An Application Context example

tingsheng發表於2011-10-21
APPContext

Creating a Context

Context is a set of session-based attributes that can be only set by the package specified in CREATE CONTEXT statement. 

   CREATE CONTEXT app1_ctx USING app1_ctx_package;

In this example, only procedures and functions of app1_ctx_package package are allowed to set or reset the attributes of the app1_ctx context.

Setting Attributes of Context

Only the package specified in CREATE CONTEXT statement can change attributes of the context using DBMS_SESSION.SET_CONTEXT procedure: 

    CREATE OR REPLACE PACKAGE app1_ctx_package IS
      PROCEDURE set_empno (empno NUMBER);
    END;
   /
   CREATE OR REPLACE PACKAGE BODY app1_ctx_package IS
     PROCEDURE set_empno (empno NUMBER) IS
     BEGIN
       DBMS_SESSION.SET_CONTEXT('app1_ctx', 'empno', empno);
     END;
   END;
   /

Note. You have to create the package (or just its specification) before you create the context.

An application can initialize context by calling the package procedure i.e 

   CALL app1_ctx_package.set_empno(11);

Restricting Data Access using Context

Assume, you have the following data: 

   CREATE TABLE orders (price NUMBER(10,2), empno NUMBER(5));
 
   INSERT INTO orders VALUES (295.00, 10);
   INSERT INTO orders VALUES (99.00, 11);
   INSERT INTO orders VALUES (125.00, 11);

Then you can restrict access to this table, so an employee can see only own data using SYS_CONTEXT function: 

   SELECT * FROM orders WHERE empno = SYS_CONTEXT('app1_ctx', 'empno');

Result:

price empno
99 11
125 11

This example shows how application can restrict access to data by adding WHERE condition with SYS_CONTEXT function.

來自 “ ITPUB部落格 ” ，連結：http://blog.itpub.net/7734298/viewspace-709479/，如需轉載，請註明出處，否則將追究法律責任。

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