如何从mongodb中的内部文档中获取字段?例如,如果我给出一个名为" idMovie"的字段,我将获得与此idMovie对应的其余字段。
我正在使用此代码:
MongoClient mongo = null;
DBCursor cursor = null;
String average = "";
String sum = "";
String numCal = "";
try {
mongo = new MongoClient ("localhost", 27017);
DB db = mongo.getDB("DBHC2");
DBCollection movieDocument = db.getCollection("movies");
BasicDBObject searchQuery = new BasicDBObject();
searchQuery.put("rateMovies.idMovie", idMovie);
cursor = movieDocument.find(searchQuery);
if(cursor.hasNext()){
average = searchQuery.getString("average");
sum = searchQuery.getString("sum");
numCal = searchQuery.getString("total");
System.out.println("***** Debug: average: "+average+" sum: "+sum+" total: "+numCal);
}
}
catch(Exception e){
System.out.println("error : " + e.getMessage());
System.out.println("error : " + e.getCause());
}
finally{
cursor.close();
}
}
当我运行它时,控制台会打印:
***** Debug: average: null sum: null total: null
这是我正在使用的mongodb文档:
{ "_id" : { "$oid" : "5320aa3c3e468eaeb52dccdc"},
"document" : "movies" ,
"rateMovies" : [
{
"idMovie" : 2 ,
"average" : "0" ,
"sum" : "0" ,
"total" : "0"
} ,
{
"idMovie" : 3 ,
"average" : "0" ,
"sum" : "0" ,
"total" : "0"
}]
}
提前谢谢!! :)对不起我的英文。
答案 0 :(得分:1)
您尝试从传入的查询对象中提取数据,而不是通过游标返回DBObject。