I would like to know how to access a deep collection class attribute in a GET request. My endpoint maps my query strings through #ModelAttribute annotation:
Given that:
public class MyEntity
{
Set<Item> items;
Integer status;
// getters setters
}
public class Item
{
String name;
// getters setters
}
And my GET request: localhost/entities/?status=0&items[0].name=Garry
Produces bellow behavior?
#RequestMapping(path = "/entities", method = RequestMethod.GET)
public List<MyEntity> findBy(#ModelAttribute MyEntity entity) {
// entity.getItems() is empty and an error is thrown: "Property referenced in indexed property path 'items[0]' is neither an array nor a List nor a Map."
}
Should my "items" be an array, List or Map? If so, there´s alternatives to keep using as Set?
Looks like there is some problem with the Set<Item>.
If you want to use Set for the items collection you have to initialize it and add some items:
e.g. like this:
public class MyEntity {
private Integer status;
private Set<Item> items;
public MyEntity() {
this.status = 0;
this.items = new HashSet<>();
this.items.add(new Item());
this.items.add(new Item());
}
//getters setters
}
but then you will be able to set only the values of this 2 items:
This will work: http://localhost:8081/map?status=1&items[0].name=asd&items[1].name=aaa
This will not work: http://localhost:8081/map?status=1&items[0].name=asd&items[1].name=aaa&items[2].name=aaa
it will say: Invalid property 'items[2]' of bean class MyEntity.
However if you switch to List:
public class MyEntity {
private Integer status;
private List<Item> items;
}
both urls map without the need to initialize anything and for various number of items.
note that I didn't use #ModelAttribute, just set the class as paramter
#GetMapping("map")//GetMapping is just a shortcut for RequestMapping
public MyEntity map(MyEntity myEntity) {
return myEntity;
}
Offtopic
Mapping a complex object in Get request sounds like a code smell to me.
Usually Get methods are used to get/read data and the url parameters are used to specify the values that should be used to filter the data that has to be read.
if you want to insert or update some data use POST, PATCH or PUT and put the complex object that you want to insert/update in the request body as JSON(you can map that in the Spring Controller with #RequestBody).
Related
Is there any good way to ignore some request query parameters from binding to DTO parameters?
#Data // setters and getters
class Dto {
private String param1;
private String param2;
}
#GetMapping("/hello-world")
#ResponseBody
public ResponseEntity<Dto> sayHello(Dto params)
{ ... }
I would like to exclude binding of specific param in such case.
After some research I can't find any solution for it, any help?
I'm using spring data mongo. I have a collection within a document that when I add an item to it I would like to assign a new automatically generated unique identifier to it e.g. (someGeneratedId)
#Document(collection = "questionnaire")
public class Questionnaire {
#Id
private String id;
#Field("answers")
private List<Answer> answers;
}
public class Answer {
private String someGeneratedId;
private String text;
}
I am aware I could use UUID.randomUUID() (wrapped in some kind of service) and set the value, I was just wondering if there was anything out of the box that can handle this? From here #Id seems to be specific to _id field in mongo:
The #Id annotation tells the mapper which property you want to use for
the MongoDB _id property
TIA
No there is no out of the box solution for generating ids for properties on embedded documents.
If you want to keep this away from your business-logic you could implement a BeforeConvertCallback which generates the id's for your embedded objects.
#Component
class BeforeConvertQuestionnaireCallback implements BeforeConvertCallback<Questionnaire> {
#Override
public Questionnaire onBeforeConvert(#NonNull Questionnaire entity, #NonNull String collection) {
for (var answer : entity.getAnswers()) {
if (answer.getId() == null) {
answer.setId(new ObjectId().toString());
}
}
return entity;
}
}
You could also implement this in a more generic manner:
Create a new annotation: #AutogeneratedId.
Then listen to all BeforeConvertCallback's of all entities and iterate through the properties with reflection. Each property annotated with the new annotation gets a unique id if null.
I have two entities: Book and Category and a repository for both. In the controller, I have set up the methods correctly as such:
#RequestMapping(value="/books", method = RequestMethod.GET)
#CrossOrigin
public #ResponseBody List<Book> bookListRest() {
return (List<Book>) bookRepository.findAll();
}
This obviously shows all books and every field in the entity that isn't #JsonIgnore'd. The problem is, I need to have:
One page with Book data (book name, author name, isbn..) without category
One page with Category data (Category name) without books
One page with Everything (book data along with categories where they belong in)
How can one accomplish this?
