关于ant打包java app,把lib/*.jar打包到 压缩包里的lib/目录下。

怎么ant打包，所有的.jar总是打在根目录下，想打到lib/*.jar下。应该怎么修改build.xml?<?xml version="1.0" encoding="UTF-8"?>
    <project default="create_run_jar" name="Create Runnable Jar ">  
        <!--ANT 1.7 is required    -->  
        <target name="create_run_jar">  
            <jar destfile="appdemo1.jar"> 
                <manifest>  
                    <attribute name="Main-Class" value="appdemo.Main"/>        
                    <attribute name="Class-Path" value="."/>  
                </manifest> 
                <fileset dir="bin"/>  
<zipfileset excludes="META-INF/*.SF" includes="commons-beanutils-1.7.0.jar"/>
<zipfileset excludes="META-INF/*.SF" includes="commons-collections-3.2.1.jar"/>
<zipfileset excludes="META-INF/*.SF" includes="commons-io-2.5.jar"/>
<zipfileset excludes="META-INF/*.SF" includes="commons-lang-2.3.jar"/>
<zipfileset excludes="META-INF/*.SF" includes="commons-logging-1.1.1.jar"/>
<zipfileset excludes="META-INF/*.SF" includes="dom4j-1.6.1.jar"/>
<zipfileset excludes="META-INF/*.SF" includes="ezmorph-1.0.3.jar"/>
<zipfileset excludes="META-INF/*.SF" includes="json-lib-2.2.3-jdk15.jar"/>
<zipfileset excludes="META-INF/*.SF" includes="jsoup-1.7.2.jar"/>
<zipfileset excludes="META-INF/*.SF" includes="mysql-connector-java-5.1.44-bin.jar"/>
<zipfileset excludes="META-INF/*.SF" includes="poi-3.8-20120326.jar"/>
<zipfileset excludes="META-INF/*.SF" includes="poi-ooxml-3.8-20120326.jar"/>
<zipfileset excludes="META-INF/*.SF" includes="poi-ooxml-schemas-3.8-20120326.jar"/>
<zipfileset excludes="META-INF/*.SF" includes="sqlitejdbc-v033-nested.jar"/>
<zipfileset excludes="META-INF/*.SF" includes="sqlitejdbc-v056.jar"/>
<zipfileset excludes="META-INF/*.SF" includes="stax-api-1.0.1.jar"/>
<zipfileset excludes="META-INF/*.SF" includes="xmlbeans-2.3.0.jar"/>
            </jar>  
        </target>  
</project>