在项目的根目录下我创建了build.xml文件，内容如下：

<?xml version="1.0" encoding="utf-8"?>
<project name="hibernate" default="schema" basedir=".">
    <!--定义一些属性-->
    <!--<property name="dir.lib" value="/Users/liaowenxiong/.m2/repository"/>-->
    <property name="dir.lib" value="/Users/liaowenxiong/.m2/repository"/>
    <property name="dir.src" value="/Users/liaowenxiong/Documents/IdeaProjects/hibernate-basic/src/main/java"/>
    <property name="dir.classes" value="/Users/liaowenxiong/Documents/IdeaProjects/hibernate-basic/target/classes
"/>
    <!--定义Build路径-->
    <path id="cp">
        <!--定义一組文件-->
        <fileset dir="${dir.lib}">
            <include name="**/*.jar"/>
        </fileset>
        <!--定义一个目录-->
        <pathelement path="${dir.classes}"/>
    </path>
    <target name="t1">
        <!--ANT Task 1-->
        <copy todir="note">
            <fileset dir="src/main/resources">
                <include name="**/*.properties"/>
            </fileset>
        </copy>
    </target>
    <target name="t2">
        <!--ANT Task 2-->
        <delete dir="note"/>
        <mkdir dir="note"/>
        <native2ascii encoding="gbk" src="src/main/resources" dest="note" includes="**/*.txt"/>
    <taskdef name="hibernatetool" classname="org.hibernate.tool.ant.HibernateToolTask" classpathref="cp"/>
    </target>
    <target name="schema">
        <hibernatetool destdir=".">
            <classpath refid="cp"/>
            <configuration configurationfile="${dir.classes}/hibernate.cfg.xml"/>
            <hbm2ddl
                    drop="true"
                    create="true"
                    console="true"
                    export="true"
                    outputfilename="schema.sql"
                    delimiter=";"
                    format="true"/>
        </hibernatetool>
    </target>
</project>

但是标签<taskdef>和<hibernatetool>报错，无法识别。为什么？