Mongo db java unwind operation in aggregate query throwing exception

Question

When working with embedded mongo document I am trying to unwind the array but I am getting exception like org.springframework.data.mapping.model.MappingInstantiationException: Failed to instantiate java.util.List using constructor NO_CONSTRUCTOR with arguments. The query what I wrote is,

Aggregation agg = newAggregation(
        unwind("recipients"),
 match(Criteria.where("recipients.userId").is("800").andOperator(Criteria.where("recipients.status").is(false)
                )));
  Logs.java
 private String id;
private String userId;
private String conversationId;
 private Date createdDate;
private List<Recipients> recipients;

Recipients.java

 private String userId;
 private boolean status;

Data set

{
"_id" : ObjectId("579099e6000fda45000c0054"),
"userId" : "800",
"conversationId" : "57907e5f000fda45000c004b",
"createdDate" : ISODate("2016-07-21T09:46:14.602Z"),
"recipients" : [
        {
                "userId" : "800",
                "status" : false
        },
        {
                "userId" : "900",
                "status" : false
        }
]
  }
 {
"_id" : ObjectId("579099e9000fda45000c0055"),
"userId" : "530a7998-ba3f-4366-8d21-bb1ca688cfdb",
"conversationId" : "57907e5f000fda45000c004b",
"createdDate" : ISODate("2016-07-21T09:46:17.915Z"),
"recipients" : [
        {
                "userId" : "800",
                "status" : true
        },
        {
                "userId" : "900",
                "status" : false
        }
]
 }
{
"_id" : ObjectId("5790adda000fda2444d6ccdf"),
"userId" : "530a7998-ba3f-4366-8d21-bb1ca688cfdb",
"conversationId" : "578df6cf000fda2640b77c45",
"createdDate" : ISODate("2016-07-21T11:11:22.522Z"),
"recipients" : [
        {
                "userId" : "800",
                "status" : false
        },
        {
                "userId" : "530a7998-ba3f-4366-8d21-bb1ca688cfdb",
                "status" : true
        }
 ]
 }
 {
"_id" : ObjectId("5790adde000fda2444d6cce0"),
"userId" : "530a7998-ba3f-4366-8d21-bb1ca688cfdb",
"conversationId" : "578df6cf000fda2640b77c45",
"createdDate" : ISODate("2016-07-21T11:11:26.479Z"),
"recipients" : [
        {
                "userId" : "800",
                "status" : false
        },
        {
                "userId" : "530a7998-ba3f-4366-8d21-bb1ca688cfdb",
                "status" : true
        }
]
 }

@Andriy Simonov : From another class I am calling, The aggregate function is in one method , I will call that method with dynamic user profile Id. But, here I have hardcoded the user profile id as 800. — Karthik
– Karthik, Commented Jul 23, 2016 at 9:53

Andriy Simonov · Accepted Answer · 2016-07-23 11:32:04Z

1

If the result of your aggregation is a list of Logs objects like this

AggregationResults<Logs> results = mongoOps.aggregate(agg, "logs", Logs.class);

then cardinality of recipients is incorrect. It must to be just a Recipients as opposed to List because after unwinding the recipients field holds a single document.

Logs.java
  private String id;
  private String userId;
  private String conversationId;
  private Date createdDate;
  private Recipients recipients; <--

edited Jul 23, 2016 at 11:32

answered Jul 23, 2016 at 10:43

Andriy Simonov

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3 Comments

Karthik Over a year ago

But, if I do like this I can have only save one recipient right? I want a array of recipient to saved for a single record.

Andriy Simonov Over a year ago

Then you need two classes. Logs for usual operations like saving and reading and an additional class for the aggregation result. You can call it LogsAggregationResult for example.

Karthik Over a year ago

How can I query a another table for aggregation results that is different from table where I stored my records. Do you think it will work.

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