Components, Repositories, and Repository Formats

A component is a package of resources that your software application uses (e.g., a library or a framework). Some examples of components include the following:

Components can come in numerous formats, including the following:

Components can be as complex as an entire application or as simple as a static resource; they can even comprise multiple nested components themselves along with assets. For example, a Java web application may be packaged as a WAR component containing multiple JAR components and a number of JavaScript libraries. These JARs and libraries are also standalone components in other contexts while also being included as part of the WAR component.

While we use the generic term "component" in Nexus Repository, components are also called artifacts, packages, bundles, archives, and other terms.

Each component is identified by a unique set of coordinates. For example, you may have heard of GAV (group, artifact, and version) coordinates for Maven; however, coordinate names and usage strategies vary between formats.

An asset is a single file associated with a component. Many formats have a one-to-one mapping for component to asset; however, more complex formats have numerous assets associated with a component. For example, a typical JAR component in a Maven repository is defined at least by the POM and the JAR files; each file as well as additional files (e.g., Javadoc, Sources JAR) is a separate asset belonging to the same component.

In the Docker format, assets have unique identifiers called Docker layers. You can reuse these assets can for different components (i.e., Docker images). As Docker can be complex, we cover it in depth in Components and Assets in Docker.

The open source community as well as proprietary vendors are continually creating new components. For example, there are libraries and frameworks written in various languages on different platforms that developers use for application development every day. Developers typically build applications for a specific domain by combining multiple components' features with their own custom components containing their application code.

To make consumption and usage easier, components are aggregated into collections called a repository; these are typically available on the internet as a service. Different platforms may use terms such as "registry" and others to refer to repositories.

Examples of repositories available on the internet as a service include the following:

Numerous tools like the following access components in these repositories: