FYI: new javadoc tag to document system properties

Bill Shannon bill.shannon at
Thu Nov 15 04:15:32 UTC 2018

JavaMail defines a bunch of System properties as well as JavaMail Session
properties.  For example:

Would this tag be usable for both?

Would there be any reason to distinguish between System properties and
Session properties when using this tag?  If it's just adding an entry to
the index that links back to the defining page, that distinction doesn't
seem necessary.

The defining entries in the page above use html anchors, e.g.,
Is there a way to cause the tag to generate an index entry that uses
the anchor, or does it just link to the defining page?

Jonathan Gibbons wrote on 11/14/18 2:27 PM:
> This is an FYI to announce some initial, long-overdue support in javadoc for
> documenting system properties (JDK-5076751).
> Currently, system properties are just documented using ad-hoc narrative text,
> which is fine if you know where to look for any given property.
> JDK 12 introduces a new inline javadoc tag, {@systemProperty /property-name/}
> which can be used to "declare" the name of a system property. You can use this
> tag as a drop-in replacement for the plain-text property name; it will have no
> overt effect on the narrative text, but it will cause the property name to be
> put into the search index and the A-Z index. Thus, property names will become
> searchable, to allow users to easily find the definition of any such system
> property.
> Adding support into javadoc is only part of the story. Now that the support is
> in javadoc, we want to update the API documentation, so that the documentation
> is updated for all Java SE and JDK system properties.
> Where should the tag be used?  The tag should be used in the text of the
> defining instance of the property.  This is where the characteristics of the
> system property are described, which may include information like: "what is the
> property for", "how and when is it set", "can it be modified", and so on. For
> example, it could be used in the docs for System.getProperties [1] or Networking
> Properties [2] In general, it should -not- be used in situations that merely
> refer to the system property by name.  For example, the docs for
> Path.toAbsolutePath [3] make a reference to the system property user.dir, but
> that is not a definition of the property.
> Going forward, in future releases, we expect to explore some enhancements to
> this feature. Here are some of the ideas that have been suggested:
>  * Create a "summary page" that lists all the system properties. This
>    would be somewhat similar to the current top-level "Constant Values"
>    page.
>  * Add information regarding the "scope" of the definition: is it
>    defined by the Java SE specification, or JDK, or JavaFX, etc. This
>    information could be used to organize the content on the summary page.
>  * Update @see and {@link} to be able to refer to system properties.
>  * Allow a short description to be included in the {@systemProperty}
>    tag. This text could be included in the search index, the A-Z index,
>    and the summary page.
> -- Jon
> [1]:
> [2]:
> [3]:

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