How to use two conditon in one array? - spring

Question

I have a list of task stored in Mongo, like below
{
"name": "task1",
"requiredOS": [
{
"name": "linux",
"version": [
"6.0"
]
},
{
"name": "windows",
"version": [
"2008",
"2008R2"
]
}
],
"requiredSW": [
{
"name": "MySQL",
"version": [
"1.0"
]
}
]
}
My purpose is to filter the task by OS and Software, for example the user give me below filter condition
{
"keyword": [
{
"OS": [
{
"name": "linux",
"version": [
"6.0"
]
},
{
"name": "windows",
"version": [
"2008"
]
}
]
},
{
"SW": [ ]
}
]
}
I need filter out all the task can both running on the windows2008 and Linux 6.0 by searching the "requiredOS" and "requiredSW" filed. As you seen, the search condition is an array (the "OS" part). I have a trouble when use an array as search condition. I expect the query to return me a list of Task which satisfy the condition.
A challenging thing is that I need to integrate the query in to spring-data using #Query. so the query must be parameterized
can anyone give me a hand ?
I have tried a query but return nothing. my purpose is to use $all to combine two condition together then use $elemMatch to search the "requiredOS" field
{"requiredOS":{"$elemMatch":{"$all":[{"name":"linux","version":"5.0"},{"name":"windows","version":"2008"}]}}}

Answer 1

If I understood correctly what you are trying, you need to use $elemMatch operator:
http://docs.mongodb.org/manual/reference/operator/query/elemMatch/#op._S_elemMatch
Taking your example, the query should be like:
#Query("{'requiredOS':{$elemMatch:{name:'linux', version:'7.0'},$elemMatch:{name:'windows', version:'2008'}}}")
It match the document you provided.

Answer 2

You basically seem to need to translate your "parameters" into a query form that produces results, rather than passing them straight though. Here is an example "translation" where the "empty" array is considered to match "anything".
Also the other conditions do not "literally" go straight through. The reason for this is that in that form MongoDB considers it to mean an "exact match". So what you want is a combination of the $elemMatch operator for multiple array conditions, and the $and operator which combines the conditions on the same property element.
This is a bit longer than $all but essentially because that operator is a "shortened" form of $and as $in is to $or:
db.collection.find({
"$and": [
{
"requiredOS": {
"$elemMatch": {
"name": "linux",
"version": "6.0"
}
}
},
{
"requiredOS": {
"$elemMatch": {
"name": "windows",
"version": "2008"
}
}
}
]
})
So it just a matter of transforming the properties in the request to actually match the required query form.
Building this into a query object can be done in a number of ways, such as using the Query builder:
DBObject query = new Query(
new Criteria().andOperator(
Criteria.where("requiredOS").elemMatch(
Criteria.where("name").is("linux").and("version").is("6.0")
),
Criteria.where("requiredOS").elemMatch(
Criteria.where("name").is("windows").and("version").is("2008")
)
)
).getQueryObject();
Which you can then pass in to a mongoOperations method as a query object or any other method that accepts the query object.