This is a little Spring Boot application where my goal was to use purely JPA queries to enable queries of a labeled (key=value) resources in a SQL database.

Storing the key and value separately in the database and then querying them became impossible (or at least very difficult). So, the solution cheats a little by textually combining the key and value into a single string each using an = delimiter. A collection membership predicate is supported for element collections that are lists of strings, so that was the predicate the queries are built around.

Supported REST operations

Bulk create resources

POST localhost:8080/resource/_batch
[
	{
		"name": "red apple",
		"labels": {
			"fruit": "apple",
			"color": "red"
		}
	},
	{
		"name": "green apple",
		"labels": {
			"fruit": "apple",
			"color": "green"
		}
	},
	{
		"name": "yellow apple",
		"labels": {
			"fruit": "apple",
			"color": "yellow"
		}
	},
	{
		"name": "green pear",
		"labels": {
			"fruit": "pear",
			"color": "green"
		}
	}
]

Get all resources

GET localhost:8080/resource

Delete all resources

DELETE localhost:8080/resource

Query with label selector(s)

POST localhost:8080/_query/resource
{
	"labelSelectors": {
		"fruit": "apple"
	}
}