1.
│©2022 VMware, Inc.
Spring CLI
A CLI focused on developer productivity
- Mark Pollack
- Janne Valkealahti

2.
│©2022 VMware, Inc.
● A Spring developer wants to
○ Create a new web project
○ Later, add single sign on functionality to the project
● Spring OSS Survey indicates that documentation and getting started are the
most important areas to improve upon
● Conducted user interviews on ‘how to create app of type x’ using spring.io
○ Folks need some help getting started
Example Problem

3.
│©2022 VMware, Inc.
A common solution
● Go to start.spring.io and select dependencies
● Code
○ Consult documentation, Stack Overflow, example repos, Baeldung..
○ Look for some sample code close to what you want to do
○ Spring guides are hard to navigate when you don’t want to follow all the
details
● The downsides:
○ Time consuming and error prone
○ Which in-house dependencies to add?
○ Can get stuck in a Google cut-n-paste loop
○ Hard to encapsulate company standards
● There should be a better way…

4.
│©2022 VMware, Inc.
Spring CLI
● Takes the knowledge of a Spring expert and makes it generally available
● Not just for initial project creation, but part of your day to day workflow
● Sample workflow
○ spring boot new
○ spring boot add jpa
○ spring controller new --feature person
● Available as a native application on Windows, Mac, Linux and uber-jar

5.
│©2022 VMware, Inc.
spring boot new
● Create a new project based off an existing working project
○ A "Plain Old Java Project"* hosted in GitHub or GitLab
● spring boot new
○ By default a simple web application
○ Can optionally specify your own project name, package name, etc.
* @SpringBootApplication at root of package hierarchy with no @Beans inside

6.
│©2022 VMware, Inc.
spring boot new
● spring boot new jpa
○ The “jpa” is an alias for a GitHub URL
● Projects are registered with the CLI so that a simple name can refer to them
● A Project catalog is a collection of projects that share a common theme
○ Once a catalog is registered with the CLI, all the projects in the catalog
become available to use
● Note: you can also specify the URL instead of the name

7.
│©2022 VMware, Inc.
Demo: spring boot new

8.
│©2022 VMware, Inc.
spring boot add
● The same projects that you use to create a new project can also be added to
an existing project
● spring boot add jpa
○ Merges the Maven build file
○ Performs a package refactoring to match current project
○ Adds annotations on the Spring Boot main application class
○ Renames the README.adoc file to README-<project-name-added>.adoc
○ Merge application.yaml and application.properties files

9.
│©2022 VMware, Inc.
Examples: spring boot add
● spring boot add scheduling
○ Add sample code with @Scheduled annotation
○ Adds test code
○ Add spring-boot starter, awaitility
○ Adds @EnableScheduling annotation to main boot class
● spring boot add feature
○ Add code for
■ Spring Data JPA, @Controller, @Service and @Repository in addition
to tests

10.
│©2022 VMware, Inc.
Demo: spring boot add

11.
│©2022 VMware, Inc.
User-defined commands
● Using an existing “Plain Old Java Project” is not always the best approach
● User-defined commands are defined declaratively
○ Integrated into the CLI
○ Live side by side with your code
○ Help you perform everyday tasks on your current project
○ Based off a templating engine of your choice
■ Handlebars and mustache for now
● Examples
○ Creating a new controller with tests
○ Adding test-container support based on project dependencies
■ In the spirit of “Auto-configuration”, but for code generation
○ Creating configuration files for your platform of choice, CI system, etc…

12.
│©2022 VMware, Inc.
User-defined Commands
● Consist of
○ Command name
○ Sub-command name
○ Options file
■ What options does the command take, default values, etc.
○ Action file contains
■ What action to perform on the code base
● Generate a new file
● Inject into an existing file
○ Code, maven dependencies, …
● Execute an arbitrary program
■ Template text
■ Conditional SpEL expression determines if the action is executed

13.
│©2022 VMware, Inc.
Creating user-defined commands
● Defined using directory structure convention
○ .spring/commands/<command>/<sub-command>
● Inside that directory
○ Optional command.yaml
○ Action file
■ No special name
■ Based on contents having a front matter section

14.
│©2022 VMware, Inc.
.spring/commands/hello/new/command.yml
command:
description: Generate hello with greeting in a file
options:
#
- name: greeting
description: what word to use to say hello
dataType: string
defaultValue: Hello
inputType: text # TEXT

15.
│©2022 VMware, Inc.
.spring/commands/hello/new/hello.txt
---
action:
generate: hello.txt
---
Hello {{greeting}} at {{now}} on {{os-name}}.

16.
│©2022 VMware, Inc.
Executing a user-defined command
$ spring hello new
$ cat hello.txt
Hello World at Tue Jun 07 18:25:02 EDT 2022

17.
│©2022 VMware, Inc.
Template Model
● The model exposed to the template engine has many useful variables
○ All command option names
○ project-root
○ project-name
○ artifact-name
○ os-name
○ maven model and easy access to the most common, eg artifactId

18.
│©2022 VMware, Inc.
Demo: User Defined Commands

19.
│©2022 VMware, Inc.
Action Files
---
action:
generate:
inject:
exec:
injectMavenDependency:
injectMavenPlugin:
injectProperties:
engine: mustache
conditional:
onDependency:
---
<< Template text goes here >>

20.
│©2022 VMware, Inc.
Other features
● Spring Initializr client with Q/A
● GitHub authentication
○ Important due to rate-limiting!
● Configuration enabling setting of default values
○ Instead of “spring boot new –packageName=com.xkcd”
○ “config set boot new packageName com.xkcd”
○ “spring boot new” - now uses com.xkcd as the default package

21.
│©2022 VMware, Inc.
Spring Shell Enhancements
● New built in interactive user question flow
○ Example: spring initializr
● Colors!
● Fluent API to define commands
● Command logic can be implemented as a Function or Consumer
● Many other improvements
● See https://spring.io/blog/2022/05/30/spring-shell-2-1-0-m4-is-now-available

22.
│©2022 VMware, Inc.
Future areas
● Incorporate the Spring Boot migrator project into the CLI
○ spring boot upgrade
● Refinements around the user-defined commands
○ Execute open-rewrite recipes
○ SpEL conditional execution expressions
● Gradle support
● Multi-module
● Import .spring/config command
● bitbucket

23.
│©2022 VMware, Inc.
Wrapping up
● A goal of the Spring CLI is for a collection of curated projects and
user-provided commands to emerge in a company.
● The Spring CLI project offers many examples of projects and user-provided
commands to help you get started.
● Hope to get feedback and contributions to tackle new important areas
○ spring add graphql
○ spring add native
○ spring test-containers add
○ …
● Not yet a milestone release, aiming for a few weeks

24.
│©2022 VMware, Inc.
Where to get it
● https://github.com/spring-projects-experimental/spring-cli
● https://spring-projects-experimental.github.io/spring-cli/spring-cli/

25.
│©2022 VMware, Inc.
Thank You!

26.
│©2022 VMware, Inc.
Appendix Slides

27.
│©2022 VMware, Inc.
Cities
Chicago New York Seattle Atlanta
Toronto Amsterdam

28.
│©2022 VMware, Inc.
City Stamps
Chicago
New York Seattle Atlanta
Toronto Amsterdam

29.
│©2022 VMware, Inc.
Logos