I'm trying to distinguish between null values and not provided values when partially updating an entity with PUT request method in Spring Rest Controller.
Consider the following entity, as an example:
#Entity
private class Person {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
/* let's assume the following attributes may be null */
private String firstName;
private String lastName;
/* getters and setters ... */
}
My Person repository (Spring Data):
#Repository
public interface PersonRepository extends CrudRepository<Person, Long> {
}
The DTO I use:
private class PersonDTO {
private String firstName;
private String lastName;
/* getters and setters ... */
}
My Spring RestController:
#RestController
#RequestMapping("/api/people")
public class PersonController {
#Autowired
private PersonRepository people;
#Transactional
#RequestMapping(path = "/{personId}", method = RequestMethod.PUT)
public ResponseEntity<?> update(
#PathVariable String personId,
#RequestBody PersonDTO dto) {
// get the entity by ID
Person p = people.findOne(personId); // we assume it exists
// update ONLY entity attributes that have been defined
if(/* dto.getFirstName is defined */)
p.setFirstName = dto.getFirstName;
if(/* dto.getLastName is defined */)
p.setLastName = dto.getLastName;
return ResponseEntity.ok(p);
}
}
Request with missing property
{"firstName": "John"}
Expected behaviour: update firstName= "John" (leave lastName unchanged).
Request with null property
{"firstName": "John", "lastName": null}
Expected behaviour: update firstName="John" and set lastName=null.
I cannot distinguish between these two cases, sincelastName in the DTO is always set to null by Jackson.
Note:
I know that REST best practices (RFC 6902) recommend using PATCH instead of PUT for partial updates, but in my particular scenario I need to use PUT.
Another option is to use java.util.Optional.
import com.fasterxml.jackson.annotation.JsonInclude;
import java.util.Optional;
#JsonInclude(JsonInclude.Include.NON_NULL)
private class PersonDTO {
private Optional<String> firstName;
private Optional<String> lastName;
/* getters and setters ... */
}
If firstName is not set, the value is null, and would be ignored by the #JsonInclude annotation. Otherwise, if implicitly set in the request object, firstName would not be null, but firstName.get() would be. I found this browsing the solution #laffuste linked to a little lower down in a different comment (garretwilson's initial comment saying it didn't work turns out to work).
You can also map the DTO to the Entity with Jackson's ObjectMapper, and it will ignore properties that were not passed in the request object:
import com.fasterxml.jackson.databind.ObjectMapper;
class PersonController {
// ...
#Autowired
ObjectMapper objectMapper
#Transactional
#RequestMapping(path = "/{personId}", method = RequestMethod.PUT)
public ResponseEntity<?> update(
#PathVariable String personId,
#RequestBody PersonDTO dto
) {
Person p = people.findOne(personId);
objectMapper.updateValue(p, dto);
personRepository.save(p);
// return ...
}
}
Validating a DTO using java.util.Optional is a little different as well. It's documented here, but took me a while to find:
// ...
import javax.validation.constraints.NotNull;
import javax.validation.constraints.NotBlank;
import javax.validation.constraints.Pattern;
// ...
private class PersonDTO {
private Optional<#NotNull String> firstName;
private Optional<#NotBlank #Pattern(regexp = "...") String> lastName;
/* getters and setters ... */
}
In this case, firstName may not be set at all, but if set, may not be set to null if PersonDTO is validated.
//...
import javax.validation.Valid;
//...
public ResponseEntity<?> update(
#PathVariable String personId,
#RequestBody #Valid PersonDTO dto
) {
// ...
}
Also might be worth mentioning the use of Optional seems to be highly debated, and as of writing Lombok's maintainer(s) won't support it (see this question for example). This means using lombok.Data/lombok.Setter on a class with Optional fields with constraints doesn't work (it attempts to create setters with the constraints intact), so using #Setter/#Data causes an exception to be thrown as both the setter and the member variable have constraints set. It also seems better form to write the Setter without an Optional parameter, for example:
//...
import lombok.Getter;
//...
