Docs

Docs

Starting a Project

Gradle is a popular build tool for Java, Groovy, Kotlin, and other projects. It is an alternative to using Maven, and in many ways much simpler to use. It is also more powerful, if that is required. You can use it to build a Vaadin application, run it, and manage dependencies during development.

This tutorial describes how to create, compile, and run a Vaadin application using the Vaadin Gradle plugin. To run the application, the Gretty plugin is used to run it in an embedded web server.

For information about the general usage of Gradle, please refer to the Gradle User Manual.

Requirements

To use the Vaadin Gradle plugin, your environment needs to meet the following requirements:

  • Windows, Mac, or Linux

  • Java SDK 11 or later

  • Gradle 5 or 6 (optional, because of the provided wrapper in the starter projects)

  • Node.js and npm (optional, because they can also be installed locally to the project using the Vaadin Gradle plugin)

Note
Installing Gradle is optional
If you plan to use Vaadin’s Gradle-based starter projects, there is no need to install Gradle on your machine. A Gradle Wrapper script is included in those starter projects. This script manages the download and execution of Gradle locally for your project. For more information on using Gradle Wrapper, please refer to the Official Gradle Documentation.

Creating a Vaadin Project

The easiest way to create a new project is to clone a starter repository containing an application skeleton.

You can also take any existing Vaadin project and make a build.gradle file for it, as described in "The Build File".

Cloning a Starter Repository

The following starter repositories are currently available:

Note
Clone the master branch of the starter projects
Please note that the following repositories default to the V14 branch when you clone them. If you plan to use them with the latest version of Vaadin, there two options. You can either clone the master branch, or just change to the master branch after you have cloned either of the starter projects.
https://github.com/vaadin/base-starter-gradle

A simple web application project to be deployed as a WAR package. This example can also be used for Java EE, by changing the servlet dependency to javax:javaee-api and perhaps also adding the dependency com.vaadin:vaadin-cdi for CDI integration.

git clone https://github.com/vaadin/base-starter-gradle my-project
https://github.com/vaadin/base-starter-spring-gradle

A web application project skeleton that uses Spring Boot.

git clone https://github.com/vaadin/base-starter-spring-gradle my-project

Starter Project Contents

When it has been cloned, the project should look as follows (imported into the Eclipse IDE):

Contents of a Gradle based project
Cloned Starter Project
Note
Only the content of a simple web application starter is depicted
Note that only the contents of base-starter-gradle (a simple web application starter without Spring Boot) are presented in the preceding figure. However, the Spring Boot-based starter project is little different, except that it has an additional class annotated with @SpringBootApplication. If this is the first time you have tried Vaadin with Spring Boot, you can refer to Using Vaadin with Spring Boot for more information.

The most important files and folders are as follows:

src/main/java/<package>/MainView.java

The application view class for the root route, built from components.

src/main/java/<package>/GreetService.java

A trivial service object to separate business data and logic from the view.

frontend/src

Folder for HTML templates and JavaScript code. See the README inside for more details.

frontend/styles/shared-styles.css

Application-specific style sheets to style the look of the application.

frontend/styles/vaadin-text-field-styles.css

An example to modify the style of the TextField component.

build.gradle

The Gradle build file as described later in The Build File.

gradlew and gradlew.bat

Gradle Wrapper build scripts for Linux/Mac (gradlew) and Windows (gradlew.bat). The build scripts enable the project to be built without having Gradle preinstalled. As the recommended way to execute any Gradle build is with the help of the Gradle Wrapper, we have also used gradlew instead of gradle throughout the documentation. However, the gradlew and gradle commands can be used interchangeably if you already have Gradle installed and you prefer to use your installed Gradle. You can find out more about the benefits of using Gradle Wrapper in the Official Gradle Documentation.

The Build File

As a minimum, the build.gradle file needs to enable the Vaadin Gradle Plugin:

plugins {
    id 'com.vaadin' version '20.0.0' (1)

    // Optional
    id 'org.gretty' version '3.0.3' (2)
    id 'war' (3)
    id 'groovy' (4)
}

  1. Use the plugin version that matches the Vaadin version.

    See the releases at github.com/vaadin/platform for the latest release.

