jpa复合主键的使用

AirLinePk复合主键类

  

   package
    com.ljq.entity;


   import
    javax.persistence.Column;

   import
    javax.persistence.Embeddable;


   /**
   
 * 使用复合主键要满足的条件
 * 
 * 1、要实现序列化 2、提供默认的构造方法 3、实现hashCope
 * 
 * 
   @author
    Administrator
 * 
 
   */
   

@SuppressWarnings(
   "
   serial
   "
   )
@Embeddable 
   //
   embeddable: 可嵌入的
   

   public
    
   class
    AirLinePk 
   implements
    java.io.Serializable {
 @Column(length 
   =
    
   3
   )
 
   private
    String startCity;
   //
    出发城市
   

   
 @Column(length 
   =
    
   3
   )
 
   private
    String endCity;
   //
    抵达城市
   

   
 
   public
    AirLinePk() {
 
   super
   ();
 }

 
   public
    AirLinePk(String startCity, String endCity) {
 
   super
   ();
 
   this
   .startCity 
   =
    startCity;
 
   this
   .endCity 
   =
    endCity;
 }

 
   public
    String getEndCity() {
 
   return
    endCity;
 }

 
   public
    
   void
    setEndCity(String endCity) {
 
   this
   .endCity 
   =
    endCity;
 }

 
   public
    String getStartCity() {
 
   return
    startCity;
 }

 
   public
    
   void
    setStartCity(String startCity) {
 
   this
   .startCity 
   =
    startCity;
 }

 @Override
 
   public
    
   int
    hashCode() {
 
   final
    
   int
    PRIME 
   =
    
   31
   ;
 
   int
    result 
   =
    
   1
   ;
 result 
   =
    PRIME 
   *
    result 
   +
    ((endCity 
   ==
    
   null
   ) 
   ?
    
   0
    : endCity.hashCode());
 result 
   =
    PRIME 
   *
    result
 
   +
    ((startCity 
   ==
    
   null
   ) 
   ?
    
   0
    : startCity.hashCode());
 
   return
    result;
 }

 @Override
 
   public
    
   boolean
    equals(Object obj) {
 
   if
    (
   this
    
   ==
    obj)
 
   return
    
   true
   ;
 
   if
    (obj 
   ==
    
   null
   )
 
   return
    
   false
   ;
 
   if
    (getClass() 
   !=
    obj.getClass())
 
   return
    
   false
   ;
 
   final
    AirLinePk other 
   =
    (AirLinePk) obj;
 
   if
    (endCity 
   ==
    
   null
   ) {
 
   if
    (other.endCity 
   !=
    
   null
   )
 
   return
    
   false
   ;
 } 
   else
    
   if
    (
   !
   endCity.equals(other.endCity))
 
   return
    
   false
   ;
 
   if
    (startCity 
   ==
    
   null
   ) {
 
   if
    (other.startCity 
   !=
    
   null
   )
 
   return
    
   false
   ;
 } 
   else
    
   if
    (
   !
   startCity.equals(other.startCity))
 
   return
    
   false
   ;
 
   return
    
   true
   ;
 }

}
  

AirLine实体类

  

   package
    com.ljq.entity;



   import
    javax.persistence.Column;

   import
    javax.persistence.EmbeddedId;

   import
    javax.persistence.Entity;

@SuppressWarnings(
   "
   serial
   "
   )
@Entity

   public
    
   class
    AirLine 
   implements
    java.io.Serializable{
 @EmbeddedId
 
   private
    AirLinePk id;
 
 @Column(length
   =
   20
   )
 
   private
    String name;

 
   public
    AirLine() {
 
   super
   ();
 }

 
   public
    AirLine(String startCity,String endCity, String name) {
 
   this
   .id 
   =
   new
    AirLinePk(startCity,endCity);
 
   this
   .name 
   =
    name;
 }


 
   public
    AirLinePk getId() {
 
   return
    id;
 }

 
   public
    
   void
    setId(AirLinePk id) {
 
   this
   .id 
   =
    id;
 }

 
   public
    String getName() {
 
   return
    name;
 }

 
   public
    
   void
    setName(String name) {
 
   this
   .name 
   =
    name;
 }
 
 
 
