Before diving into the details of developing for the Marketplace, it is important to have a good grasp of new concepts introduced in the Marketplace. The following list of questions will help in understanding the concepts that you will use over and over again as a Marketplace developer.
What is an app?
As a Liferay Developer, you will undoubtedly already be familiar with the concept of plugins (portlets, hooks, themes, etc). If not, review chapter 1 of this guide. A Liferay App (sometimes just called an app) is a collection of one or more of these plugins, packaged together to represent the full functionality of an application on the Liferay platform. In addition to the plugins contained within an app, apps have metadata such as names, descriptions, versions, and other ancillary information used to describe and track the app throughout its lifecycle.
Much like standard Liferay plugins, Liferay apps are also hot-deployable. If you were to download an app from the Marketplace, you would find that it is a special file type with a
.lpkg extension. This file can be dropped into Liferay’s hot-deploy folder like any other plugin, and it is deployed into the running instance of Liferay Portal.
Developers are not required to create the actual Liferay app files. Instead, your app’s individual plugins (
.war files) are uploaded as part of the publish process, along with identifying information (name, description, version, icon, etc). This is described in detail later on in this chapter.
What is a version?
The concept of versioning is well known in software, and it is no different here. A version of an app represents the functionality of the app at a given point in time. When an app is first created, it is given an initial version (often
1.0). When updates are needed for the app, a new version is created (e.g.
1.1), and new files are uploaded representing that version. In some cases, additional qualifiers can be found in the version specifier, to which developers often give special meaning. For example, a developer may declare that the version of their app is always in x.y.z format (where the significance of each x, y, and z are defined). Liferay itself also does this.
In any case, as developer of your app, you have complete freedom in how you wish to assign version designators. It is highly recommended that you stick to a well known and easy to understand format, such as
1.2, and so on. You may also include alphabetical characters (e.g
1.0 Beta 2 or
6.3 Patch 123235-01), but this is not recommended, as it makes it difficult to understand how versions relate to one another.
Keep in mind that the version of your app is completely up to you to specify, but the releases of Liferay with which your app works must be specified using the Liferay versioning scheme. See the Specify App Packaging Directives section below for details on how to specify the releases of Liferay for which your app is designed.
What is a package?
Apps can be written to work across many different versions of Liferay. For example, suppose you wish to publish version 1.0 of your app, which you’re supporting on Liferay 6.1 and 6.2. It may not be possible to create a single binary
.war file that works across both Liferay versions, due to incompatibilities between these Liferay versions. In this case, you need to compile your app twice: once against Liferay 6.1 and once against 6.2, producing 2 different packages (also called variations) of your version 1.0 app. Each package has the same functionality, but they’re different files, and it is these packages that you can upload in support of different versions of Liferay, as you will see in a later section. In this guide, packages are sometimes referred to as files that make up your app.
How do apps relate to users and companies?
When publishing an app, it is possible to publish it on behalf of yourself (an individual) or a company with which you are associated. The selection you make determines who has access to the app, once published. To understand the concepts of a Marketplace user, admin, and company, and the ramifications of choosing one vs. the other, visit the Liferay Marketplace chapter in the User Guide.
What are the requirements for publishing apps?
Liferay apps are “normal” Liferay plugins with additional information about them. Therefore, most of the requirements are the same as those that exist for other Liferay plugins that are detailed in the Portlet Development chapter of this guide. In addition to those, there are some Marketplace-specific requirements to keep in mind.
Things you need before you can publish
You must first develop your app using your preferred development tool (for example, using Liferay Developer Studio or the Plugins SDK). Your app will consist of one or more Liferay plugins. Ensure your app is designed to work with Liferay 6.1 or later. If you wish to target multiple versions of Liferay (for example, you may wish to support both 6.1 CE GA2 and 6.1 EE GA1), ensure you have built binary images of your app for each supported minor family release, if necessary. If a single set of files will work across all supported Liferay versions, you do not need to build multiple plugins. Liferay guarantees compatibility within a given minor release family, so your users can rest assured that your app will work with the minor release that you specify, along with all future maintenance releases of that minor release.
Next, think of a good name and description of your app, along with a versioning scheme you wish to use. Take some screenshots, design an icon, create web sites for your app (if they do not already exist), and have a support plan in place.
Image and Naming Requirements
Icons for your app must be exactly 90 pixels in both height and width and must be in PNG, JPG, or GIF format. The image size cannot exceed 512kb. Animated images are prohibited. Screenshots for your app must not exceed 1080 pixels in width x 678 pixels in height and must be in the JPG format. The file size of each screenshot must not exceed 384KB. Each screenshot should preferably be the same size (each will be automatically scaled to match the aspect ratio of the above dimensions), and it is preferable if they are named sequentially, for example
fluffy-puppies-02.png, and so on. Titles of Apps: In some views with Marketplace, titles of applications longer than 18 characters will be shortened with ellipsis. In the Marketplace, titles must not be longer than 50 characters. Description, Tags, Websites and Version Numbers: Descriptions, web sites and version numbers are to be as reflective to the product as possible. Please do not use misleading names, information, or icons. A tags suggestion tool has been provided to aid with tagging your asset. Descriptions should be as concise as possible. Ensure your icons, images, descriptions, and tags are free of profanity or other offensive material.
Above and beyond these basics of creating apps in the form of Liferay plugins, there are additional considerations to take into account when designing and publishing apps.
What kind of validations are performed by Liferay?
Liferay will ensure that apps meet a minimum set of requirements, such as:
- Running basic anti-virus checks
- Ensuring titles, descriptions, images, etc. are appropriate
- Basic sanity checking of functionality (e.g. deployment testing, etc)
Liferay does not do source code reviews and will not ask for your source code. Further, Liferay is not responsible for the behavior (or misbehavior) of apps on the Marketplace. For details regarding this, consult the Liferay Marketplace User Agreement, Liferay Marketplace Developer Agreement, and the individual End User License Agreements associated with each app.
What versions of Liferay should I target?
Of course, targeting the widest possible range of versions will ensure you a larger audience. However, there are certain features in specific versions of Liferay that you may wish to take advantage of. When uploading apps, you can specify which versions your app is compatible with and you can have multiple files for your app designed for different versions of the Liferay Platform.
Note that apps on the Liferay Marketplace must be designed for Liferay 6.1 and later. That’s not to say that they will not work with prior versions. However, only Liferay 6.1 has support for installing Apps directly from the Marketplace and safeguards against malicious Apps that will be ineffective on earlier versions of Liferay. If you wish to use an app for an earlier version, consult the documentation for that app, as it may or may not be supported on earlier versions of Liferay.
Read the Specify App Compatibility section below for details on how to specify which versions of Liferay your app works with.
Note: If you haven’t yet done so, be sure to read the Marketplace chapter of Using Liferay Portal!
Now that we have covered the basics, you’re armed with enough knowledge to start creating apps on the Marketplace, so let’s see what that looks like in the next section.