How to count members with jsonpath?

Question

To test size of array: jsonPath("$", hasSize(4))

To count members of object: jsonPath("$.*", hasSize(4))

I.e. to test that API returns an array of 4 items:

accepted value: [1,2,3,4]

mockMvc.perform(get(API_URL))
       .andExpect(jsonPath("$", hasSize(4)));

to test that API returns an object containing 2 members:

accepted value: {"foo": "oof", "bar": "rab"}

mockMvc.perform(get(API_URL))
       .andExpect(jsonPath("$.*", hasSize(2)));

I’m using Hamcrest version 1.3 and Spring Test 3.2.5.RELEASE

hasSize(int) javadoc

Note:
You need to include hamcrest-library dependency and import static org.hamcrest.Matchers.*; for hasSize() to work.