Apache Ant Custom Components

Ant allows us to create custom components according to our requirement. The custom components can be condition, filter, selector etc, and are defined outside the ant core api.

The custom components behave like Ant core components.

The custom components are the normal Java classes which can implement classes and interface. It looks like writing a custom task which defines attributes by setter and getter methods.

The <typedef> element is used to implement the custom components into the Ant core.

Creating Custom Component

It is a three phase process. First create a Java class then define <typedef> element and after that use it within build file.

Example

Create a Java class for condition.

package com.javatpoint;
import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.taskdefs.condition.Condition;
public class AllUpperCaseCondition implements Condition {
    private String value;
    // The setter for the "value" attribute
    public void setValue(String value) {
        this.value = value;
    }
    // This method evaluates the condition
    public boolean eval() {
        if (value == null) {
            throw new BuildException("value attribute is not set");
        }
        return value.toUpperCase().equals(value);
    }
}

Now define <typedef> by specifying Java class.

<typedef name="alluppercase" classname="com.javatpoint.AllUpperCaseCondition"
			     classpath="test.com.javatpoint"/>

By doing this, we have successfully created a custom element <alluppercase> which further can be used in our project. See the build.xml file.

// build.xml

<project name="java-ant project" default="abc">	
	<typedef name="alluppercase" classname="com.javatpoint.AllUpperCaseCondition"
			     classpath="test.com.javatpoint"/>
	<target name="abc" >
		<condition property="allupper">
    		<alluppercase value="THIS IS ALL UPPER CASE"/>
		</condition>	
	</target>
</project>

Custom Selector

In the above example, we created a custom condition element.Now we will create a custom selector.Selectors are datatypes and to create custom selector, it must implement

org.apache.tools.ant.types.selectors.FileSelector interface. This interface has a single method isSeletected(File basedir, String filename, File file) which must be overridden. An example of custom selector is given below.

// Java Class

package com.javatpoint;
import java.io.File;
import org.apache.tools.ant.types.selectors.FileSelector;
public class JavaSelector implements FileSelector {
    public boolean isSelected(File b, String filename, File f) {
        return filename.toLowerCase().endsWith(".java");
    }
}

// Type Defining

<typedef name="javaselector" classname="com.javatpoint.JavaSelector"
    		classpath="test"/>

// build.xml

<project name="java-ant project" default="abc">	
	<target name="abc">
		<typedef name="javaselector" classname="com.javatpoint.JavaSelector"
    		classpath="test"/>
    	<copy todir="destdir">
    		<fileset dir="src">
        		<javaselector/>
    		</fileset>
		</copy>
    </target>
</project>

Same like, we can create custom filters as well.

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