@NamedQuery(query = "Select e from Employee e where e.eid = :id", 
name = "find employee by id")
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.NamedQuery;
import javax.persistence.Table;

@Entity
@Table
@NamedQuery(query = "Select e from Employee e where e.eid = :id",
name = "find employee by id")
public class Employee
{
@Id
@GeneratedValue(strategy= GenerationType.AUTO)
private int eid;
private String ename;
private double salary;
private String deg;
public Employee(int eid, String ename, double salary, String deg)
{
super( );
this.eid = eid;
this.ename = ename;
this.salary = salary;
this.deg = deg;
}
public Employee( )
{
super();
}

public int getEid( )
{
return eid;
}
public void setEid(int eid)
{
this.eid = eid;
}

public String getEname( )
{
return ename;
}
public void setEname(String ename)
{
this.ename = ename;
}

public double getSalary( )
{
return salary;
}
public void setSalary(double salary)
{
this.salary = salary;
}

public String getDeg( )
{
return deg;
}
public void setDeg(String deg)
{
this.deg = deg;
}
@Override
public String toString() {
return "Employee [eid=" + eid + ", ename=" + ename + ", salary="
+ salary + ", deg=" + deg + "]";
}
}

实体类之间的关系如下:

@ManyToOne 关系
@OneToMany 关系
@OneToOne 关系
@ManyToMany 关系