Develop Reference

Validating multipart/form-data in Spring REST api

I recently came up to an issue related to validation. Typically, I am building a REST api that allow users to create their account including avatars. All of the information should be submitted when user clicks to Register button. So, my server will then receive a request that includes some fields like name (string), birthday (datetime), ... and avatar (multipart file). So, the question is how to validate the received file is a truly image and has an allowed size and simultaneously validate that the others (email, password) are also valid.
For the case that all fields is text, we can easily validate them using the combination of annotations like this
Controller
#PostMapping(path = "")
public ResponseEntity<?> createNewAccount(#RequestBody #Valid RegisterRequest registerRequest) {
Long resourceId = service.createNewCoderAccount(registerRequest);
return ResponseEntity.created(location(resourceId)).build();
}
Request DTO
#ConfirmedPassword
public class RegisterRequest extends BaseRequest implements ShouldConfirmPassword {
#NotBlank(message = "Field 'email' is required but not be given")
#Email
#Unique(message = "Email has been already in use", service = UserValidatorService.class, column = "email")
private String email;
#NotBlank(message = "Field 'password' is required but not be given")
#Size(min = 6, message = "Password should contain at least 6 characters")
private String password;
#NotBlank(message = "Field 'confirmPassword' is required but not be given")
private String confirmPassword;
#NotBlank(message = "Field 'firstName' is required but not be given")
private String firstName;
#NotBlank(message = "Field 'lastName' is required but not be given")
private String lastName;
}
Or in case that the request containing only file(s), we can absolutely do like this
Controller
#PostMapping(path = "/{id}")
public ResponseEntity<?> editChallengeMetadata(
#ModelAttribute ChallengeMetadataRequest request,
BindingResult bindingResult,
#PathVariable("id") Long id,
#CurrentUser User user
) throws BindException {
challengeMetadataRequestValidator.validate(request, bindingResult);
if (bindingResult.hasErrors()) {
throw new BindException(bindingResult);
}
Long challengeId = service.updateChallengeMetadata(id, request, user);
return ResponseEntity.ok(RestResponse.build(challengeId, HttpStatus.OK));
}
Validator
public class ChallengeMetadataRequestValidator implements Validator {
#Override
public boolean supports(#NonNull Class<?> aClass) {
return ChallengeMetadataRequest.class.isAssignableFrom(aClass);
}
#Override
public void validate(#NonNull Object o, #NonNull Errors errors) {
ChallengeMetadataRequest request = (ChallengeMetadataRequest) o;
if (request.getBanner() != null && !request.getBanner().isEmpty()) {
if (!List.of("image/jpeg", "image/png").contains(request.getBanner().getContentType())) {
errors.rejectValue("banner", "challenge.mime-type.not-supported", new String[]{request.getBanner().getContentType()}, "Mime-type is not supported");
}
}
}
}
As you seen above, if I wrap all data (including avatar) in a DTO class, I definitely write its own validator. But what will happen if then I have to write manually hundreds validators like that.
So, do anyone have any idea about it, typically, make the multipart/form-data request becomes simalar with application/json request ?
Thanks and regards,

Spring Boot #GetMapping rule for multiple mapping

I have 3 different method in controller for get requests.
-the 1st one to get a user by id with a path variable:
#GetMapping(path="/{id}")
public ResponseEntity<UserInfoDTO> getUserById(#PathVariable Long id)
The 2nd gets a user based on the username parameter:
public ResponseEntity<UserInfoDTO> getUserByUsername(#RequestParam String username)
And finally another one to get all users
public ResponseEntity<List<UserInfoDTO>> getAllUsers()
What should be the #GetMapping for the 2nd and 3rd method?
For exemple #GetMapping for all users and #GetMapping(path="/") for a user by username?
Or whatever...
Thanks.

Defining the Mappings purely depends on the context of your application and its usecases.
We can define a context prefixed by users and modified mappings are show in the snippet below and at the time of invocation it can be called like mentioned in the comments,
#GetMapping(path="/users/")
public ResponseEntity<UserInfoDTO> getUserByUsername(#RequestParam String username) {
}
// GET: <protocol>://<hostUrl>/users?username=<username>
#GetMapping(path="/users")
public ResponseEntity<List<UserInfoDTO>> getAllUsers() {
}
// GET: <protocol>://<hostUrl>/users
#GetMapping(path="/users/{id}")
public ResponseEntity<UserInfoDTO> getUserById(#PathVariable Long id)
// GET: <protocol>://<hostUrl>/users/<userid>

For example, optional username param:
#GetMapping(path = "/")
public ResponseEntity<?> getUserByUsername(#RequestParam(required = false) final String username) {
if (username != null) {
// http://localhost:8080/?username=myname
return new ResponseEntity<>(new UserInfoDTO("by username: " + username), HttpStatus.OK);
} else {
// http://localhost:8080/
return getAllUsers();
}
}
private ResponseEntity<List<UserInfoDTO>> getAllUsers() {
return new ResponseEntity<>(List.of(new UserInfoDTO("user1-of-all"), new UserInfoDTO("user2-of-all")),
HttpStatus.OK);
}
public static class UserInfoDTO {
public UserInfoDTO(final String name) {
this.name = name;
}
private final String name;
public String getName() {
return name;
}
}

