I'm running Jboss4.2.0

Composite Primary Key Class:

package com.foshanshop.ejb3.bean;
import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Embeddable;

@SuppressWarnings("serial")
@Embeddable
public class AirtLinePK implements Serializable {
 private String leavecity;
 private String arrivecity;

 public AirtLinePK(){}

 public AirtLinePK(String leavecity, String arrivecity) {
 this.leavecity = leavecity;
 this.arrivecity = arrivecity;
 }

 @Column(nullable=false,length=3,name="LEAVECITY")
 public String getLeavecity() {
 return leavecity;
 }
 public void setLeavecity(String leavecity) {
 this.leavecity = leavecity;
 }

 @Column(nullable=false,length=3,name="ARRIVECITY")
 public String getArrivecity() {
 return arrivecity;
 }
 public void setArrivecity(String arrivecity) {
 this.arrivecity = arrivecity;
 }

 public boolean equals(Object o) {
 if (this == o) return true;
 if (!(o instanceof AirtLinePK)) return false;

 final AirtLinePK airtLinePK = (AirtLinePK) o;

 if (!leavecity.equals(airtLinePK.getLeavecity())) return false;
 if (!arrivecity.equals(airtLinePK.getArrivecity())) return false;
 return true;

 }
 public int hashCode() {
 int result;
 result = leavecity.hashCode();
 result = 29 * result + arrivecity.hashCode();
 return result;
 }
}

package com.foshanshop.ejb3.bean;
import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;
import javax.persistence.CascadeType;
import javax.persistence.EmbeddedId;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.OneToMany;
import javax.persistence.OrderBy;
import javax.persistence.Table;

@SuppressWarnings("serial")
@Entity
@Table(name = "AirLine")
public class AirLine implements Serializable {

 private AirtLinePK id;
 private Boolean onoff;

 public AirLine(){}

 public AirLine(AirtLinePK id, Boolean onoff){
 this.id = id;
 this.onoff = onoff;
 }

 @EmbeddedId
 public AirtLinePK getId() {
 return id;
 }
 public void setId(AirtLinePK id) {
 this.id = id;
 }

 public Boolean getOnoff() {
 return onoff;
 }

 public void setOnoff(Boolean onoff) {
 this.onoff = onoff;
 }
}

Session bean:

package com.foshanshop.ejb3.impl;
import javax.ejb.Remote;
import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.Query;
import com.foshanshop.ejb3.AirLineDAO;
import com.foshanshop.ejb3.bean.AirLine;
import com.foshanshop.ejb3.bean.AirtLinePK;

@Stateless
@Remote ({AirLineDAO.class})
public class AirLineDAOBean implements AirLineDAO {
 @PersistenceContext
 protected EntityManager em;

 public Long getAirLineTotal() {
 Query query = em.createQuery("select count(a) from AirLine a where a.id.leavecity =?1 and a.id.arrivecity=?2");
 query.setParameter(1, "PEK");
 query.setParameter(2, "CAN");
 return query.getSingleResult();
 }
}

Jboss Log print Error:

2007-04-12 21:03:24,031 DEBUG [org.hibernate.util.JDBCExceptionReporter] could not execute query [select count((airline0_.LEAVECITY, airline0_.ARRIVECITY)) as col_0_0_ from AirLine airline0_ where airline0_.LEAVECITY=? and airline0_.ARRIVECITY=?]
java.sql.SQLException: Operand should contain 1 column(s)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2975)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1600)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1695)
at com.mysql.jdbc.Connection.execSQL(Connection.java:3004)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1128)
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1222)

above code run in Toplink, it work fine
I am using following code in jboss,it work fine:

Query query = em.createQuery("select count(a.id.leavecity) from AirLine a where a.id.leavecity =?1 and a.id.arrivecity=?2");