#Getter
private class PersonDTO {
private Optional<#NotNull String> firstName;
private Optional<#NotBlank #Pattern(regexp = "...") String> lastName;
public void setFirstName(String firstName) {
this.firstName = Optional.ofNullable(firstName);
}
// etc...
}
There is a better option, that does not involve changing your DTO's or to customize your setters.
It involves letting Jackson merge data with an existing data object, as follows:
MyData existingData = ...
ObjectReader readerForUpdating = objectMapper.readerForUpdating(existingData);
MyData mergedData = readerForUpdating.readValue(newData);
Any fields not present in newData will not overwrite data in existingData, but if a field is present it will be overwritten, even if it contains null.
Demo code:
ObjectMapper objectMapper = new ObjectMapper();
MyDTO dto = new MyDTO();
dto.setText("text");
dto.setAddress("address");
dto.setCity("city");
String json = "{\"text\": \"patched text\", \"city\": null}";
ObjectReader readerForUpdating = objectMapper.readerForUpdating(dto);
MyDTO merged = readerForUpdating.readValue(json);
Results in {"text": "patched text", "address": "address", "city": null}
Note that text and city were patched (city is now null) and that address was left alone.
In a Spring Rest Controller you will need to get the original JSON data instead of having Spring deserialize it in order to do this. So change your endpoint like this:
#Autowired ObjectMapper objectMapper;
#RequestMapping(path = "/{personId}", method = RequestMethod.PATCH)
public ResponseEntity<?> update(
#PathVariable String personId,
#RequestBody JsonNode jsonNode) {
RequestDTO existingData = getExistingDataFromSomewhere();
ObjectReader readerForUpdating = objectMapper.readerForUpdating(existingData);
RequestDTO mergedData = readerForUpdating.readValue(jsonNode);
...
}
Use boolean flags as jackson's author recommends.
class PersonDTO {
private String firstName;
private boolean isFirstNameDirty;
public void setFirstName(String firstName){
this.firstName = firstName;
this.isFirstNameDirty = true;
}
public String getFirstName() {
return firstName;
}
public boolean hasFirstName() {
return isFirstNameDirty;
}
}
Actually,if ignore the validation,you can solve your problem like this.
public class BusDto {
private Map<String, Object> changedAttrs = new HashMap<>();
/* getter and setter */
}
First, write a super class for your dto,like BusDto.
Second, change your dto to extend the super class, and change the
dto's set method,to put the attribute name and value to the
changedAttrs(beacause the spring would invoke the set when the
attribute has value no matter null or not null).
Third,traversal the map.
I have tried to solve the same problem. I found it quite easy to use JsonNode as the DTOs. This way you only get what is submitted.
You will need to write a MergeService yourself that does the actual work, similar to the BeanWrapper. I haven't found an existing framework that can do exactly what is needed. (If you use only Json requests you might be able to use Jacksons readForUpdate method.)
We actually use another node type as we need the same functionality from "standard form submits" and other service calls. Additionally the modifications should be applied within a transaction inside something called EntityService.
This MergeService will unfortunately become quite complex, as you will need to handle properties, lists, sets and maps yourself :)
The most problematic piece for me was to distinguish between changes within an element of a list/set and modifications or replacements of lists/sets.