Spring #RequestMapping with optional parameters when using custom request object

Hello I want to make an optional parameter on my controller, id that so far looks like this
#ApiOperation(value = "get runs by date in order to paginate")
#ApiResponses({ #ApiResponse(code = 200, message = "Success"),
#ApiResponse(code = 500, message = "Unexpected failure") })
#RequestMapping(value = "/time/{date}/to/{toPage}/from/{fromPage}",
params = {"pageSize", "id"},
method = RequestMethod.GET)
public RunCollection getPolicyByDate(GetPolicyByDateRequest request) {
return serviceImpl.getListOfRunsByDate(request);
}
But this means the parameter is required. I want it to be optional. I saw this answer where they use #RequestParam Spring #RequestMapping with optional parameters but I want to include it in my GetPolicyByDateRequest object. Is this possible? The spring docs don't allude to turning off the required attribute. Could I possibly use Optional

2 options :
If your GetPolicyByDateRequest has not primitive attribute, they should be inserted by Spring in your object. If your parameter is not set (i.e there is no pageSize in your url) then Spring injects NULL in your attribute.
public class GetPolicyByDateRequest {
private String date;
private int toPage;
private int fromPage;
private Integer pageSize;
private Integer id;
public GetPolicyByDateRequest() {
}
public String getDate() {
return date;
}
public void setDate(String date) {
this.date = date;
}
public int getToPage() {
return toPage;
}
public void setToPage(int toPage) {
this.toPage = toPage;
}
public int getFromPage() {
return fromPage;
}
public void setFromPage(int fromPage) {
this.fromPage = fromPage;
}
public Integer getPageSize() {
return pageSize;
}
public void setPageSize(Integer pageSize) {
this.pageSize = pageSize;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
#Override
public String toString() {
return "MyRequest{" +
"date='" + date + '\'' +
", toPage=" + toPage +
", fromPage=" + fromPage +
", pageSize=" + pageSize +
", id=" + id +
'}';
}
}
Weirdly, I think it is some king of bug in Spring, even when using Optional you get a null object if the parameter in the requestParam is not provided.
If you want to get all parameters, you need to use #PathVariable with #RequestParam in your case. Here is how to get your parameters :
#RequestMapping(value = "/time/{date}/to/{toPage}/from/{fromPage}", method = RequestMethod.GET)
public RunCollection getPolicyByDate(#PathVariable String date, #PathVariable int toPage, #PathVariable int fromPage, #RequestParam(required = false) Optional<Integer> pageSize, #RequestParam(required = false) Optional<Integer> id) {
// then use your parameters the way you to use then.
}
Please note :
#PathVariable retrieves the parameter in the URL, where the value is between {}, like {date} -> #PathVariable String date
#RequestParam retrieves the parameter after the ? in the URL. ?pageSize=10 -> #RequestParam int pageSize.
Both of this annotation takes as parameters, among others, required=true|false. When do mark a parameter as not required, make sure you don't use a primitive type, like int, otherwise, you can set null to this object, and your code will fail at runtime. This is the reason why I have used Optional<Integer>, to allow the type. But Spring is clever, and if it detects the Optional in your parameter, then you are forced to use required=false in the #RequestParam.
If you wanted to populate your GetPolicyByDateRequest, then you should have done a POST mapping, and use the annotation #RequestBody GetPolicyByDateRequest request, and send a JSON body in your request to make Spring (actually Jackson) translate your JSON into a GetPolicyByDateRequest object.
Hope it helps

