode}

/*
 * Return the stacks (actually, List<String> or List<TemplateMode>) of
 * templates being processed. The first element will be the 
 * 'processedTemplate' (the root one), the last one will be the 'leaf'
 * template, and in the middle all the fragments inserted in nested
 * manner to reach the leaf from the root will appear.
 */
${#execInfo.templateNames}
${#execInfo.templateModes}

/*
 * Return the stack of templates being processed similarly (and in the
 * same order) to 'templateNames' and 'templateModes', but returning
 * a List<TemplateData> with the full template metadata.
 */
${#execInfo.templateStack}

Messages

• #messages：用于获取变量表达式内的外部化消息的实用程序方法，与使用 #{...} 语法获得消息的方式相同。

/*
 * ======================================================================
 * See javadoc API for class org.thymeleaf.expression.Messages
 * ======================================================================
 */

/*
 * Obtain externalized messages. Can receive a single key, a key plus arguments,
 * or an array/list/set of keys (in which case it will return an array/list/set of 
 * externalized messages).
 * If a message is not found, a default message (like '??msgKey??') is returned.
 */
${#messages.msg('msgKey')}
${#messages.msg('msgKey', param1)}
${#messages.msg('msgKey', param1, param2)}
${#messages.msg('msgKey', param1, param2, param3)}
${#messages.msgWithParams('msgKey', new Object[] {param1, param2, param3, param4})}
${#messages.arrayMsg(messageKeyArray)}
${#messages.listMsg(messageKeyList)}
${#messages.setMsg(messageKeySet)}

/*
 * Obtain externalized messages or null. Null is returned instead of a default
 * message if a message for the specified key is not found.
 */
${#messages.msgOrNull('msgKey')}
${#messages.msgOrNull('msgKey', param1)}
${#messages.msgOrNull('msgKey', param1, param2)}
${#messages.msgOrNull('msgKey', param1, param2, param3)}
${#messages.msgOrNullWithParams('msgKey', new Object[] {param1, param2, param3, param4})}
${#messages.arrayMsgOrNull(messageKeyArray)}
${#messages.listMsgOrNull(messageKeyList)}
${#messages.setMsgOrNull(messageKeySet)}

URI / URL

• #uris：在Thymeleaf标准表达式内执行URI / URL操作（尤其是转义/转义）的实用程序对象。

/*
 * ======================================================================
 * See javadoc API for class org.thymeleaf.expression.Uris
 * ======================================================================
 */

/*
 * Escape/Unescape as a URI/URL path
 */
${#uris.escapePath(uri)}
${#uris.escapePath(uri, encoding)}
${#uris.unescapePath(uri)}
${#uris.unescapePath(uri, encoding)}

/*
 * Escape/Unescape as a URI/URL path segment (between '/' symbols)
 */
${#uris.escapePathSegment(uri)}
${#uris.escapePathSegment(uri, encoding)}
${#uris.unescapePathSegment(uri)}
${#uris.unescapePathSegment(uri, encoding)}

/*
 * Escape/Unescape as a Fragment Identifier (#frag)
 */
${#uris.escapeFragmentId(uri)}
${#uris.escapeFragmentId(uri, encoding)}
${#uris.unescapeFragmentId(uri)}
${#uris.unescapeFragmentId(uri, encoding)}

/*
 * Escape/Unescape as a Query Parameter (?var=value)
 */
${#uris.escapeQueryParam(uri)}
${#uris.escapeQueryParam(uri, encoding)}
${#uris.unescapeQueryParam(uri)}
${#uris.unescapeQueryParam(uri, encoding)}

conversions

• #conversions：允许在模板的任何位置执行转换服务的实用程序对象。

/*
 * ======================================================================
 * See javadoc API for class org.thymeleaf.expression.Conversions
 * ======================================================================
 */

/*
 * Execute the desired conversion of the 'object' value into the
 * specified class.
 */
${#conversions.convert(object, 'java.util.TimeZone')}
${#conversions.convert(object, targetClass)}

dates

• #dates：java.util.Date 对象的实用程序方法。

/*
 * ======================================================================
 * See javadoc API for class org.thymeleaf.expression.Dates
 * ======================================================================
 */

