What is the build.xml Required by Apache Ant?

The build.xml file required by Apache Ant is XML file that contains instructions to build final targets using system commands and source files.

Here is a tutorial on how to create a build.xml file and use "ant" to build a simple Java project.

1. Create a build.xml as shown below:

> type build.xml 

<?xml version="1.0" encoding="UTF-8"?>
 <!-- Set the project name, basedir and default target to be executed-->
<project name="Ant-Build-Project-Test" default="mainTarget" basedir=".">

  <!-- Sets the properties here-->
  <property name="src.dir" location="src" />
  <property name="build.dir" location="bin" />
 
  <!-- Target for deleting the existing directories-->
  <target name="clean">
    <delete dir="${build.dir}" />
  </target>
 
  <!-- Target for creating the new directories-->
  <target name="makedir">
    <mkdir dir="${build.dir}" />
  </target>
 
  <!-- Target for compiling the java code-->
  <target name="compile" depends="clean, makedir">
    <javac srcdir="${src.dir}" destdir="${build.dir}">
    </javac>  
  </target>
 
  <!-- Defualt target to run all targets-->
  <target name="mainTarget" depends="compile">
    <description>Main target</description>
  </target>

</project>

2. Verify your Apache Ant installation:

> \local\ant\bin\ant.bat -version 

Apache Ant(TM) version 1.10.10 compiled on April 12 2021

3. Run the default target defined in the build.xml. The build process will fail, because there is no "src" sub-directory and Java source code to compile.

> \local\ant\bin\ant.bat 

Buildfile: \Users\fyicenter\build.xml

clean:

makedir:
    [mkdir] Created dir: \Users\fyicenter\bin

compile:
    [javac] build.xml:21: warning: 'includeantruntime' was not set, 
  defaulting to build.sysclasspath=last; set to false for repeatable builds

BUILD FAILED
  build.xml:21: srcdir "\Users\fyicenter\src" does not exist!

Total time: 0 seconds

4. Run the default target again with a sample Java source code.

> mkdire src 
> edit src\Hello.java 

public class Hello {
   public static void main(String[] args) {
      System.out.println("Hello world!");
   }
}

> \local\ant\bin\ant.bat 
Buildfile: build.xml

clean:
   [delete] Deleting directory bin

makedir:
    [mkdir] Created dir: bin

compile:
    [javac] Compiling 1 source file to bin

mainTarget:

BUILD SUCCESSFUL
Total time: 0 seconds

5. Verify the build result:

> dir bin 
336   Hello.class

> java -cp bin Hello 
Hello world!

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