JsonGetter giving null value

In my Spring Boot application I am creating a REST API, which is calling some other external REST API. I created User class, which is a object that is received by my Rest API downloaded from the external API. My user model looks like:
#JsonIgnoreProperties(ignoreUnknown = true)
public class User {
private String fullName;
private String department;
#JsonGetter("fullName")
public String getFullName() {
return fullName;
}
#JsonSetter("full_name")
public void setFullName(String fullName) {
this.fullName = fullName;
}
#JsonGetter("department")
public String getDepartment() {
return department;
}
#JsonSetter("department")
public void setDepartment(String department) {
this.department = department;
}
}
I am using JsonGetter and JsonSetter properties, because I would like to have my json properties in response returned in camelCase, but the properties given in external API are returned with underscore:
External API Response:
{
"full_name": "User A",
"department": "A",
}
My API Response:
{
"fullName": "User A",
"department": "A",
}
And everything seems to be working fine (hitting my API with Postman gives proper responses) until I started to create some Http request tests. In tests I receive assertion error that fullName property is null, while doing the same request in postman is responding with proper responses.
My test class:
#RunWith(SpringRunner.class)
#SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class HttpRequestTest {
#LocalServerPort
private int port;
#Autowired
private TestRestTemplate restTemplate;
#Test
public void shouldReturnUserFullName() throws Exception {
assertThat(this.restTemplate.getForObject("http://localhost:" + port + "/users/a",
User.class)).extracting(User::getFullName)
.contains("User A");
}
}
My controller method:
#GetMapping("users/{name}")
public ResponseEntity<User> getSpecificUserByName(#PathVariable("name") String name) {
HttpHeaders headers = new HttpHeaders();
headers.add(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE);
headers.add(HttpHeaders.ACCEPT, MediaType.APPLICATION_JSON_VALUE);
HttpEntity<?> entity = new HttpEntity<>(headers);
ResponseEntity<User> response = restTemplate.exchange(createUriString(name), HttpMethod.GET, entity, User.class);
return response;
}
Test result:
java.lang.AssertionError:
Expecting:
<[null]>
to contain:
<["User A"]>
but could not find:
<["User A"]>
I would appreciate any help with this issue :)

#JsonSetter("full_name") expects your API response to contain a property full_name during deserialzation. Since #JsonGetter("fullName") converts full_name to fullName, field private String fullName; is never set.
You should change #JsonSetter("full_name") to #JsonSetter("fullName").

Let us take an example
Suppose your REST API returns below Object of User class
User reponse = new User();
response.setFullName("User A");
response.setDepartment("A");
So, when we call your REST API, the JSON response would look like as below
{
"fullName":"User A",
"department":"A"
}
Now, When you pass this JSON to convert into User class, Jackson will look for methods with the name setFullName and setDepartment.
In your test case, something similar is happening,
for code
this.restTemplate.getForObject("http://localhost:" + port + "/users/a",User.class)
First, it calls your API to get the User object Serialized and then it Deserialized it to User class. While Deserializing, it looks for a method named
setFullName without any
#Setter
#JsonProperty
#JsonAlias
annotations
or will look for any setter method with
#Setter("fullName")
#JsonProperty("fullName"),
#JsonAlias("fullName")
but in your case, the fullName setter is treated as
public void setFull_name(String fullName) {
this.fullName = fullname;
}
So, setter for fullName is not found but since you marked your User class as
#JsonIgnoreProperties(ignoreUnknown = true)
hence any exception is not thrown but fullName for your Response JSON is ignored, so fullName is never set, which remains null and your Test case is failing.
So, either change your test case or mark your setter with
#JsonAlias("fullName")
annotation.
i.e. Your User class will look like as below
#JsonIgnoreProperties(ignoreUnknown = true)
public class User {
private String fullName;
private String department;
#JsonGetter("fullName")
public String getFullName() {
return fullName;
}
#JsonAlias({"fullName","full_name"})
public void setFullName(String fullName) {
this.fullName = fullName;
}
#JsonGetter("department")
public String getDepartment() {
return department;
}
#JsonSetter("department")
public void setDepartment(String department) {
this.department = department;
}
}

How to receive json param in spring boot

I have a Json like the following.
{"person":[{"name":"asd","age":"22"},{"name":"asd","age":"22"}]}
but it could also be:
{"person":[{"name":"asd","age":"22"},{"name":"asd","age":"22"}],"city":["NewYork"],"student":"false"}
How can I receive it in a Spring Boot Controller?

You should use #RequestBody annotation.
#RequestMapping("/api/example")
public String example(#RequestBody String string) {
return string;
}
Later, add some validations and business logic.
You can generate custom class with http://www.jsonschema2pojo.org/. Once generated you can expect your custom class instead of String.
For further instructions, I find this tutorial interesting.

You can receive the json like below, Spring Boot will convert your json into model(For example "Comment" model below) which you defined.
#RequestMapping(value = "/create", method = RequestMethod.POST)
public ResultModel createComment(#RequestBody Comment comment) {...}

1) You need to difine your rest controllers. Example
#Autowired
UserService userService;
#RequestMapping(value = "/user/", method = RequestMethod.GET)
public ResponseEntity<List<User>> listAllUsers() {
List<User> users = userService.findAllUsers();
if (users.isEmpty()) {
return new ResponseEntity(HttpStatus.NOT_FOUND);
}
return new ResponseEntity<List<User>>(users, HttpStatus.OK);
}
2) Define your pojo: Example
public class User {
String name;
String age;
public User(String name, String age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public String getAge() {
return age;
}
}
3) Define a service
#Service
public class UserService {
public List<User> findAllUsers(){
// Those are mock data. I suggest to search for Spring-data for interaction with DB.
ArrayList<User> users = new ArrayList<>();
User user = new User("name", "5");
users.add(user);
return users;
}
}
You can follow this tutorial. If you want to just send a json message to a spring boot rest controller you can use a rest client like postman.