/*
 * Format date with the standard locale format
 * Also works with arrays, lists or sets
 */
${#dates.format(date)}
${#dates.arrayFormat(datesArray)}
${#dates.listFormat(datesList)}
${#dates.setFormat(datesSet)}

/*
 * Format date with the ISO8601 format
 * Also works with arrays, lists or sets
 */
${#dates.formatISO(date)}
${#dates.arrayFormatISO(datesArray)}
${#dates.listFormatISO(datesList)}
${#dates.setFormatISO(datesSet)}

/*
 * Format date with the specified pattern
 * Also works with arrays, lists or sets
 */
${#dates.format(date, 'dd/MMM/yyyy HH:mm')}
${#dates.arrayFormat(datesArray, 'dd/MMM/yyyy HH:mm')}
${#dates.listFormat(datesList, 'dd/MMM/yyyy HH:mm')}
${#dates.setFormat(datesSet, 'dd/MMM/yyyy HH:mm')}

/*
 * Obtain date properties
 * Also works with arrays, lists or sets
 */
${#dates.day(date)}                    // also arrayDay(...), listDay(...), etc.
${#dates.month(date)}                  // also arrayMonth(...), listMonth(...), etc.
${#dates.monthName(date)}              // also arrayMonthName(...), listMonthName(...), etc.
${#dates.monthNameShort(date)}         // also arrayMonthNameShort(...), listMonthNameShort(...), etc.
${#dates.year(date)}                   // also arrayYear(...), listYear(...), etc.
${#dates.dayOfWeek(date)}              // also arrayDayOfWeek(...), listDayOfWeek(...), etc.
${#dates.dayOfWeekName(date)}          // also arrayDayOfWeekName(...), listDayOfWeekName(...), etc.
${#dates.dayOfWeekNameShort(date)}     // also arrayDayOfWeekNameShort(...), listDayOfWeekNameShort(...), etc.
${#dates.hour(date)}                   // also arrayHour(...), listHour(...), etc.
${#dates.minute(date)}                 // also arrayMinute(...), listMinute(...), etc.
${#dates.second(date)}                 // also arraySecond(...), listSecond(...), etc.
${#dates.millisecond(date)}            // also arrayMillisecond(...), listMillisecond(...), etc.

/*
 * Create date (java.util.Date) objects from its components
 */
${#dates.create(year,month,day)}
${#dates.create(year,month,day,hour,minute)}
${#dates.create(year,month,day,hour,minute,second)}
${#dates.create(year,month,day,hour,minute,second,millisecond)}

/*
 * Create a date (java.util.Date) object for the current date and time
 */
${#dates.createNow()}

${#dates.createNowForTimeZone()}

/*
 * Create a date (java.util.Date) object for the current date (time set to 00:00)
 */
${#dates.createToday()}

${#dates.createTodayForTimeZone()}

calendars

• #calendars：与 #dates 类似，但基于 java.util.Calendar 对象。

/*
 * ======================================================================
 * See javadoc API for class org.thymeleaf.expression.Calendars
 * ======================================================================
 */

/*
 * Format calendar with the standard locale format
 * Also works with arrays, lists or sets
 */
${#calendars.format(cal)}
${#calendars.arrayFormat(calArray)}
${#calendars.listFormat(calList)}
${#calendars.setFormat(calSet)}

/*
 * Format calendar with the ISO8601 format
 * Also works with arrays, lists or sets
 */
${#calendars.formatISO(cal)}
${#calendars.arrayFormatISO(calArray)}
${#calendars.listFormatISO(calList)}
${#calendars.setFormatISO(calSet)}

/*
 * Format calendar with the specified pattern
 * Also works with arrays, lists or sets
 */
${#calendars.format(cal, 'dd/MMM/yyyy HH:mm')}
${#calendars.arrayFormat(calArray, 'dd/MMM/yyyy HH:mm')}
${#calendars.listFormat(calList, 'dd/MMM/yyyy HH:mm')}
${#calendars.setFormat(calSet, 'dd/MMM/yyyy HH:mm')}

