Question

u在mongodb的文档中有一个子文档数组我想对那些子文档进行排序。我发现在更新阵列时可以进行排序链接：http://docs.mongodb.org/manual/reference/operator/update/sort/

我想在java中这样做。这是我的代码的一部分：

BasicDBObject each = new BasicDBObject("$each", input);
BasicDBObject operations = each.append("$slice", "-10").append("$sort", new BasicDBObject("order",1));
push = new BasicDBObject("$push", new BasicDBObject("datas", operations));
collection.update(query,  push);

但事实证明，它没有将“操作”转变为操作员，而是将它们直接推入文档中，并将“$ each”，“$ slice”和“$ sort”作为字段。我哪里做错了？

Answer 1

我已经实现了您在上面提到的link中显示的java版本的查询。

查询是：

db.students.update( { name: "joe" },
                    { $push: { quizzes: { $each: [ { id: 3, score: 8 },
                                                   { id: 4, score: 7 },
                                                   { id: 5, score: 6 } ],
                                          $sort: { score: 1 },
                                          $slice: -5
                                        }
                             }
                    }
                  )

使用Java Driver可以按如下方式实现：

DBCollection coll = db.getCollection("students");

DBObject query = new BasicDBObject("name", "joe");

DBObject dbObj1 = new BasicDBObject();
dbObj1.put("id", 3);
dbObj1.put("score", 8);

DBObject dbObj2 = new BasicDBObject();
dbObj2.put("id", 4);
dbObj2.put("score", 7);

DBObject dbObj3 = new BasicDBObject();
dbObj3.put("id", 5);
dbObj3.put("score", 6);

BasicDBList eachList = new BasicDBList();
eachList.add(dbObj1);
eachList.add(dbObj2);
eachList.add(dbObj3);

BasicDBObject quizzesObj = new BasicDBObject();
quizzesObj.put("$each", eachList);
quizzesObj.put("$sort", new BasicDBObject("score", 1));
quizzesObj.put("$slice", -5);

coll.update(query, new BasicDBObject("$push", new BasicDBObject("quizzes", quizzesObj)));

使用java对mongodb中的子文档数组进行排序

1 个答案: