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FreeMarker is a Java-based template engine that is a great alternative to JSP. FreeMarker is ideal for situations where your action results can possibly be loaded from outside a Servlet container. For example, if you wished to support plugins in your application, you might wish to use FreeMarker so that the plugins could provide the entire action class and view in a single jar that is loaded from the classloader.

For more information on FreeMarker itself, please visit the FreeMarker website.

Note

Struts2 itself The framework utilizes FreeMarker templates for its own tags because the engine can load templates from the classpath (unlike JSPs), has includes strong error reporting, built-in internationalization and powerful macro libraries.

Note

The framework also supports Support is also included for Velocity templates. For a comparison of Velocity vs FreeMarker see here.

...

Code Block
xml
xml
titlestruts.xml

<action name="test" class="com.acme.TestAction">
    <result name="success" type="freemarker">test-success.ftl</result>
</action>

...

Code Block
xml
xml
titletest-success.ftl

<html>
<head>
    <title>Hello</title>
</head>
<body>

Hello, ${name}

</body>
</html>

...

Assuming there's an attribute with name myApplicationAttribute in the Application scope.

Code Block

<#if Application.myApplicationAttribute?exists>
     ${Application.myApplicationAttribute}
</#if>

or

Code Block

<@s.property value="%{#application.myApplicationAttribute}" />

...

Assuming there's an attribute with name mySessionAttribute in the Session scope.

Code Block

<#if Session.mySessionAttribute?exists>
     ${Session.mySessionAttribute}
</#if>

or

Code Block

<@s.property value="%{#session.mySessionAttribute}" />

...

Assuming there's an attribute with name 'myRequestAttribute' in the Request scope.

Code Block

<#if Request.myRequestAttribute?exists>
      ${Request.myRequestAttribute}
</#if>

or

Code Block

<@s.property value="%{#request.myRequestAttribute}" />

...

Assuming there's a request parameter myParameter (eg. http://host/myApp/myAction.action?myParameter=one).

Code Block

<#if Parameters.myParameter?exists>
     ${Parameters.myParameter}
</#if>

or

Code Block

<@s.property value="%{#parameters.myParameter}" />

...

Assuming there's a parameter with the name myContextParam in framework context.

Code Block

${stack.findValue('#myContextParam')}

or

Code Block

<@s.property value="%{#myContextParam}" />

...

In addition, you can specify a location (directory on your file system) through the templatePath or TemplatePath context variable (in the {{ web.xml)}. If a variable is specified, the content of the directory it points to will be searched first.

...

Note that the action context is looked up after the value stack. This means that you can reference the variable without the typical preceding has marker (#) like you would have to when using the JSP s:property tag. This is a nice convenience, though be careful because there is a small chance it could trip you up.

Code Block
xml
xml

<@s.url id="url" value="http://www.yahoo.com"/>
Click <a xhref="${url}">here</a>!

...

FreeMarker includes complete tag support. See the FreeMarker Tags documentation for information on how to use the generic Struts Tags provided by Struts. In addition to this, you can use any JSP tag, like so:

Code Block
xml
xml

<#assign mytag=JspTaglibs["/WEB-INF/mytag.tld"]>
<@mytag.tagx attribute1="some ${value}"/>

...

Code Block
xml
xml
titleAdding JspSupportSerlvet to web.xml

<servlet>
    <servlet-name>JspSupportServlet</servlet-name>
    <servlet-class>org.apache.struts2.views.JspSupportServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
</servlet>

...

To extend the Freemarker support, develop a class that extends org.apache.struts2.views.freemarker.FreemarkerManager, overriding methods as needed, and plugin the class through the struts.properties:

Code Block
none
none

struts.freemarker.manager.classname = com.yourcompany.YourFreeMarkerManager

...

As of FreeMarker 2.3.4, an alternative syntax is supported. This alternative syntax is great if you find that your IDE (especially IntelliJ IDEA) makes it difficult to work with the default syntax. You can read more about this syntax here.

...

Cache

You can enable FreeMarker cache mechanism by specifying below options in struts.xml:

  • <constant name="struts.freemarker.templatesCache.updateDelay" value="1800" /> - default update cache interval (5 seconds)
  • <constant name="struts.freemarker.templatesCache" value="true" /> - *DEPRECATED* this option will use a internal ConcurrentHashMap in FreemarkerTemplateEngine but not freemarker native cache

Setting devMode to true will disable cache and updateDelay immediately, but you can explicit specify these constants to enable cache even in devMode, see devMode

Incompatible Improvements

By default Struts is using FreeMarker in way to be backward compatible as much as possible but if you need to enable new features you can do it via freemarker.properties by defining incompatible improvements settings, ie.:

Code Block
titlefreemarker.properties
incompatible_improvements=2.3.22

This can impact your freemarker powered pages and Struts tags as well, so please careful test this change.

Next: FreeMarker Tags