And also validation will not be easy as you need to validate some properties against another model (the JPA entities in my case)
EDIT - Some mapping code (pseudo-code):
class SomeController {
#RequestMapping(value = { "/{id}" }, method = RequestMethod.POST, consumes = MediaType.APPLICATION_JSON_VALUE)
#ResponseBody
public void save(
#PathVariable("id") final Integer id,
#RequestBody final JsonNode modifications) {
modifierService.applyModifications(someEntityLoadedById, modifications);
}
}
class ModifierService {
public void applyModifications(Object updateObj, JsonNode node)
throws Exception {
BeanWrapperImpl bw = new BeanWrapperImpl(updateObj);
Iterator<String> fieldNames = node.fieldNames();
while (fieldNames.hasNext()) {
String fieldName = fieldNames.next();
Object valueToBeUpdated = node.get(fieldName);
Class<?> propertyType = bw.getPropertyType(fieldName);
if (propertyType == null) {
if (!ignoreUnkown) {
throw new IllegalArgumentException("Unkown field " + fieldName + " on type " + bw.getWrappedClass());
}
} else if (Map.class.isAssignableFrom(propertyType)) {
handleMap(bw, fieldName, valueToBeUpdated, ModificationType.MODIFY, createdObjects);
} else if (Collection.class.isAssignableFrom(propertyType)) {
handleCollection(bw, fieldName, valueToBeUpdated, ModificationType.MODIFY, createdObjects);
} else {
handleObject(bw, fieldName, valueToBeUpdated, propertyType, createdObjects);
}
}
}
}
Maybe too late for an answer, but you could:
By default, don't unset 'null' values. Provide an explicit list via query params what fields you want to unset. In such a way you can still send JSON that corresponds to your entity and have flexibility to unset fields when you need.
Depending on your use case, some endpoints may explicitly treat all null values as unset operations. A little bit dangerous for patching, but in some circumstances might be an option.
Another solution would be to imperatively deserialize the request body. By doing it, you will be able to collect user provided fields and selectively validate them.
So your DTO might look like this:
public class CatDto {
#NotBlank
private String name;
#Min(0)
#Max(100)
private int laziness;
#Max(3)
private int purringVolume;
}
And your controller can be something like this:
#RestController
#RequestMapping("/api/cats")
#io.swagger.v3.oas.annotations.parameters.RequestBody(
content = #Content(schema = #Schema(implementation = CatDto.class)))
// ^^ this passes your CatDto model to swagger (you must use springdoc to get it to work!)
public class CatController {
#Autowired
SmartValidator validator; // we'll use this to validate our request
#PatchMapping(path = "/{id}", consumes = "application/json")
public ResponseEntity<String> updateCat(
#PathVariable String id,
#RequestBody Map<String, Object> body
// ^^ no Valid annotation, no declarative DTO binding here!
) throws MethodArgumentNotValidException {
CatDto catDto = new CatDto();
WebDataBinder binder = new WebDataBinder(catDto);
BindingResult bindingResult = binder.getBindingResult();
List<String> patchFields = new ArrayList<>();
binder.bind(new MutablePropertyValues(body));
// ^^ imperatively bind to DTO
body.forEach((k, v) -> {
patchFields.add(k);
// ^^ collect user provided fields if you need
validator.validateValue(CatDto.class, k, v, bindingResult);
// ^^ imperatively validate user input
});
if (bindingResult.hasErrors()) {
throw new MethodArgumentNotValidException(null, bindingResult);
// ^^ this can be handled by your regular exception handler
}
// Here you can do normal stuff with your catDto.
// Map it to cat model, send to cat service, whatever.
return ResponseEntity.ok("cat updated");
}
}
No need for Optional's, no extra dependencies, your normal validation just works, your swagger looks good. The only problem is, you don't get proper merge patch on nested objects, but in many use cases that's not even required.
Probably to late but following code works for me to distinguish between null and not provided values
if(dto.getIban() == null){
log.info("Iban value is not provided");
}else if(dto.getIban().orElse(null) == null){
log.info("Iban is provided and has null value");
}else{
log.info("Iban value is : " + dto.getIban().get());
}
Related
My REST controller :
#RestController
#RequestMapping("/api/people")
public class PersonController {
#Autowired
private PersonRepository people;
#Transactional
#RequestMapping(path = "/{personId}", method = RequestMethod.PUT)
public ResponseEntity<?> update(
#PathVariable String personId,
#RequestBody PersonDTO dto) {
// get the entity by ID
Person p = people.findOne(personId); // we assume it exists
// update ONLY entity attributes that have been defined
if(/* dto.getFirstName is defined */)
p.setFirstName = dto.getFirstName;
if(/* dto.getLastName is defined */)
p.setLastName = dto.getLastName;
System.out.println(dto);
return ResponseEntity.ok(p);
}
}
My People DTO :
private class PersonDTO {
private String firstName;
private String lastName;
private List<String> designations;
private String location;
/* getters and setters ... */
}
I'm not passing the value designations in my REST request made through postman here and i see the values in the DTO while debuging in local or when printing, it says the designations is "Null" but i want it to be seen as blank arraylist. How can i do it?
