Hello World Java Web Application in Eclipse (Part 3)

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Building with ANT and Deploying to Tomcat

Download .war and full source code of this and other sample Java Web Applications here.

This is the third of a three part series of tutorials that shows how to create a Hello World Java Web Application in Eclipse. In Part 1, I demonstrate how to create your Java Web Application project in Eclipse and set up the directory structure of the project. In Part 2, I take you through getting the Java jar needed to code Java servlets, creating a Java Servlet and a JSP file, configuring the web.xml and build.xml files. In this part, I show how to build the project with ANT using the build.xml file and how to deploy the project to a Tomcat server running on your development computer. Along the way, I point out a few tips and tricks for using the Eclipse EE IDE.



Step 1: Understand the build.xml file. After Part 2, we have a Hello World Java Web Application project in Eclipse named HelloWebApp with the build.xml file shown below. The build file is used by ANT to take all the source code and configuration files in the Web App project, compile them, and package them in a .war file, which Tomcat needs to run your application.



build.xml

<?xml version="1.0"?>
<project name="hello" default="deploy_local" basedir=".">

<property file="build.properties"/>

<path id="classpath">
<fileset dir="${lib.dir}" includes="servlet-api.jar"/>
</path>

<target name="clean">
<echo>Cleaning the ${build.dir}</echo>
<delete dir="${build.dir}"/>
<delete dir="${dist.dir}"/>
</target>

<target name="init" depends="clean">
<echo>Creating the build directory</echo>
<mkdir dir="${build.dir}/WEB-INF/classes"/>
<mkdir dir="${build.dir}/WEB-INF/lib"/>
<mkdir dir="${dist.dir}"/>
</target>

<target name="compile" depends="init">
<echo>Compile the source files</echo>
<javac srcdir="${src.dir}" destdir="${build.dir}/WEB-INF/classes">
<classpath refid="classpath"/>
</javac>
</target>

<target name="copy" depends="compile">
<copy todir="${build.dir}/WEB-INF">
<fileset dir="${web.dir}/WEB-INF"/>
</copy>
<copy todir="${build.dir}">
<fileset dir="${web.dir}"/>
</copy>
<copy todir="${build.dir}/WEB-INF/lib">
<fileset dir="${lib.dir}">
<exclude name="servlet-api.jar"/>
</fileset>
</copy>
</target>

<target name="war" depends="copy">
<echo>Building the war file</echo>
<war destfile="${dist.dir}/${project.name}.war" webxml="${build.dir}/WEB-INF/web.xml">
<fileset dir="${build.dir}"/>
</war>
</target>

<target name="deploy_local" depends="war">
<echo>Deploying .war to local Tomcat</echo>
<copy todir="${tomcat.dir}">
<fileset dir="${dist.dir}">
<include name="${project.name}.war"/>
</fileset>
</copy>
</target>

</project>

build.properties

project.name=HelloWebApp
lib.dir=lib
src.dir=src
web.dir=web
build.dir=build
dist.dir=dist
tomcat.dir=/Library/Tomcat/webapps

The build file consists of several targets and a properties file and classpath definition. The ANT builder, which comes bundled with Eclipse parses this file and carries out the instructions defined within it. Here, I'll go through the file step-by-step and explain what the ANT builder does.

Line 2: The "deploy_local" target is the default target and will be implemented first. The "basedir", where all the paths will be relative to is defined as "." meaning the directory where the build.xml file is found.

Line 4: The properties file "build.properties" is imported by ANT and stores certain key value pairs used for the build. Mostly directory names and paths are defined in the properties file.

Line 6: The jars in the classpath are used by ANT when compiling the Java source code.

Line 51: Let's skip down to this line because ANT starts with this target because it is defined as the default target. This target depends on the "war" target, which depends on the "copy" target, which depends on the "compile" target, which depends on the "init" target, which depends on the "clean" target. So actually, this means the "clean" target will be implemented first, then the "init" and so on...

Line 10: The "echo" element just prints out to the console what you tell it to. In this case, "Cleaning the ${build.dir}", where "${build.dir}" is replaced with the value "build" from the build.properties file, and "Cleaning the build" is printed out. The "delete" elements delete the "build" and "dist" folders in the project if they exist.

Line 16: The "init" target creates 3 folders in the project: "build/WEB-INF/classes", "build/WEB-INF/lib", and "dist".

Line 23: The "compile" target compiles all the java files found in the src folder and puts them in the "build/WEB-INF/classes" folder. It uses the jars defined on the classpath on line 6.

Line 30: The "copy" target moves files from the "web" and "lib" folders to the "build" folder.

Line 39: We don't copy over the servlet-api.jar because the Tomcat server already contains this jar. After all, that we're the jar came from in the first place.

Line 44: The "war" target takes everything in the "build folder", makes a WAR file and puts it in the "dist" folder.

Line 53: Inside the "deploy_local" target, the war is copied from the "dist" folder to the "/Library/Tomcat/webapps" folder, which is where the Tomcat installation resides.

Step 2: Run ANT to build the project. Right-click on build.xml and choose Run As --> Ant Build.



Here's what your new HelloWebApp Java project should now look like in the Eclipse Package Explorer View after the ANT build:



Step 3: Startup Tomcat. Now that the Tomcat installation has the WAR file in it's webapps folder, you need to start Tomcat up so it runs the web app. To do this, fire up the terminal and type: "sh /Library/Tomcat/bin/startup.sh". If you're using a non-UNIX-based computer (Windows), you have to start the startup.bat file instead, remove the sh at the front of the command, and adjust your path appropriately.

Step 4: Check out your web application in action. Point your browser to http://127.0.0.1:8080/HelloWebApp/ . You should see the Hello Web App web application in it's full glory!





Piece of Cake!!

Download .war and full source code of this and other sample Java Web Applications here.
Hello World Java Web Application in Eclipse (Part 1)
Hello World Java Web Application in Eclipse (Part 2)

See Also:
Java Ant - Build Jar with Auto-Incrementing Build Number
Java Ant - Build .War file with Auto-Incrementing Build Number