In this tutorial, I am going to show you how to work with Spring Boot Validation framework.

Technologies :

• SpringBoot_1.5.9.RELEASE
• spring-boot-thymeleaf
• Apache Tomcat Embed
• Java 8

Spring Boot Validation :

I am going to create a simple Spring Boot Login form using a thymeleaf template and validate username and passwords.

Project Structure :

Project Dependencies :

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.onlinetutorialspoint.springbootvalidation</groupId>
    <artifactId>springbootvalidation</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.9.RELEASE</version>
    </parent>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-validator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.tomcat.embed</groupId>
            <artifactId>tomcat-embed-el</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <repositories>
        <repository>
            <id>spring-releases</id>
            <name>Spring Releases</name>
            <url>https://repo.spring.io/libs-release</url>
        </repository>
    </repositories>
    <pluginRepositories>
        <pluginRepository>
            <id>spring-releases</id>
            <name>Spring Releases</name>
            <url>https://repo.spring.io/libs-release</url>
        </pluginRepository>
    </pluginRepositories>
</project>

Login Controller :

package com.onlinetutorialspoint.login;

import javax.validation.Valid;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.config.annotation.ViewControllerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

@Controller
public class LoginController extends WebMvcConfigurerAdapter {
    @Override
    public void addViewControllers(ViewControllerRegistry registry) {
        registry.addViewController("/home").setViewName("home");
    }

    @GetMapping("/")
    public String showForm(LoginForm loginForm) {
        return "login";
    }

    @PostMapping("/")
    public String validateLoginInfo(Model model, @Valid LoginForm loginForm, BindingResult bindingResult) {
        if (bindingResult.hasErrors()) {
            return "login";
        }
        model.addAttribute("user", loginForm.getuserName());
        return "home";
    }
}

LoginForm.java

package com.onlinetutorialspoint.login;

import javax.validation.constraints.Min;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;

public class LoginForm {
    @NotNull
    @Size(min = 2, max = 30)
    private String userName;

    @NotNull
    @Min(5)
    private String password;

    public String getuserName() {
        return this.userName;
    }

    public void setuserName(String userName) {
        this.userName = userName;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String toString() {
        return "LoginForm(UserName: " + this.userName + ", Password: " + this.password + ")";
    }
}

Login.html

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<title>Spring Boot Validation Login Form Example</title>
<link rel="stylesheet"
    href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" />
<link rel="stylesheet"
    href="https://maxcdn.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css" />
<link rel="stylesheet" href="style.css" />
</head>
<body>
    <div class="login-form">
        <form action="#" th:action="@{/}" th:object="${loginForm}"
            method="post">
            <h2 class="text-center">Sign in</h2>
            <div class="form-group">
                <div class="input-group">
                    <span class="input-group-addon"><i class="fa fa-user"></i></span> <input
                        type="text" class="form-control" th:field="*{userName}"
                        placeholder="Username" />

                </div>
                <span class="red" th:if="${#fields.hasErrors('userName')}"
                    th:errors="*{userName}"></span>
            </div>
            <div class="form-group">
                <div class="input-group">
                    <span class="input-group-addon"><i class="fa fa-lock"></i></span> <input
                        type="password" class="form-control" th:field="*{password}"
                        placeholder="Password" />

                </div>
                <span class="red" th:if="${#fields.hasErrors('password')}"
                    th:errors="*{password}"></span>
            </div>
            <div class="form-group">
                <button type="submit" class="btn btn-primary login-btn btn-block">Sign
                    in</button>
            </div>
        </form>
    </div>
</body>
</html>

home.html

<html>
<head>
<meta charset="ISO-8859-1"/>
<title>Spring Boot Validation Home</title>
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css"/>
</head>
<body>
<div class="alert alert-success">
  <strong>Success!</strong> Hello <span th:text="${user}" /> !
</div>
</body>

</html>

package com.onlinetutorialspoint.login;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

Run Application :

mvn spring-boot:run

Access: http://localhost:8080/

Success :

Error Validation :

Happy Learning 🙂