Reaching Out From PL/SQL (OPP 2010)

Reaching Out
from PL/SQL
Engaging with the world

Do not ask what your
country can do for
you
Ask what you can do for your
country?!

By all means, ask what
the world around you can
mean for your PL/SQL
application
and Also Ask what you (through
PL/SQL & the Database) can do for
your “environment”?!

Database
(SQL & PL/SQL)
• Channel
• Initiative
• Frequency
• Format
• Synchronous vs Asynchronous
• Volume

Database
(SQL & PL/SQL)
Email
User
Interface
Chat
(IM)
File
(Excel, PDF,…)
RSS
Queue
REST
Web
Servic
e
File, O/S
JDBC,
SQL Net,
DB Link

Demo steps
• Java to receive email
• Load Java and Expose as JSP
• Create AQ
• Create Job & Schedule that calls JSP
and puts results on AQ
• Create AQ listener
–That sends email with response

1
• Write Functional Java
2
• Wrap with PL/SQL
3
• Load into Database
4
• Set appropriate Privs
5
• Invoke JSP via PL/SQL
Interface

Other scenario with database as
initiator of the dialog
• An Update of an Employee’s Salary takes place
• After Update Row level trigger fires
– creates job to send out an email to
have someone approve the salary raise
– Sets the status of the salary to ‘awaiting approval’
• Email is sent to approver
• Approvers sends an answer
– Decision and comments
• Answer is received & processed by database
– Status of salary record is updated

dbms_epg
(mod_plsql)
http
XMLDB
http
ftp
webdav
utl_mailutl_file
external
table

Expose recent HRM Data
Changes• Several parties are interested in all changes in
the area of Human Resources
– We have received a request to make an overview of
all recent changes available, preferably in XML format

Flashback Versions
• Retrieve all states each record has been in
– Every transaction that touched a row left a
version of it
– Pseudocolumns: xid, operation, starttime,
endtime

Expose HRM Changes in XML
document• Create package HRM_CHANGE_HISTORY
– Containing procedure EMP_HISTORY that writes an XML
document to htp.p with Employee change records
• Using DBMS_EPG
– Create DAD hrmhistory on path /hrm/*
– Authorize DAD hrmhistory
for schema SCOTT
• Access URL
http://localhost:2100/hrm/scott.
hrm_change_history.
emp_history
J(2)EE Application
Server
Service
http://host/../emp_history

Pull EMP change overview from browser

Publish Changes in Pretty
Format• A simple XSLT style sheet can be applied
in the hrm_change_history package
– To transform XML data to an XHTML human
readable format

Expose EMP Changes as RSS
feed
• RSS feed is an
HTTP response
in a predefined
XML format
(ATOM)
• DBMS_EPG can
be used to produce
RSS feeds

Pull model: DBMS_EPG/Web Toolkit
• Pull model means create on request
– Always the most fresh data
– Potentially large load on the database
as for every request the
XML document is recreated
– Document is retrieved
through a download by
an HTTP client
• Alternative: push (publish) model
– Periodically create the XML document
– Make it available to various clients
• On the file system, on the web
J(2)EE Application
Server
Service
XDB
Folder
WEBDAV
FTP
HTTP
PL/SQL
SQL

Periodically publish XML Report
• Create XML DB Folder
– Is also a ‘directory page’ via HTTP
– And a WEBDAV folder
– And an FTP directory
• Schedule Job to Create
Resource in the XDB Folder
– Based on XMLType: the result of
a query that collects the desired data
• To access:
– Go to URL & open in browser
– Map Network Drive via WEBDAV
– Open FTP session
J(2)EE Application
Server
Service
XDB
Folder
WEBDAV
FTP
HTTP
PL/SQL
SQL

Create XML Resource
DECLARE
CURSOR xmlcur IS
SELECT xmlelement("EMPHISTORY", ...
l_xml_dir VARCHAR2(30) := '/public/hrmData';
l_doc_name VARCHAR2(30) := 'EmpChangeHistory.xml';
l_emp xmltype;
l_res boolean
BEGIN
IF dbms_xdb.CreateFolder(l_xml_dir)
THEN
... some ACL setting up
END IF;
open xmlcur;
fetch xmlcur into l_emp;
close xmlcur;
l_res := dbms_xdb.createResource
( abspath=> l_xml_dir||l_doc_name
, data=> l_emp
);
COMMIT;
end;

HRM Report via WEBDAV, SQL &
HTTP

Viewing&Editing XDB Resource in
Excel

Uploading data from file to
database

APEX
The Ultimate Database
User Interface
dbms_epg
(mod_plsql)

