Manually handling UTF-8 encoding failures

App.java

import java.io.UnsupportedEncodingException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.CharacterCodingException;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.StandardCharsets;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@RestController
public class App {

    public static void main(String[] args) {
        SpringApplication.run(App.class, args);
    }

    @PostMapping("/")
    public String test(@RequestBody byte[] body) throws CharacterCodingException, UnsupportedEncodingException {
        final CharsetDecoder newDecoder = StandardCharsets.UTF_8.newDecoder();
        final CharBuffer decode = newDecoder.decode(ByteBuffer.wrap(body));
        return decode.toString();
    }

    @ResponseStatus(HttpStatus.BAD_REQUEST)
    @ExceptionHandler(value = { CharacterCodingException.class, UnsupportedEncodingException.class })
    void handleEncodingFuckup(Exception e) {

    }
}

AppTest.java

import static org.assertj.core.api.Assertions.assertThat;

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
import org.springframework.boot.test.web.client.TestRestTemplate;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;

@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
public class AppTest {

    @Autowired
    private TestRestTemplate testResttemplate;

    @Test
    void testPostWrongEncoding() throws Exception {
        final byte[] body = "Tölzer Str.".getBytes("ISO-8859-1");
        final ResponseEntity<String> forEntity = testResttemplate.postForEntity("/", body, String.class);
        assertThat(forEntity.getStatusCode()).isEqualTo(HttpStatus.BAD_REQUEST);
    }

    @Test
    void testPostCorrectEncoding() throws Exception {
        final byte[] body = "Tölzer Str.".getBytes("UTF-8");
        final ResponseEntity<String> forEntity = testResttemplate.postForEntity("/", body, String.class);
        assertThat(forEntity.getStatusCode()).isEqualTo(HttpStatus.OK);
    }
}