What is Velocity?
Ans: Velocity is a Java-based template engine. It permits anyone
to use a simple yet powerful template language to reference objects defined in
Java code.
When Velocity is used for web development, Web designers can
work in parallel with Java programmers to develop web sites according to the
Model-View-Controller (MVC) model, meaning that web page designers can focus
solely on creating a site that looks good, and programmers can focus solely on
writing top-notch code. Velocity separates Java code from the web pages, making
the web site more maintainable over its lifespan and providing a viable
alternative to
Java Server
Pages (JSPs) or
PHP.
For
first App you need jars required for velocity.
1.
Create a Dynamic web application.
2.
Put all the required jars in /WEB-INF/lib directory of your application
antlr-2.7.5.jar
avalon-logkit-2.1.jar
commons-collections-3.2.1.jar
commons-lang-2.4.jar
commons-logging-1.1.jar
jdom-1.0.jar
log4j-1.2.12.jar
maven-ant-tasks-2.0.9.jar
oro-2.0.8.jar
servletapi-2.3.jar
werken-xpath-0.9.4.jar
Note: you can find all these jars in lib
folder of downloaded zip of Velocity (Ex. velocity-1.7.zip).
3.
Map a servlet in your web.xml
<servlet>
<servlet-name>velocity</servlet-name>
<servlet-class>org.apache.velocity.tools.view.VelocityViewServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>velocity</servlet-name>
<url-pattern>*.vm</url-pattern>
</servlet-mapping>
4.
In case of Struts 2.x map struts filter
<filter>
<filter-name>struts2</filter-name>
<filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>*</url-pattern>
</filter-mapping>
5. Create a UserAction
package com.ankit.web;
import com.opensymphony.xwork2.ActionSupport;
public class UserLogin extends ActionSupport {
private String name;
private String email;
private int random;
public String getName() {
return name;
}
public void setName(String name)
{
this.name = name;
}
public String getEmail() {
return email;
}
public void setEmail(String
email) {
this.email = email;
}
public int getRandom() {
return random;
}
public void setRandom(int random) {
this.random = random;
}
public String login() {
random=(int)( Math.random()*10);
System.out.println("Name->"+name+"
random->"+random);
return SUCCESS;
}
}
6. Struts.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE
struts PUBLIC "-//Apache Software Foundation//DTD Struts
Configuration 2.1//EN" "http://struts.apache.org/dtds/struts-2.1.dtd">
<struts>
<package
name="default" extends="struts-default"
>
<action name="login"
class="com.ankit.web.UserLogin" method="login" >
<result>index.vm</result>
</action>
</package>
</struts>
7. index.jsp
<%@
page language="java"
contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<%@taglib uri="/struts-tags" prefix="s"
%>
<%@taglib uri="http://velocity.apache.org/velocity-view" prefix="velocity"
%>
<!DOCTYPE
html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<s:form
action="login" >
<s:textfield name="name"
label="Name" labelSeparator=":-"
></s:textfield>
<s:textfield name="Email"
label="Email" labelSeparator=":-"
></s:textfield>
<s:submit></s:submit>
</s:form>
</body>
</html>
8. index.vm
#set($a="Welcome")
$a
<b>$name</b>
<br>
Your
Email is <b>$email</b>
<br>
Generated
Random Number is in RED
#set($i=10)
#foreach($i in [1..10])
<b
#if($i==$random)
style="color:red;"
#else
style="color:green;"
#end
>$i</b>
#set($i=$i+1)
#end
<br>Check
if user is Admin
#if($name=="Admin")
<b>User
is Admin</b>
#end
Output:-
Page1
Page2
Download:-