Database Reaching Out
to Human partners
• DBMS_EPG (or good old mod_plsql)
– Expose HTML and RSS & Process HTTP
requests
• XMLDB
– Expose and allow manipulation of resources
through HTTP, FTP and WEBDAV
• Stored Java Procedures to
– Interact with Mail Server, Chat; leverage
– Process human file formats (PDF, Excel,
images, …)

Database
(SQL & PL/SQL)
Email
Chat
(IM)
RSS
Queue
REST
Web
Servic
e
File, O/S
JDBC,
SQL Net,
DB Link
dbms_epg
(mod_plsql)
http
XMLDB
http
ftp
webdav
utl_mailutl_file
external
table
utl_http
(httpuritype
)
http
JDBC/ODBC
OCI, DB Link
utl_tcp
Advanced
Queuing
AQ
jms
native
dbws

Tables & Business Rules
Views
PL/SQL “Services”
Oracle
Forms
Forms
DWH
External Partners
Web Application
Email
Server
Java based
SQL*
Loader
Modern Architecture
and the role of the database

Tables & Business Rules
Views
PL/SQL “Services”
Oracle
Forms
Forms
External Partners
Web Application
Email
Server
Java based
(extranet)
Web Application
Internal Users
(outside
intranet/firewall)
“Mobile
Enabled”
ADF 11g
ADF 11g
Enterprise Service and Process Bus
(SOA Suite 11g: BPEL, Mediator,
Human Task, Business Rules, Technology Adapters)
file
s
UCM
(Document
Management)
DWH
Operational
Dashboard
APEX

Be a good host
• Provide services
–Views for easy querying
–Stored Procedure based APIs
• For data retrieval and data manipulation
–Queues as way-in (publish) as well as
way-out (allow subscription) for events
–Query Result Change Notification

API Services for consumers
• Views – for encapsulation of (legacy) model,
multi-table join, collection integration, SQL
hiding
• PL/SQL – for encapsulation, cursor based
data retrieval, DML hiding, table decoupling
View

Views hiding data model
USERS
PERSONS EMAIL_
ADDRESSES
EMAIL_TYPE
USERS

Providing a ‘business object’
API
• DML API: still the View – aided by Instead Of
trigger
• Insert of one new row in
USERS_VW can actually
be four new records
– USER, PERSON,
EMAIL_TYPE
EMAIL_ADDRESS
USERS
PERSONS EMAIL_
ADDRESSES
EMAIL_TYPE
USERS
*
* *
*

FIY Data Service API:
returning cursors
• Fetch it Yourself!
• Cursor is opened to be fetched from
– Data is gathered and
pre-processed before being returned
– SQL is wrapped
• And can be constructed at run-time
– Access privileges are taken care of
– Cursors can be handled elegantly
in most client languages and technologies
• For example Java: JDBC ResultSet
Prompt
Prompt
Prompt
Prompt
Prompt
Prompt Prompt Prompt Prompt
A
ct
ie
A
ct
ie
HRM_API
CURSOR

FIY Data Service API for
Employees
• Package HRM_API
– Function get_managers
– Return SYS_REFCURSOR
HRM_AP
I
EMPDEPT

FIY Data Service API for
Employees
HRM_AP
I
EMPDEPT
create or replace package body hrm_api
as
function get_managers
return SYS_REFCURSOR
is
c_mgr sys_refcursor;
begin
open c_mgr for
select empno
, ename
, sal
, hiredate
, deptno
from emp
where job = 'MANAGER'
;
return c_mgr;
end get_managers;
end hrm_api;

Using FIY HRM API from
PL/SQL HRM_AP
I
EMPDEPT
declare
l_mgr sys_refcursor:= hrm_api.get_managers;
l_id number(10);
l_name varchar2(25);
l_salary number(8,2);
l_hiredate date;
l_deptno number(10);
begin
LOOP
FETCH l_mgr
INTO l_id, l_name, l_salary, l_hiredate, l_deptno;
EXIT WHEN l_mgr%NOTFOUND;
dbms_output.put_line
( 'Manager '||l_name
||' started on '||l_hiredate
||' and makes $'||l_salary
);
END LOOP;
CLOSE l_mgr;
end;

Cursor can be for Dynamic
SQL
function get_employees_on_condition
( p_condition in varchar2
) return SYS_REFCURSOR
is
c_emp sys_refcursor;
begin
open c_emp for
' select empno
, ename
, sal
, hiredate
, deptno
from emp
where '||p_condition
;
return c_emp;
end get_employees_on_condition;
declare
c_emp sys_refcursor:=
hrm_api.get_employees_on_condition
( p_condition => 'job=''CLERK''
and sal < 1200'
);
l_id number(10);
...