/*
 * Obtain calendar properties
 * Also works with arrays, lists or sets
 */
${#calendars.day(date)}                // also arrayDay(...), listDay(...), etc.
${#calendars.month(date)}              // also arrayMonth(...), listMonth(...), etc.
${#calendars.monthName(date)}          // also arrayMonthName(...), listMonthName(...), etc.
${#calendars.monthNameShort(date)}     // also arrayMonthNameShort(...), listMonthNameShort(...), etc.
${#calendars.year(date)}               // also arrayYear(...), listYear(...), etc.
${#calendars.dayOfWeek(date)}          // also arrayDayOfWeek(...), listDayOfWeek(...), etc.
${#calendars.dayOfWeekName(date)}      // also arrayDayOfWeekName(...), listDayOfWeekName(...), etc.
${#calendars.dayOfWeekNameShort(date)} // also arrayDayOfWeekNameShort(...), listDayOfWeekNameShort(...), etc.
${#calendars.hour(date)}               // also arrayHour(...), listHour(...), etc.
${#calendars.minute(date)}             // also arrayMinute(...), listMinute(...), etc.
${#calendars.second(date)}             // also arraySecond(...), listSecond(...), etc.
${#calendars.millisecond(date)}        // also arrayMillisecond(...), listMillisecond(...), etc.

/*
 * Create calendar (java.util.Calendar) objects from its components
 */
${#calendars.create(year,month,day)}
${#calendars.create(year,month,day,hour,minute)}
${#calendars.create(year,month,day,hour,minute,second)}
${#calendars.create(year,month,day,hour,minute,second,millisecond)}

${#calendars.createForTimeZone(year,month,day,timeZone)}
${#calendars.createForTimeZone(year,month,day,hour,minute,timeZone)}
${#calendars.createForTimeZone(year,month,day,hour,minute,second,timeZone)}
${#calendars.createForTimeZone(year,month,day,hour,minute,second,millisecond,timeZone)}

/*
 * Create a calendar (java.util.Calendar) object for the current date and time
 */
${#calendars.createNow()}

${#calendars.createNowForTimeZone()}

/*
 * Create a calendar (java.util.Calendar) object for the current date (time set to 00:00)
 */
${#calendars.createToday()}

${#calendars.createTodayForTimeZone()}

numbers

• #numbers：用于数字对象的实用方法。

/*
 * ======================================================================
 * See javadoc API for class org.thymeleaf.expression.Numbers
 * ======================================================================
 */

/*
 * ==========================
 * Formatting integer numbers
 * ==========================
 */

/* 
 * Set minimum integer digits.
 * Also works with arrays, lists or sets
 */
${#numbers.formatInteger(num,3)}
${#numbers.arrayFormatInteger(numArray,3)}
${#numbers.listFormatInteger(numList,3)}
${#numbers.setFormatInteger(numSet,3)}


/* 
 * Set minimum integer digits and thousands separator: 
 * 'POINT', 'COMMA', 'WHITESPACE', 'NONE' or 'DEFAULT' (by locale).
 * Also works with arrays, lists or sets
 */
${#numbers.formatInteger(num,3,'POINT')}
${#numbers.arrayFormatInteger(numArray,3,'POINT')}
${#numbers.listFormatInteger(numList,3,'POINT')}
${#numbers.setFormatInteger(numSet,3,'POINT')}


/*
 * ==========================
 * Formatting decimal numbers
 * ==========================
 */

/*
 * Set minimum integer digits and (exact) decimal digits.
 * Also works with arrays, lists or sets
 */
${#numbers.formatDecimal(num,3,2)}
${#numbers.arrayFormatDecimal(numArray,3,2)}
${#numbers.listFormatDecimal(numList,3,2)}
${#numbers.setFormatDecimal(numSet,3,2)}

/*
 * Set minimum integer digits and (exact) decimal digits, and also decimal separator.
 * Also works with arrays, lists or sets
 */
${#numbers.formatDecimal(num,3,2,'COMMA')}
${#numbers.arrayFormatDecimal(numArray,3,2,'COMMA')}
${#numbers.listFormatDecimal(numList,3,2,'COMMA')}
${#numbers.setFormatDecimal(numSet,3,2,'COMMA')}

