count members with jsonpath?

Is it possible to count the number of members using JsonPath?

Using spring mvc test I'm testing a controller that generates

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

with

standaloneSetup(new FooController(fooService)).build()
            .perform(get("/something").accept(MediaType.APPLICATION_JSON)).andExpect(status().isOk())
            .andExpect(jsonPath("$.foo").value("oof"))
            .andExpect(jsonPath("$.bar").value("rab"));

I'd like to make sure that no other members are present in the generated json. Hopefully by counting them using jsonPath. Is it possible? Alternate solutions are welcome too.

Solution 1:

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.

Solution 2:

You can also use the methods inside the jsonpath, so instead of

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

you can do

mockMvc.perform(get(API_URL))
   .andExpect(jsonPath("$.length()", is(2)));