How to use $facet , $addFields and $function in Spring-Data-MongoDB - mongodb

Question

I'm developing a method in Spring-Data-MongoDB that use $facet,$addFields and $function but it return null.
This is the aggregation in MongoDB
db.utenti.aggregate([
{
$facet:
{
"aggregation": [
{
$match: { age: { $gt: 18 } }
},
{
$addFields:{
max: {
$function: {
body: function(name, scores) {
let max = Math.max(...scores);
return `Hello ${name}. Your max score is ${max}.`
},
args: [ "$name", "$scores"],
lang: "js"
}
}
}
}
]
}
}
]).pretty()
This the expected result
{
"aggregation" : [
{
"_id" : ObjectId("62c5f16b39b3d635ab6bf60d"),
"username" : "james34",
"name" : "james",
"role" : [
"user",
"specialuser"
],
"age" : 34,
"scores" : [
10,
9,
10
],
"_class" : "com.project.ecommercemongo.model.User",
"max" : "Hello james. Your max score is 10."
},
{
"_id" : ObjectId("62c5f1b839b3d635ab6bf60e"),
"username" : "elizabeth54",
"name" : "elizabeth",
"role" : [
"user",
"specialuser"
],
"age" : 54,
"scores" : [
10,
10,
10
],
"_class" : "com.project.ecommercemongo.model.User",
"max" : "Hello elizabeth. Your max score is 10."
},
{
"_id" : ObjectId("62c5f1f139b3d635ab6bf60f"),
"username" : "frank50",
"name" : "frank",
"role" : [
"user"
],
"age" : 50,
"scores" : [
10,
10,
10
],
"_class" : "com.project.ecommercemongo.model.User",
"max" : "Hello frank. Your max score is 10."
},
{
"_id" : ObjectId("62c5f27a39b3d635ab6bf610"),
"username" : "john26",
"name" : "john",
"role" : [
"user"
],
"age" : 26,
"scores" : [
8,
8,
10
],
"_class" : "com.project.ecommercemongo.model.User",
"max" : "Hello john. Your max score is 10."
}
]
}
This is the result I get
[
{
"_id": null,
"username": null,
"name": null,
"role": null,
"age": null,
"scores": null
}
]
this is the method that call facet addFields and function,but it don't add the field "max" and returns null
public List<User> aggregation1() {
List<Object> bl = new LinkedList<Object>();
bl.add("$name");
bl.add("$scores");
ScriptOperators.Function function= Function.function("function(name, scores) {let max = Math.max(...scores); return `Hello ${name}. Your max score is ${max}`}").args(bl).lang("js");//`Hello ${name}. Your max score is ${max}.`}");
System.out.println(function.toDocument());
FacetOperation facetOperation1 = Aggregation.facet(Aggregation.match(Criteria.where("age").gte(18)),Aggregation.addFields().addFieldWithValue("max", function).build()).as("aggregation");
Aggregation agg = Aggregation.newAggregation(facetOperation1);
return mongoTemplate.aggregate(agg, "utenti",User.class).getMappedResults();
}
And this is the User class
#Document(collection="utenti")
//#Sharded(shardKey = { "country", "userId" })
public class User {
#Id
private String _id;
private String username;
private String name;
private String[] role;
private Integer age;
private Integer[] scores;
public User() {
super();
}
public String get_id() {
return _id;
}
public void set_id(String _id) {
this._id = _id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String[] getRole() {
return role;
}
public void setRole(String[] role) {
this.role = role;
}
public Integer[] getScores() {
return scores;
}
public void setScores(Integer[] scores) {
this.scores = scores;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
}
how can i put all the users into the facet and add a field ? Thank you
Update
Now it work, I had to map the output with the aggregation fields
public List<MaxFacet> aggregation1() {
List<Object> bl = new LinkedList<Object>();
bl.add("$name");
bl.add("$scores");
ScriptOperators.Function function = Function.function(
"function(name, scores) {let max = Math.max(...scores); return `Hello ${name}. Your max score is ${max}.`}")
.args(bl).lang("js");// `Hello ${name}. Your max score is ${max}.`}");
System.out.println(function.toDocument());
FacetOperation facetOperation = Aggregation.facet().and(match(Criteria.where("age").gte(18)),
Aggregation.addFields().addFieldWithValue("max", function).build()).as("aggregation");
Aggregation agg = Aggregation.newAggregation(facetOperation);
return mongoOperations.aggregate(agg, mongoTemplate.getCollectionName(User.class), MaxFacet.class)
.getMappedResults();
}
public class MaxFacet {
private List<UserOut> aggregation;
public List<UserOut> getAggregation() {
return aggregation;
}
public void setAggregation(List<UserOut> facet1) {
this.aggregation = facet1;
}
public MaxFacet() {
// TODO Auto-generated constructor stub
}
}
#JsonPropertyOrder({"id","username","name","age","scores","max"})
public class UserOut {
#JsonProperty(value="id")
private String id;
private String username;
private String name;
private String []scores;
private String max;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String[] getScores() {
return scores;
}
public void setScores(String[] scores) {
this.scores = scores;
}
public String getMax() {
return max;
}
public void setMax(String value) {
this.max= value;
}
}
[
{
"aggregation": [
{
"id": "62c5f16b39b3d635ab6bf60d",
"username": "james34",
"name": "james",
"scores": [
"10",
"9",
"10"
],
"max": "Hello james. Your max score is 10."
},
{
"id": "62c5f1b839b3d635ab6bf60e",
"username": "elizabeth54",
"name": "elizabeth",
"scores": [
"10",
"10",
"10"
],
"max": "Hello elizabeth. Your max score is 10."
},
{
"id": "62c5f1f139b3d635ab6bf60f",
"username": "frank50",
"name": "frank",
"scores": [
"10",
"10",
"10"
],
"max": "Hello frank. Your max score is 10."
},
{
"id": "62c5f27a39b3d635ab6bf610",
"username": "john26",
"name": "john",
"scores": [
"8",
"8",
"10"
],
"max": "Hello john. Your max score is 10."
}
]
}
]

Answer 1

Alternative soluition: You can simplify your code this way
1- Use inheritance mecanism for the UserOut class
public class UserOut extends User {
private String max;
public String getMax() {
return max;
}
public void setMax(String value) {
this.max= value;
}
}
2- For the complex pipelines, the custom AggregationOperation implementation is friendlier than Spring Data builder.
AggregationOperation facetOperation = ao ->
new Document("$facet",
new Document("aggregation", Arrays.asList(
new Document("$match", new Document("age", new Document("$gt", 18))),
new Document("$addFields",
new Document("max",
new Document("$function",
new Document("body", "function(name, scores) {"+
" let max = Math.max(...scores);"+
" return `Hello ${name}. Your max score is ${max}.`"+
"}")
.append("args", Arrays.asList("$name", "$scores"))
.append("lang", "js")
)
)
)
))
);
Aggregation agg = Aggregation.newAggregation(facetOperation);
return mongoOperations
.aggregate(agg, mongoTemplate.getCollectionName(User.class), MaxFacet.class)
.getMappedResults();
Alternatively, just parse your shell JSON query this way (triple quotes starting from Java 13):
Document.parse("""
{
"$facet":
{
"aggregation": [
{
"$match": { "age": { "$gt": 18 } }
},
{
"$addFields":{
"max": {
"$function": {
"body": function(name, scores) {
let max = Math.max(...scores);
return `Hello ${name}. Your max score is ${max}.`
},
"args": [ "$name", "$scores"],
"lang": "js"
}
}
}
}
]
}
}
""")