I somehow need to in a way ignore #jsonignore on some occasions. Should I make a new entity that extends say, Question and also make a repository for that? Surely that can't be the correct way to do this.
As khalid Ahmed Said you can use costum dtos or you can add Filters to ignore specific fields in Jackson. First, we need to define the filter on the java object:
#JsonFilter("myFilterBook")
public class Book{
...
}
#JsonFilter("myFilterCategory")
public class Category{
...
}
Before you return your ResponseBody you try to use ObjectMapper (Jackson):
The case of one page with Book data (book name, author name, isbn..) without category:
ObjectMapper mapper = new ObjectMapper();
SimpleBeanPropertyFilter theFilter = SimpleBeanPropertyFilter
.serializeAllExcept("category");
FilterProvider filters = new SimpleFilterProvider()
.addFilter("myFilterBook", theFilter);
String dtoAsString = mapper.writer(filters).writeValueAsString(book);
You can do the same think by putting what you want o ignore for the other example.
And for more details to ignore field during marshalling with jackson you can check here
What about using DTOs data transfer objects
you can create multiple DTOs to use them in the response of your API
DTO is a pojo class that customize the returning data from your entity
public class BookWithoutCategoryDTO {
private String name;
private String authorName;
.....
/// and make setters and getters for them
}
public class BookWithCategoryDTO {
private String name;
private String authorName;
private String category;
.....
/// and make setters and getters for them
}
and create your custom mapper to convert from Book to BookDTO
I have a repository called BananaRepositoryImpl that contains a function that return a list of BananaDTO ( the legacy code can't return the mapped entity ( Banana.java ),it's a constraint and I can't change this behavior :( )
public class BananaRepositoryImpl implements BananaRepository{
#Autowired
EntityManager em;
public List<BananaDTO> findAllBananes(){
//logic to get list of bananasDTO object types using Query query = em.createQuery(JPQL_QUERY_HERE);
}
}
Knowing that the BananaDTO object is a DTO for Banana.java class which looks like this :
#Data
#Entity
public class Banana{
private Long id;
private Double price;
private Double weight;
}
What I should do is to implement pagination over the findAllBananes() method so that I can return a Page using spring Data ( or another approach ).
Assuming the attributes of the BananaDTO is a subset of the Banana entities attributes you can use class-based projection support of Spring Data JPA, i.e. you just add a Pageable as a parameter to your method and return a Page<BananaDTO>:
interface BananaRepository extends CrudRepository<Banana, Long> {
Page<BananaDTO> findAllBananes(Pageable page)
}
I've the following domain and needs to return selected field in response to client. How can I achieve that using Spring?
public class Vehicle {
private String vehicleId;
private Long dateCreated;
private String ownerId;
private String colourCode;
private String engineNumber;
private String transmission;
//getters & setters
}
My objective is to return only colourCode and transmission fields to client request. I've read about DTO and seems like I can achieve my objective with DTO but I don't find any good example how to implement it. Is DTO is the correct way to achieve my objective ?
Basically you just create VehicleDTO class with parameters you need
public class VehicleDTO {
private String colourCode;
private String transmission;
//getters and setters
}
and then in your code you construct VehicleDTO from your Vehicle class. Fortunately, we have BeansUtils class from Spring, that uses reflection to copy properties of one object to another, because you do not want to repeat logic for copying properties for every object. So it would be something like:
BeanUtils.copyProperties(v1, dto);
At the end your return VehicleDTO in your response instead of Vehicle
You can return IVehicle interface which exposes your properties of choice
public interface IVehicle {
String getTransmission();
String getColourCode();
}
and your Vehicle implents it
public class Vehicle implements IVehicle{ }
There are various ways you can achieve what you want.
You can add relevant usecase / APi specific DTO for the resource.
e.g. If your API return the vehical general details you may want to expose some level of details,
public class VehicleDetailsDTO {
private String colourCode;
private String transmission;
private String engineNumber; //more
//getters and setters
}
You can then either use BeanUtils or Dozzer to convert your Vehical resource to transportable object like your DTO.
BeanUtils : http://commons.apache.org/proper/commons-beanutils/
Dozzer : http://dozer.sourceforge.net/documentation/mappings.html
Assuming you use JSON as output format and Jackson as serialization engine (default in Spring MVC), you can tell Jackson to not serialize null properties. Now you just need to populate the properties you need and can return the original business object.