Ant / Eclipse complains about artifact:dependencies

I need to use XML to JSON lib in my war. I followed a tutorial explaining that dependencies are required in the project.

But when I add the following in my ant build.xml (the file used to create the war), Eclipse complains about the artifact:dependencies, seems like it does not like the :.I have the following error message:

The prefix artifact for element artifact:dependencies is not bound...

<artifact:dependencies filesetId="dependency.fileset"
    sourcesFilesetId="sources.dependency.fileset"
    javadocFilesetId="javadoc.dependency.fileset"
    versionsId="dependency.versions">
    <!-- DEPENCIES GO HERE -->
</artifact:dependencies>

Any idea ?

UPDATE

I have the same problem trying to define an in-memory pom with:

<artifact:pom id="mypom" groupId="org.acme" artifactId="project1" version="1.0">
   <dependency groupId="junit" artifactId="junit" version="4.1"/>
   <dependency groupId="org.codehaus.plexus" artifactId="plexus-utils" version="1.5.5"/>
   <license name="apache" url="http://www.apache.org"/>
</artifact:pom>

The prefix artifact for element artifact:pom is not bound...

UPDATE 2

I installed maven-ant jar in ant/lib and change the build.xml so it contains the definition of the artifact stuff but I have an error message while running it.

<project name="test" default="install" xmlns:artifact="antlib:org.apache.maven.artifact.ant">

<artifact:dependencies pathId="dependency.classpath">
   <dependency>
        <groupId>net.sf.json-lib</groupId>
        <artifactId>json-lib</artifactId>
        <version>2.3</version>
        <type>jar</type>
        <classifier>jdk15</classifier>
        <scope>compile</scope>
       </dependency>
       ...

The error message Eclipse gave is:

BUILD FAILED
D:\J2EE\workspace\Test\build.xml:3: Problem: failed to create task or type antlib:org.apache.maven.artifact.ant:dependencies
Cause: The name is undefined.
Action: Check the spelling.
Action: Check that any custom tasks/types have been declared.
Action: Check that any <presetdef>/<macrodef> declarations have taken place.
No types or tasks have been defined in this namespace yet
This appears to be an antlib declaration. 
    Action: Check that the implementing library exists in one of:
    -D:\eclipse\plugins\org.apache.ant_1.8.2.v20110505-1300\lib
    -C:\Documents and Settings\luc\.ant\lib
    -a directory added on the command line with the -lib argument

The maven-ant jar does exist in -D:\eclipse\plugins\org.apache.ant_1.8.2.v20110505-1300\lib

UPDATE 3

This is the build.xml file I'm using.

<!--
<project name="Monitoring" default="install" xmlns:artifact="urn:maven-artifact-ant" xmlns:test="urn:test-tasks">
-->
<project name="Monitoring" default="install" xmlns:artifact="antlib:org.apache.maven.artifact.ant">

<!-- project-specific variables -->
<property environment="env" />
<property name="project_home" value="D:\J2EE\workspace\Monitoring"/>
<property name="webapp.dir" value="${project_home}/target" />
<property name="jboss.dir" value="D:\J2EE\jboss\standalone\deployments" />  
<property name="package.name" value="monitoring.war" />
<property name="lib.dir" value="${project_home}/lib" />
<property name="src.dir" value="${project_home}/src" />
<property name="resources.dir" value="${project_home}/resources" />
<property name="dest.dir" value="${project_home}/target" />
<property name="package.file" value="${dest.dir}/${package.name}" />

<!-- put everything in a temp folder with the right structure during the build -->
<property name="temp.dir" value="${project_home}/temp" />
<property name="temp.dir.web-inf" value="${temp.dir}/WEB-INF" />
<property name="temp.dir.lib" value="${temp.dir.web-inf}/lib" />
<property name="temp.dir.classes" value="${temp.dir.web-inf}/classes" />
<property name="temp.dir.meta-inf" value="${temp.dir}/META-INF" />


<path id="build.class.path">
    <fileset dir="${env.JAVA_HOME}/lib">
        <include name="**/*.jar" />
    </fileset>
    <fileset dir="D:\ant\lib">
            <include name="**/*.jar" />
    </fileset>
</path>

