Module jdk.javadoc
Package jdk.javadoc.doclet

# Interface Taglet

public interface Taglet
The interface for a custom taglet supported by doclets such as the `standard doclet`. Custom taglets are used to handle custom tags in documentation comments; custom tags can be instantiated individually as either block tags, which appear at the end of a comment, or inline tags, which can appear within the main body of a documentation comment.

Each implementation of a taglet must provide a public no-argument constructor to be used by doclets to instantiate the taglet. A doclet will interact with classes implementing this interface as follows:

1. The doclet will create an instance of a taglet using the no-arg constructor of the taglet class.
2. Next, the doclet calls the `init` method with an appropriate environment and doclet.
3. Afterwards, the doclet calls `getName`, `getAllowedLocations`, and `isInlineTag`, to determine the characteristics of the tags supported by the taglet.
4. As appropriate, the doclet calls the `toString` method on the taglet object, giving it a list of tags and the element for which the tags are part of the element's documentation comment, from which the taglet can determine the string to be included in the documentation. The doclet will typically specify any requirements on the contents of the string that is returned.

If a taglet object is created and used without the above protocol being followed, then the taglet's behavior is not defined by this interface specification.

API Note:
  It is typical for a taglet to be designed to work in conjunction with a specific doclet.
Since:
  9
See Also:
  - User-Defined Taglets for the Standard Doclet

- ## Nested Class Summary

  Nested Classes
  Modifier and Type
  Interface
  Description
  `static enum`
  `Taglet.Location`
  The kind of location in which a tag may be used.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `Set<Taglet.Location>`
  `getAllowedLocations()`
  Returns the set of supported locations for block tags.
  `String`
  `getName()`
  Returns the name of the tag supported by this taglet.
  `default void`
  `init(DocletEnvironment env, Doclet doclet)`
  Initializes this taglet with the given doclet environment and doclet.
  `default boolean`
  `isBlockTag()`
  Indicates whether this taglet supports block tags.
  `boolean`
  `isInlineTag()`
  Indicates whether this taglet supports inline tags.
  `String`
  `toString(List<? extends DocTree> tags, Element element)`
  Returns the string representation of a series of instances of this tag to be included in the generated output.

- ## Method Details

  - ### getAllowedLocations

    Set<Taglet.Location> getAllowedLocations()
    Returns the set of supported locations for block tags.
    Returns:
      the set of supported locations for block tags

  - ### isInlineTag

    boolean isInlineTag()
    Indicates whether this taglet supports inline tags.
    Returns:
      true if this taglet supports inline tags

  - ### isBlockTag

    default boolean isBlockTag()
    Indicates whether this taglet supports block tags.
    Implementation Requirements:
      This implementation returns the inverse result to `isInlineTag`.
    Returns:
      true if this taglet supports block tags

  - ### getName

    String getName()
    Returns the name of the tag supported by this taglet.
    Returns:
      the name of this tag

  - ### init

    default void init(DocletEnvironment env, Doclet doclet)
    Initializes this taglet with the given doclet environment and doclet.
    API Note:
      The environment may be used to access utility classes for `elements` and `types` if needed.
    Implementation Requirements:
      This implementation does nothing.
    Parameters:
      `env` - the environment in which the doclet and taglet are running
      `doclet` - the doclet that instantiated this taglet

  - ### toString

    String toString(List<? extends DocTree> tags, Element element)
    Returns the string representation of a series of instances of this tag to be included in the generated output.

    If this taglet supports `inline` tags, it will be called once per instance of the inline tag, each time with a singleton list. If this taglet supports `block` tags, it will be called once for each comment containing instances of block tags, with a list of all the instances of the block tag in that comment.

    Parameters:
      `tags` - the list of instances of this tag
      `element` - the element to which the enclosing comment belongs
    Returns:
      the string representation of the tags to be included in the generated output
    See Also:
      - User-Defined Taglets for the Standard Doclet