com.mongodb.DBRefBase Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2014 MongoDB, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
// DBRefBase.java
package com.mongodb;
import java.io.Serializable;
/**
* Represents a database reference, which points to an object stored in the database.
*
* While instances of this class are {@code Serializable}, deserialized instances can not be fetched,
* as the {@code db} property is transient.
*/
public class DBRefBase implements Serializable {
private static final long serialVersionUID = 3031885741395465814L;
/**
* Creates a DBRefBase
* @param db the database
* @param ns the namespace where the object is stored
* @param id the object id
*/
public DBRefBase(DB db , String ns , Object id) {
_db = db;
_ns = ns.intern();
_id = id;
}
/**
* For use only with serialization framework.
*/
protected DBRefBase() {
_id = null;
_ns = null;
_db = null;
}
/**
* fetches the object referenced from the database
* @return the referenced document
* @throws MongoException
*/
public DBObject fetch() throws MongoException {
if (_loadedPointedTo)
return _pointedTo;
if (_db == null)
throw new MongoInternalException("no db");
final DBCollection coll = _db.getCollectionFromString(_ns);
_pointedTo = coll.findOne(_id);
_loadedPointedTo = true;
return _pointedTo;
}
@Override
public String toString(){
return "{ \"$ref\" : \"" + _ns + "\", \"$id\" : \"" + _id + "\" }";
}
/**
* Gets the object's id
* @return the id of the reference
*/
public Object getId() {
return _id;
}
/**
* Gets the object's namespace (collection name)
* @return the name of the collection in which the reference is stored
*/
public String getRef() {
return _ns;
}
/**
* Gets the database, which may be null, in which case the reference can not be fetched.
*
* @return the database
* @see #fetch()
*/
public DB getDB() {
return _db;
}
@Override
public boolean equals(final Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
final DBRefBase dbRefBase = (DBRefBase) o;
if (_id != null ? !_id.equals(dbRefBase._id) : dbRefBase._id != null) return false;
if (_ns != null ? !_ns.equals(dbRefBase._ns) : dbRefBase._ns != null) return false;
return true;
}
@Override
public int hashCode() {
int result = _id != null ? _id.hashCode() : 0;
result = 31 * result + (_ns != null ? _ns.hashCode() : 0);
return result;
}
final Object _id;
final String _ns;
final transient DB _db;
private boolean _loadedPointedTo = false;
private DBObject _pointedTo;
}