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Spring Initializr initializr

Spring Initializr provides an extensible API to generate quickstart projects. It also provides a configurable service: you can see our default instance at https://start.spring.io. It provides a simple web UI to configure the project to generate and endpoints that you can use via plain HTTP.

Spring Initializr also exposes an endpoint that serves its meta-data in a well-known format to allow third-party clients to provide the necessary assistance.

Finally, Initializr offers a configuration structure to define all the aspects related to the project to generate: list of dependencies, supported java and boot versions, etc. Check the configuration of our instance for an example. Such configuration is also described in details on the wiki.

Note
 We use the continuous deployment technique to manage our instance; check the milestones page for an overview of changes

Modules

Spring Initializr has the following modules:

  • initializr-generator: standalone project generation library that can be reused in many environments (including embedded in your own project)

  • initializr-web: REST endpoints and web interface

  • initializr-actuator: optional module to provide statistics and metrics on project generation

initializr-service is an additional module that represents the production instance that is available at https://start.spring.io. It is not enabled by default but you can enable the full profile in your IDE to easily run it locally.

Supported interfaces

Spring Initializr can be used as follows:

Tip

You can "curl" an instance to get a usage page with examples (try curl start.spring.io)

Generating a project

If you click on "Generate Project" on the web ui of our instance, it will download a project archive with a Maven-based project and the necessary infrastructure to start a basic Spring Boot app.

You could achieve the same result with a simple curl command

$ curl https://start.spring.io/starter.zip -o demo.zip

The web ui exposes a bunch of options that you can configure. These are mapped to the following request attributes:

  • Basic information for the generated project: groupId, artifactId, version, name, description and packageName

    • The name attribute is also used to generate a default application name. The logic is that the name of the application is equal to the name attribute with an Application suffix (unless said suffix is already present). Of course, if the specified name contains an invalid character for a java identifier, Application is used as fallback.

    • The artifactId attribute not only defines the identifier of the project in the build but also the name of the generated archive.

  • dependencies (or style): the identifiers of the dependencies to add to the project. Such identifiers are defined through configuration and are exposed in the meta-data.

  • type: the kind of project to generate (e.g. maven-project). Again, each service exposes an arbitrary number of supported types and these are available in the meta-data.

  • javaVersion: the language level (e.g. 1.8).

  • bootVersion: the Spring Boot version to use (e.g. 1.2.0.RELEASE).

  • language: the programming language to use (e.g. java).

  • packaging: the packaging of the project (e.g. jar).

  • applicationName: the name of the application class (inferred by the name attribute by default).

  • baseDir: the name of the base directory to create in the archive. By default, the project is stored in the root.

This command generates an another-project directory holding a Gradle web-based Groovy project using the actuator:

$ curl https://start.spring.io/starter.tgz -d dependencies=web,actuator \
-d language=groovy -d type=gradle-project -d baseDir=another-project | tar -xzvf -
Note
 The /starter.tgz endpoint offers the same feature as /starter.zip but generates a compressed tarball instead.

You could use this infrastructure to create your own client since the project is generated via a plain HTTP call.

Customize form inputs

You can share or bookmark URLs that will automatically customize form inputs. For instance, the following URL from the default instance uses groovy by default and set the name to Groovy Sample:

https://start.spring.io/#!language=groovy&name=Groovy%20Sample

The following hashbang parameters are supported: type, groupId, artifactId, name, description, packageName, packaging, javaVersion and language. Review the section above for a description of each of them.

Service meta-data

The service meta-data is used by the web UI and is exposed to ease the creation of third-party clients. You can grab the meta-data by curling the root

$ curl -H 'Accept: application/json' https://start.spring.io
Note
 As stated above, if you use curl without an accept header, you’ll retrieve a human readable text version of the metadata. HTTPie is also supported.

The meta-data basically lists the capabilities of the service, that is the available options for all request parameters (dependencies, type, bootVersion, etc.) The web UI uses that information to initialize the select options and the tree of available dependencies.

The meta-data also lists the default values for simple text parameter (i.e. the default name for the project).

Note
 More details about the structure of the meta-data are available on the wiki.

Running your own instance

You can easily run your own instance. The initializr-web modules uses Spring Boot so when it is added to a project, it will trigger the necessary auto-configuration to deploy the service.

You first need to create or update your configuration to define the necessary attributes that your instance will use. Again, check the wiki for a description of the configuration and review our own config for a sample.

You can integrate the library in a traditional Java-based project or by writing the super-simple script below

package org.acme.myapp

@Grab('io.spring.initializr:initializr-web:1.0.0.BUILD-SNAPSHOT')
@Grab('spring-boot-starter-web')
class YourInitializrApplication { }
Note
 Spring Initializr is not available on Maven central yet so you will have to build it from source in order to use it in your own environment.

Once you have created that script (my-instance.groovy), place your configuration in the same directory and simply execute this command to start the service:

$ spring run my-instance.groovy

You may also want to run the default instance locally.

Building from Source

You need Java (1.8 or better), Maven 3.2+ and a bash-like shell.

Building

Just invoke the build at the root of the project

$ mvn clean install

If you want to run the smoke tests using Geb, you need to enable the smokeTests profile. Firefox should also be installed on your machine:

$ mvn verify -PsmokeTests

Running the app locally

Once you have built the library, you can easily start the app as any other Spring Boot app from the initializr-service directory:

$ cd initializr-service
   $ mvn spring-boot:run

Running the app in an IDE

You should be able to import the projects into your IDE with no problems (STS with the m2e Groovy compiler support or IntelliJ IDEA definitely work). Once there you can run the initializr-service from its main method, debug it, and it will reload if you make changes to other modules. (You may need to manually enable the "full" profile.) This is the recommended way to operate while you are developing the application, especially the UI.

Deploying to Cloud Foundry

If you are on a Mac and using homebrew, install the Cloud Foundry CLI:

$ brew install cloudfoundry-cli

Alternatively, download a suitable binary for your platform from Pivotal Web Services.

You should ensure that the application name and URL (name and host values) are suitable for your environment before running cf push.

First, make sure that you have built the library, the build the service from the initializr-service directory: Make sure first that the jar has been created:

$ cd initializr-service
$ mvn package

Once the jar has been created, you can push the application:

$ cf push your-initializr -p target/initializr-service.jar

License

Spring Initializr is Open Source software released under the Apache 2.0 license.