JSP Custom Label (2) __jsp

Iv. Write labels with label bodies

Need to return to Tagsupport.eval_body_include, you can enter the label body;

Attributetag.java

Package org.tagext;
Import javax.servlet.jsp.tagext.*;
Import javax.servlet.jsp.*;

public class Attributetag extends tagsupport{
	private String name;
	Public String GetName () {return
		name;
	}
	public void SetName (String name) {
		this.name = name;
	}
	public int doStartTag () throws jspexception{
		Object value = null;
		Value = Super.pageContext.getAttribute (name,pagecontext.page_scope);
		if (value==null) {return
			tagsupport.skip_body;
		}
		else{return
			tagsupport.eval_body_include
		}}

Xiazdong.tld

    <tag>
	<name>attribute</name>
	<tag-class>org.tagext.attributetag</tag-class >
	<body-content>JSP</body-content>
	<attribute>
		<name>name</name>
		<required>true</required>
		<rtexprvalue>true</rtexprvalue>
	</attribute >
  </tag>

attributetag.jsp

<%@ page contenttype= "text/html" pageencoding= "GBK"%> <%@ taglib prefix=
"Xiazdong" uri= "Xiazdong"%>
 

 
v. Iterative labels 

 
Iterative labels are defined as repeated execution of the label body, often used in the output set, and often used in MVC;


Code instance:



I will not write some documents that are not changed;

Iteratetag.java


Package org.tagext;
Import javax.servlet.jsp.tagext.*;
Import javax.servlet.jsp.*;
Import java.util.*;
	public class Iteratetag extends tagsupport{private String name;
	Private String ID;
	Private iterator<string> iter;
	Public String GetName () {return name;
	public void SetName (String name) {this.name = name;
	Public String GetId () {return id;
	public void SetId (String id) {this.id = ID;
		public int doStartTag () throws jspexception{Object value = null;
		Value = Super.pageContext.getAttribute (Name,pagecontext.page_scope); if (value==null| |! (Value instanceof list<?>))
		{return tagsupport.skip_body;
			else{iter = ((list<string>) value). iterator ();
				if (Iter.hasnext ()) {Super.pageContext.setAttribute (Id,iter.next ());
			return tagsupport.eval_body_include;
			} else{return tagsupport.skip_body; The public int doafterbody () throws jspexception{if (Iter.hasnext ()) {Super.pageContext.setAttribute (Id,iter.nex
T ());			return tagsupport.eval_body_again;
		} else{return tagsupport.skip_body; }
	}
}
 

 
iteratetag.jsp 


<%@ page contenttype= "text/html" pageencoding= "GBK" import= "java.util.*"%> "<%@ taglib" prefix= "Xiazdong"
Uri= "Xiazdong"%>
 


Six, Bodytagsupport class



The characteristic of Bodytagsupport is that the output content can be bodycontent and all output at once.

According to the above iteration output code, a slight change can be, the main change is in Iteratetag.java, need extends bodytagsupport;

Common methods of Bodytagsupport:

(1) Bodytagsupport. eval_body_buffered;

(2) Getpreviousout      (); Get output stream from output to Web page

(3) The Bodycontent object stores the data;


Package org.tagext;
Import javax.servlet.jsp.tagext.*;
Import javax.servlet.jsp.*;
Import java.util.*;
	public class Iteratetag extends bodytagsupport{private String name;
	Private String ID;
	Private iterator<string> iter;
	Public String GetName () {return name;
	public void SetName (String name) {this.name = name;
	Public String GetId () {return id;
	public void SetId (String id) {this.id = ID;
		public int doStartTag () throws jspexception{Object value = null;
		Value = Super.pageContext.getAttribute (Name,pagecontext.page_scope); if (value==null| |! (Value instanceof list<?>))
		{return tagsupport.skip_body;
			else{iter = ((list<string>) value). iterator ();
				if (Iter.hasnext ()) {Super.pageContext.setAttribute (Id,iter.next ());    return tagsupport.eval_body_buffered;
			exists in Bodycontent} else{return tagsupport.skip_body; '} ' public int doafterbody () throws jspexception{if (Iter.hasnext ()) {super.pageContext.setAtTribute (Id,iter.next ());
		return tagsupport.eval_body_again;
		} else{return tagsupport.skip_body; The public int Doendtag () throws jspexception{if (super.bodycontent!=null) {try{Super.bodyContent.writeOut (supe    R.getpreviousout ());
	Output to Page} catch (Exception e) {}} return bodytagsupport.eval_page; }
}
 

 
Vii. use of Tagextrainfo and Variableinfo

The id attribute in the <jsp:usebean id = "" > represents the object name, and the method can be invoked by this name, and if the effect is to be achieved, the Tagextrainfo class must be inherited;

We need to create a separate file to indicate that the object of the attribute can be used in the script;

Myextrainfo.java


Package Org.tag;
Import javax.servlet.jsp.tagext.*;
public class Mytagextrainfo extends tagextrainfo{public
	variableinfo[] Getvariableinfo (tagdata data) {
		return New Variableinfo[]{new Variableinfo (Data.getid (), "java.lang.String", true,variableinfo.nested)}
 

 
After writing, add in Xiazdong.tld:


	<tei-class>			/Note
		org.tag.MyTagExtraInfo
	</tei-class>
The last xiazdong.tld to:


<tag>
	<name>iterate</name>
	<tag-class>org.tagext.IterateTag</tag-class>
	<body-content>JSP</body-content>


	<tei-class>			/Note
		org.tag.MyTagExtraInfo
	</tei-class>


	<attribute>
		<name>name</name>
		<required>true</ required>
		<rtexprvalue>true</rtexprvalue>
	</attribute>
	<attribute>
		<name>id</name>
		<required>true</required>
		<rtexprvalue>true</ rtexprvalue>
	</attribute>
  </tag>
 



In this way in the JSP can be used in scriptlet;


<%@ page contenttype= "text/html" pageencoding= "GBK" import= "java.util.*"%> "<%@ taglib" prefix= "Xiazdong"
Uri= "Xiazdong"%>