Uploading file other than post

Restful style of API designing broaden my horizon by standardizing the rule for API.

POST

must be something new into server, which means creating a new resource.

PUT

Must be updating existing resources in server.

DELETE

Must delete a exist resource in server, if not so, ignore its operation.

GET

Obviously, it is read only operation.

But most of the uploading APIs are designed to use POST, even in springmvc’s org.springframework.test.web.servlet.request.MockMvcRequestBuilders.fileUpload, it use POST method only. I think this is not a good practise, especially for a person who want to insist on using Restful style.

Other than using POST, what we could do to achieve this is like below, idea is part from SOF:

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MultipartResovler

Extends CommonsMultipartResolver to enable multipart resolvation other than POST.

public class ExtendedMultipartResolver extends CommonsMultipartResolver
{
    private static final String MULTIPART = "multipart";
    private boolean isMultipartContent(HttpServletRequest request)
    {
        String httpMethod = request.getMethod().toLowerCase();
        // test for allowed methods here...
        String contentType = request.getContentType();
        return (contentType != null && contentType.toLowerCase().startsWith(MULTIPART));
    }

    @Override
    public boolean isMultipart(HttpServletRequest request)
    {
        return (request != null && isMultipartContent(request));
    }
}

Springmvc configuration

In springmvc application context file, add the last class we created:

@Bean
//bean name must be exactly "multipartResolver"
public MultipartResolver multipartResolver()
{
    ExtendedMultipartResolver emr = new ExtendedMultipartResolver();
    //notice this parameter is also important to configure
    cmr.setMaxUploadSize(9999999);
    return emr;
}

JAR

Because we introduced CommonsMultipartResolver, which uses 2 apache jars, we also need to import them in pom file:

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.4</version>
</dependency>
<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.3.1</version>
</dependency>

Unit test

Now seems all configuration are done, time to start coding for unit test:

@Test
public void testUpdateOperation() throws Exception
{
    System.out.println("update operation");
    FileInputStream fis = new FileInputStream(file);
    MockMultipartFile multipartFile = new MockMultipartFile("file", fis);
    Map<String, String> contentTypeParams = new HashMap<>();
    //The boundary parameter is important!
    contentTypeParams.put("boundary", "RugalBernstein");
    MediaType mediaType = new MediaType("multipart", "form-data", contentTypeParams);
    MvcResult result = this.mockMvc.perform(put("/tag/" + db.getTid())
        .header(SystemDefaultProperties.ID, user.getUid())
        .header(SystemDefaultProperties.CREDENTIAL, user.getPassword())
        .param("name", db.getName() + "Updated")
        .content(multipartFile.getBytes())
        .contentType(mediaType)
        .accept(MediaType.APPLICATION_JSON))
        .andExpect(status().isOk())
        .andDo(print())
        .andReturn();
}

This should be pretty satisfying, because we not only stick to the Restful style, but also upload file successfully.

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Notice the boundary parameter in content type is mandatory. For people do not know what boundary is, here are some posts.
Hope this post could help someone!