HTML5 validation dialect for the Thymeleaf 3 template engine.

Overview

This Thymeleaf dialect reads JSR-380 annotations and modifies HTML code introducing HTML5 form validation code matching the annotations.

Rationale

JSR-380 provides server-side validation for Java web applications, but client side validation has usually been achieved using Javascript.
Fortunately, HTML5 has brought new attributes for simple browser validation.
Although HTML5 validation is not supported by all browsers, nowadays the form validation support is quite good, so we prefer favoring users with modern browsers and rely on server validation for users with older browsers.

Installation

Gradle + Spring Boot users

Add the dependence to the build.gradle

ext['thymeleaf.version'] = '3.0.7.RELEASE'
ext['thymeleaf-layout-dialect.version'] = '2.2.2'

repositories {
    mavenCentral()
    maven { url 'https://masa-kunikata.github.io/maven/' }
}
dependencies {
    compile(group: 'javax.validation', name: 'validation-api', version:'2.0.0.Final')
    compile(group: 'com.github.masa-kunikata.html5valdialect', name: 'html5valdialect', version:'3.0.3')
}

Note that 3.0.x versions are compatible with Thymeleaf 3.0.x versions.

Add the dialect bean to your Spring configuration

• Spring Boot xml configuration example

<bean id="html5ValDialect" class="com.github.masa_kunikata.html5val.Html5ValDialect"/>

• Spring java configuration example

@Bean
Html5ValDialect html5ValDialect() {
    return new Html5ValDialect();
}

Custom validation rules

In order to add a custom validation rule you have to implement the IValidationPerformer interface and add it to the configuration:

• Spring Boot xml configuration example

<bean id="html5ValDialect" class="com.github.masa_kunikata.html5val.Html5ValDialect">
    <property name="additionalPerformers">
        <set>
            <bean class="fqcn.to.MyCustomPerformer" />
        </set>
    </property>
</bean>

• Spring java configuration example

@Bean
Html5ValDialect html5ValDialect() {

    IValidationPerformer myCustomPerformer = new fqcn.to.MyCustomPerformer();
    final Set<IValidationPerformer> performers = new HashSet<>();
    performers.add(myCustomPerformer);
    
    final Html5ValDialect html5ValDialect = new Html5ValDialect();
    html5ValDialect.setAdditionalPerformers(performers);

    return html5ValDialect;
}

Default supported constraints

Constraint	Usage	Before	After
javax.validation.constraints.Size	@Size(min = 5, max = 10)	<input type="text" name="code" />	<input type="text" name="code" pattern=".{5,10}" required="required" />
javax.validation.constraints.Min	@Min(value = 18)	<input type="text" name="age" />	<input type="number" name="age" min="18" />
javax.validation.constraints.Max	@Max(value = 65)	<input type="text" name="age" />	<input type="number" name="age" max="65" />
javax.validation.constraints.Digits	@Digits(integer = 3, fraction = 2)	<input type="text" name="price" />	<input type="text" name="price" pattern="([0-9]{1,3}\.?|\.[0-9]{1,2}|[0-9]{1,3}\.[0-9]{1,2}){1}" />
javax.validation.constraints.NotNull	@NotNull	<input type="text" name="code" />	<input type="text" name="code" required="required" />
javax.validation.constraints.NotEmpty	@NotEmpty	<input type="text" name="code" />	<input type="text" name="code" required="required" />
javax.validation.constraints.NotBlank	@NotBlank	<input type="text" name="code" />	<input type="text" name="code" required="required" />
org.hibernate.validator.constraints.Range	@Range(min = 0, max = 10)	<input type="text" name="rank" />	<input type="range" name="rank" min="0" max="10" />
org.hibernate.validator.constraints.Length	@Length(min = 1, max = 10)	<input type="text" name="rank" />	<input type="text" name="rank" pattern=".{1,10}" required="required" />
javax.validation.constraints.Email	@Email	<input type="text" name="userEmail" />	<input type="email" name="userEmail" />
org.hibernate.validator.constraints.URL	@URL(protocol = "https")	<input type="text" name="website" />	<input type="text" name="website" pattern="^https://.+(:[0-9]+)?(/.*)?" />

Usage

Spring users

Configure JSR-380 annotations in your form bean

class UserFormBean {

    @Email
    @NotEmpty
    private String username;

    @Size(min = 5, max = 10)
    private String code;

    @Min(value = 18)
    @Max(value = 100)
    @NotNull
    private Integer age;

    @Range(min = 0, max = 10)
    private Integer highSchoolMark;

    @URL(regexp = URLPerformer.URL_REGEXP)
    private String personalWebPage;

    @URL(protocol = "http", host = "localhost", port = 8080)
    private String applicationWebPage;

    ...
}

Add a instance of the form bean to your model in your controller

    @RequestMapping("/userCreate.html")
    public String userCreate(Model model) {
        model.addAttribute("userFormBean", new UserFormBean());
        return "userCreate.html";
    }

Use val:validate in your HTML form

    <form action="userSave.do" val:validate="${userFormBean}" method="post">
        <p>
            <label for="username">E-mail</label>
            <input type="text" name="username" id="username" />
        </p>
        <p>
            <label for="code">Code</label>
            <input type="text" name="code" id="code" />
        </p>
        <p>
            <label for="age">Age</label>
            <input type="text" name="age" id="age" />
        </p>
        <p>
            <label for="highSchoolMark">Mark</label>
            <input type="text" name="highSchoolMark" id="highSchoolMark" />
        </p>
        <p>
            <label for="personalWebPage">Personal Web Page</label>
            <input type="text" name="personalWebPage" id="personalWebPage" />
        </p>
        <p>
            <label for="applicationWebPage">Demo application Web Page</label>
            <input type="text" name="applicationWebPage" id="applicationWebPage" />
        </p>
        <input type="submit" />
    </form>

Use @Valid annotation in your controller

    @RequestMapping(value = "/userSave.do", method = RequestMethod.POST)
    public String userSave(@Valid UserFormBean userForm) {
        userDAO.save(userForm.buildUser());
        return "redirect:/userList.html";
    }

In order to make the example simpler, th:field is not used, but you usually would combine val:validate with th:object and th:errors.

Quick start the example application

1. Install JDK and Gradle.
2. Download source code
3. At the command prompt, execute cd html5valdialect-example-webapp and make it current directory.
4. Run gradle bootRun
5. Open http://localhost:8080/ (User: user Password: password)

License

This software is licensed under the [Apache License 2.0] (http://www.apache.org/licenses/LICENSE-2.0.html).