Java Morphia展开聚合返回的结果与Mongo db查询不同？

我在这里尝试做一个简单的MongoDB聚合。基本上我有这样的文件：

{
timestampInMs: 1444094140442,
records: [
{
value: "testvalue",
experiment: {
id: "56105b0af2763b25806d1365",
name: "integrationtest-kkkk",
created: "2015-10-03T22:47:38.479+0000",
updated: null
},
sensorId: "testsensor",
dataType: 1
},
{
value: "testvalue2",
experiment: {
id: "56105b0af2763b25806d1365",
name: "integrationtest-kkkk",
created: "2015-10-03T22:47:38.479+0000",
updated: null
},
sensorId: "testsensor2",
dataType: 1
},
{
value: "testvalue3",
experiment: {
id: "56105b0af2763b25806d1365",
name: "integrationtest-kkkk",
created: "2015-10-03T22:47:38.479+0000",
updated: null
},
sensorId: "testsensor3",
dataType: 1
},
{
value: "testvalue4",
experiment: {
id: "56105b0af2763b25806d1365",
name: "integrationtest-kkkk",
created: "2015-10-03T22:47:38.479+0000",
updated: null
},
sensorId: "testsensor4",
dataType: 1
}
],
created: "2015-10-06T01:15:40.501+0000",
updated: "2015-10-06T01:15:40.528+0000"
}

Iterator<DbSensorDataDocument> iter = datastore.createAggregation(DbSensorDataDocument.class)
        .unwind("records").aggregate(DbSensorDataDocument.class);

{
timestampInMs: 1444094140442,
sensorId: "testsensor",
value: "testvalue",
experimentId: "56105b0af2763b25806d1365",
dataType: 1
},
{
timestampInMs: 1444094140442,
sensorId: "testsensor",
value: "testvalue",
experimentId: "56105b0af2763b25806d1365",
dataType: 1
},
{
timestampInMs: 1444094140442,
sensorId: "testsensor",
value: "testvalue",
experimentId: "56105b0af2763b25806d1365",
dataType: 1
},
{
timestampInMs: 1444094140442,
sensorId: "testsensor",
value: "testvalue",
experimentId: "56105b0af2763b25806d1365",
dataType: 1
}

java模型如下所示

@Entity("sensordatadocs")
@Indexes ({
    @Index(fields = @Field("timestampInMs"), options = @IndexOptions(name = "timestamp_ms_index"))
})
public class DbSensorDataDocument {

    @Id
    // Should be milliseconds since Epoch
    private Long timestampInMs;

    @Embedded
    private List<DbSensorDataRecord> records;

    private Date created;

    private Date updated;
}

public class DbSensorDataRecord {

    private String value;

    @Reference
    private Experiment experiment;

    private String sensorId;

    private int dataType;
}

它给了我4个文档，每个文档的“记录”包含一个与原始数组中的项相对应的项。但是，当我使用Morphia的API时，如下所示：

{
timestampInMs: 1444094140442,
records: [
{
value: "testvalue",
experiment: {
id: "56105b0af2763b25806d1365",
name: "integrationtest-kkkk",
created: "2015-10-03T22:47:38.479+0000",
updated: null
},
sensorId: "testsensor",
dataType: 1
},
{
value: "testvalue2",
experiment: {
id: "56105b0af2763b25806d1365",
name: "integrationtest-kkkk",
created: "2015-10-03T22:47:38.479+0000",
updated: null
},
sensorId: "testsensor2",
dataType: 1
},
{
value: "testvalue3",
experiment: {
id: "56105b0af2763b25806d1365",
name: "integrationtest-kkkk",
created: "2015-10-03T22:47:38.479+0000",
updated: null
},
sensorId: "testsensor3",
dataType: 1
},
{
value: "testvalue4",
experiment: {
id: "56105b0af2763b25806d1365",
name: "integrationtest-kkkk",
created: "2015-10-03T22:47:38.479+0000",
updated: null
},
sensorId: "testsensor4",
dataType: 1
}
],
created: "2015-10-06T01:15:40.501+0000",
updated: "2015-10-06T01:15:40.528+0000"
}

Iterator<DbSensorDataDocument> iter = datastore.createAggregation(DbSensorDataDocument.class)
        .unwind("records").aggregate(DbSensorDataDocument.class);

{
timestampInMs: 1444094140442,
sensorId: "testsensor",
value: "testvalue",
experimentId: "56105b0af2763b25806d1365",
dataType: 1
},
{
timestampInMs: 1444094140442,
sensorId: "testsensor",
value: "testvalue",
experimentId: "56105b0af2763b25806d1365",
dataType: 1
},
{
timestampInMs: 1444094140442,
sensorId: "testsensor",
value: "testvalue",
experimentId: "56105b0af2763b25806d1365",
dataType: 1
},
{
timestampInMs: 1444094140442,
sensorId: "testsensor",
value: "testvalue",
experimentId: "56105b0af2763b25806d1365",
dataType: 1
}

这就是我的迭代代码的样子：

while (iter.hasNext()) {
            DbSensorDataDocument doc = iter.next();
            final SensorDataRecord record = SensorDataUtils.flattenSensorDataDocument(doc);  
            result.add(record);
        }

请注意，项目的数量是正确的，但是“记录”中的值是不正确的，事实上，它们只是原始数组**中**第一个项目的值。为什么会这样？请帮忙。谢谢

---

Morphia 1.0.1版

该行为的原因是Morphia缓存问题。在您的例子中，Morphia将DbSensorDataDocument实体的所有结果视为同一行（因为主键timestaminms相同），并返回缓存版本

要解决此问题，必须使用聚合投影从结果中排除字段timestampInMs：

Iterator<DbSensorDataDocument> iter = datastore.createAggregation(DbSensorDataDocument.class)
        .unwind("records").project(
 Projection.projection("timestampInMs").suppress(), 
 Projection.projection("XXXXXX").aggregate(DbSensorDataDocument.class);

Iterator iter=datastore.createAggregation（DbSensorDataDocument.class）
.展开（“记录”）.项目(
Projection.Projection（“timestaminms”）.suppress（），
Projection.Projection（“XXXXXX”）.aggregate（DbSensorDataDocument.class）；

---

其中XXXXX是您想要包含的字段。

听起来很愚蠢，但您确定迭代正确完成了吗？我已经在帖子中更新了迭代代码。应该正确吗？O.O