Spring Controller - Testing to receive nested dto with multipartfile inside with postman - spring

Question

I'm working on a service which accepts a DTO in a POST method and creates an entity based on that DTO. Nested inside is a multipart file, which is going to be an image used by the entity that will be created.
Using postman to test my backend, I keep receiving an seemingly empty DTO. The three logs inside the controller return null, 0 and null respectively.
This is how I setup my data, which I am quite sure is the problem:
I converted my image into a base64 string, which as far as I know is the only way I can post a nested image.
Code
Controller
#PostMapping(consumes = MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity<InventoryComponentDto> create(#ModelAttributee InventoryComponentDto request) {
System.out.println(request.getDescription());
System.out.println(request.getMinimal_supply());
System.out.println(request.getComponent());
InventoryComponentDto result = inventoryComponentService.create(request);
if (result == null) {
return new ResponseEntity<>(null, HttpStatus.BAD_REQUEST);
}
return ResponseEntity.ok(result);
}
InventoryComponentDto
public class InventoryComponentDto {
private ComponentDto component;
private String description;
private Date createdAt;
private Date updatedAt;
private int minimal_supply;
private int supply;
}
ComponentDto
public class ComponentDto {
private Long id;
private int number;
private String name;
private FileDto image;
}
FileDto
public class FileDto {
private String name;
private String type;
private String url;
private MultipartFile data;
}
What would be the way for me to adequately create my dto in postman, including an image?
Update
"status": 400,
"error": "Bad Request",
"message": "JSON parse error: (was java.lang.NullPointerException); nested exception is com.fasterxml.jackson.databind.JsonMappingException: (was java.lang.NullPointerException) (through reference chain: com.package.MCI.dto.InventoryComponentDto[\"component\"]->com.package.MCI.dto.ComponentDto[\"image\"])",
"trace": "org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: (was java.lang.NullPointerException); nested...

Answer 1

You need to create a custom jackson deserializer.
//CustomDeserializer
import java.io.IOException;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.deser.std.StdDeserializer;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItem;
import org.springframework.util.Base64Utils;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.multipart.commons.CommonsMultipartFile;
public class CustomDeserializer extends StdDeserializer<FileDTO> {
public CustomDeserializer() {
super(FileDTO.class);
}
protected CustomDeserializer(Class<?> vc) {
super(vc);
}
#Override
public FileDTO deserialize(JsonParser jsonParser,
DeserializationContext deserializationContext)
throws IOException, JsonProcessingException {
JsonNode node = jsonParser.getCodec().readTree(jsonParser);
String name = node.get("name").asText();
String url = node.get("url").asText();
String type = "." + node.get("type").asText();
String fileBase64 = node.get("data").asText();
byte[] fileBytes = Base64Utils.decodeFromString(fileBase64);
FileItem fileItem = new DiskFileItem(name, "image/jpg", false, name + type,
fileBytes.length, null);
fileItem.getOutputStream().write(fileBytes);
fileItem.getOutputStream().flush();
MultipartFile file = new CommonsMultipartFile(fileItem);
fileItem.getOutputStream().close();
FileDTO fileDTO = new FileDTO();
fileDTO.setName(name);
fileDTO.setUrl(url);
fileDTO.setType(type);
fileDTO.setData(file);
return fileDTO;
}
}
And use it like:
//FileDTO
#JsonDeserialize(using = CustomDeserializer.class)
public class FileDTO {
You need these two dependencies:
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.2</version>
</dependency>
<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>2.5</version>
</dependency>