[JAVA] Until you run the Apache Velocity sample code

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

1. Install Tomcat
2. Set Tomcat as a server in Eclipse
3. Create a Maevn project in Eclipse
4. Download dependent libraries with Maven
5. Display the Velocity template file in your browser
6. 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

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

Create a Maven project in Eclipse

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

Download dependent libraries with Maven

1. 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>

2. Run ** Project> Run As> Maven build **

Display Velocity template file in browser

1. 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>

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

sample.vm

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

3. Launch Tomcat from the ** Servers ** view of Eclipse

4. 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

1. 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);
	}
}

2. 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>

3. 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.