THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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While HTML provides a simple |
Linking
A very common use cases case in web applications is linking to other pages. Now that we know Struts is up and running, let's add a Welcome page with links to other actions.
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Another common use case is using a link to change locales. On the HelloWorld page, let's add links to change the user's locale and to display a message from the application resources.
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<body>
<h2><s:property value="message"/></h2>
<h3>Languages</h3>
<ul>
<li>
<s:url idvar="url" action="HelloWorldWelcome">
<s:param name="request_locale">en</s:param>
</s:url>
<s:a href="%{url}">English</s:a>
</li>
<li>
<s:url idvar="url" action="HelloWorldWelcome">
<s:param name="request_locale">es</s:param>
</s:url>
<s:a href="%{url}">Espanol</s:a>
</li>
</ul>
</body>
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The |
How the Code Works
"%{url}" will be evaluated to the url defined with the s:url tag. On the Welcome and HelloWorld pages, we use two different Struts tags to create links. We create
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Note that the reference is absolute. We can move the page containing the link around without worrying about resolving relative references.
The url tag will also inject the web application context name.
Direct links
In the "Commands" section, we use the url link tag again, to link to inject a reference to an Struts 2 Action.
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<li><a href="<s:url action="Register"/>">Register</a></li> |
When the link is rendered, the tag will automatically append the appropriate extension, so that we do not need to embed that fact all over information across the application.
The tag will also URL-encode the link with the Java session ID, if needed, so that the Java session can be retained accross across requests.
Links with parameters
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<s:url idvar="url" action="Welcome"> <s:param name="request_locale">en</s:param> </s:url> <s:a href="%{url}">English</s:a> |
The This param tag will add the parameter "?request_locale=en" to the Welcome Action URL, and store it under the name "url". The a tag then injects the "url" reference into the hyperlink. This request_locale parameter will be picked up by the I18n Interceptor, and change your Locale accordingly.
Any number of parameters can be added to the URI by adding more param etags tags.
Wildcard Mappings
Since the Welcome page is nothing but links, we don't need an Action class. But, we should still add We'll still use a mapping, however, so that we can use use an action URI. If we link only to actions, and never to pages, then it's easy to add a an Action class later.
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<action name="Welcome" >
<result>/tutorial/Welcome.jsp</result>
</action>
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<action name="*" >
<result>/tutorial/{1}.jsp</result>
</action>
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Wildcard mappings let you create your own conventions, so that you can avoid redundant configuration. The first mapping that matches a request wins. (So put a mapping like <action name="*" > last!)
If you are coding along, you can replace the Welcome action in your strutstruts.xml with the Wildcard version.
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