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";
}
最佳答案
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”
关于java - MongoDB Java : Finding objects in Mongo using QueryBuilder $in operator returns nothing,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/11650970/