/*
 * Set minimum integer digits and (exact) decimal digits, and also thousands and 
 * decimal separator.
 * Also works with arrays, lists or sets
 */
${#numbers.formatDecimal(num,3,'POINT',2,'COMMA')}
${#numbers.arrayFormatDecimal(numArray,3,'POINT',2,'COMMA')}
${#numbers.listFormatDecimal(numList,3,'POINT',2,'COMMA')}
${#numbers.setFormatDecimal(numSet,3,'POINT',2,'COMMA')}


/* 
 * =====================
 * Formatting currencies
 * =====================
 */

${#numbers.formatCurrency(num)}
${#numbers.arrayFormatCurrency(numArray)}
${#numbers.listFormatCurrency(numList)}
${#numbers.setFormatCurrency(numSet)}


/* 
 * ======================
 * Formatting percentages
 * ======================
 */

${#numbers.formatPercent(num)}
${#numbers.arrayFormatPercent(numArray)}
${#numbers.listFormatPercent(numList)}
${#numbers.setFormatPercent(numSet)}

/* 
 * Set minimum integer digits and (exact) decimal digits.
 */
${#numbers.formatPercent(num, 3, 2)}
${#numbers.arrayFormatPercent(numArray, 3, 2)}
${#numbers.listFormatPercent(numList, 3, 2)}
${#numbers.setFormatPercent(numSet, 3, 2)}


/*
 * ===============
 * Utility methods
 * ===============
 */

/*
 * Create a sequence (array) of integer numbers going
 * from x to y
 */
${#numbers.sequence(from,to)}
${#numbers.sequence(from,to,step)}

strings

• #strings：String 对象的实用方法。

/*
 * ======================================================================
 * See javadoc API for class org.thymeleaf.expression.Strings
 * ======================================================================
 */

/*
 * Null-safe toString()
 */
${#strings.toString(obj)}                           // also array*, list* and set*

/*
 * Check whether a String is empty (or null). Performs a trim() operation before check
 * Also works with arrays, lists or sets
 */
${#strings.isEmpty(name)}
${#strings.arrayIsEmpty(nameArr)}
${#strings.listIsEmpty(nameList)}
${#strings.setIsEmpty(nameSet)}

/*
 * Perform an 'isEmpty()' check on a string and return it if false, defaulting to
 * another specified string if true.
 * Also works with arrays, lists or sets
 */
${#strings.defaultString(text,default)}
${#strings.arrayDefaultString(textArr,default)}
${#strings.listDefaultString(textList,default)}
${#strings.setDefaultString(textSet,default)}

/*
 * Check whether a fragment is contained in a String
 * Also works with arrays, lists or sets
 */
${#strings.contains(name,'ez')}                     // also array*, list* and set*
${#strings.containsIgnoreCase(name,'ez')}           // also array*, list* and set*

/*
 * Check whether a String starts or ends with a fragment
 * Also works with arrays, lists or sets
 */
${#strings.startsWith(name,'Don')}                  // also array*, list* and set*
${#strings.endsWith(name,endingFragment)}           // also array*, list* and set*

/*
 * Substring-related operations
 * Also works with arrays, lists or sets
 */
${#strings.indexOf(name,frag)}                      // also array*, list* and set*
${#strings.substring(name,3,5)}                     // also array*, list* and set*
${#strings.substringAfter(name,prefix)}             // also array*, list* and set*
${#strings.substringBefore(name,suffix)}            // also array*, list* and set*
${#strings.replace(name,'las','ler')}               // also array*, list* and set*

/*
 * Append and prepend
 * Also works with arrays, lists or sets
 */
${#strings.prepend(str,prefix)}                     // also array*, list* and set*
${#strings.append(str,suffix)}                      // also array*, list* and set*

/*
 * Change case
 * Also works with arrays, lists or sets
 */
${#strings.toUpperCase(name)}                       // also array*, list* and set*
${#strings.toLowerCase(name)}                       // also array*, list* and set*

