Overview

Usage in Tests

Setup of RestTemplateBuilder Programatically

This setup is useful for unit tests which should be independent of spring application context. Like described in the javadoc of the class org.springframework.boot.test.web.client.MockServerRestTemplateCustomizer.

MockServerRestTemplateCustomizer mockServerCustomizer = new MockServerRestTemplateCustomizer();
MyService companyService = new MyService(new RestTemplateBuilder(mockServerCustomizer));
MockRestServiceServer server = mockServerCustomizer.getServer();
...

Modul Tests

Test the module / applicaton without external dependencies. The setup corresponds to the setup of the spring boot application.

When using the RestTemplateBuilder there is a quite high possibility that there are more than one RestTemplates created and used. In order to build expectations against the RestTemplate invocations, one can use MockServerRestTemplateCustomizer like described in the javadoc. The disadvantage is that for each RestTemplate there is one MockRestServiceServer (and RequestExpectationManager) which make it difficult to formulate expactations.

A easy way to circumvent this problem is to create a custom RestTemplateCustomizer which has similar functionality but uses only one RequestExpectationManager for all RestTemplates.

public class MockRestServerRestTemplateCustomizer implements RestTemplateCustomizer {

    private final RequestExpectationManager expectationManager = new SimpleRequestExpectationManager();

    private final ClientHttpRequestFactory factory = (uri, httpMethod) -> {
        return new MockClientHttpRequest(httpMethod, uri) {
            @Override
            protected ClientHttpResponse executeInternal() throws IOException {
                return createResponse(this);
            }
        };
    };

    private ClientHttpResponse createResponse(final ClientHttpRequest clientHttpRequest) throws IOException {
        Assert.notNull(clientHttpRequest.getURI(), "'uri' must not be null");
        Assert.notNull(clientHttpRequest.getMethod(), "'httpMethod' must not be null");
        return this.expectationManager.validateRequest(clientHttpRequest);
    }

    @Override
    public void customize(final RestTemplate restTemplate) {
        restTemplate.setRequestFactory(this.factory);
    }
...
}

@RunWith(SpringRunner.class)
@SpringBootTest(classes = {..., MockRestServerRestTemplateCustomizer.class })
@AutoConfigureMockMvc
public class CMyTest {

    @Autowired
    private MockRestServerRestTemplateCustomizer mockServer;
    ...
    
     @Test
    public void test(){
      this.mockServer.expect(requestTo(...);
      ...
    }

References