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File upload using Spring boot rest service with unit testing

We will create a REST service using spring boot which will have an endpoint to upload the file. Then we create JUnit test for upload service using mocking.

Maven dependency



REST Service for file upload

Below service reads the content of uploaded file and print on the console. Client application will upload the file using given endpoint "loadFile".
    public void loadWordsFromFile(MultipartFile file) throws IOException {
        try(BufferedReader reader = new BufferedReader(new InputStreamReader(file.getInputStream()))){
        Set<String> dictList = new HashSet<>();
            .filter(ln->ln!=null && !ln.trim().equals(""))
                .map(str->str.replaceAll("[.!]", ""))

JUnit Test

Below is the complete code for unit testing where we are creating a mock file with given text and then uploading it to our mocked service.
public class WordDictionaryApplicationTests {
    private MockMvc mockMvc;
    WebApplicationContext wContext;

    public void setup() {
       this.mockMvc = MockMvcBuilders.webAppContextSetup(wContext)

    public void firstUploadWordsTest() throws Exception {
        String text ="Text to be uploaded.";
        MockMultipartFile file = new MockMultipartFile("file","test.txt", "text/plain", text.getBytes());

Test output:

After executing the test you will see similar output where it has printed the submitted text from uploaded file.
2019-11-17 16:02:36.122  INFO 10269 --- [           main] com.wd.WordDictionaryApplicationTests    : Started WordDictionaryApplicationTests in 7.13 seconds (JVM running for 8.675)
2019-11-17 16:02:36.281  INFO 10269 --- [           main] o.s.b.t.m.w.SpringBootMockServletContext : Initializing Spring TestDispatcherServlet ''
2019-11-17 16:02:36.281  INFO 10269 --- [           main] o.s.t.web.servlet.TestDispatcherServlet  : Initializing Servlet ''
2019-11-17 16:02:36.323  INFO 10269 --- [           main] o.s.t.web.servlet.TestDispatcherServlet  : Completed initialization in 41 ms


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