/*
 * Split and join
 */
${#strings.arrayJoin(namesArray,',')}
${#strings.listJoin(namesList,',')}
${#strings.setJoin(namesSet,',')}
${#strings.arraySplit(namesStr,',')}                // returns String[]
${#strings.listSplit(namesStr,',')}                 // returns List<String>
${#strings.setSplit(namesStr,',')}                  // returns Set<String>

/*
 * Trim
 * Also works with arrays, lists or sets
 */
${#strings.trim(str)}                               // also array*, list* and set*

/*
 * Compute length
 * Also works with arrays, lists or sets
 */
${#strings.length(str)}                             // also array*, list* and set*

/*
 * Abbreviate text making it have a maximum size of n. If text is bigger, it
 * will be clipped and finished in "..."
 * Also works with arrays, lists or sets
 */
${#strings.abbreviate(str,10)}                      // also array*, list* and set*

/*
 * Convert the first character to upper-case (and vice-versa)
 */
${#strings.capitalize(str)}                         // also array*, list* and set*
${#strings.unCapitalize(str)}                       // also array*, list* and set*

/*
 * Convert the first character of every word to upper-case
 */
${#strings.capitalizeWords(str)}                    // also array*, list* and set*
${#strings.capitalizeWords(str,delimiters)}         // also array*, list* and set*

/*
 * Escape the string
 */
${#strings.escapeXml(str)}                          // also array*, list* and set*
${#strings.escapeJava(str)}                         // also array*, list* and set*
${#strings.escapeJavaScript(str)}                   // also array*, list* and set*
${#strings.unescapeJava(str)}                       // also array*, list* and set*
${#strings.unescapeJavaScript(str)}                 // also array*, list* and set*

/*
 * Null-safe comparison and concatenation
 */
${#strings.equals(first, second)}
${#strings.equalsIgnoreCase(first, second)}
${#strings.concat(values...)}
${#strings.concatReplaceNulls(nullValue, values...)}

/*
 * Random
 */
${#strings.randomAlphanumeric(count)}

objects

• #objects：一般对象的实用方法。

/*
 * ======================================================================
 * See javadoc API for class org.thymeleaf.expression.Objects
 * ======================================================================
 */

/*
 * Return obj if it is not null, and default otherwise
 * Also works with arrays, lists or sets
 */
${#objects.nullSafe(obj,default)}
${#objects.arrayNullSafe(objArray,default)}
${#objects.listNullSafe(objList,default)}
${#objects.setNullSafe(objSet,default)}

bools

• #bools：用于布尔值评估的实用方法。

/*
 * ======================================================================
 * See javadoc API for class org.thymeleaf.expression.Bools
 * ======================================================================
 */

/*
 * Evaluate a condition in the same way that it would be evaluated in a th:if tag
 * (see conditional evaluation chapter afterwards).
 * Also works with arrays, lists or sets
 */
${#bools.isTrue(obj)}
${#bools.arrayIsTrue(objArray)}
${#bools.listIsTrue(objList)}
${#bools.setIsTrue(objSet)}

/*
 * Evaluate with negation
 * Also works with arrays, lists or sets
 */
${#bools.isFalse(cond)}
${#bools.arrayIsFalse(condArray)}
${#bools.listIsFalse(condList)}
${#bools.setIsFalse(condSet)}

/*
 * Evaluate and apply AND operator
 * Receive an array, a list or a set as parameter
 */
${#bools.arrayAnd(condArray)}
${#bools.listAnd(condList)}
${#bools.setAnd(condSet)}

/*
 * Evaluate and apply OR operator
 * Receive an array, a list or a set as parameter
 */
${#bools.arrayOr(condArray)}
${#bools.listOr(condList)}
${#bools.setOr(condSet)}

arrays

• #arrays：数组的实用方法

/*
 * ======================================================================
 * See javadoc API for class org.thymeleaf.expression.Arrays
 * ======================================================================
 */
/*
 * Converts to array, trying to infer array component class.
 * Note that if resulting array is empty, or if the elements
 * of the target object are not all of the same class,
 * this method will return Object[].
 */
${#arrays.toArray(object)}
/*
 * Convert to arrays of the specified component class.
 */
${#arrays.toStringArray(object)}
${#arrays.toIntegerArray(object)}
${#arrays.toLongArray(object)}
${#arrays.toDoubleArray(object)}
${#arrays.toFloatArray(object)}
${#arrays.toBooleanArray(object)}
/*
 * Compute length
 */
${#arrays.length(array)}
/*
 * Check whether array is empty
 */
${#arrays.isEmpty(array)}
/*
 * Check if element or elements are contained in array
 */
${#arrays.contains(array, element)}
${#arrays.containsAll(array, elements)}

lists

• #lists：列表的实用方法。

/*
 * ======================================================================
 * See javadoc API for class org.thymeleaf.expression.Lists
 * ======================================================================
 */