<target name="deps">
    <artifact:dependencies pathId="dependency.classpath">
        <dependency>
            <groupId>net.sf.json-lib</groupId>
            <artifactId>json-lib</artifactId>
            <version>2.3</version>
            <type>jar</type>
            <classifier>jdk15</classifier>
            <scope>compile</scope>
        </dependency>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-io</artifactId>
            <version>1.3.2</version>
            <type>jar</type>
            <scope>compile</scope>
        </dependency>
        <dependency>
            <groupId>xom</groupId>
            <artifactId>xom</artifactId>
            <version>1.1</version>
        </dependency>
    </artifact:dependencies>
</target>

<target name="clean" depends="deps">
    <delete>
        <fileset dir="${dest.dir}" includes="**/*"/>
    </delete>
    <delete dir="${temp.dir}" />
    <delete dir="${temp.dir.classes}" />
    <delete dir="${temp.dir.meta-inf}" />
    <delete dir="${temp.dir.web-inf}" />
</target>

<target name="prepare" depends="clean">
    <mkdir dir="${dest.dir}" />
    <mkdir dir="${temp.dir}" />
    <mkdir dir="${temp.dir.lib}" />
    <mkdir dir="${temp.dir.meta-inf}" />
    <mkdir dir="${temp.dir.web-inf}" />
    <mkdir dir="${temp.dir.classes}" />
</target>

<!-- COMPILE -->
<target name="compile" depends="prepare">
    <echo>=== COMPILE ===</echo>
    <echo>Compiling ${src.dir} files ...</echo>
    <javac debug="on" srcdir="${src.dir}" destdir="${temp.dir.classes}" includes="**/*" includeantruntime="false">
        <classpath refid="build.class.path" />
        <classpath refid="dependency.classpath" />
    </javac>
</target>

<!-- PACKAGE -->
<target name="package" depends="compile">
  <echo>=== PACKAGE ===</echo>

  <!-- copy the config files -->
  <copy file="${resources.dir}/web.xml" tofile="${temp.dir.web-inf}/web.xml" overwrite="true" />
  <copy file="${resources.dir}/manifest.mf" tofile="${temp.dir.meta-inf}/manifest.mf" overwrite="true" />
  <copy todir="${temp.dir.classes}">
    <fileset dir="${src.dir}">
      <include name="**/*.xml"/>
      <include name="**/*.xsl"/>
    </fileset>
  </copy>

  <!-- the ant war task. with all resources in place, create the war file -->
  &l开发者_开发技巧t;war destfile="${package.file}" webxml="${temp.dir.web-inf}/web.xml" basedir="${temp.dir}">
    <lib dir="${lib.dir}" />
    <classes dir="${temp.dir.classes}" />
  </war>
</target>

<!-- INSTALL -->
<target name="install" depends="package">
  <echo>=== INSTALL ===</echo>
  <copy file="${package.file}" tofile="${webapp.dir}/${package.name}" overwrite="true" />
  <copy file="${package.file}" tofile="${jboss.dir}/${package.name}" overwrite="true" />        
</target>

</project>

It was working well before I added all the dependencies stuff... still cannot find out the pb here. Any help would be very welcome.

---

It looks like you're making use of Maven Ant Tasks. To do this you'll need a copy of the jar from the download area here. Once (or if) you've got that, you'll need to modify your buildfile to use it.

The main things that are needed are to define the artifact namespace, and add the typedef for the ant-lib:

<project name="foo" default="foo" xmlns:artifact="antlib:org.apache.maven.artifact.ant">

  <path id="maven-ant-tasks.classpath" path="lib/maven-ant-tasks-2.1.3.jar" />
  <typedef resource="org/apache/maven/artifact/ant/antlib.xml"
       uri="antlib:org.apache.maven.artifact.ant"
       classpathref="maven-ant-tasks.classpath" />

---

I had the same error message but the cause was different.

Going to Window -> Preferences -> Ant -> Runtime and setting Ant Home solved my problem.

So for anyone that above solution doesn't work, check if "Ant Home" is pointing to the right direction