Objectives
1. Create custom tag: Basis, Iteration and Complex tag
- Implement Interface
- Extend from Build in class
2. Using custom tag in JSP pages
Hits: Steps to create and call custom tag
1. Describe tag structure (Tag Library Description)
2. Process tag (Tag handler)
3. Register and call custom tag on JSP pages (<%@taglib ......%>
Source codeCreate custom tag
1. Empty tag:
header tag, footer tag
2. If – then – else tag
3. Iteration tag: loop tag
4. Employee list tag
HEADER tag (Implement Tag interface)
Create Tag Library Descriptor (customTag.tlb) file and insert xml section below
<tag>
<name>header</name>
<tag-class>MySource.header</tag-class>
<body-content>empty</body-content>
<attribute>
<name>companyname</name>
<required>true</required>
</attribute>
</tag>
Create tag handler
Create java class (header.java) in MySource package implement Tag interface
package MySource;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.Tag;
public class header implements Tag{
String companyname ="";
public void setCompanyname(String companyname) {
this.companyname = companyname;
}
PageContext context;
Tag parrent;
public void setPageContext(PageContext pc) {
context = pc;
}
public void setParent(Tag t) {
parrent = t;
}
public Tag getParent() {
return parrent;
}
public int doStartTag() throws JspException {
try {
context.getOut().print("<h1>"+companyname+"</h1>");
context.getOut().print("<h3>Education Department</h3>");
} catch (IOException ex) {
Logger.getLogger(header.class.getName()).log(Level.SEVERE, null, ex);
}
return SKIP_BODY;
}
public int doEndTag() throws JspException {
return SKIP_BODY;
}
public void release() {
}
}
Call header from jsp page
Create jsp page (home.jsp), using taglib tag register header tag
<%@page contentType="text/html" pageEncoding="windows-1252"%>
<%@taglib prefix="my" uri="/WEB-INF/MyLib.tld" %>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<title>Home</title>
</head>
<body>
<my:header companyname="Can Tho University Software Center (CUSC)"/>
</body>
</html>
Now build and run home.jsp page
Home.jsp
FOOTER tag (extend from Simple Tag Support class)
Create Tag Handler (footer.java)
Select Tag Handler from netbean template
Provide tag name as footer and click next
Click Browse to select tld file, click New to add companyname attribute as figure
Modified home.jsp as below
<%@page contentType="text/html" pageEncoding="windows-1252"%>
<%@taglib prefix="my" uri="/WEB-INF/MyLib.tld" %>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<title>Home</title>
</head>
<body>
<my:header companyname="Can Tho University Software Center (CUSC)"/>
<my:footer companyname="Can Tho University Software Center (CUSC)"/>
</body>
</html>
Now build and run home.jsp page
Home.jsp
Loop tag
Create Tag Handler (loop.java) extend from Simple Body Tag Support, with 2 attribute start and end
Modified writeTagBodyContent as below
private void writeTagBodyContent(JspWriter out, BodyContent bodyContent) throws IOException {
if(start < end)
{
out.print("<ol>");
while(start < end)
{
out.print("<li>");
bodyContent.writeOut(out);
out.print("</li>");
start++;
}
out.print("</ol>");
}
bodyContent.clearBody();
}
Modified home.jsp as below
<%@page contentType="text/html" pageEncoding="windows-1252"%>
<%@taglib prefix="my" uri="/WEB-INF/MyLib.tld" %>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<title>Home</title>
</head>
<body>
<my:header companyname="Can Tho University Software Center (CUSC)"/>
<hr/>
<my:loop start="0" end="10">
<%= new java.util.Date()%>
</my:loop>
<my:footer companyname="Can Tho University Software Center (CUSC)"/>
</body>
</html>
Now build and run home.jsp page
Employee list tag
Create Tag Handler (employee.java) extend from Simple Body Tag Support (same above)
Modified employee.java as:
private void writeTagBodyContent(JspWriter out, BodyContent bodyContent) throws IOException {
try {
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
Connection conn;
conn = DriverManager.getConnection("jdbc:sqlserver://ntdan-lt;user=sa;password=Admin@123;database=NorthWind;");
PreparedStatement command = conn.prepareStatement(bodyContent.getString());
java.sql.ResultSet result = command.executeQuery();
ResultSetMetaData meta = result.getMetaData();
out.print("<table border='1px'>");
out.print("<tr bgcolor='#ACE768'>");
int count = 1;
while(count <= meta.getColumnCount()) {
out.print("<td>"+meta.getColumnName(count)+"</td>");
count++;
}
out.print("</tr>");
while(result.next()) {
count=1;
out.print("<tr>");
while(count <= meta.getColumnCount()) {
out.print("<td>"+result.getString(meta.getColumnName(count))+"</td>");
count++;
}
out.print("</tr>");
}
out.print("</table>");
conn.close();
} catch(Exception ex) {
out.print(ex.toString());
}
bodyContent.clearBody();
}
Open home.jsp, insert code as
<body>
<my:header companyname="Can Tho University Software Center (CUSC)"/>
<hr/>
<my:loop start="0" end="2">
<%= new java.util.Date()%>
</my:loop>
<my:employee>Select Top 5 EmployeeID, FirstName, LastName From Employees</my:employee>
<my:footer companyname="Can Tho University Software Center (CUSC)"/>
</body>
Now build and run home.jsp page
Hello World, Basic Server/Client Example of WCF[/caption]