/*
 * Converts to list
 */
${#lists.toList(object)}

/*
 * Compute size
 */
${#lists.size(list)}

/*
 * Check whether list is empty
 */
${#lists.isEmpty(list)}

/*
 * Check if element or elements are contained in list
 */
${#lists.contains(list, element)}
${#lists.containsAll(list, elements)}

/*
 * Sort a copy of the given list. The members of the list must implement
 * comparable or you must define a comparator.
 */
${#lists.sort(list)}
${#lists.sort(list, comparator)}

sets

• #sets：集合的实用方法。

/*
 * ======================================================================
 * See javadoc API for class org.thymeleaf.expression.Sets
 * ======================================================================
 */

/*
 * Converts to set
 */
${#sets.toSet(object)}

/*
 * Compute size
 */
${#sets.size(set)}

/*
 * Check whether set is empty
 */
${#sets.isEmpty(set)}

/*
 * Check if element or elements are contained in set
 */
${#sets.contains(set, element)}
${#sets.containsAll(set, elements)}

maps

• #maps：地图的实用方法。

/*
 * ======================================================================
 * See javadoc API for class org.thymeleaf.expression.Maps
 * ======================================================================
 */

/*
 * Compute size
 */
${#maps.size(map)}

/*
 * Check whether map is empty
 */
${#maps.isEmpty(map)}

/*
 * Check if key/s or value/s are contained in maps
 */
${#maps.containsKey(map, key)}
${#maps.containsAllKeys(map, keys)}
${#maps.containsValue(map, value)}
${#maps.containsAllValues(map, value)}

aggregates

• #aggregates：在数组或集合上创建聚合的实用程序方法。

/*
 * ======================================================================
 * See javadoc API for class org.thymeleaf.expression.Aggregates
 * ======================================================================
 */

/*
 * Compute sum. Returns null if array or collection is empty
 */
${#aggregates.sum(array)}
${#aggregates.sum(collection)}

/*
 * Compute average. Returns null if array or collection is empty
 */
${#aggregates.avg(array)}
${#aggregates.avg(collection)}

ids

• #ids：用于处理 id 可能重复（例如，由于迭代的结果）的属性的实用方法。

/*
 * ======================================================================
 * See javadoc API for class org.thymeleaf.expression.Ids
 * ======================================================================
 */

/*
 * Normally used in th:id attributes, for appending a counter to the id attribute value
 * so that it remains unique even when involved in an iteration process.
 */
${#ids.seq('someId')}

/*
 * Normally used in th:for attributes in <label> tags, so that these labels can refer to Ids
 * generated by means if the #ids.seq(...) function.
 *
 * Depending on whether the <label> goes before or after the element with the #ids.seq(...)
 * function, the "next" (label goes before "seq") or the "prev" function (label goes after 
 * "seq") function should be called.
 */
${#ids.next('someId')}
${#ids.prev('someId')}

/*
 * ======================================================================
 * See javadoc API for class org.thymeleaf.expression.Ids
 * ======================================================================
 */

/*
 * Normally used in th:id attributes, for appending a counter to the id attribute value
 * so that it remains unique even when involved in an iteration process.
 */
${#ids.seq('someId')}

/*
 * Normally used in th:for attributes in <label> tags, so that these labels can refer to Ids
 * generated by means if the #ids.seq(...) function.
 *
 * Depending on whether the <label> goes before or after the element with the #ids.seq(...)
 * function, the "next" (label goes before "seq") or the "prev" function (label goes after 
 * "seq") function should be called.
 */
${#ids.next('someId')}
${#ids.prev('someId')}