In this article, via a Gradle project, let us see how to validate a sample application and show the output in the browser. The application is prepared as of type Spring Boot and in this article let us see how to execute via the command line as well.
Example Project
Project Structure:
As this is the Gradle project, we need to check for
build.gradle
buildscript {
ext {
springBootVersion = '2.3.1.RELEASE'
}
repositories {
mavenCentral()
}
dependencies {
classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
}
}
apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'org.springframework.boot'
apply plugin: 'io.spring.dependency-management'
group = 'gfg'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = 8
repositories {
mavenCentral()
}
dependencies {
implementation('org.springframework.boot:spring-boot-starter-data-jpa')
// This is very much essential for validation
implementation('org.springframework.boot:spring-boot-starter-validation')
implementation('org.springframework.boot:spring-boot-starter-web')
runtimeOnly('com.h2database:h2')
testImplementation('org.springframework.boot:spring-boot-starter-test')
testImplementation('org.junit.jupiter:junit-jupiter-engine:5.0.1')
// these dependencies are needed when running with Java 11, since they
// are no longer part of the JDK
implementation('javax.xml.bind:jaxb-api:2.3.1')
implementation('org.javassist:javassist:3.23.1-GA')
}
test{
useJUnitPlatform()
}
gradlew.bat (Gradle startup script for Windows)
@if "%DEBUG%" == "" @echo off @rem ########################################################################## @rem @rem Gradle startup script for Windows @rem @rem ########################################################################## @rem Set local scope for the variables with windows NT shell if "%OS%"=="Windows_NT" setlocal set DIRNAME=%~dp0 if "%DIRNAME%" == "" set DIRNAME=. set APP_BASE_NAME=%~n0 set APP_HOME=%DIRNAME% @rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script. set DEFAULT_JVM_OPTS= @rem Find java.exe if defined JAVA_HOME goto findJavaFromJavaHome set JAVA_EXE=java.exe %JAVA_EXE% -version >NULL 2>&1 if "%ERRORLEVEL%" == "0" goto init echo. echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. echo. echo Please set the JAVA_HOME variable in your environment to match the echo location of your Java installation. goto fail :findJavaFromJavaHome set JAVA_HOME=%JAVA_HOME:"=% set JAVA_EXE=%JAVA_HOME%/bin/java.exe if exist "%JAVA_EXE%" goto init echo. echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME% echo. echo Please set the JAVA_HOME variable in your environment to match the echo location of your Java installation. goto fail :init @rem Get command-line arguments, handling Windows variants if not "%OS%" == "Windows_NT" goto win9xME_args :win9xME_args @rem Slurp the command line arguments. set CMD_LINE_ARGS= set _SKIP=2 :win9xME_args_slurp if "x%~1" == "x" goto execute set CMD_LINE_ARGS=%* :execute @rem Setup the command line set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar @rem Execute Gradle "%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS% :end @rem End local scope for the variables with windows NT shell if "%ERRORLEVEL%"=="0" goto mainEnd :fail rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of rem the _cmd.exe /c_ return code! if not "" == "%GRADLE_EXIT_CONSOLE%" exit 1 exit /b 1 :mainEnd if "%OS%"=="Windows_NT" endlocal :omega
Now let us see the main application file from which the application starts to execute
SampleValidationApplication.java
Java
import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplicationpublic class SampleValidationApplication { public static void main(String[] args) { SpringApplication.run(SampleValidationApplication.class, args); }} |
Let us see the necessary files that are helpful to produce the validation errors in a meaningful and clear way
ErrorHandlingControllerAdviceSample.java
Java
import javax.validation.ConstraintViolation;import javax.validation.ConstraintViolationException;import org.springframework.http.HttpStatus;import org.springframework.validation.FieldError;import org.springframework.web.bind.MethodArgumentNotValidException;import org.springframework.web.bind.annotation.ControllerAdvice;import org.springframework.web.bind.annotation.ExceptionHandler;import org.springframework.web.bind.annotation.ResponseBody;import org.springframework.web.bind.annotation.ResponseStatus;@ControllerAdviceclass ErrorHandlingControllerAdviceSample { @ExceptionHandler(ConstraintViolationException.class) @ResponseStatus(HttpStatus.BAD_REQUEST) @ResponseBody ValidationErrorResponse onConstraintValidationException(ConstraintViolationException e) { ValidationErrorResponse error = new ValidationErrorResponse(); for (ConstraintViolation violation : e.getConstraintViolations()) { error.getViolations().add(new Violation(violation.getPropertyPath().toString(), violation.getMessage())); } return error; } @ExceptionHandler(MethodArgumentNotValidException.class) @ResponseStatus(HttpStatus.BAD_REQUEST) @ResponseBody ValidationErrorResponse onMethodArgumentNotValidException(MethodArgumentNotValidException e) { ValidationErrorResponse error = new ValidationErrorResponse(); for (FieldError fieldError : e.getBindingResult().getFieldErrors()) { error.getViolations().add(new Violation(fieldError.getField(), fieldError.getDefaultMessage())); } return error; }} |