 
}
  

PKTest测试类

  

   package
    com.ljq.test;


   import
    java.util.List;


   import
    javax.persistence.EntityManager;

   import
    javax.persistence.EntityManagerFactory;

   import
    javax.persistence.Persistence;


   import
    org.junit.Test;


   import
    com.ljq.entity.AirLine;

   import
    com.ljq.entity.AirLinePk;


   public
    
   class
    PKTest {

 @Test
 
   public
    
   void
    save() {
 EntityManagerFactory factory 
   =
    Persistence.createEntityManagerFactory(
   "
   ljq
   "
   );
 EntityManager em
   =
   factory.createEntityManager();
 em.getTransaction().begin();
 
 em.persist(
   new
    AirLine(
   "
   PEK
   "
   ,
   "
   SHA
   "
   ,
   "
   北京飞上海
   "
   ));
 
 
 em.getTransaction().commit();
 em.close();
 factory.close();
 
 }
 
 @Test
 
   public
    
   void
    find() {
 EntityManagerFactory factory 
   =
    Persistence.createEntityManagerFactory(
   "
   ljq
   "
   );
 EntityManager em
   =
   factory.createEntityManager();
 em.getTransaction().begin();
 
 AirLine airLine
   =
   em.find(AirLine.
   class
   , 
   new
    AirLinePk(
   "
   PEK
   "
   ,
   "
   SHA
   "
   ));
 System.out.println(airLine.getName());
 
 
 em.getTransaction().commit();
 em.close();
 factory.close();
 
 }
 
 @Test
 
   public
    
   void
    update() {
 EntityManagerFactory factory 
   =
    Persistence.createEntityManagerFactory(
   "
   ljq
   "
   );
 EntityManager em
   =
   factory.createEntityManager();
 em.getTransaction().begin();
 
 AirLine airLine
   =
   em.getReference(AirLine.
   class
   , 
   new
    AirLinePk(
   "
   PEK
   "
   ,
   "
   SHA
   "
   ));
 airLine.setName(
   "
   北京飞上海北京飞上海
   "
   );
 em.merge(airLine);
 
 
 em.getTransaction().commit();
 em.close();
 factory.close();
 
 }
 
 @SuppressWarnings({ 
   "
   unused
   "
   , 
   "
   unchecked
   "
    })
 @Test
 
   public
    
   void
    list() {
 EntityManagerFactory factory 
   =
    Persistence.createEntityManagerFactory(
   "
   ljq
   "
   );
 EntityManager em
   =
   factory.createEntityManager();
 em.getTransaction().begin();
 
 
 List
   <
   AirLine
   >
    airLines
   =
   em.createQuery(
   "
   select o from AirLine o
   "
   ).getResultList();
 
   for
   (AirLine air:airLines){
 System.out.println(air.getName());
 }
 
 em.getTransaction().commit();
 em.close();
 factory.close();
 
 }
 
 @SuppressWarnings({ 
   "
   unused
   "
   , 
   "
   unchecked
   "
    })
 @Test
 
   public
    
   void
    detele() {
 EntityManagerFactory factory 
   =
    Persistence.createEntityManagerFactory(
   "
   ljq
   "
   );
 EntityManager em
   =
   factory.createEntityManager();
 em.getTransaction().begin();
 
 
 em.remove(em.getReference(AirLine.
   class
   , 
   new
    AirLinePk(
   "
   PEK
   "
   ,
   "
   SHA
   "
   )));
 
 em.getTransaction().commit();
 em.close();
 factory.close();
 
 }

 
   /**
   
 * 用来判断映射是否成功
 * 
 
   */
   
 @Test
 
   public
    
   void
    test() {
 Persistence.createEntityManagerFactory(
   "
   ljq
   "
   );
 }

}