Question

我在Mongo有一棵这样的树：

> db.data.find()
{ "_id" : "07c", "path" : null }
{ "_id" : "a", "path" : "07c,a" }
{ "_id" : "b", "data" : "{\"c\":\"olaC\",\"d\":\"olaD\"}", "path" : "07c,a,b" }
{ "_id" : "c", "c" : "{\"c\":\"olaC\",\"d\":\"olaD\"}", "path" : "07c,a,b,c" }
{ "_id" : "d", "d" : "{\"d\":\"olaD\"}", "data" : "{\"c\":\"olaC\",\"d\":\"olaD\"}", "path" : "07c,a,b,c,d" }

我想检索b。

的所有后代

如果我在MongoDB控制台中执行此操作，我可以很好地了解后代：

> db.data.find({ path: /,b,/ } )
{ "_id" : "c", "c" : "{\"c\":\"olaC\",\"d\":\"olaD\"}", "path" : "07c,a,b,c" }
{ "_id" : "d", "d" : "{\"d\":\"olaD\"}", "data" : "{\"c\":\"olaC\",\"d\":\"olaD\"}",     "path" : "07c,a,b,c,d" }

但如果我在Java中这样做：

BasicDBObject query = new BasicDBObject();
query.put("path", "/,"+array[i]+",/");
DBCursor cursor = coll.find(query);
while(cursor.hasNext()){
   System.out.println(cursor.next().toString());
}

在调试器中，查询包含：{“path”：“/，b，/”}

我根本没有后代......为什么这不起作用？

http://docs.mongodb.org/manual/tutorial/model-tree-structures-with-materialized-paths/

Answer 1

/../在MongoDB shell中很特别。它不仅仅是一个包含正则表达式的字符串，而是由shell解析并用作正则表达式的字符串。

要从Java执行此操作，您可以执行以下操作：

BasicDBObject query = new BasicDBObject();
query.put("name", Pattern.compile(","+array[i]+","));
DBCursor cursor = coll.find(query);
while(cursor.hasNext()){
   System.out.println(cursor.next().toString());
}

另请参阅：How to query mongodb with “like” using the java api?

MongoDB Tree找到后代Java

1 个答案: