Spring Web MVC - validate individual request params

Spring Web MVC - validate individual request params

In a Spring Web MVC application, you can validate individual request parameters using several approaches, including validation annotations, custom validator classes, and programmatic validation. Here's a step-by-step guide on how to validate individual request parameters in a Spring Web MVC controller:

1. Add Dependencies: Ensure you have the necessary dependencies in your pom.xml or build.gradle file for Spring Web MVC and validation. For example, in Maven:

<dependencies> <!-- Spring Web MVC --> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <!-- Validation API --> <dependency> <groupId>javax.validation</groupId> <artifactId>validation-api</artifactId> <version>2.0.1.Final</version> </dependency> </dependencies>

2. Create a Request Object: Define a Java class to represent the request parameters that you want to validate. Use validation annotations from the javax.validation.constraints package to specify validation rules. For example:

import javax.validation.constraints.Min; import javax.validation.constraints.NotBlank; public class MyRequest { @NotBlank(message = "Name is required") private String name; @Min(value = 18, message = "Age must be at least 18") private int age; // Getters and setters }

3. Create a Controller: Create a Spring MVC controller that handles the incoming request and uses the @Valid annotation to trigger validation on the request object. Additionally, use the BindingResult parameter to check for validation errors. For example:

import org.springframework.validation.BindingResult; import org.springframework.web.bind.annotation.*; import javax.validation.Valid; @RestController @RequestMapping("/api") public class MyController { @PostMapping("/validate") public String validateRequest(@Valid @RequestBody MyRequest request, BindingResult result) { if (result.hasErrors()) { // Handle validation errors, e.g., return error messages return result.getFieldErrors().toString(); } // Process the valid request return "Request is valid: " + request.getName() + ", " + request.getAge(); } }

In this example:

  • We use the @Valid annotation to trigger validation on the request object.
  • The BindingResult parameter is used to capture validation errors, which we can check using result.hasErrors().

4. Configure Validation Message Source (Optional): You can configure a message source bean to customize validation error messages in your application.properties or application.yml file:

spring.messages.basename=messages/validation

This configuration tells Spring to look for validation error messages in a properties file named validation.properties or validation.yml.

5. Create Validation Error Messages (Optional): Create a validation.properties (or validation.yml) file in the src/main/resources/messages directory with custom error messages:

NotBlank.myRequest.name=Name is required Min.myRequest.age=Age must be at least {value}

6. Test the Validation: Send a POST request to your controller with JSON data that includes the request parameters to be validated. For example, using a tool like Postman or curl:

curl -X POST -H "Content-Type: application/json" -d '{"name": "", "age": 17}' http://localhost:8080/api/validate

You should receive validation error messages if the request parameters don't meet the validation criteria.

By following these steps, you can validate individual request parameters in a Spring Web MVC controller using validation annotations and the @Valid annotation. Custom error messages can also be provided for a more user-friendly experience.

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