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Vistasjava MongoTemplate aggregate with project nested document
I have a document.
{
"errors" : [
{
"priority" : 3,
"category" : "aaa"
"other":"nothing"
},
{
"priority" : 4,
"category" : "bbb"
"other":"nothing"
},
{
"priority" : 2,
"category" : "ccc"
"other":"nothing"
},
{
"priority" : 3,
"category" : "ddd"
"other":"nothing"
},
{
"priority" : 2,
"category" : "eee"
"other":"nothing"
}
],
"file_name" : "xxx.json",
"vehicle_id" : "esdf",
"day" : "2022-03-08"
}
I execute a command with js client.
db.wty_test.aggregate({
$project: {
'_id': 0, 'errors.priority': 1, 'errors.category': 1, 'file_name': 1, 'vehicle_id': 1,
}
})
I get the result I want.
The errors is an array containing objects.
Now I need to overwrite this command with java client(springboot-data-mongo). This is my java code.
import org.springframework.data.mongodb.core.MongoTemplate;
...
Aggregation aggregation = Aggregation.newAggregation(Aggregation.project("errors.priority", "errors.category", "file_name", "vehicle_id"));
mongoTemplate.aggregate(aggregation, "wty_test", HashMap.class).getMappedResults();
The priority and category is not in errors.
How to use java to get the same result as js?
I try the nested.But it's not what I want.
2 Respuestas
Responde la pregunta0
Here is a way to get the desired result.
Document projectn = new Document("$project",
new Document("_id", 0L)
.append("file_name", 1L)
.append("vehicle_id", 1L)
.append("errors",
new Document("$map",
new Document("input", "$errors")
.append("in",
new Document("priority", "$$this.priority")
.append("category", "$$this.category")
)
)
)
);
List<Document> pipeline = Arrays.asList(projectn);
List<Document> results = mongoOps.getCollection("collection_name")
.aggregate(pipeline)
.into(new ArrayList<>());
Note that this uses MongoDB Java Driver API query syntax, and Document is org.bson.Document. The conversion of the native query to Java Driver uses $map aggregation array operator (and it looks like thats the (maybe only) way).
With MongoTemplate.aggregate the code is:
Aggregation agg = newAggregation(
project()
.and(
VariableOperators.Map.itemsOf("errors")
.as("e")
.andApply(ctx -> new Document("priority", "$$e.priority").append("category", "$$e.category") ))
.as("errors")
.andExclude("_id")
.andInclude("file_name", "vehicle_id")
);
AggregationResults<Document> results = mongoOps.aggregate(agg, "collection_name", Document.class);
Alternate Method:
In case your query is just about the projection, you can use the following query using MongoTemplate#find method. This is much simpler to construct and understand:
db.collection.find(
{}, // your query filter
{ _id: 0, 'errors.category': 1, 'errors.priority': 1, file_name: 1, vehicle_id: 1 }
)
The MongoTemplate version of it:
Query query = new Query();
query.fields()
.include("errors.priority", "errors.category", "file_name", "vehicle_id")
.exclude("_id");
List<Document> results = mongoOps.find(query, Document.class, "collection_name");
0
You want to be using the nested() function, like so:
AggregationOperation project = Aggregation.project("file_name", "vehicle_id").
and("errors").nested(Fields.fields("priority","category"))
Aggregation aggregation = Aggregation.newAggregation(project);