There is nothing stopping you from defining the your PersonDto like so:
private List<String> designations = new ArrayList<>();
Meaning that even if the client sends null you'll be deserializing into an empty list.
First initialize your designations array in PersonDTO like so:
private List<String> designations = new ArrayList<String>();
Then make the following changes to your setter method for designations
public void setDesignations(List<String> designations) {
if (designations != null)
this.designations = designations;
}
It's pretty like params in #RequestMapping annotation, which narrows down the matching methods with query parameters. Instead, I want to achieve this with body parameters (like JSON-format). Do I need to implement a custom #RequestMapping annotation?
YOu can achieve it using #RequestBody. It matches payload with names specified in code.
https://www.baeldung.com/spring-request-response-body
You just have to use #RequestBody. Note that this not only allows POJO, you can use it with a Map too.
With a POJO:
#RequestMapping(value="/",method = RequestMethod.POST)
public String doSomething(#RequestBody MyDto dto) {
return service.requestOTP(dto.getField1(), dto.getField2());
}
With a Map:
#RequestMapping(value="/",method = RequestMethod.POST)
public String doSomething(#RequestBody Map<String, Object> body) {
return service.requestOTP(body.get("field1").toString(), body.get("field2").toString());
}
NOTE: If you would like to validate properties of an object used with #RequestBody, you can add #Valid annotation. For instance, the following will cascade the validation on the model and the models sub model fields(if found).
public class MyDto {
#NotNull
#Valid
private String field1;
private String field2;
//getters and setters
}
#RequestMapping(value="/",method = RequestMethod.POST)
public String doSomething(**#Valid** #RequestBody MyDto dto) {
return service.requestOTP(dto.getField1(), dto.getField2());
}
Check here for a brave introduction for #Valid https://www.logicbig.com/tutorials/java-ee-tutorial/bean-validation/cascaded-validation.html
I want to return an error when the body of a REST request is empty (e.g contains only {}) but there is no way to detect if the request body contains an empty JSON or not.
I tried to change #RequestBody(required = true) but it's not working.
#PatchMapping("{id}")
public ResponseEntity<Book> updateAdvisor(#PathVariable("id") Integer id,
#Valid #RequestBody BookDto newBook) {
Book addedBook = bookService.updateBook(newBook);
return new ResponseEntity<>(addedBook,HttpStatus.OK);
}
If the body sent contains an empty JSON I should return an exception.
If the body is not empty and at least one element is provided I won't return an error.
Try #RequestBody(required = false)
This should cause the newBook parameter to be null when there is no request body.
The above still stands and is the answer to the original question.
To solve the newly edited question:
Change the #RequestBody BookDto newBook parameter to a String parameter
(for example, #RequestBody String newBookJson).
Perform pre-conversion validation (such as, "is the body an empty JSON string value").
If the body contains valid JSON,
parse the JSON into to an object (example below).
#Autowired
private ObjectMapper objectMapper; // A Jackson ObjectMapper.
#PatchMapping("{id}")
public ResponseEntity<Book> updateAdvisor(
#PathVariable("id") Integer id,
#Valid #RequestBody String newBookJson)
{
if (isGoodStuff(newBookJson)) // You must write this method.
{
final BookDto newBook = ObjectMapper.readValue(newBookJson, BookDto.class);
... do stuff.
}
else // newBookJson is not good
{
.. do error handling stuff.
