MongoDB對象映射框架 Morphia

Morphia 是一個輕量級的類型安全的 Java 類庫，用來將在 MongoDB 和 Java 對象之間進行映射。

• Easy to use, and very lightweight; reflection is used once per type and cached for good performance.
• Datastore and DAO<T,V> access abstractions, or roll your own...
• Type-safe, and Fluent Query support with (runtime) validation
• Annotations based mapping behavior; there are no XML files.
• Extensions: Validation (jsr303), and SLF4J Logging

@Entity("employees")
class Employee {
  @Id ObjectId id; // auto-generated, if not set (see ObjectId)
  String firstName, lastName; // value types are automatically persisted
  Long salary = null; // only non-null values are stored

@Embedded Address address;
@Reference Employee manager; // refs are stored*, and loaded automatically
  @Reference List<Employee> underlings; // interfaces are supported
@Serialized EncryptedReviews; // stored in one binary field
@Property("started") Date startDate; //fields can be renamed
  @Property("left")Date endDate;
@Indexed boolean active = false; //fields can be indexed for better performance
  @NotSaved string readButNotStored; //fields can read, but not saved
  @Transient int notStored; //fields can be ignored (load/save)
  transient boolean stored = true; //not @Transient, will be ignored by Serialization/GWT for example.
//Lifecycle methods -- Pre/PostLoad, Pre/PostSave...
  @PostLoad void postLoad(DBObject dbObj) { ... }
}</pre> 
  
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