Support default character encoding for response in MockMvc

[sbrannen]

Overview

#27214 introduced support for setting the default character encoding in MockHttpServletResponse, and the focus of this issue is to make that configurable when building an instance of MockMvc.

Deliverables

• Introduce defaultResponseCharacterEncoding(Charset) in ConfigurableMockMvcBuilder and use it to configure the default character encoding in the underlying MockHttpServletResponse.

[lonre]

Hi @sbrannen

Could you please help to check this test case, it still fails

import static java.nio.charset.StandardCharsets.UTF_8;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
import static org.springframework.test.web.servlet.result.MockMvcResultHandlers.print;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
import static org.springframework.test.web.servlet.setup.MockMvcBuilders.standaloneSetup;

import org.junit.jupiter.api.Test;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;


class ResponseBodyTests {

	@Test
	void text() throws Exception {

		standaloneSetup(new PersonController()).defaultResponseCharacterEncoding(UTF_8).build()
				.perform(post("/person").characterEncoding(UTF_8).content("Jürgen"))
				.andDo(print())
				.andExpect(status().isOk())
				.andExpect(content().string("Jürgen"));
	}


	@RestController
	private static class PersonController {
		@PostMapping("/person")
		String post(@RequestBody String content) {
			return content;
		}
	}

}

[sbrannen]

Hi @lonre,

Thanks for providing the failing test case.

I took a look at it, and it appears that the defaultResponseCharacterEncoding has no effect for String payloads with the default configuration for Spring MVC.

Behind the scenes, a default instance of StringHttpMessageConverter is used for reading and writing the content, and in order to have it treat the content as UTF-8 encoded text for both the request and the response, you have to explicitly specify that as follows.

class RestUtf8StringPayloadTests {

	@Test
	void test() throws Exception {
		MockMvc mockMvc = standaloneSetup(new PersonController())
				// .defaultResponseCharacterEncoding(StandardCharsets.UTF_8)
				.build();

		mockMvc.perform(post("/person")
							.contentType("text/plain;charset=UTF-8")
							.accept("text/plain;charset=UTF-8")
							.content("Jürgen")
						)
				.andDo(print())
				.andExpect(status().isOk())
				.andExpect(content().encoding(StandardCharsets.UTF_8))
				.andExpect(content().string("Jürgen"));
	}


	@RestController
	private static class PersonController {
		@PostMapping("/person"))
		String post(@RequestBody String content) {
			return content;
		}
	}

}

As an alternative to specifying .accept("text/plain;charset=UTF-8") for the POST with MockMvc, you can specify that the controller method produces text/plain;charset=UTF-8 as in the following modified example.

class RestUtf8StringPayloadTests {

	@Test
	void test() throws Exception {
		standaloneSetup(new PersonController()).build()
				.perform(post("/person")
							.contentType("text/plain;charset=UTF-8")
							.content("Jürgen")
						)
				.andDo(print())
				.andExpect(status().isOk())
				.andExpect(content().encoding(StandardCharsets.UTF_8))
				.andExpect(content().string("Jürgen"));
	}


	@RestController
	private static class PersonController {
		@PostMapping(path = "/person", produces = "text/plain;charset=UTF-8")
		String post(@RequestBody String content) {
			return content;
		}
	}

}

⚠️ In both examples above, it is required that you specify not only the character encoding (UTF-8) but also the Content-Type (text/plain).

I believe this may be the expected behavior for StringHttpMessageConverter; however, I'll clarify that with @rstoyanchev.