To: http://blog.csdn.net/jiangwei0910410003/article/details/23915373
http://blog.csdn.net/jiangwei0910410003/article/details/23915373
--------------------------
JSP custom tag Tag file version
Implement a Select Label feature similar to the previous article
1. In Web-inf/tags/select.tag
<%@ tag body-content= "Empty"%>
<%@ tag dynamic-attributes= "Tagattrs"%>
<%@ attribute Name= "optionslist" type= "Java.util.List" required= "true" rtexprvalue= "true"%>
<%@ attribute name= "name" required= "true"%>
<%@ attribute name= "Size" required= "true"%>
<%@ taglib prefix= "C" uri= "Http://java.sun.com/jstl/core_rt"%>
<select name= "${name}" size= "${size}"
<c:foreach var= "Attrentry" items= "${tagattrs}" >
${attrentry.key}= "${attrentry.value}"
</c:forEach>
>
<c:foreach var= "option" items= "${optionslist}" >
<option value= "${option}" >${option}</option>
</c:forEach>
</select>
Note here that the tag file can only be placed in the following location:
1.web-inf/tags
Sub-directories for 2.web-inf/tags
Meta-inf/tags of jar packages in 3.web-inf/lib
Subdirectories under Meta-inf/tags for jar packages in 4.web-inf/lib
The tag file in the 5.jar package requires a TLD
Add Jstl.jar and Standard.jar to the Web-inf/lib directory, and one point is the red part: Do not use http://java.sun.com/jstl/core this URL, Otherwise, the Item property in foreach is reported as having a problem
2. Use in JSP
<%@ page language= "java" contenttype= "text/html; Charset=utf-8 "
pageencoding= "UTF-8"%>
<%@ page import= "java.util.*"%>
<%@ taglib prefix= "Formtag" tagdir= "/web-inf/tags"%>
<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" "HTTP://WWW.W3.ORG/TR/HTML4/LOOSE.DTD" >
<meta http-equiv= "Content-type" content= "text/html; Charset=utf-8 ">
<title>insert title here</title>
<body>
<%
list<string> colorlist = new arraylist<string> ();
Colorlist.add ("Red");
Colorlist.add ("Blue");
Colorlist.add ("white");
Request.setattribute ("ColorList", colorlist);
%>
<form action= "" method= "POST" >
<formtag:select name= "Color" size= "1" optionslist= "${requestscope.colorlist}" style= "width:140px"/>
</form>
</body>
--------------------------------------------------------------------------------------------------------------- --------------------------------------------------
JSP Custom Labels
JSP tags have two sets of APIs
Jsptag->simpletag->simpletagsupport
Jsptag->tag->iterationtag->bodytag
The second group is classic, relatively early use of the way, doStartTag (), Doendtag () has n multiple return value of the kind, and really inconvenient to use, today learned another use of the first set of API way, let people great satisfaction, stickers
Example is a select tag that supports dynamic property settings
1. Writing label classes
public class Selecttaghandler extends Simpletagsupport implements Dynamicattributes {
private static final String attr_template = "%s= '%s '";
private static final String option_template = "<option value= '%1 $ S ' >%1$s</option>";
Private List optionslist;
private String name;
private String size;
Private map<string, object> tagattrs = new hashmap<string, object> ();
public void SetName (String name) {
THIS.name = name;
}
public void SetSize (String size) {
this.size = size;
}
public void Setoptionslist (List optionslist) {
This.optionslist = optionslist;
}
@Override
public void Dotag () throws Jspexception, IOException {
PageContext PageContext = (PageContext) getjspcontext ();
JspWriter out = Pagecontext.getout ();
Out.print ("<select");
Out.print (String.Format (attr_template, "name", THIS.name));
Out.print (String.Format (attr_template, "size", this.size));
For (String AttrName:tagAttrs.keySet ()) {
String attrdefinition = String.Format (Attr_template, Attrname, Tagattrs.get (attrname));
Out.print (attrdefinition);
}
Out.print (">");
for (Object option:this.optionsList) {
String Optiontag = String.Format (Option_template, option.tostring ());
Out.println (Optiontag);
}
Out.println ("</select>");
}
@Override
public void Setdynamicattribute (string uri, string name, Object value) throws Jspexception {
Tagattrs.put (name, value);
}
}
See no, the code is so concise, dynamic property configuration is also very convenient, do not write n multiple setter and getter method.
<?xml version= "1.0" encoding= "UTF-8"?>
<taglib xmlns= "HTTP://JAVA.SUN.COM/XML/NS/J2EE"
Xmlns:xsi= "Http://www.w3g.org/2001/XMLSchema-instance"
xsi:schemalocation= "Http://java.sun.com/xml/ns/j2ee web-jsptaglibrary_2_0.xsd"
version= "2.0" >
<tlib-version>1.2</tlib-version>
<jsp-version>1.2</jsp-version>
<short-name>forms taglib</short-name>
<uri>http://hi.baidu.com/tags/forms</uri>
<description>
An example tab library of replacements for the HTML form tags.
</description>
<tag>
<name>select</name>
<tag-class>com.baidu.hi.tag.SelectTagHandler</tag-class>
<body-content>empty</body-content>
<attribute>
<name>optionsList</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
<type>java.util.List</type>
</attribute>
<attribute>
<name>name</name>
<required>true</required>
</attribute>
<attribute>
<name>size</name>
<required>true</required>
</attribute>
<dynamic-attributes>true</dynamic-attributes>
</tag>
</taglib>
<%@ page language= "java" contenttype= "text/html; Charset=utf-8 "
pageencoding= "UTF-8"%>
<%@ page import= "java.util.*"%>
<%@ taglib prefix= "formtags" uri= "/tld/select.tld"%>
<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" "HTTP://WWW.W3.ORG/TR/HTML4/LOOSE.DTD" >
<% @page import= "Java.util.ArrayList"%><meta http-equiv= "Content-type" content= "text/html; Charset=utf-8 ">
<title>insert title here</title>
<body>
<%
list<string> colorlist = new arraylist<string> ();
Colorlist.add ("Red");
Colorlist.add ("Blue");
Colorlist.add ("white");
Request.setattribute ("ColorList", colorlist);
%>
<form action= "" method= "POST" >
<formtags:select name= "Color" size= "1" optionslist= "${requestscope.colorlist}" style= "width:140px"/>
</form>
</body>
Java JSP Custom Tags
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