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JServer - Java In The Database

Oracle 8i allows Java to be stored and executed from within the database. The following code gives is an example of how to use Java Stored Procedure/Functions. The function (addNumbers) is pretty stupid since it makes a database connection to add two numbers together, but it does serve as an example of the use of JDBC within the database. Using Java Stored Procedures requires the following steps:

Create a Java Stored Procedure

First we need to create a Java class so we have something to call.

CREATE OR REPLACE AND COMPILE JAVA SOURCE NAMED "Mathematics" AS
import java.lang.*;
import java.sql.*;
import oracle.sql.*;
import oracle.jdbc.driver.*;

public class Mathematics
{
  
  public static int addNumbers (int Number1, int Number2)
  {
    try
    {
      int iReturn = -1;
      
      // Connect to the database
      Connection conn = null;
      OracleDriver ora = new OracleDriver(); 
      conn = ora.defaultConnection(); 
      
      // Check record exists, and create it if it doesn't
      Statement statement = conn.createStatement();
      ResultSet resultSet = statement.executeQuery("SELECT " + Number1 + " + " + Number2 + " FROM dual");
      if (resultSet.next())
      {
        iReturn = resultSet.getInt(1);
      }
      resultSet.close();
      statement.close();
      conn.close();

      return iReturn;
    }
    catch (Exception e)
    {
      return -1;
    }
  } 

};
/

show errors java source "Mathematics"

Publish the Java call specification

Once this Java class is compiled into the database you will need to publish a call specification for it's method. This involves writing a PL/SQL "Wrapper" to allow the method to be called from PL/SQL. The following code sample creates a function called Addition which publishes the Mathematics method Add.

CREATE OR REPLACE FUNCTION AddNumbers (p_number1  IN  NUMBER, p_number2  IN  NUMBER) RETURN NUMBER
AS LANGUAGE JAVA 
NAME 'Mathematics.addNumbers (int, int) return int';
/

Test It

We are now ready to use the Java class. The PL/SQL Wrapper allows it to be called from both SQL and PL/SQL.

SELECT addNumbers(1,2)
FROM   dual;

For a more realistics example of using Java within the database check out the article on Oracle interMedia.

Hope this helps. Regards Tim...

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