You can invoke Java methods in SQL by referencing them, with name qualification, on instances for instance methods, and on either instances or classes for static methods.
Instance methods are generally closely tied to the data encapsulated in a particular instance of their class. Static (class) methods affect the whole class, not a particular instance of the class. Static methods often apply to objects and values from a wide range of classes.
Once you have installed a static method, it is ready for use. A class that contains a static method for use as a function must be public, but it does not need to be serializable.
One of the primary benefits of using Java with Adaptive Server is that you can use static methods that return a value to the caller as user-defined functions (UDFs).
You can use a Java static method as a UDF in a stored procedure, a trigger, a where clause, or anywhere that you can use a built-in SQL function.
Java methods invoked directly in SQL as UDFs are subject to these limitations:
If the Java method accesses the database through JDBC, result-set values are available only to the Java method, not to the client application.
Output parameters are not supported. A method can manipulate the data it receives from a JDBC connection, but the only value it can return to its caller is a single return value declared as part of its definition.
Cross-database invocations of static methods are supported only if you use a class instance as a column value.
Permission to execute any UDF is granted implicitly to public. If the UDF performs SQL queries via JDBC, permission to access the data is checked against the invoker of the UDF. Thus, if user A invokes a UDF that accesses table t1, user A must have select permission on t1 or the query will fail. For a more detailed discussion of security models for Java method invocations, see “Security and permissions”.
To use Java static methods to return result sets and output parameters, you must enclose the methods in SQL wrappers and invoke them as SQLJ stored procedures or functions. See “Invoking Java methods in Adaptive Server” for a comparison of the ways you can invoke Java methods in Adaptive Server.
