Manually Registering Extensions with javaExtensionRegistry

Extensions can be registered individually accessing the default extension registry directly from the Asciidoctor instance.

Asciidoctor asciidoctor = Asciidoctor.Factory.create();

asciidoctor.javaExtensionRegistry()
         .treeprocessor(Tre.class);

There is a method in the API for each extension point.

asciidoctor.javaExtensionRegistry()
        .blockMacro(GistBlockMacroProcessor.class);

asciidoctor.javaExtensionRegistry()
        .inlineMacro(IssueInlineMacroProcessor.class);

asciidoctor.javaExtensionRegistry()
        .block(YellBlockProcessor.class);

asciidoctor.javaExtensionRegistry()
        .includeProcessor(LsIncludeProcessor.class);

asciidoctor.javaExtensionRegistry()
        .preprocessor(CommentPreprocessor.class);

asciidoctor.javaExtensionRegistry()
        .postprocessor(CopyrightFooterPostprocessor.class);

asciidoctor.javaExtensionRegistry()
        .treeprocessor(TerminalCommandTreeprocessor.class);

extensionRegistry
        .docinfoProcessor(RobotsDocinfoProcessor.class);

Each method is overloaded to accept:

A Class: As seen in the examples, in this case AsciidoctorJ will take care of the complete lifecycle (initialization, etc.) of the extension.
An instance: This is useful when the extension requires pre-initialization or has a complex creation. For example, the extension instance could be managed in a Spring context making use of injected components.
A full canonical class name: This allows to pass the extension as a String type. This can be used when the extension class is not known at compile time.
String name macro name: Optional and only for blockMacro, inlineMacro and block. Allows defining the name of the macro if it’s not set in the extension class.