    To try the prerelease version of the Vaadin Gradle plugin, see Using plugin prerelease version

  2. Use the Gretty embedded web server to run the application during development. See Running the Application for details.

  3. Build a WAR package to deploy to a traditional servlet container. You also need to define the Servlet API using providedCompile "javax.servlet:javax.servlet-api:3.1.0" in the dependencies section.

  4. By default, the plugin supports Java. You can include Groovy or Kotlin as an optional plugin.

Vaadin Plugin Configuration

Vaadin Gradle plugin options are configured in a vaadin block.

For development, the block is usually like this:

vaadin {
    optimizeBundle = false
}

If the parameter is true, the front-end bundle is optimized for all supported browsers, but compilation is much slower.

For configuration options, see plugin configuration options

Configuring Repositories

The repositories section defines the locations to search for packages. The repository that contains the Vaadin libraries is required as a minimum:

repositories {
    mavenCentral()
    maven { url = "https://maven.vaadin.com/vaadin-addons" }
}

If you want to try the Vaadin platform prerelease versions,you can add the following repository, as well:

repositories {
    maven { url = "https://maven.vaadin.com/vaadin-prereleases" }
}
Note
Vaadin recommends using final releases
To avoid any inconsistencies, do not use any prerelease versions in your production environment, especially snapshots. Vaadin always recommends using the LTS or Final releases of the newer versions. Visit the Vaadin platform release page for the latest releases of LTS versions and Final releases of newer versions.

You can use any Gradle repository definitions in the block. See Declaring repositories in the Gradle documentation for more information.

Configuring Dependencies

You need to add the vaadin-core or vaadin library as a Java dependency:

dependencies {
    implementation "com.vaadin:vaadin-core:20.+"
}

When you specify a version of 20.+, you are choosing to use the latest version of Vaadin, but you can also specify the exact version.

See Declaring dependencies in the Gradle documentation for further details.

Other Configuration

In the starter project, default targets are defined for convenience, so that you can run gradle without specifying any tasks:

defaultTasks("clean", "vaadinBuildFrontend", "build")

Compiling

If you have defined the default tasks as described earlier, in Other Configuration, you can run:

./gradlew

on Windows:

gradlew
Note
The Unix style of running gradlew is used for the rest of this document
To avoid unnecessary verbosity, only the Unix style of running ./gradlew is used for the rest of this document. You obviously need to replace it with gradlew if you are on a Windows machine.

Otherwise, the project builds with the standard build task. However, on the first build and also at other times when necessary, you need to build the Vaadin front end.

./gradlew vaadinBuildFrontend build

Vaadin Tasks

The Vaadin-related tasks handled by the plugin are as follows:

vaadinPrepareFrontend

Checks that Node.js and npm are installed, copies front-end resources, and creates or updates the package.json and webpack.config.json files. The front-end resources are inside .jar dependencies, and copied to node_modules.

vaadinBuildFrontend

Builds the front-end bundle with the webpack utility. Vaadin front-end resources, such as HTML, JavaScript, CSS, and images, are bundled to optimize loading the front-end. This task is not executed automatically on the build and other targets, so you need to run it explicitly.

vaadinClean

Cleans the project and removes node_modules, package-lock.json, webpack.generated.js, tsconfig.json, types.d.ts, pnpm-lock.yaml and pnpmfile.js. You need to run this task if you upgrade the Vaadin version, and in other similar situations.

To get the complete list of tasks handled by the configured plugins, enter:

./gradlew tasks

Running the Application

You use a Spring Boot-based starter (Vaadin with Spring Boot) to run the application during development in a similar way to any normal Spring Boot application. This means you can run it either from the class containing the main() method (normally annotated with @SpringBootApplication), or by using Spring Boot’s Gradle plugin bootRun task:

./gradlew bootRun

If you are using a simple web application (Vaadin without Spring Boot) to run the application during development, the Gradle plugin supports the Gretty plugin, which runs the application in an embedded web server. You can do this either in an IDE or at the command line.

One way to enable the Gretty plugin is in the plugin section of the gradle.build file, as in the starter project:

plugins {
    ...
    id 'org.gretty' version '3.0.3'
}

You can configure Gretty further in an optional gretty block:

gretty {
    contextPath = "/" (1)
    servletContainer = "jetty9.4" (2)
}

  1. Sets the context path to the root path. The default context path contains the project name, so the URL would be http://localhost:8080/myproject (or whatever your project name is).

