JSP series: (6) JSP advanced-imitate JSTL core Tag Library

1. If label

Iftag.java file

Package Com.rk.tag;import Java.io.ioexception;import Javax.servlet.jsp.jspexception;import Javax.servlet.jsp.tagext.jspfragment;import Javax.servlet.jsp.tagext.simpletagsupport;public class IfTag extends Simpletagsupport{private boolean test;public void Settest (Boolean test) {this.test = test;} @Overridepublic void Dotag () throws Jspexception, ioexception{//determines whether to output the label body content if (test = = True), based on the return value of the test {//jspfragment Jspbody = Getjspbody ();//jspbody.invoke (null); This.getjspbody (). Invoke (null);}}

. tld File Configuration:

<tag><name>if</name><tag-class>com.rk.tag.IfTag</tag-class><body-content> Scriptless</body-content><attribute><name>test</name><required>true</required ><rtexprvalue>true</rtexprvalue><type>boolean</type></attribute></tag>

JSP file

<! doctype html public  "-//w3c//dtd html 4.01 transitional//en" >

2, choose, when, otherwise label
Choosetag.java file
Package Com.rk.tag;import Java.io.ioexception;import Javax.servlet.jsp.jspexception;import Javax.servlet.jsp.tagext.simpletagsupport;public class Choosetag extends simpletagsupport{//is not a property but a temporary variable that is used to pass in the middle of a child label "State" private Boolean executed = False;public Boolean isexecuted () {return executed;} public void setexecuted (Boolean executed) {this.executed = executed;} @Overridepublic void Dotag () throws Jspexception, Ioexception{this.getjspbody (). Invoke (null);}}

. tld File Configuration:
<tag><name>choose</name><tag-class>com.rk.tag.ChooseTag</tag-class>< Body-content>scriptless</body-content></tag>

Whentag.java file
Package Com.rk.tag;import Java.io.ioexception;import Javax.servlet.jsp.jspexception;import Javax.servlet.jsp.tagext.jsptag;import Javax.servlet.jsp.tagext.simpletagsupport;public class WhenTag extends Simpletagsupport{private boolean test;public void Settest (Boolean test) {this.test = test;} @Overridepublic void Dotag () throws Jspexception, ioexception{//gets the parent tag choosetag parent = (Choosetag) this.getparent ();// If the contents of the parent tag have not been executed and the current judging condition (test) is true, then the output if (!parent.isexecuted () && test==true) {this.getjspbody () is executed. Invoke (NULL);p arent.setexecuted (True);}}}




. tld File Configuration:
<tag><name>when</name><tag-class>com.rk.tag.whentag</tag-class><body-content >scriptless</body-content><attribute><name>test</name><required>true</ required><rtexprvalue>true</rtexprvalue><type>boolean</type></attribute></ Tag>



Otherwisetag.java file
Package Com.rk.tag;import Java.io.ioexception;import Javax.servlet.jsp.jspexception;import Javax.servlet.jsp.tagext.jsptag;import Javax.servlet.jsp.tagext.simpletagsupport;public class OtherWiseTag extends simpletagsupport{@Overridepublic void Dotag () throws Jspexception, ioexception{//get parent tag Choosetag father = (Choosetag) This.getparent (); if (!parent.isexecuted ()) {this.getjspbody (). Invoke (null);}}

. tld File Configuration:
<tag><name>otherwise</name><tag-class>com.rk.tag.OtherWiseTag</tag-class>< Body-content>scriptless</body-content></tag>

jsp file 
 
<%@ page language= "java"  import= "java.util.*"  pageencoding= "Utf-8"%><% @taglib  uri= "Http://www.lsieun.com/rk"  prefix= "RK"  %><! doctype html public  "-//w3c//dtd html 4.01 transitional//en" >


3. Foreach Label
Foreachtag.java file
package com.rk.tag;import java.io.ioexception;import java.util.collection;import  java.util.list;import java.util.map;import javax.servlet.jsp.jspexception;import  javax.servlet.jsp.pagecontext;import javax.servlet.jsp.tagext.simpletagsupport;public class  foreachtag extends simpletagsupport{private object items;private string var; Public void setitems (object items) {this.items = items;} Public void setvar (String var) {This.var = var;} @Overridepublic  void dotag ()  throws JspException, IOException{PageContext  pagecontext =  (PageContext) this.getjspcontext (); Collection colls = null;if (items instanceof list) {colls =  (List) items;} if (items instanceof map) {map map =  (MAP) Items;colls = map.entryset ();}      for (object object:colls) {//Put eachThe object is placed in the domain object (pagecontext) Pagecontext.setattribute (var, object);//Displays the contents of the tag body this.getjspbody (). Invoke (null);}} 

. tld File Configuration:
<tag><name>forEach</name><tag-class>com.rk.tag.ForEachTag</tag-class>< Body-content>scriptless</body-content><attribute><name>items</name><required> true</required><rtexprvalue>true</rtexprvalue><type>java.lang.object</type></ Attribute><attribute><name>var</name><required>true</required><rtexprvalue >false</rtexprvalue><type>java.lang.String</type></attribute></tag>

JSP file
<%@ page language= "java"  import= "Java.util.*,com.rk.entity.student"  pageEncoding= "Utf-8 "%><% @taglib  uri=" Http://www.lsieun.com/rk " prefix=" RK " %><! doctype html public  "-//w3c//dtd html 4.01 transitional//en" >


JSP series: (6) JSP advanced-imitate JSTL core Tag Library