在mongodb中使用ReflectionDBObject类插入一个java对象? [英] Inserting an java object using ReflectionDBObject class in mongodb?
问题描述
我试图在java中将用户定义类的对象插入到mongodb集合中。
I am trying to insert objects of user-defined class in java into mongodb collection.
我的类是这样的:
class C extends ReflectionDBObject
{
int i;
C(){}
}
/ p>
and the code for insertion is
Mongo m = new Mongo("localhost");
com.mongodb.DB appdb = m.getDB("appdb");
DBCollection cmpcol = appdb.getCollection("feed");
DBObject bdbo = new BasicDBObject();
C c = new C();
c.i = 1;
bdbo.put("a",c);
cmpcol.insert(bdbo);
但在插入时,对象由数据库中的空值表示。我不想使用gson或morphia。
But on insertion the object is represented by a null value in the database. What am I doing wrong??I dont want to use gson or morphia.
推荐答案
Java驱动程序使用getter和setter方法
The Java driver uses getter and setter methods (not variables) on a ReflectionDBObject class to determine the properties to include in the document.
因此,您的代码应该是:
Hence your code should be:
public class C extends ReflectionDBObject
{
int i;
public int geti()
{
return i;
}
public void seti(int i)
{
this.i = i;
}
}
这将导致一个对象,如下面的集合:
This will result in an object such as the following in the collection:
{ "_id" : ObjectId("504567d903641896aa40bde6"), "a" : { "_id" : null, "i" : 1 } }
我不知道如何摆脱< c $ c>_ id:null 。这是ReflectionDBObject类的一个特性。子文档通常没有_ids,但是如果你想要一个非空的_id为子文档,你可以把下面的代码在你的C()构造函数:
I am not aware of a means of getting rid of the "_id" : null
in the sub-document. This is a characteristic of the ReflectionDBObject class. Sub-documents do not usually have _ids, but if you want a non-null _id for the subdocument, you can put the following code in your C() constructor:
public C()
{
set_id(ObjectId.get());
}
这将导致一个对象,如下所示:
This will result in an object such as the following:
{
"_id" : ObjectId("504568ff0364c2a4a975b375"),
"a" : { "_id" : ObjectId("504568ff0364c2a4a975b374"), "i" : 1 }
}
属性i的 geti()
和 seti()
约定略有不同。 JavaBeans规范说,您需要具有属性i的 getI()
和 setI()
方法。但是MongoDB驱动程序对ReflectionDBObject类不起作用。
Finally, note that the geti()
and seti()
convention for a property "i" is slightly unusual. The JavaBeans spec says that you need getI()
and setI()
methods to have a property "i". However the MongoDB driver doesn't work that way for the ReflectionDBObject class.
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