  2. Use Jetty as the servlet container, with the specified version.

The application is started with the appRun task:

 ./gradlew appRun

The task compiles the application and starts the web server in http://localhost:8080/ (if the root context path is configured as described earlier).

Note that you might need to add jcenter() to the list of repositories to be able to run Gretty tasks, depending on the situation at the time you are following this documentation. Some artifacts from jcenter() have not yet been moved to mavenCentral(). In the future, this step will be unnecessary:

repositories {
    // should be removed in the future as jcenter() is obsolete.
    jcenter()
}

See the Gretty documentation for a complete reference on using Gretty.

For issues when running the application in development mode, see Known Issues for possible solutions.

Developing in the Eclipse IDE

Gradle has first-class support in the Eclipse IDE, IDEA, NetBeans, and Android Studio, among others. The following section describes creating, importing, and developing a Vaadin Gradle project in the Eclipse IDE.

Importing a New Project

You create a new Vaadin project by cloning the repository on the command line and importing it to Eclipse as a Gradle project.

  1. Clone the starter repository of your choice, as described earlier.

  2. Select File › Import › Gradle › Existing Gradle Project.

  3. Enter or select the Project root directory.

  4. Click Finish.

The project should appear in the Project Explorer and look as shown in Cloned Starter Project.

You should now see the Gradle Tasks tab. You can browse the available tasks.

Gradle Tasks tab in eclipse
Gradle Tasks tab in Eclipse

Running the Application

You can run the project using Gretty in an embedded web server.

  1. Open the Gradle Tasks tab

  2. Double-click the gretty → appRun task

    • The Gradle Executions tab opens and shows the build progress

  3. When the :apprun task is running, open http://localhost:8080 in the browser.

  4. To stop the server, go to the Console tab and press any key.

Going to Production

To build a web application as a WAR package, you need the war plugin. You also need to enable it.

In build.gradle, include the plugin and enable WAR build:

plugins {
  ...
  id 'war'
}

war {
    enabled = true
}

When doing a production-ready build, the Vaadin Gradle plugin transpiles the client-side dependencies to legacy browsers, as described in Deploying to Production. You enable this by either setting it in build.gradle or at the command line when invoking Gradle.

In build.gradle:

vaadin {
   productionMode = true
}

At the command line:

./gradlew -Pvaadin.productionMode=true war
Note
Spring Boot-specific configuration
If you are using Vaadin with Spring Boot, the default packaging for production would normally be the jar. But, if you intend to package a Spring Boot application as a WAR to be deployed on a standalone container, such as tomcat, there are two additional steps you need to perform:

  • Your application class that is annotated with @SpringBootApplication should extend SpringBootServletInitializer and override the configure() method:

@SpringBootApplication
public class DemoApplication extends SpringBootServletInitializer {
    @Override
    protected SpringApplicationBuilder configure(
	                     SpringApplicationBuilder application) {
        return application.sources(DemoApplication.class);
    }
}

  • Adding the following dependency:

dependencies {
    providedRuntime 'org.springframework.boot:spring-boot-starter-tomcat'
}

Using Gradle Plugin Snapshot Versions

A snapshot version of the plugin is pushed to the prerelease repository. Note that this section is about trying the prerelease and snapshot versions of the Vaadin Gradle plugin itself, not the Vaadin platform.

To use the prereleased plugin, add the vaadin-prereleases repository to the project settings.gradle file. settings.gradle is mostly used within multi-module projects, but it comes in handy for other configurations, too. Thus, if you do not already have it in your project, go ahead and create a plain text file called settings.gradle next to your build.gradle file (normally in the project root folder).

pluginManagement {
    repositories {
        maven { url = 'https://maven.vaadin.com/vaadin-prereleases' }
        gradlePluginPortal()
    }
}

The plugin then needs to be defined and applied in the build.gradle file.

buildscript {
    ...
    dependencies {
        classpath group: 'com.vaadin',
                name: 'vaadin-gradle-plugin',
                version: '20.0-SNAPSHOT'
    }
}

plugins {
    ...
}

apply plugin: 'com.vaadin'
Note
Remember to update the plugins block
Note that id 'com.vaadin' version 'xyz' should also be removed from the plugins block. The plugin is applied just by specifying apply plugin: 'com.vaadin' (as demonstrated in the preceding file extract).

