Could not parse mapping document from resource com/hib/Unit.hbm.xml

Hello!

I had created 3 pojo classes and 3 mapping files.

District.java
Unit.java
and Missing.java

District.hbm.xml
Unit.hbm.xml
Missing.hbm.xml

The primary key of District table is one of the composite primary keys in Unit table and Missing table.
Also primary key of Unit table is one of the composite primary keys in Missing table.

i am getting an error like ::org.hibernate.InvalidMappingException: Could not parse mapping document from resource com/hib/Unit.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
    <class name="com.hib.District" table="DISTRICT">
        <id name="distCd" type="int">
            <column name="dist_cd" />
            <generator class="assigned" />
        </id>
        <property name="distName" type="java.lang.String">
            <column name="dist_name" />
        </property>
        <one-to-one name="coll" class="com.hib.Collector" cascade="save-update"></one-to-one>
        <set name="miss" table="missing" cascade="all">
        <key column="dist_cd" not-null="true"></key>
        <one-to-many class="com.hib.Missing"></one-to-many>
        </set>
        <set name="units" table="UNIT" cascade="all">
        <key column="dist_cd" not-null="true"></key>
        <one-to-many class="com.hib.Unit"></one-to-many>
        </set>
        
    </class>
</hibernate-mapping>

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
    <class name="com.hib.Missing" table="missing">
       <composite-id name="mk">
       <key-many-to-one name="unitCd" column="unit_cd"></key-many-to-one>
       <key-many-to-one name="distCd" column="dist_cd"></key-many-to-one>
        <key-property name="firNo" column="fir_cd"></key-property>
       </composite-id> 
       
        <property name="name" type="java.lang.String">
            <column name="name" />
        </property>
        <property name="age" type="java.lang.String">
            <column name="age" />
        </property>
        <property name="gender" type="java.lang.String">
            <column name="gender" />
        </property>
        <many-to-one name="dist" class="com.hib.District" fetch="join">
            <column name="dist_cd" />
        </many-to-one>
        <many-to-one name="unit" class="com.hib.Unit" fetch="join">
            <column name="unit_cd" />
        </many-to-one>
    </class>
</hibernate-mapping>

package com.main;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import java.util.*;

import com.hib.District;
import com.hib.Missing;
import com.hib.Unit;

public class MissingTransaction {

public static void main(String[] args) {

Session session=null;
			try{
				Configuration cfg=new Configuration().configure();
				SessionFactory sf=cfg.buildSessionFactory();
				session=sf.openSession();
				
				District dist=new District();
				dist.setDistCd(2);
				dist.setDistName("Vizianagaram");
				
				Set<Unit> units=new HashSet<Unit>();
				Unit unit1=new Unit();
				
				unit1.setUnitCd(1);
				unit1.setUnitName("Vizianagaram I town");
				units.add(unit1);
				
				Unit unit2=new Unit();
				
				unit2.setUnitCd(1);
				unit2.setUnitName("Vizianagaram I town");
				units.add(unit2);
				dist.setUnits(units);
				Set<Missing> missing1=new HashSet<Missing>();
				Set<Missing> missing2=new HashSet<Missing>();
				Missing miss1=new Missing();
				miss1.setFirNo("12/2013");
				miss1.setName("Raja Rao");
				miss1.setAge(23);
				miss1.setGender("Male");
				missing1.add(miss1);
				
				Missing miss2=new Missing();
				miss2.setFirNo("12/2013");
				miss2.setName("Raja Rao");
				miss2.setAge(23);
				miss2.setGender("Male");
				missing1.add(miss2);
				
				Missing miss3=new Missing();
				miss3.setFirNo("12/2013");
				miss3.setName("Roja Rani");
				miss3.setAge(25);
				miss3.setGender("Female");
				missing2.add(miss3);
				
				unit1.setMiss(missing1);
				unit2.setMiss(missing2);
				
				miss1.setUnit(unit1);
				miss2.setUnit(unit1);
				miss3.setUnit(unit2);
				
				miss1.setDist(dist);
				miss2.setDist(dist);
				miss3.setDist(dist);
				
				
				Transaction t=session.beginTransaction();
				
				session.save(dist);
				session.save(unit1);
				session.save(unit2);
				session.save(miss1);
				session.save(miss2);
				session.save(miss3);
				
				t.commit();
			}
			catch (Exception e) {
				System.out.println(e);
			}

}

Can you help me to avoid the error.....?