Spring HATEOAS RepresentationModelAssembler toCollectionModel() - spring

Question

I'm creating Spring Boot HATEOAS REST application. Code below shows how am I adding links, while GET request is send for specific Employee. I'm using RepresentationModelAssembler toModel function. There's also toCollectionModel function to Override, which I would like to use to convert List<Employees> to CollectionModel. -> This will be returned in /Employees/all endpoint.
And I dunno how to do that. So what I need is to pass List<Employees>, then all list elements needs to be processed by toModel functions, and then, like in toModel function I need possibility to add more links to it -> links to entire new collection (not individual items).
Looking forward for your answers!
#Component
public class EmployeeModelAssembler implements RepresentationModelAssembler<Employee, EntityModel<Employee>> {
#Override
public EntityModel<Employee> toModel(Employee employee) {
EntityModel<Employee> employeeEntityModel = EntityModel.of(employee);
Link selfLink = linkTo(methodOn(EmployeeController.class).getEmployeeById(employee.getId())).withSelfRel();
employeeEntityModel.add(selfLink);
return employeeEntityModel;
}
#Override
public CollectionModel<EntityModel<Employee>> toCollectionModel(Iterable<? extends Employee> entities) {
?? ?? ??
}
}

Answer 1

You can use something like this:
#GetMapping(produces = { "application/hal+json" })
public CollectionModel<Customer> getAllCustomers() {
List<Customer> allCustomers = customerService.allCustomers();
for (Customer customer : allCustomers) {
String customerId = customer.getCustomerId();
Link selfLink = linkTo(CustomerController.class).slash(customerId).withSelfRel();
customer.add(selfLink);
if (orderService.getAllOrdersForCustomer(customerId).size() > 0) {
Link ordersLink = linkTo(methodOn(CustomerController.class)
.getOrdersForCustomer(customerId)).withRel("allOrders");
customer.add(ordersLink);
}
}
Link link = linkTo(CustomerController.class).withSelfRel();
CollectionModel<Customer> result = CollectionModel.of(allCustomers, link);
return result;
}
Visit https://www.baeldung.com/spring-hateoas-tutorial#springhateoasinaction for detailed explanation