package  object;
@Entity
 public   class  Client {
    
     private   int  id;
     private   int  name;

    @Id
     public   int  getId() {  return  id; }
     public   int  getName() {  return  name; }
    ...
}

 package  object;
@Entity
 public   class  Entry {
    
     private   int  id;
     private  Client client;

    @Id
     public   int  getId() {  return  id; }
    @ManyToOne
    @JoinColumn(name="client_id")
     public  Client getName() {  return  client; }
    ...
}

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence">
	<persistence-unit name="unit">
	    <jta-data-source>java:/datasource</jta-data-source>
	    < class >object.Client</ class >
	</persistence-unit>
</persistence>