How to check JSON in response body with mockMvc

There are 2 ways to check JSON responses. Lemme guide you through both of them, (taking test method from the question above, and assuming response {"data":[{"useRegEx":"false","hosts":"v2v2v2"}]} as given above)

Method 1) Asserting complete JSON

@Test
public final void testAlertFilterView() {       
    mockMvc.perform(get("/getServerAlertFilters/v2v2v2/")
           .contentType("application/json"))
           .andExpect(status().isOk())
           // you may even read bigger json responses from file and convert it to string, instead of simply hardcoding it in test class
           .andExpect(content().json("{"data":[{"useRegEx":"false","hosts":"v2v2v2"}]}"))     
}

Method 2) Asserting specific key-value of response (not writing redundant piece of code)

.andExpect(jsonPath("$.data[0].useRegEx").value(false))
.andExpect(jsonPath("$.data[0].hosts").value("v2v2v2"));

Another thing you might need is the import statement,

import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;

I use TestNG for my unit testing. But in Spring Test Framework they both looks similar. So I believe your test be like below

@Test
public void testAlertFilterView() throws Exception {
    this.mockMvc.perform(get("/getServerAlertFilters/v2v2v2/").
            .andExpect(status().isOk())
            .andExpect(content().json("{'data':[{'useRegEx':'false','hosts':'v2v2v2'}]}"));
    }

If you want check check json Key and value you can use jsonpath .andExpect(jsonPath("$.yourKeyValue", is("WhatYouExpect")));

You might find thatcontent().json() are not solveble please add

import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;

The 406 Not Acceptable status code means that Spring couldn't convert the object to json. You can either make your controller method return a String and do return json.toString(); or configure your own HandlerMethodReturnValueHandler. Check this similar question Returning JsonObject using @ResponseBody in SpringMVC

You can try the below for get and post methods

@Autowired
private MuffinRepository muffinRepository;

@Test
public void testGetMethod throws Exception(){
    Muffin muffin = new Muffin("Butterscotch");
    muffin.setId(1L);
    
    BddMockito.given(muffinRepository.findOne(1L)).
        willReturn(muffin);
        
    mockMvc.perform(MockMvcRequestBuilders.
        get("/muffins/1")).
        andExpect(MockMvcResutMatchers.status().isOk()).
        andExpect(MockMvcResutMatchers.content().string("{\"id\":1, "flavor":"Butterscotch"}"));    
}

//Test to do post operation
@Test
public void testPostMethod throws Exception(){
    Muffin muffin = new Muffin("Butterscotch");
    muffin.setId(1L);
    
    BddMockito.given(muffinRepository.findOne(1L)).
        willReturn(muffin);
        
    mockMvc.perform(MockMvcRequestBuilders.
        post("/muffins")
        .content(convertObjectToJsonString(muffin))
        .contentType(MediaType.APPLICATION_JSON)
        .accept(MediaType.APPLICATION_JSON))
        .andExpect(MockMvcResutMatchers.status().isCreated())
        .andExpect(MockMvcResutMatchers.content().json(convertObjectToJsonString(muffin))); 
}

If the response is empty then make sure to override equals() and hashCode() methods on the Entity your repository is working with:

//Converts Object to Json String
private String convertObjectToJsonString(Muffin muffin) throws JsonProcessingException{
    ObjectWriter writer = new ObjectWriter().writer().withDefaultPrettyPrinter();
    return writer.writeValueAsString(muffin);
}