Until you run the Apache Velocity sample code

I will write it as a memo for myself. I made it because I wanted an environment to check the behavior of Velocity while reading the official website.

I built the environment with the feeling that "If Velocity works, it's OK", so I'd be happy if you could point out any mistakes.

Things necessary

--Tomcat 9 (Servlet container) --Eclipse (Integrated Development Environment)

Complete source code

This is a Git repository with a set of source code created by following the steps below. https://github.com/vicboss1002/velocity_sample

procedure

Install Tomcat
Set Tomcat as a server in Eclipse
Create a Maevn project in Eclipse
Download dependent libraries with Maven
Display the Velocity template file in your browser
Pass variables from Java to the Velocity context for display

Install tomcat

I downloaded and installed ** 32-bit / 64-bit Windows Service Installer ** from the following site. https://tomcat.apache.org/download-90.cgi

Set Tomcat as a server in Eclipse

Open ** Window> Preferences> Server> Runtime Environment **

Create a Maven project in Eclipse

Select ** File> New> Maven Project **
Select maven-archetype-webapp in ** Select an Archetype **
Specify ** GroupId **, ** ArtifactId ** and create Maven project

Download dependent libraries with Maven

In ** pom.xml **, specify the following for the dependent library

`pom.xml`


<dependency>
	<groupId>javax.servlet</groupId>
	<artifactId>javax.servlet-api</artifactId>
	<version>4.0.0</version>
</dependency>
<dependency>
	<groupId>org.apache.velocity.tools</groupId>
	<artifactId>velocity-tools-generic</artifactId>
	<version>3.0</version>
</dependency>
<dependency>
	<groupId>org.apache.velocity.tools</groupId>
	<artifactId>velocity-tools-view</artifactId>
	<version>3.0</version>
</dependency>
<dependency>
	<groupId>org.apache.velocity.tools</groupId>
	<artifactId>velocity-tools-view-jsp</artifactId>
	<version>3.0</version>
</dependency>
<dependency>
	<groupId>com.republicate</groupId>
	<artifactId>webapp-slf4j-logger</artifactId>
	<version>1.3</version>
</dependency>

Run ** Project> Run As> Maven build **

Display Velocity template file in browser

Add ** VelocityViewServlet ** settings to web.xml Add the ** VelocityViewServlet ** settings to web.xml based on the description in here.

`web.xml`


<!--Log output settings-->
<context-param>
	<param-name>webapp-slf4j-logger.level</param-name>
	<param-value>debug</param-value>
</context-param>
<context-param>
	<param-name>webapp-slf4j-logger.format</param-name>
	<param-value>%logger [%level] [%ip] %message</param-value>
</context-param>
<servlet>
	<servlet-name>velocity</servlet-name>
	<servlet-class>
		org.apache.velocity.tools.view.VelocityViewServlet
	</servlet-class>

	<!-- Unless you plan to put your tools.xml and velocity.properties under 
		different folders or give them different names, then these two init-params 
		are unnecessary. The VelocityViewServlet will automatically look for these 
		files in the following locations. -->
	<init-param> 
		<param-name>org.apache.velocity.toolbox</param-name> 
		<param-value>/WEB-INF/tools.xml</param-value> 
	</init-param> 
	<init-param> 
		<param-name>org.apache.velocity.properties</param-name> 
		<param-value>/WEB-INF/velocity.properties</param-value> 
	</init-param>
</servlet>

<!-- Map *.vm files to Velocity -->
<servlet-mapping>
	<servlet-name>velocity</servlet-name>
	<url-pattern>*.vm</url-pattern>
</servlet-mapping>

Create a template file directly under ** project root> src **

`sample.vm`


#set($text = "Velocity World!")
Hello $text

Launch Tomcat from the ** Servers ** view of Eclipse
Display and confirm ** sample.vm ** via the browser Enter http: // localhost: 8080 / velocity_sample / sample.vm in the URL of the browser to display it.

That's it. It was confirmed that the Velocity process described in ** sample.vm ** was executed and the contents were displayed.

Pass variables from Java to Velocity context for display

Create a subclass of VelictyViewServlet.

`MyVelocityViewServlet.java`


public class MyVelocityViewServlet extends VelocityViewServlet {
	private static final long serialVersionUID = 1L;
    protected Template handleRequest(HttpServletRequest request,
            HttpServletResponse response,
            Context ctx)
	{

    	ctx.put("boolTrue", true);
    	ctx.put("boolFalse", false);
    	ctx.put("number", 1234);
    	ctx.put("string", "abcd");
    	ctx.put("list", Arrays.asList("a", "b", "c", "d"));
    	
    	Map<String, String> map = new HashMap<>();
    	map.put("key1", "value1");
    	map.put("key2", "value2");
    	ctx.put("map", map);
    	return super.handleRequest(request, response, ctx);
	}
}

Rewrite web.xml for the VelictyViewServlet subclass as follows:

`web.xml`


<servlet>
	<servlet-name>velocity</servlet-name>
<!-- 		<servlet-class> -->
<!-- 			org.apache.velocity.tools.view.VelocityViewServlet -->
<!-- 		</servlet-class> -->
	<servlet-class>velocity_sample.MyVelocityViewServlet</servlet-class>

	<!-- Unless you plan to put your tools.xml and velocity.properties under 
		different folders or give them different names, then these two init-params 
		are unnecessary. The VelocityViewServlet will automatically look for these 
		files in the following locations. -->
	<init-param>
		<param-name>org.apache.velocity.toolbox</param-name>
		<param-value>/WEB-INF/tools.xml</param-value>
	</init-param>
	<init-param>
		<param-name>org.apache.velocity.properties</param-name>
		<param-value>/WEB-INF/velocity.properties</param-value>
	</init-param>
</servlet>

Create a template file that calls the variables set from Java

`sample_of_context.vm`


\${boolTrue}: ${boolTrue}<br/>
\${boolFalse}: ${boolFalse}<br/>
\${number}: ${number}<br/>
\${string}: ${string}<br/>
\${list}: ${list}<br/>
\${map}: ${map}<br/>

The output is as follows.