myeclipse中Web App Libraries无法自动识别lib下的jar包

<natures>
        <nature>org.eclipse.jem.workbench.JavaEMFNature</nature>
        <nature>com.genuitec.eclipse.ast.deploy.core.deploymentnature</nature>
        <nature>com.genuitec.eclipse.j2eedt.core.webnature</nature>
        <nature>org.eclipse.jdt.core.javanature</nature>
        <nature>org.eclipse.wst.jsdt.core.jsNature</nature>
        <nature>org.eclipse.wst.common.project.facet.core.nature</nature>
        <nature>org.eclipse.wst.common.modulecore.ModuleCoreNature</nature>
</natures>

<?xml version="1.0" encoding="UTF-8"?>
<project-modules id="moduleCoreId" project-version="1.5.0">
    <wb-module deploy-name="工程名">
        <wb-resource deploy-path="/" source-path="/WebRoot"/>
        <wb-resource deploy-path="/WEB-INF/classes" source-path="/src"/>
        <property name="context-root" value="/工程名"/>
        <property name="Java-output-path" value="/工程名/WebRoot/WEB-INF/classes"/>
    </wb-module>
</project-modules>