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This tutorial shows how to Validate Request Parameters when using @RequestParam.
If Parameter is missing or contains invalid value, MissingServletRequestParameterException is thrown.
We will create Endpoint that catches Exception and returns error back to the User.
If Endpoint uses multiple @RequestParam, Exception is thrown only for the first error.
If you want all of the errors to be reported then you need to use DTO approach
● DTO - From Request Parameters
● DTO - From JSON
Application Schema [Results]
Spring Boot Starters
GROUP
DEPENDENCY
DESCRIPTION
Web
Spring Web
Enables: Controller Annotations, Tomcat Server
http://localhost:8080/Hello
Tomcat
hello()
Browser
MyController
AgeConstraint
AgeConstraintImpl
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Create Project: springboot_dto_json_object_constructor (add Spring Boot Starters from the table)
Edit File: pom.xml (add validation dependency)
Create Package: validators (inside main package)
– Create Class: AgeConstraintImpl.java (inside package validators)
– Create Class: AgeConstraint.java (inside package validators)
Create Package: controllers (inside main package)
– Create Class: MyController.java (inside package controllers)
pom.xml
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-validation</artifactId>
</dependency>
AgeConstraintImpl.java
package com.ivoronline.springboot_validation_custom.validators;
import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
public class AgeConstraintImpl implements ConstraintValidator<AgeConstraint, Integer> {
@Override
public boolean isValid(Integer age, ConstraintValidatorContext cxt) {
return 18 < age && age < 100;
}
}
AgeConstraint.java
package com.ivoronline.springboot_validation_custom.validators;
import javax.validation.Constraint;
import javax.validation.Payload;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = AgeConstraintImpl.class)
public @interface AgeConstraint {
String message() default "Must be between 18 and 100";
Class<?>[] groups () default {};
Class<? extends Payload>[] payload() default {};
}
MyController.java
package com.ivoronline.springboot_validation_custom.controllers;
import com.ivoronline.springboot_validation_custom.validators.AgeConstraint;
import org.springframework.http.HttpStatus;
import org.springframework.stereotype.Controller;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.*;
import javax.validation.ConstraintViolation;
import javax.validation.ConstraintViolationException;
import javax.validation.Path;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
@Controller
@Validated
public class MyController {
//==================================================================
// HELLO
//==================================================================
@ResponseBody
@RequestMapping("/Hello")
public String hello(@AgeConstraint @RequestParam Integer age) {
return "John is " + age + " years old";
}
//==================================================================
// HANDLE EXCEPTIONS (it only catches first exception)
//==================================================================
@ResponseBody
@ResponseStatus(HttpStatus.BAD_REQUEST)
@ExceptionHandler(ConstraintViolationException.class)
public Map<String, String> handleExceptions(ConstraintViolationException exception) {
//CREATE MAP FOR STORING ERRORS
Map<String, String> errors = new HashMap<>();
//ITERATE THROUGH ERRORS
Set<ConstraintViolation<?>> violations = exception.getConstraintViolations();
for(ConstraintViolation<?> violation : violations) {
//GET PROPERTY NAME
String propertyName = null;
for (Path.Node node : violation.getPropertyPath()) { propertyName = node.getName(); }
//GET OTHER ERROR COMPONENTS
String message = violation.getMessage();
Integer invalidValue = (Integer) violation.getInvalidValue();
//STORE ERROR
errors.put(propertyName, message + " (" + invalidValue + ")");
}
//RETURN MESSAGE
return errors;
}
}
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http://localhost:8080/Hello?age=2
Application Structure
pom.xml
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-validation</artifactId>
</dependency>
</dependencies>
