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How to implement Validation for RESTful Web Services?

Deepika Sahu answered on December 16, 2022 Popularity 3/10 Helpfulness 1/10

answer How to implement Validation for RESTful Web Services?

How to implement Validation for RESTful Web Services?

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Implementing Validations on the Bean
Before we add validations, we need to add a dependency.

<dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-validation</artifactId>
</dependency>
Let’s add a few validations to the Student bean. We are using @Size to specify the minimum length and also a message when a validation error occurs.

@Entity
public class Student {
  @Id
  @GeneratedValue
  private Long id;
  
  @NotNull
  @Size(min=2, message="Name should have atleast 2 characters")
  private String name;
  
  @NotNull
  @Size(min=7, message="Passport should have atleast 2 characters")
  private String passportNumber;
  

Bean Validation API provides a number of such annotations. Most of these are self explanatory.

DecimalMax
DecimalMin
Digits
Email
Future
FutureOrPresent
Max
Min
Negative
NegativeOrZero
NotBlank
NotEmpty
NotNull
Null
Past
PastOrPresent
Pattern
Positive
PositiveOrZero
Enabling Validation on the Resource
Simple. Add @Valid in addition to @RequestBody.

public ResponseEntity<Object> createStudent(@Valid @RequestBody Student student) {
That’s it.

When you execute a request with attributes not matching the constraint, you get a 404 BAD Request status back.

Request

{
    "name": "",
    "passportNumber": "A12345678"
  }
But the problem is that there are no details returned indicating what went wrong.

The consumer knows its a bad request.
But, how do they no what is wrong? Which element did not pass the validation? What should the consumer do to fix it?
Customizing Validation Response
Let’s define a simple error response bean.

public class ErrorDetails {
  private Date timestamp;
  private String message;
  private String details;

  public ErrorDetails(Date timestamp, String message, String details) {
    super();
    this.timestamp = timestamp;
    this.message = message;
    this.details = details;
  }
Let’s now define a @ControllerAdvice to handle validation errors. We do that by overriding handleMethodArgumentNotValid(MethodArgumentNotValidException ex, HttpHeaders headers, HttpStatus status, WebRequest request) method in the ResponseEntityExceptionHandler.

@ControllerAdvice
@RestController
public class CustomizedResponseEntityExceptionHandler extends ResponseEntityExceptionHandler {

  @Override
  protected ResponseEntity<Object> handleMethodArgumentNotValid(MethodArgumentNotValidException ex,
      HttpHeaders headers, HttpStatus status, WebRequest request) {
    ErrorDetails errorDetails = new ErrorDetails(new Date(), "Validation Failed",
        ex.getBindingResult().toString());
    return new ResponseEntity(errorDetails, HttpStatus.BAD_REQUEST);
  } 
To use ErrorDetails to return the error response, let’s define a ControllerAdvice as shown below.

@ControllerAdvice
@RestController
public class CustomizedResponseEntityExceptionHandler extends ResponseEntityExceptionHandler {

  @ExceptionHandler(StudentNotFoundException)
  public final ResponseEntity<ErrorDetails> handleUserNotFoundException(StudentNotFoundException ex, WebRequest request) {
    ErrorDetails errorDetails = new ErrorDetails(new Date(), ex.getMessage(),
        request.getDescription(false));
    return new ResponseEntity<>(errorDetails, HttpStatus.NOT_FOUND);
  }
When you execute a request with attributes not matching the constraint, you get a 404 BAD Request status back.

Request

{
    "name": "",
    "passportNumber": "A12345678"
  }
You also get a Response Body indicating what is wrong!

{
  "timestamp": 1512717715118,
  "message": "Validation Failed",
  "details": "org.springframework.validation.BeanPropertyBindingResult: 1 errors\nField error in object 'student' on field 'name': rejected value []; codes [Size.student.name,Size.name,Size.java.lang.String,Size]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [student.name,name]; arguments []; default message [name],2147483647,2]; default message [Name should have atleast 2 characters]"
}

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Contributed on Dec 16 2022

Deepika Sahu

0 Answers Avg Quality 2/10

How to implement Validation for RESTful Web Services?

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