This tutorial shows you how to use Appsody to take care of packaging applications for the cloud so that you can focus on writing code. The tutorial uses the application provided in the Open Liberty guide for Creating a RESTful Web Service.
Appsody simplifies developing apps for the cloud. It helps teams share common foundations on which to build applications; where they can embed their expertise and standards, and reduce the learning curve before new folks can start writing apps.
At its core, Appsody provides:
Stacks which include language runtimes, frameworks, libraries, and tools.
Project Templates which build upon these Stacks and provide an initial project structure, and just enough code to get started with your own “cloud native” application.
A CLI which allows you to manage the full development lifecycle.
Applications can be iteratively developed while they are deployed in a locally running Docker container, with code changes automatically detected and reflected in the app.
This tutorial shows you how existing applications can be built on top of a Stack to take advantage of Appsody’s workflows for development and deployment.
Install the Appsody CLI by following the Installing Appsody guide for your platform.
You also need to install Docker and Maven.
This guide shows you how to develop a simple JAX-RS web service, which responds to a GET request by returning the JVM’s system properties. You can either follow the guide and build the app yourself, or skip to the end as the finished application is provided within a folder called finish.
To work with the finished application:
git clone https://github.com/OpenLiberty/guide-rest-intro
/guide-rest-intro/finish that contains the completed application.As mentioned, Appsody provides both a Stack and Project Templates. If you already have your own application, and therefore don’t require the project template, you can initialize the Appsody development environment with just the Stack that is required by your application. To do this issue the appsody init command with none specified for the template.
The JAX-RS and JSON-P features used by the sample application are part of Eclipse Microprofile specification. You can use the java-openliberty stack to build MicroProfile compliant applications. Initialize your Appsody development environment by issuing the following command within the finish directory:
appsody init java-openliberty none
The output includes a statement similar to:
[InitScript] [INFO] --------------------< dev.appsody:java-openliberty >--------------------
[InitScript] [INFO] Building java-openliberty 0.2.5
There is one change that you need to make in order for the app to run.
Both the application and the java-openliberty Stack include a pom.xml file. The Stack’s pom.xml file acts as the parent. Therefore, before you can run the app you need to update the <parent> field in the application's pom.xml to reference the Stack. The application's pom.xml is in the directory you are currently in, open the file and add the following code:
You can find the correct parent pom version in the output from the
appsody initcommand.
<parent>
<groupId>dev.appsody</groupId>
<artifactId>java-openliberty</artifactId>
<version>0.2.5</version>
</parent>
Start your Appsody development environment by entering: appsody run.
The run command starts a Docker container and mounts the workspace and the local maven repository (~/.m2/repository). Open Liberty's "dev mode" is enabled which automatically detects changes to the application's configuration and source, triggering a recompile and redeploy of the application.
You can test the app by going to: http://localhost:9080/LibertyProject/System/properties
You now have a fully functional development environment, where you can make code changes in your IDE of choice, save, and refresh the above URL to see the changes take effect.
For a simple example, open src/main/java/io/openliberty/guides/rest/PropertiesResource.java and replace:
return System.getProperties();
with
Properties prop = new Properties();
prop.setProperty("Hello", "World");
return prop;
You can see that the changes are picked up automatically by looking at the output from the appsody run command. If you then revisit: http://localhost:9080/LibertyProject/System/properties you now see the output:
{"Hello":"World"}
With the Appsody CLI, you can build a local Dockerfile and deploy the application to a Kubernetes cluster. More information about how to build and deploy your app can be found in the deploying documentation.
If you have any questions or would like to chat, come join us on Slack!
You can also find other helpful guides for creating Java applications with Open Liberty here.