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1. Write a Java class that implements the tag interface
packagetagdemo;Importjavax.servlet.http.HttpServletRequest;Importjavax.servlet.jsp.JspException;Importjavax.servlet.jsp.JspWriter;Importjavax.servlet.jsp.PageContext;Importjavax.servlet.jsp.tagext.Tag;Importjava.io.IOException; public classViewiptagImplementsTag {PrivatePageContext pagecontext; @Override public voidSetpagecontext (pagecontext Pagecontext) { this. PageContext =pagecontext; } @Override public voidsetParent (tag tag) {} @Override publicTag getParent () {return NULL; } @Override public intdoStartTag ()throwsjspexception {System.out.println ("call doStartTag method"); HttpServletRequest Request=(httpservletrequest) pagecontext.getrequest (); JspWriter writer=Pagecontext.getout (); String IP=request.getremoteaddr (); Try{writer.write (ip); } Catch(ioexception E) {e.printstacktrace (); } return0; } @Override public intDoendtag ()throwsjspexception {System.out.println ("call Doendtag method"); return0; } @Override public voidrelease () {System.out.println ("call Release method"); }}Viewiptag
2, write the TLD tag library file, the TLD file must be placed in the Web-inf folder or its sub-folder, this file is used to describe the label processor class
<?XML version= "1.0" encoding= "UTF-8"?><taglibxmlns= "http://java.sun.com/xml/ns/j2ee"Xmlns:xsi= "http://www.w3.org/2001/XMLSchema-instance"xsi:schemalocation= "http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"version= "2.0"> <Description>Custom labels</Description> <tlib-version>1.0</tlib-version> <Short-name>SDT</Short-name> <URI>/sefdefinetag</URI> <Tag> <Description>Output Client Address</Description> <name>Viewiptag</name> <Tag-class>Tagdemo.viewiptag</Tag-class> <body-content>Empty</body-content> </Tag></taglib>TLD
Taglib Tag Library Label overview
Description: describing information to the tag library
Tlib-version: Tag Library version
Short-name: Tag Library Name
Uri: the tag library uniquely identifies that the JSP is referring to the tag through a uri, and the URI must be preceded/prefaced, as long as the name is unique, as in the following reference <% @taglib prefix= "sdt" uri= "/sefdefinetag"%>
Tag:taglib Tag Library can contain more than one custom label, each tag corresponds to a custom label
Description: description of the current label
Name: define a name that references the tag processor class by this name in the JSP
Tag-class: corresponding Label Processor class
Body-content: Defining the label body
3. Test in JSP file
<%@ PageContentType= "text/html;charset=utf-8"language= "java" %><% @taglibprefix= "sdt"URI= "/sefdefinetag" %><HTML><Head> <title></title></Head><Body>IP:<Sdt:viewiptag/></Body></HTML>JSP
JSP can be introduced into the tag library, using prefix can set the tag library alias, label use is the < tag library alias: tag name >
Getting Started with customizing JSP tags
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