Component Plugins

Component plugin modules are available in Confluence 1.4 and later

Component plugin modules enable you to add components to Confluence's internal component system (powered by Spring).

For more information about plugins in general, read Confluence Plugin Guide.
To learn how to install and configure plugins (including macros), read Installing and Configuring Plugins manually.
For an introduction to writing your own plugins, read Writing Confluence Plugins

Component Plugin Module

Each component module adds a single object to Confluence's component management system.

Other plugins and objects within Confluence can then be autowired with your component. This is very useful for having a single component that is automatically passed to all of your other plugin modules (ie a Manager object).

Here is an example atlassian-plugin.xml file containing a single component module:

<atlassian-plugin name="Sample Component" key="confluence.extra.component">
    ...
    <component name="Keyed Test Component" 
        key="testComponent" 
        alias="bogusComponent"
        class="com.atlassian.confluence.plugin.descriptor.BogusComponent" />
    ...
</atlassian-plugin>

the name attribute represents how this component will be referred to in the interface.
the key attribute represents the internal, system name for your component.
the class attribute represents the class of the component to be created
the alias attribute represents the alias this component will be stored with. This element is optional, if not specified the module key will be used instead.

Accessing Your Components

Accessing your components is extremely simple.

Autowired Objects

If your object is being autowired (for example another plugin module or an XWork action), the easiest way to access a component is to add a basic Java setter method.

For example, if you use the above BogusComponent module your object would retrieve the component as follows:

public void setBogusComponent(BogusComponent bogusComponent)
{
    this.bogusComponent = bogusComponent;
}

Non-autowired Objects

If your object is not being autowired, you may need to retrieve the component explicitly. This is done via the ContainerManager like so:

BogusComponent bc = (BogusComponent) ContainerManager.getComponent("bogusComponent");

Notes

Some issues to be aware of when developing a component:

One component module can depend on another component module but be careful of circular references (ie A requires B, B requires A).
The component "namespace" is flat at the moment, so choose a sensible alias for your component.