Question

Hi i am trying to build an ant script that copies a certain lib file based on a if condition. however it doesnt seem to work as i get this error:

build.xml:20: fileset doesn’t support the nested “if” element.

this is the part where it fails:

<target name="resolve">
        <delete dir="${lib.dir}">
            <include name="*" />
        </delete>

        <copy todir="${lib.dir}">
            <fileset dir="ext-libs" >
                <if name="${release}" value="true">
                    <include name="hello-client-[^DEBUG]*.jar" />
                </if>
                <else>
                    <include name="hello-client-*DEBUG.*.jar" />
                </else>

            </fileset>
        </copy>
    </target>

Answer 1

@JoseK is right. ANT filesets do not support nested “if” statements. In fact the “if” statement is not part of core ANT the recommended approach is to use conditional targets (See example)

@slipset is on the right track. Ivy configurations can be used to selectively choose your dependencies.

Example

This example is designed to be invoked in one of two ways

$ ant clean build
$ tree
.
|-- build.xml
|-- ivy.xml
`-- lib
    |-- slf4j-api-1.6.4.jar
    `-- slf4j-simple-1.6.4.jar

Or

$ ant -Drelease=1 clean build
$ tree
.
|-- build.xml
|-- ivy.xml
`-- lib
    |-- logback-classic-1.0.3.jar
    |-- logback-core-1.0.3.jar
    `-- slf4j-api-1.6.4.jar

build.xml

<project name="demo" default="build" xmlns:ivy="antlib:org.apache.ivy.ant">

    <target name="resolve">
        <ivy:resolve/>
    </target>

    <target name="retrieve-alt" depends="resolve" unless="release">
        <ivy:retrieve pattern="lib/[artifact]-[revision](-[classifier]).[ext]" conf="altruntime"/>
    </target>

    <target name="retrieve-release" depends="resolve" if="release">
        <ivy:retrieve pattern="lib/[artifact]-[revision](-[classifier]).[ext]" conf="runtime"/>
    </target>

    <target name="build" depends="retrieve-alt,retrieve-release"/>

    <target name="clean">
        <delete dir="lib"/>
    </target>

</project>

Notes:

• The if and unless clauses on the targets perform a conditional test on the existence of the “release” property.
• The ivy retrieve task uses a configuration to decide which jars should be used to populate the “lib” directory.
• The retrieve pattern includes a “classifier” pattern, just in case you ivy mapping pulls down additional Maven artifacts like the source or javadoc jars.

ivy.xml

<ivy-module version="2.0">
    <info organisation="com.myspotontheweb" module="demo"/>

    <configurations>
        <conf name="compile" description="Required to compile application"/>
        <conf name="runtime" description="Additional run-time dependencies" extends="compile"/>
        <conf name="altruntime"   description="Alternative 'runtime' configuration" extends="compile"/>
        <conf name="test"    description="Required for test only" extends="altruntime"/>
    </configurations>

    <dependencies>
        <!-- compile dependencies -->
        <dependency org="org.slf4j" name="slf4j-api" rev="1.6.4" conf="compile->default"/>

        <!-- runtime dependencies -->
        <dependency org="ch.qos.logback" name="logback-classic" rev="1.0.3" conf="runtime->default"/>

        <!-- altruntime dependencies -->
        <dependency org="org.slf4j" name="slf4j-simple" rev="1.6.4" conf="altruntime->default"/>

        <!-- test dependencies -->
        <dependency org="junit" name="junit" rev="4.10" conf="test->default"/>
    </dependencies>

</ivy-module>

Note:

• I would highly recommend always specifying a configuration mapping for each dependency. This will then map directly to how you intend to use the jars, for example populate a classpath.

Appendix

How to use ivy configurations

Ivy configurations can be used to emulate Maven scopes, but in fact an ivy configuration can represent any logical grouping of dependencies.

Here are the 3 standard classpaths required in any Java build:

<configurations>
    <conf name="compile" description="Required to compile application"/>
    <conf name="runtime" description="Additional run-time dependencies" extends="compile"/>
    <conf name="test"    description="Required for test only" extends="runtime"/>
</configurations>

Note the “extends” syntax that enables you to create larger sets. For example, the runtime set of jars also includes anything needed to compile the code your code.

Ivy configurations are difficult to understand until you realise that they can be used to selectively populate an ANT path:

<ivy:cachepath pathid="compile.path" conf="compile"/>

<javac ..... classpathref="compile.path"/>

Or used to selectively populate a directory

<ivy:retrieve pattern="build/WEB-INF/lib/[artifact].[ext]" conf="runtime"/>

Configuration mappings

Mappings are used to decide how groups of jars in your project relate to groups of jars in other projects.

This normally happens as follows:

<dependency org="org.slf4j" name="slf4j-api" rev="1.6.4" conf="compile->default"/>

Here our compile configuration is populate by the remote default configuration (normally the other modules compile dependencies)