6.14. JPA 缓存存储

流程

1. 在 persistence.xml 中定义持久性单元 "myPersistenceUnit"。

   <persistence-unit name="myPersistenceUnit">
   	<!-- Persistence configuration goes here. -->
   </persistence-unit>

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2. 创建用户实体类。

   @Entity
   public class User implements Serializable {
   	@Id
   	private String username;
   	private String firstName;
   	private String lastName;
   
   	...
   }

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3. 使用 JPA 缓存存储配置名为"usersCache"的缓存。

   然后，您可以将缓存"usersCache"配置为使用 JPA Cache Store，以便在将数据放置到缓存中时，数据将基于 JPA 配置持久到数据库中。

   EmbeddedCacheManager cacheManager = ...;
   
   Configuration cacheConfig = new ConfigurationBuilder().persistence()
               .addStore(JpaStoreConfigurationBuilder.class)
               .persistenceUnitName("org.infinispan.loaders.jpa.configurationTest")
               .entityClass(User.class)
               .build();
   cacheManager.defineCache("usersCache", cacheConfig);
   
   Cache<String, User> usersCache = cacheManager.getCache("usersCache");
   usersCache.put("raytsang", new User(...));

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   • 使用 JPA 缓存存储的缓存只能存储一种数据类型，如下例所示：

     Cache<String, User> usersCache = cacheManager.getCache("myJPACache");
     // Cache is configured for the User entity class
     usersCache.put("username", new User());
     // Cannot configure caches to use another entity class with JPA cache stores
     Cache<Integer, Teacher> teachersCache = cacheManager.getCache("myJPACache");
     teachersCache.put(1, new Teacher());
     // The put request does not work for the Teacher entity class

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   • @EmbeddedId 注释允许您使用复合键，如下例所示：

     @Entity
     public class Vehicle implements Serializable {
     	@EmbeddedId
     	private VehicleId id;
     	private String color;	...
     }
     
     @Embeddable
     public class VehicleId implements Serializable
     {
     	private String state;
     	private String licensePlate;
     	...
     }

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