Liferay: How to configure Service Builder to use MySQL generated Primary Key - liferay

Question

I have a liferay entity (log table) that has a primary key auto generated by Liferay Service Builder (service.xml).
However now an external application need to add entries to this same database table.
Looking at this requirement I see only two options to achieve this:
If I can specify within service.xml that can allow this database entity to use MySQL generated primary key (rather than Liferay counter services), then Liferay or External application both can add entries without any worries.
If #1 is not possible due to Service Builder limitations, then only option is to expose this entity using a liferay web service for the external application to add entries to this db table.

Answer 1

DTD Service Builder 6.2.0
The answer to your question is directly in the xml document description.
First Example
The second implementation generates identifiers that are unique only when no
other process is inserting data into the same table. This implementation should
NOT be used in a clustered environment, but it does work for all supported
databases.
Example
<column
name="id"
type="Integer"
primary="true"
id-type="increment"
/>
Second Example
The third implementation uses an identity column to generate a primary key. In this implementation, the create table SQL generated for this entity will
create an identity column that natively auto-generates a primary key whenever
an insert occurs. This implementation is only supported by DB2, MySQL, and
MS SQL Server.
Example
<column
name="id"
type="Integer"
primary="true"
id-type="identity"
/>
A hard to come by piece of information is how to override the create method in your generated persistenceImpl class. When you create a surrogate key in Liferay you generally use the CounterLocalService to increment. However, when your key is handled by the database you need to send in 0 as the argument.
public SoftwareKey createSoftwareKey() {
return softwareKeyPersistence.create(0);
}

Answer 2

Your first point it is not a good idea, primary keys would be managed entirely by Liferay.
However your second point it's the correct way to accomplish what you want, take a look here.