FYI: new javadoc tag to document system properties

[Weijun Wang]

I had also thought about this. In JCE, the API and implementation (aka provider) might even be in different modules, if some system properties only apply a specific provider, we can put them into module-info.java of that module.

We do support the new tag in module-info.java, right?

Thanks
Max

> On Nov 16, 2018, at 12:31 AM, Roger Riggs <Roger.Riggs at oracle.com> wrote:
> 
> Hi,
> 
> If a system property is defined and specified as supported then it needs a public declaration and specification as part of the public class or package documentation.
> Checking for and adding the tag will be a good way to reconfirm property definitions are in the right place.
> 
> Would it be reasonable to use only core-libs-dev for any remaining discussion?
> Seeing it on 5 aliases doesn't seem productive.
> 
> $.02, Roger
> 
> 
> On 11/15/2018 11:17 AM, Xuelei Fan wrote:
>> In JCE and JSSE, the public APIs definition (javax.net.ssl) and the internal implementation (sun.security.ssl) are separated.  The system property can be defined in the internal implementation classes.  I think we should add the @systemProperty on the public APIs, right?
>> 
>> The public API class and the implementation class may be not a one-to-one map.  Multiple public APIs may be impacted by the system property.  How to handle such cases?
>> 
>> Thanks,
>> Xuelei
>> 
>> On 11/14/2018 2:27 PM, Jonathan Gibbons wrote:
>>> 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]: https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/System.html#getProperties() 
>>> [2]: https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/net/doc-files/net-properties.html 
>>> [3]: https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/nio/file/Path.html#toAbsolutePath() 
>>> 
>>> 
>