docs/org.eclipse.wst.webtools.doc.user/topics/twfltwiz.dita

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<task id="twfltwiz" xml:lang="en-us">
<title>Creating Filters</title>
<shortdesc>The filters wizard helps you to create <tm tmclass="special" tmowner="Sun Microsystems, Inc."
tmtype="tm" trademark="Java">Java</tm> servlet filters
by walking you through the creation process and and by providing you with output files
that you can use or that you can modify for use with your Web
application. The filters can run on Java EE-compliant Web servers.</shortdesc>
<prolog><metadata>
<keywords><indexterm>servlets<indexterm>creating</indexterm></indexterm></keywords>
</metadata></prolog>
<taskbody>
<context> <p>To create a filter, complete the following steps: </p></context>
<<steps>
<step><cmd>In the Java EE perspective, expand your  <xref href="ccwebprj.dita"
scope="peer"><desc></desc>dynamic project</xref> in the Project Explorer view.</cmd></step>
<step><cmd>Right click on the <b>Filter</b> icon, and select <menucascade>
<uicontrol>New</uicontrol><uicontrol>Filter</uicontrol></menucascade> from
the pop-up menu.</cmd><stepresult> The <uicontrol>Create FIlter</uicontrol> wizard
appears.</stepresult></step>
<step><cmd>Follow the project wizard prompts.</cmd></step>
</steps>
<postreq><p><b>General Information</b></p><dl><dlentry>
<p><dt>Modifiers</dt></p>
<dd>The <cite>Sun
Microsystems <tm tmclass="special" tmowner="Sun Microsystems, Inc." tmtype="tm"
trademark="Java">Java</tm> Servlet 2.3 Specification</cite> states that a
	Servlet class must be <b>public</b> and not <b>abstract</b>. Therefore,
	you cannot change these modifiers. The only one available for change is
	the <b>final</b> modifier.</dd>
</dlentry><dlentry>
<p><dt>Interfaces</dt></p>
<dd>There is one obligatory interface that filter classes must
	implement: <b>javax.servlet.Filter</b>. This interface is
	provided by javax.servlet package and is used to represent the
	life-cycle of the filter. This interface has three methods: init,
	doFilter and destroy. <ul>
	<li>The <b>init</b> method is called by the servlet
	container only once, when it finishes instantiating the filter.</li>	
	<li>The	<b>doFilter</b> method is where the filtering is performed and is called every
	time a user requests a resource, such as a servlet, to which the filter
	is mapped.</li> 
	<li>The <b>destroy</b> method is called by the servlet container to
	tell the filter that it will be taken out of service.</li>
	</ul> Although, that the javax.servlet.Filter interface is provided in the <b>Interfaces</b>
	field by default, you can add additional interfaces to implement by using the <b>Add</b> button.</dd>
</dlentry><dlentry>
<p><dt>Interface selection dialog</dt></p>
<dd>This dialog appears if you select to add an interface to your
	filter. As you type the name of the interface that you are adding, a
	list of available interfaces listed in the <b>Matching items</b> list box
	updates dynamically to display only the interfaces that match the
	pattern. Choose an interface to see the qualifier, and then
	click <b>OK</b> when finished.</dd>
</dlentry><dlentry>
<p><dt>Filter Mappings</dt></p>	
<dd>For a filter to intercept a request to a servlet, you must:
	<ol>
		<li>declare the filter with a <b>&lt;filter&gt;</b> element in
		the deployment descriptor</li>
		<li>map the filter to the servlet using the <b>&lt;filter-mapping&gt;</b>
		element.</li>
	</ol>
	Sometimes you want a filter to work on multiple servlets. You can do
	this by mapping a filter to a URL pattern so that any request that
	matches that URL pattern will be filtered. All this is made
	automatically if you use the <b>Filter Mappings</b> field.</dd>
</dlentry><dlentry>
<p><dt>Method stubs</dt></p>
<dd>Because each filter must implement the javax.servlet.Filter
	interface, the <b>Inherited abstract methods</b> option is always
	checked and cannot be changed.</dd>
</dlentry></dl></postreq>
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