Partial update REST in Spring Boot and Kotlin - spring

Question

I have a project with Spring Boot + Kotlin + Morphia.
I need add partial update of my entities. My actual post method:
#PostMapping("update/")
fun updateStudent(#RequestBody #Valid student: Student, results: BindingResult): ResponseData<Student> {
if (results.hasErrors())
return ResponseData(errors = results.errors)
if (!student.canEdit(login.user))
return ResponseData()
student.save()
return ResponseData(data = student)
}
I need read student from database and update only the sended fields

Answer 1

This is my solution:
import org.springframework.beans.BeanWrapperImpl
import java.util.HashSet
fun getNullPropertyNames(source: Any): Array<String> {
val src = BeanWrapperImpl(source)
val pds = src.propertyDescriptors
val emptyNames = HashSet<String>()
for (pd in pds) {
if (src.getPropertyValue(pd.name) == null) emptyNames.add(pd.name)
}
return emptyNames.toTypedArray()
}
And in controller
import org.springframework.beans.BeanUtils
#RestController
class GateController {
#Autowired
private val modelRepository: MyRepository? = null
// allow both 'full' and 'partial' update
#PutMapping("/somemodel/{Id}")
fun updateModel(
#PathVariable Id: Long,
#RequestBody requestBody: SomeModel
): SomeModel {
var objFromDb = modelRepository!!.findById(Id).orElseThrow { ResourceNotFoundException("Object not found with id: " + Id) }
BeanUtils.copyProperties(requestBody, objFromDb, *getNullPropertyNames(requestBody))
return modelRepository.save(objFromDb)
}
...
}

Answer 2

There are 2 things to implement. Reading Student from DB and copying properties from the student from request.
I post java code but it's no problem to convert to kotlin
Morphia morphia = new Morphia();
db = new Mongo();
Datastore ds = morphia.createDatastore(db, appname, user, pass.toCharArray());
morphia.map(Student.class);
Student existing= ds.find(Student.class).field("id").equal(student.id).get();
Then you can use Apache BeanUtils
http://commons.apache.org/proper/commons-beanutils/javadocs/v1.8.3/apidocs/org/apache/commons/beanutils/BeanUtils.html#copyProperties%28java.lang.Object,%20java.lang.Object%29
BeanUtils.copyProperties(existing, student);
then
existing.save();