}
}
Let's suppose you have a Class BookDto :
public class BookDto {
private String bookName;
private String authorName;
}
We can use #ScriptAssert Annotation on Class BookDto:
#ScriptAssert(lang = "javascript", script = "_this.bookName != null || _this.authorName != null")
public class BookDto {
private String bookName;
private String authorName;
}
then in the resource/controller Class:
#PatchMapping("{id}")
public ResponseEntity<Book> updateAdvisor(#PathVariable("id") Integer id,
#Valid #RequestBody BookDto newBook) {
Book addedBook = bookService.updateBook(newBook);
return new ResponseEntity<>(addedBook,HttpStatus.OK);
}
Now #Valid annotation will validate whatever we have asserted in the #ScriptAssert annotation's script attribute. i.e it now checks if the body of a REST request is empty (e.g contains only {}).
I want to ignore some fields during deserialization of json data in spring. I cannot use #JsonIgnore as the same model will be used in different methods and different fields need to be ignored.
I have tried to explain the situation with the below example.
class User
{
private String name;
private Integer id;
//getters and setters
}
This is the User class that will be used as model.
#RequestMapping(value = '/path1', method = RequestMethod.POST)
#ResponseBody
public ResponseEntity<CustomResponse> loadUser1(#RequestBody User user){
System.out.println(user.name);
//user.id is not required here
}
This is the first method that will use user.name and ignore user.id.
#RequestMapping(value = '/path2', method = RequestMethod.POST)
#ResponseBody
public ResponseEntity<CustomResponse> loadUser2(#RequestBody User user){
System.out.println(user.id);
//user.name is not required here
}
This is the second method that will use user.id and ignore user.name.
You can use #JsonFilter to achieve dynamic filtering.
First, create a filter using com.fasterxml.jackson.databind.ser.impl.SimpleBeanPropertyFilter and pass it to a filter provider com.fasterxml.jackson.databind.ser.impl.SimpleFilterProvider.
Then, declare this filter on your bean using #JsonFilter.
In your case, this will do it:
#JsonFilter("myFilter")
public class User {
private String name;
private int id;
// Getters and setters
}
This will apply the filter on your POJO:
public MappingJacksonValue getFiltered() {
SimpleFilterProvider filterProvider = new SimpleFilterProvider();
filterProvider.addFilter("myFilter", SimpleBeanPropertyFilter.filterOutAllExcept("id"));
User user = new User();
user.setId(1);
user.setName("Me");
MappingJacksonValue jacksonValue = new MappingJacksonValue(user);
jacksonValue.setFilters(filterProvider);
return jacksonValue;
}
Edit:
SimpleBeanPropertyFilter has factory methods to tender to almost all practical filtering scenarios. Use them appropriately.
I am using Springfox and Swagger to generate swagger files. Right now I'm using #ModelAttribute to pull the variables from an object (NetworkCmd) to show as query params in the swagger doc.
I currently have the following controller:
#RequestMapping(value = "/{product_id}", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
#ResponseHeader()
public ResponseEntity<?> networkResponse(
#RequestHeader HttpHeaders headers,
#PathVariable("product_id")String productId,
#Valid #ModelAttribute NetworkCmd cmd,
BindingResult result)
throws Exception {
...
}
And here is a sample of NetworkCmd:
#ItemId
#NotNull(message = "product cannot be null")
#ApiModelProperty(
value = "testing")
private String product_id;
#ApiModelProperty(
value = "key",
private String key;
#ApiModelProperty(
value = "parent")
private Boolean is_parent_id;
#Min(0)
#ApiModelProperty(
value = "radius")
private double radius = 10d;
One of the variables in this class is a custom domain object Nearby.
private Nearby nearby = null;
public Nearby getNearby() {
return nearby;
}
public void setNearby(String nearby) throws ParseException {
this.nearby = Nearby.parse(nearby);
}
This is kind of a special variable because it takes in a String, and then parses that string and turns it into the Nearby object.
My problem is that this Nearby variable isn't showing up on the generated swagger document through #ModelAttribute. I'm happy to provide any more information.
One way to get around this problem is to create an alternate type rule in your docket. This way anytime we encounter the nearby type we treat it as a string.
new Docket(...)
.directModelSubstitute(Nearby.class, String.class)