Allow a set of SQLDialect to be supported by any jOOQ statement in the scope of this annotation.

This annotation can be used at the use-site of jOOQ API at any given scope ElementType#PACKAGE, ElementType#TYPE, ElementType#METHOD in order to specify that the given scope allows ANY of the supplied SQLDialect to be supported by all usage of jOOQ API within the scope. For example:

// Allow only MYSQL or ORACLE dialect support to be used within the class scope
@Allow(MYSQL, ORACLE)
public class MySQLAndOracleDAO {

    // Allow rule from class applies to this method
    public void mysqlAndOracleMethod() {
        DSL.using(configuration)
           .insertInto(TABLE, TABLE.COLUMN)
           .values(1)
           // This type checks as it works on both MySQL and Oracle
           .onDuplicateKeyUpdate()
           .set(TABLE.COLUMN, 2)
           .execute();
    }

    // Refine class Allow rule with additional requirement
    @Require(ORACLE)
    public void oracleOnlyMethod() {
        DSL.using(configuration)
           .mergeInto(TABLE)
           .using(selectOne())
           .on(TABLE.COLUMN.eq(1))
           .whenMatchedThenUpdate()
           .set(TABLE.COLUMN, 2)
           .whenNotMatchedThenInsert(TABLE.COLUMN)
           .values(1)
           .execute();
    }
}

Type checking for these annotations can be supplied by org.jooq.checker.SQLDialectChecker from the jOOQ-checker module.

Rules:

• In the absence of any Allow annotation, no jOOQ API usage is allowed.
• The combination of all Allow annotations and of the inner-most Require annotation is applied for any given scope.
• Nested packages are not creating nested scopes.
• If a versioned SQLDialect is allowed (rather than a SQLDialect#family()), then the allowed version, all of its SQLDialect#predecessor(), and its SQLDialect#family() are allowed.

Apart from the above main purpose, the Allow annotation also serves as a semantic namespace for other annotations, such as Allow.PlainSQL