Attributes In JSP Custom Tag

There may be described too many attributes for any custom tag. To define the characteristic, you want to carry out tasks:

• Define the property withinside the TagHandler class with the characteristic name and define the setter method
• define the characteristic detail in the tag element withinside the TLD file

Let's recognize the characteristic through the tag given below:

<m:cube number="4"></m:cube>

Here, prefix is m, tag name is cube and attribute is the number.

Easy Example of Attribute in JSP Custom Tag

In this example, we're going to use the cube tag which give back the cube of any given quantity. Here, we're defining the quantity characteristic for the cube tag. We are the use of the 3 document here:

• index.jsp
• CubeNumber.java
• mytags.tld

index.jsp

<%@ taglib uri="WEB-INF/mytags.tld" prefix="m" %>  
Cube of 4 is: <m:cube number="4"></m:cube>
CubeNumber.java
package com.javatpoint.taghandler;  
import javax.servlet.jsp.JspException;  
import javax.servlet.jsp.JspWriter;  
import javax.servlet.jsp.tagext.TagSupport;  

public class CubeNumber extends TagSupport{  
private int number;      

public void setNumber(int number) {  
    this.number = number;  
}  

public int doStartTag() throws JspException {  
    JspWriter out=pageContext.getOut();  
    try{  
        out.print(number*number*number);  
    }catch(Exception e){e.printStackTrace();}     

    return SKIP_BODY;  
}  

}  

mytags.tld

<?xml version="1.0" encoding="ISO-8859-1" ?>  
<!DOCTYPE taglib  
        PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"  
        "http://java.sun.com/j2ee/dtd/web-jsptaglibrary_1_2.dtd">  

<taglib>  
  <tlib-version>1.0</tlib-version>  
  <jsp-version>1.2</jsp-version>  
  <short-name>simple</short-name>  
  <uri>http://tomcat.apache.org/example-taglib</uri>  
  <description>A simple tab library for the examples</description>  

  <tag>  
    <name>cube</name>  
    <tag-class>com.javatpoint.taghandler.CubeNumber</tag-class>  
    <attribute>  
    <name>number</name>  
    <required>true</required>  
    </attribute>  
  </tag>  
</taglib>  

Result
Cube of 4 is : 64

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JSP Custom Tag Attribute example with Database

Let's create a custom tag that prints a specific document of desk for the given table name and id.

So, you need to have properties withinside the tag handler class.

PrintRecord.java

package com.javatpoint;  
import javax.servlet.jsp.JspException;  
import javax.servlet.jsp.JspWriter;  
import javax.servlet.jsp.tagext.TagSupport;  
import java.sql.*;  

public class PrintRecord extends TagSupport{  
private String id;  
private String table;  
  
public void setId(String id) {  
    this.id = id;  
}  
public void setTable(String table) {  
    this.table = table;  
}  

public int doStartTag()throws JspException{  
    JspWriter out=pageContext.getOut();  
    try{   
        Class.forName("oracle.jdbc.driver.OracleDriver");  
        Connection con=DriverManager.getConnection(  
                 "jdbc:oracle:thin:@localhost:1521:xe","system","oracle");  
        PreparedStatement ps=con.prepareStatement("select * from "+table+" where id=?");  
        ps.setInt(1,Integer.parseInt(id));  
        ResultSet rs=ps.executeQuery();  
        if(rs!=null){  
        ResultSetMetaData rsmd=rs.getMetaData();  
        int totalcols=rsmd.getColumnCount();  
        //column name  
        out.write("<table border='1'>");  
        out.write("<tr>");  
        for(int i=1;i<=totalcols;i++){  
            out.write("<th>"+rsmd.getColumnName(i)+"</th>");  
        }  
        out.write("</tr>");  
        //column value  
          
        if(rs.next()){  
            out.write("<tr>");  
                for(int i=1;i<=totalcols;i++){  
                out.write("<td>"+rs.getString(i)+"</td>");  
            }  
            out.write("</tr>");  
                  
        }else{  
            out.write("Table or Id doesn't exist");  
        }  
        out.write("</table>");            
        }  
        con.close();  
    }catch(Exception e){System.out.println(e);}  
    return SKIP_BODY;  
}  
}  

m.tld

<?xml version="1.0" encoding="ISO-8859-1" ?>    
<!DOCTYPE taglib    
        PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"    
    "http://java.sun.com/j2ee/dtd/web-jsptaglibrary_1_2.dtd">     

<taglib>  

  <tlib-version>1.2</tlib-version>  
  <jsp-version>2.0</jsp-version>  
  <short-name>c</short-name>  
  <uri>javatpoint</uri>  
  
<tag>  
<name>printRecord</name>  
<tag-class>com.javatpoint.PrintRecord</tag-class>  
<attribute>  
<name>id</name>  
<required>true</required>  
</attribute>  
<attribute>  
<name>table</name>  
<required>true</required>  
</attribute>    

</tag>  
</taglib>

index.jsp

<%@ taglib uri="javatpoint" prefix="j" %>  
<j:printRecord table="user874" id="1"></j:printRecord>

Output

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