java - MongoDB Java : Finding objects in Mongo using QueryBuilder $in operator returns nothing

Question

我有一个名为 MongoRule 的 JUnit 规则

public class MongoRule extends ExternalResource {

    private static final Logger LOGGER = LoggerFactory.getLogger(MongoRule.class);
    private final MongoService mongoService;

    public MongoRule() throws UnknownHostException {
        mongoService = new MongoService(getConfiguredHost(), getConfiguredPort(), getConfiguredDatabase());
    }

    @Override
    protected void before() throws Throwable {
        LOGGER.info(" Setting up Mongo Database - " + getConfiguredDatabase());
    }

    @Override
    protected void after() {
        LOGGER.info("Shutting down the Mongo Database - " + getConfiguredDatabase());
        mongoService.getMongo().dropDatabase(getConfiguredDatabase());
    }

    @Nonnull
    public DB getDatabase() {
        return mongoService.getMongo().getDB(getConfiguredDatabase());
    }

    @Nonnull
    public Mongo getMongo() {
        return mongoService.getMongo();
    }

    @Nonnull
    public MongoService getMongoService() {
        return mongoService;
    }

    public static int getConfiguredPort() {
        return Integer.parseInt(System.getProperty("com.db.port", "27017"));
    }

    @Nonnull
    public static String getConfiguredDatabase() {
        return System.getProperty("com.db.database", "database");
    }

    @Nonnull
    public static String getConfiguredHost() {
        return System.getProperty("com.db.host", "127.0.0.1");
    }
}

然后我尝试如下插入一些文档

 public static void saveInDatabase() {
        LOGGER.info("preparing database - saving some documents");
        mongoRule.getMongoService().putDocument(document1);
        mongoRule.getMongoService().putDocument(document2);
    }

其中 document1 和 document2 是有效的 DBObject 文档。架构看起来像

{
    Id: 001
    date_created: 2012-10-31
    vars: {
      '1': {
           name: n1
           value:v1
       }
      '2': {
           name: n2
           value:v2
       }
      '3': {
           name: n3
           value:v3
       }

} 
{
    Id: 002
    date_created: 2012-10-30
    vars: {
      '1': {
           name: n4
           value:v4
       }
      '2': {
           name: n5
           value:v5
       }
      '3': {
           name: n6
           value:v6
       }

}

现在我尝试查询集合并获取这些对象，所以我这样做

public static void getDocuments(List<String> documentIds) {
        BasicDBList docIds = new BasicDBList();
        for (String docId: documentIds) {
            docIds.add(new BasicDBObject().put("Id", docId));
        }
        DBObject query = new BasicDBObject();
        query.put("$in", docIds);
        DBCursor dbCursor = mongoRule.getDatabase().getCollection("mycollection").find(query);
        System.out.println(dbCursor == null);
        if (dbCursor != null) {
            while (dbCursor.hasNext()) {
                System.out.println("object -  " + dbCursor.next());
            }
        }
    }  

mycollection 是保存所有文档的集合，它来自外部服务。
当我运行此文档时，我看到以下内容

preparing database - saving some documents
inserting document - DBProposal # document1
inserting document - DBProposal # document2
false

这意味着 collection.find() 找不到这些文件。

我在这里没有做什么？我怎样才能取回文件？

我对将 Java 与 Mongo 结合使用还很陌生，并使用了这个 reference构造查询

更新
更改构造查询的方式后，我仍然看不到文档

public static void getDocuments(List<String> documentIds) {
            BasicDBList docIds = new BasicDBList();
            docIds.addAll(documentIds)
            DBObject query = new BasicDBObject();
            query.put("$in", docIds);
            DBCursor dbCursor = mongoRule.getDatabase().getCollection("mycollection").find(query);
            System.out.println(dbCursor == null);
            if (dbCursor != null) {
                while (dbCursor.hasNext()) {
                    System.out.println("object -  " + dbCursor.next());
                }
            }
        } 

集合名称通过

返回

private static String getCollectionName(@Nonnull final DBObject dbObject) {
        return "mycollection";
    }

Answer 1

你现在做的相当于:

db.col.find({$in:[{Id:id1}, {Id:id2}, ..., {Id:idN}]})

这不是一个有效的查询，因为您没有指定要 $in 的字段。我假设你想要:

db.col.find({Id:{$in:[id1, id2, ..., idN]}})

相应地更改您的查询构造代码，您应该没问题。

编辑:添加正确的代码:

public static void getDocuments(List<Integer> documentIds) {

            BasicDBList docIds = new BasicDBList();
            docIds.addAll(documentIds)
            DBObject inClause = new BasicDBObject("$in", docIds);
            DBObject query = new BasicDBObject("Id", inClause);
            DBCursor dbCursor = mongoRule.getDatabase().getCollection("mycollection").find(query);
            System.out.println(dbCursor == null);
            if (dbCursor != null) {
                while (dbCursor.hasNext()) {
                    System.out.println("object -  " + dbCursor.next());
                }
            }
        } 

请注意，这里假设“Id”不是“_id”