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Date: Mon, 28 Jan 2008 11:29:42 -0800
From: Darren James <jdjames@netflix.com>
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To: Struts Users Mailing List <user@struts.apache.org>
Subject: Re: tag writers resources?
References: <479DE6EF.5090107@ksi.gr>
In-Reply-To: <479DE6EF.5090107@ksi.gr>
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Hi Joachim,

This gives me something to start with.   Time to dig into the struts2
source code to help me grok the sample you've provided.

thanks,

- Darren.

Joachim Ansorg wrote:
>
> Hi Darren,
> writing a simple Struts2 tag is not that difficult. But getting 
> started is.
> The documentation of the tag api is not very good, imho. The best start
> is in my opinion to get the Struts2 sources and read the source code of
> the existing struts2 tags.
>
> I'm posting a simple example with this mail so it's in the archives for
> anybody. A tag writers guide would be a very useful resource for S2 users.
>
> For a S2 body you basically need:
>
> -A JSP tag implementation. e.g.:
>
> public class NameValueTag extends AbstractUITag{
>     private String editMode;
>
>     public Component getBean(ValueStack valueStack, HttpServletRequest
> httpServletRequest, HttpServletResponse httpServletResponse) {
>         return new NameValue(valueStack, httpServletRequest,
> httpServletResponse);
>     }
>
>     protected void populateParams() {
>         super.populateParams();
>         ((NameValue) component).setEditMode(editMode);
>     }
>
>     public String isEditMode() {
>         return editMode;
>     }
>
>     public void setEditMode(String editMode) {
>         this.editMode = editMode;
>     }
> }
>
> -A Struts2 component which is used by Struts. The JSP tags sets the
> attributed on the component. The annotations are later used for
> automatic .tld generation. I'm using Maven for that.
>
> @StrutsTag(name = "nameValue", description = "Inserts a formatted
> name-value html code construct.", tldTagClass =
> "gr.ksi.tags.ksiplugin.views.jsp.NameValueTag")
> public class NameValue extends ClosingUIBean {
>     private String editMode;
>
>     public NameValue(ValueStack valueStack, HttpServletRequest
> httpServletRequest, HttpServletResponse httpServletResponse) {
>         super(valueStack, httpServletRequest, httpServletResponse);
>     }
>
>     public String getDefaultOpenTemplate() {
>         return "ksinamevalue";
>     }
>
>     protected String getDefaultTemplate() {
>         return "ksinamevalue-end";
>     }
>
>     @StrutsTagAttribute(description = "Set to true to display edit boxes
> instead of text labels.", required = false, type = "Boolean")
>     public void setEditMode(String editMode) {
>         this.editMode = editMode;
>     }
>
>     public String isEditMode() {
>         return editMode;
>     }
>
>     protected void evaluateExtraParams() {
>         if (editMode != null) {
>             addParameter("editMode", findValue(editMode, Boolean.class));
>         }
>     }
> }
>
> And you need Freemarker templates which render the html. Have a look at
> the getDefaultTemplate() and getDefaultOpenTemplate() methods above.
> These point to the corresponding freemarker templates.
> The open template in this example is:
>
> [#ftl]
> [#if parameters.editMode?exists && parameters.editMode == true]
> <div class="name_value_edit">
>     <span class="name">
>         [#if parameters.label?exists] [@s.property
> value="parameters.label" /] [/#if]
>     </span>
>     <span class="value">
> [#else]
> <div class="name_value">
>     <span class="name">
>         [#if parameters.label?exists] [@s.property
> value="parameters.label" /] [/#if]
>     </span>
>     <span class="value">
> [/#if]
>
> The closing template is just:
> [#ftl]
> </ul>
>
> The rendered body is put in between.
>
> These examples are a full implementation of a S2 tag.
> If you want to place custom actions before and after the body rendering
> I think overriding ClosingUIBean.start and ClosingUIBean.end (don't
> remember the right name atm).
>
> Hope that helps,
> Joachim
> > Hi All,
> >
> > Does anyone (know of/have any) resources that cover writing a tag?
> > I want to write a struts2 body tag that sets some applications specific
> > state before it emits it's body, and clears the state once the body has
> > been emitted.  Any tag-writers guides out there???
>
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