(Hash)-Map as RequestParam in a spring-boot application

Question

• I want to specify filters for a CRUD GET REST controller for a list of items.

• The items I do return have a name name: String, a boolean property isFoo: boolean and labels: Map<String, String>.

• My list controller uses q for the name-filter and isFoo for the boolean property.

• Now I want to filter on labels as well.

• Additionally I use org.springframework.data.domain.Page to return sub-sets.

• I declared it naively like this and tested by adding labels=%7Ba%3Db%2C+c%3Dd%7D

@GetMapping("")
MyReturnType list(
  @RequestParam(defaultValue = 0) final int page,
  @RequestParam(defaultValue = 10) final int size,
  @RequestParam(defaultValue = true) final boolean isFoo,
  @RequestParam(required = false) final String q,
  @RequestParam(required = false, name = "labels") final Map<String, String> labels) {
...
}

• However I get a HTTP 500
• How may I specify this?