Plugin Configuration Options

Here are all the configuration options with their default values:

productionMode: Boolean = false

Indicates that the application is running in production mode. Defaults to false. For production, the front end is transpiled for older browsers and optimized, as described in Deploying to Production. Running the vaadinBuildFrontend task automatically switches this to true, so there is no need to configure anything.

webpackOutputDirectory: File = null

The folder where webpack should output index.js and other generated files. Defaults to null, which uses the automatically detected value of the main SourceSet, usually build/resources/main/META-INF/VAADIN/webapp/.

npmFolder: File = project.projectDir

The folder where the package.json file is located. Defaults to the project root directory.

webpackTemplate: String = FrontendUtils.WEBPACK_CONFIG

Copy the webapp.config.js from the specified URL if it is missing. Defaults to the template provided by this plugin. Set it to an empty string to disable the feature.

webpackGeneratedTemplate: String = FrontendUtils.WEBPACK_GENERATED

Copy the webapp.generated.js from the specified URL. Defaults to the template provided by this plugin. Set it to an empty string to disable the feature.

generatedFolder: File(project.projectDir, "target/frontend")

The target folder for generated files used by webpack.

frontendDirectory: File(project.projectDir, "frontend")

The directory with the front-end source files of the project.

generateBundle: Boolean = true

Set to true to generate a bundle from the project front-end sources.

runNpmInstall: Boolean = true

Run npm install after updating dependencies.

generateEmbeddableWebComponents: Boolean = true

Generate web components from WebComponentExporter inheritors.

frontendResourcesDirectory: File = File(project.projectDir, Constants.LOCAL_FRONTEND_RESOURCES_PATH)

Identifies the project front-end directory from where resources should be copied for use with webpack.

optimizeBundle: Boolean = true

Use byte code scanner strategy to discover front-end components.

pnpmEnable: Boolean = true

Use pnpm for installing npm front-end resources. Defaults to true.

useGlobalPnpm: Boolean = false

Use the globally installed pnpm tool or the default supported pnpm version. Defaults to false.

requireHomeNodeExec: Boolean = false

Force use of Vaadin home node executable. If it is set to true, Vaadin home node is checked, and installed if absent. This is then be used instead of the globally or locally installed node.

useDeprecatedV14Bootstrapping: Boolean = false

Run the application in legacy V14 bootstrap mode. Defaults to false.

eagerServerLoad: Boolean = false

Add the initial UIDL object to the bootstrap index.html. Defaults to false.

applicationProperties: File = File(project.projectDir, "src/main/resources/application.properties")

Application properties file in a Spring project.

openApiJsonFile: File = File(project.buildDir, "generated-resources/openapi.json")

Generated path of the OpenAPI JSON.

javaSourceFolder: File = File(project.projectDir, "src/main/java")

Java source folders for connect scanning.

generatedTsFolder: File = File(project.projectDir, "frontend/generated")

The folder where Flow puts TS API files for client projects.

nodeVersion: String = "v14.15.4"

The Node.js version to be used when Node.js is installed automatically by Vaadin, for example "v14.15.4". Defaults to [FrontendTools.DEFAULT_NODE_VERSION].

nodeDownloadRoot: String = "https://nodejs.org/dist/"

URL to download Node.js from. This can be needed in corporate environments where the Node.js download is provided from an intranet mirror. Defaults to [NodeInstaller.DEFAULT_NODEJS_DOWNLOAD_ROOT].

nodeAutoUpdate: Boolean = false

Flag to enable automatic update of the Node.js version installed in ~/.vaadin if it is older than the default or defined nodeVersion.

resourceOutputDirectory: File = File(project.buildDir, "vaadin-generated")

The output directory for generated non-served resources, such as the token file. Defaults to build/vaadin-generated.

Known Issues

Spring Boot

When the list of dependencies causes the classpath to go over a set limit on Windows, the build will automatically generate a JAR containing a manifest with the classpath. In some cases, when running a Spring Boot application, the resource loader does not load the classpath packages correctly from the manifest. The failed annotation scanning makes the required npm packages unavailable.

There are two ways to fix this:

Updated 2022-02-03