Calling External Subprograms
Calling External Subprograms
PL/SQL is a powerful development tool; you can use it for almost any purpose.
However, it is specialized for SQL transaction processing. So, some tasks are more quickly done in a lower-level language such as C, which is very efficient at machine-precision calculations. Other tasks are more easily done in a fully object-oriented, standardized language such as Java.
To support such special-purpose processing, you can use PL/SQL call specs to invoke external subprograms (that is, subprograms written in other languages). This makes the strengths and capabilities of those languages available to you from
PL/SQL.
For example, you can call Java stored procedures from any PL/SQL block, subprogram, or package. Suppose you store the following Java class in the database: import java.sql.*; import oracle.jdbc.driver.*; public class Adjuster {
public static void raiseSalary (int empNo, float percent)
throws SQLException {
Connection conn = new OracleDriver().defaultConnection();
String sql = "UPDATE emp SET sal = sal * ? WHERE empno = ?";
try {
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setFloat(1, (1 + percent / 100));
pstmt.setInt(2, empNo);
pstmt.executeUpdate();
pstmt.close();
} catch (SQLException e) {System.err.println(e.getMessage());}
}
}
The class
Adjuster
has one method, which raises the salary of an employee by a given percentage. Because raiseSalary
is a void
method, you publish it as a procedure using this call spec:
CREATE PROCEDURE raise_salary (empno NUMBER, pct NUMBER)
AS LANGUAGE JAVA
NAME ’Adjuster.raiseSalary(int, float)’;
PL/SQL Subprograms
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