我正在使用datanucleus/jdo在mongodb db中持续存在对象。我试图坚持一个包含地图的对象,哪种值类型是抽象类。
当我尝试坚持一个对象的实例时,抽象类的字段持续存在,但不是子类的字段。
以下是一些代码。
Zoo.java
@PersistenceCapable
public class Zoo {
@Persistent
private String fieldZoo;
@Persistent
private Map<String, Animal> mapStringAnimal;
// etc... basic constructor...
}
Animal.java
@PersistenceCapable(embeddedOnly = "true")
public abstract class Animal {
@Persistent
private String fieldAnimal;
}
dog.java
@PersistenceCapable(embeddedOnly = "true")
public class Dog extends Animal {
@Persistent
private String fieldDog;
}
test.java
public static void main(String[] args) {
Map<String, Animal> mapStringAnimal = new HashMap<String, Animal>();
Dog dog = new Dog("valueFieldAnimal", "valueFieldDog");
mapStringAnimal.put("dogKey", dog);
Zoo zoo = new Zoo("valueFieldZoo", mapStringAnimal);
Properties properties = new Properties();
properties.setProperty("javax.jdo.PersistenceManagerFactoryClass", "org.datanucleus.api.jdo.JDOPersistenceManagerFactory");
properties.setProperty("javax.jdo.option.ConnectionURL", "mongodb:/dbtest");
properties.setProperty("javax.jdo.option.Mapping", "mongodb");
properties.setProperty("datanucleus.autoCreateSchema", "true");
PersistenceManagerFactory pmf = JDOHelper.getPersistenceManagerFactory(properties);
PersistenceManager pm = pmf.getPersistenceManager();
pm.makePersistent(zoo);
pm.close();
}
,当我看着mongodb时:
> db.Zoo.find().pretty();
{
"_id" : ObjectId("50d2f5f7e4b0cae285990b2d"),
"fieldZoo" : "valueFieldZoo",
"mapStringAnimal" : [
{
"key" : "dogKey",
"value" : {
"fieldAnimal" : "valueFieldAnimal"
}
}
]
}
是的,但是datanucleus不支持嵌入式继承 map键/值。它确实支持嵌入的继承的收集元素(尚未发行的JDO3.1的一部分),但不相同地图。显然,该代码是开源的,任何人都可以潜入并做出贡献(当然,一旦您添加了一个歧视者,当然是"动物")。