我正在尝试传递多个集合作为执行map reduce hadoop作业的输入。我发现版本1.2中的multicollectionsplitbuilder具有此功能。下面的示例发布在github中，但它不起作用，非常感谢您的帮助。

MultiCollectionSplitBuilder mcsb = new MultiCollectionSplitBuilder();
        mcsb.add(new MongoURI("mongodb://localhost:27017/mongo_hadoop.yield_historical.in"),
                 (MongoURI)null, // authuri
                 true, // notimeout
                 (DBObject)null, // fields
                 (DBObject)null, // sort
                 (DBObject)null, // query
                 false,
                 MultiMongoCollectionSplitter.class)
            .add(new MongoURI("mongodb://localhost:27017/mongo_hadoop.yield_historical.in"),
                 (MongoURI)null, // authuri
                 true, // notimeout
                 (DBObject)null, // fields
                 (DBObject)null, // sort
                 new BasicDBObject("_id", new BasicDBObject("$gt", new Date(883440000000L))),
                 false, // range query
                 MultiMongoCollectionSplitter.class);

        Configuration conf = new Configuration();
        conf.set(MultiMongoCollectionSplitter.MULTI_COLLECTION_CONF_KEY, mcsb.toJSON());