THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
In the Hello World lesson, we presented a page with a simple Welcome message. In the Using Tags lesson, we create a Welcome page with links to other actions in the application.
Web applications differ from conventional websites in that web applications can create a dynamic response. To make it easier to reference dynamic data from a page, the framework offers a set of tags. Some of the tags mimic standard HTML tag , but provided while providing added value. Other tags create non-standard, but useful controls.
One use of the Struts Tags is to create links to other web resources, especially to other resources in the local application.
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While HTML provides a simple |
Linking
A very common use cases 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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<%@ taglib prefix="s" uri="/struts-tags" %>
<html>
<head>
<title>Welcome</title>
<link href="<s:url value="/css/tutorial.css"/>" rel="stylesheet"
type="text/css"/>
</head>
<body>
<h3>Commands</h3>
<ul>
<li><a href="<s:url action="Register"/>">Register</a></li>
<li><a href="<s:url action="Logon"/>">Sign On</a></li>
</ul>
<h3>Languages</h3>
<ul>
<li>
<s:url id="url" action="Welcome">
<s:param name="request_locale">en</s:param>
</s:url>
<s:a href="%{url}">English</s:a>
</li>
<li>
<s:url id="url" action="Welcome">
<s:param name="request_locale">ja</s:param>
</s:url>
<s:a href="%{url}">Japanese</s:a>
</li>
</ul>
</body>
</html>
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How the Code Works
On the Welcome page, we use two different Struts tags to create links. We create
- Resource links
- Direct links, and
- Links with parameters.
Let's look at each in turn.
Resource links
First, in the head element, we use the url tag to inject a page reference into the HTML link tag.
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As we create the application, we will often want to go directly to a page. To make prototyping easy, we can change the Welcome entry to a wilcard mapping.
The Code
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<action name="*" > <result>/tutorial/(1).jsp</result> </action> |
How the Code Works
If no other mapping matches, the framework will
- match "Welcome" to the asterisk, and
- substitute "Welcome" for any "{1}" tokens in the mapping.
Likewise, if there is a link to a "Logon" action, and nothing else matches, then the "/Logon.jsp" page is returned instead.
Wildcard mappings let you create your own conventions, so that you can avoid redundant configuration. The first mapping that matches a request wins.
If you are coding along, you can replace the Welcome action in your strut.xml with the Wildcard version.
Data Entry Forms
Most applications will use several data entry forms. The Struts tags Tags make creating input forms easy.
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The Code
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<%@ taglib prefix="s" uri="/struts-tags" %> <html> <head> <title>Logon</title> </head> <body> <s:form action="Logon"> <s:textfield label="User Name" name="username"/> <s:password label="Password" name="password" /> <s:submit/> </s:form> </body> </html> |
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- The JSP engine reads the taglib reference at the top of the page and loads the Struts Tags for use with this page under the prefix "s".
- The Struts Tags – textfield, password, and submit – each emit the appropriate label and control type.
Summary
The hardest part of writing a web application can be coding the pages. The framework makes coding pages easier by providing a set of custom tags. The Struts Tags can access dynamic data provided by the fraemwork, and reduce the amount of markup needed to create a page.
For about Struts Tags, see the Tag Developers Guide.
Next | Onward to Coding Actions |
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Prev | Return to Hello World |