ValidationErrorResponse.java
Java
import java.util.ArrayList;import java.util.List;public class ValidationErrorResponse { private List<Violation> violations = new ArrayList<>(); public List<Violation> getViolations() { return violations; } public void setViolations(List<Violation> violations) { this.violations = violations; }} |
Violation.java
Java
public class Violation { private final String fieldName; private final String message; public Violation(String fieldName, String message) { this.fieldName = fieldName; this.message = message; } public String getFieldName() { return fieldName; } public String getMessage() { return message; }} |
ValidateGivenParametersByController.java
This is the controller file where we can put the annotations for conditional checking
Java
import javax.validation.ConstraintViolationException;import javax.validation.constraints.Min;import javax.validation.constraints.Max;import javax.validation.constraints.Email;import javax.validation.constraints.Positive;import javax.validation.constraints.NegativeOrZero;import org.springframework.http.HttpStatus;import org.springframework.http.ResponseEntity;import org.springframework.validation.annotation.Validated;import org.springframework.web.bind.annotation.ExceptionHandler;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.PathVariable;import org.springframework.web.bind.annotation.RequestParam;import org.springframework.web.bind.annotation.ResponseBody;import org.springframework.web.bind.annotation.ResponseStatus;import org.springframework.web.bind.annotation.RestController;@RestController@Validatedclass ValidateGivenParametersByController { @GetMapping("/validatePathVariable/{id}") ResponseEntity<String> validatePathVariable(@PathVariable("id") @Min(5) int id) { return ResponseEntity.ok("valid"); } @GetMapping("/validateRequestParameterWithMin") ResponseEntity<String> validateRequestParameterWithMin(@RequestParam("id") @Min(0) int id) { return ResponseEntity.ok("valid"); } @GetMapping("/validateRequestParameterWithMax") ResponseEntity<String> validateRequestParameterWithMax(@RequestParam("id") @Max(5) int id) { return ResponseEntity.ok("valid"); } @GetMapping("/validateRequestParameterWithEmailId") ResponseEntity<String> validateRequestParameterWithEmailId(@Email @RequestParam(name = "emailId") String emailId) { return ResponseEntity.ok("valid"); } @GetMapping("/validateRequestParameterWithPositive") ResponseEntity<String> validateRequestParameterWithPositive(@Positive @RequestParam(name = "id") int id) { return ResponseEntity.ok("valid"); } @GetMapping("/validateRequestParameterWithNegativeOrZero") ResponseEntity<String> validateRequestParameterWithNegativeOrZero(@NegativeOrZero @RequestParam(name = "id") int id) { return ResponseEntity.ok("valid"); } @ExceptionHandler(ConstraintViolationException.class) @ResponseStatus(HttpStatus.BAD_REQUEST) @ResponseBody String handleConstraintViolationException(ConstraintViolationException e) { return "Given input is not valid due to validation error: " + e.getMessage(); }} |
Via the command line, we can execute the project as follows
Now let us test the following
Test 1:
http://localhost:8080/validatePathVariable/90
This is valid as we have the code as id should be @Min(5)). At the same time, if we pass as
http://localhost:8080/validatePathVariable/1
the error will be thrown
Test 2:
http://localhost:8080/validateRequestParameterWithMin?id=-10
Here @Min(0) is applied and hence we can see below the validation error message
Test 3:
http://localhost:8080/validateRequestParameterWithMax?id=10
Here @Max(5) is applied and hence
Test 4:
http://localhost:8080/validateRequestParameterWithEmailId?emailId=a.com
Here emailId is not properly given
Test 5:
http://localhost:8080/validateRequestParameterWithPositive?id=-200
So only positive numbers alone are accepted
Test 6:
http://localhost:8080/validateRequestParameterWithNegativeOrZero?id=100
So only negative or zero only accepted
Conclusion
Throughout the entire project, we can use the necessary annotation and validate the input fields. We also can give a proper error message and make the software more productive.