Cursor can be created inside
SQL• The SQL CURSOR expression
returns sys_refcursor based on
query passed in
– Cursor expressions can be nested
• Cursor can even fetch data from
a Collection (returned for
example
by a PL/SQL function)
• CURSOR expression can be
fetched into PL/SQL variable of
type SYS_REFCURSOR
• Note: SQL*Plus knows how to
deal with cursor-types results
– It automatically opens them and
fetches records

The Super Host
Query Result Change Notification

Query Result Change
Notification• Continuous Query Notification:
– Send an event when the result set for a query changes
– Background process calls PL/SQL Handler or Java Listener or
OCI client when the
commit has occurred
– Event contains rowid
of changed rows
• Used for:
– Refreshing specific
data caches (middle
tier, global context)
– (custom) Replication
PL/SQL
Java
Listener

Implementing QRCN in PL/SQL
• Set up the privileges for the user
– CHANGE NOTIFICATION and EXECUTE on
DBMS_CQ_NOTIFICATION
• Create the Callback Handler procedure
• Create a new QRCN registration
• Add query (or queries) to the registration
– The queries for which a change in the result
set should trigger a call to the Callback
Handler
• Make sure job_queue_processes
parameter is set to a nonzero value

QRCN Callback Handler
• Signature is crucial!
• The CHNF$_DESC type contains a lot
information
– Including operation, queries and rowids
CREATE OR REPLACE PROCEDURE
change_notification_callback
( ntfnds IN SYS.CHNF$_DESC
) IS
...

Registration of QCRN interest
DECLARE
reginfo cq_notification$_reg_info;
l_cursor SYS_REFCURSOR;
regid NUMBER;
qosflags NUMBER;
BEGIN
qosflags := DBMS_CQ_NOTIFICATION.QOS_QUERY+
DBMS_CQ_NOTIFICATION.QOS_ROWIDS;
/* 1. Construct registration information.
'change_notification_callback' is name of
notification handler.
QOS_QUERY specifies result-set-change notifications.
*/
reginfo := cq_notification$_reg_info
( 'scott.change_notification_callback'
, qosflags
, 0
);

Registration of QCRN interest
(2)/* 2. Create registration */
regid :=
DBMS_CQ_NOTIFICATION.NEW_REG_START(reginfo);
OPEN l_cursor FOR
SELECT mgr
FROM emp
WHERE empno = 7902;
CLOSE l_cursor;
DBMS_CQ_NOTIFICATION.REG_END;
END;
...

To look for the registered
QCRNs
• Inspect Data Dictionary View
user_cq_notification_queries
SELECT queryid
, regid
, to_char(querytext)
FROM user_cq_notification_queries

To see the QRCN in action…
• Perform a DML statement that will apply
changes that modify the Query Result
• Look for whatever effect the Callback
Handler should have
– Message to the middle tier via UTL_HTTP
– Event on Advanced Queue
– Audit Table updated
– Asynchronous validations/calculations
performed
– Some custom-built form of replication
– …

More Interaction from & to the
database
• Files into the database
• Database to leverage O/S
• Stored Java for non-human
interactions
• WebServices – publish and consume
• Engage Middle Tier as ‘agent’

File Processing into the
Database
• Files can be
–uploaded through dbms_epg
–put on FTP/WEBDAV through XMLDB
–read by utl_file or dbms_lob (from O/S)
and by utl_http (from intranet/internet)
–exposed into the database via External
Tables
–retrieved by Java Stored Procedure (e.g.
from email attachment or remote FTP
server)

Interaction from Database with
O/S
• Database can interact with operating
system through
–external jobs (through dbms_scheduler)
–the External Table Preprocessor
–utl_file (only for some file manipulation)
–Java Stored Procedures
–(C-based) External Procedures

EJB
JMS
Email
Libraries for:
• Graphical Manipulation
• Translation,
• Calculation,
• Encryption,
• …
Communication
Protocols: http, ftp,
tcp ip, sms, grid, JDBC,
JDBC-ODBC, .Net, …
Operating Syste
& File System

The database can ask the
middle tier to access and
provide services
• Get information from (or to) services on the
intranet or internet
• Publish/Send information to the internet
(RSS, email, chat)
• Can tell the middle tier
– Interesting events
– Alert about (im)pending issues,
attempted rule violations, …
– The outcome of batch calculations
• DB vs. Middle Tier: Security,
Functionality, Load Balance
WebLogic Server 11g
SOA Suite
11g
AQ
Web App

• Database can call a middle
tier service using utl_http
– Passing in the destination
and the message content
• This Service sends it
onwards to the Google
Talk Server
WebLogic Server 11g
Service
CHAT_
MGR
Service
Happy Chatting – IM from the
Database

Database actively informs on
events
WebLogic Server 11g
Service
CHAT_
MGR
Service
EMP

Chat Manager package
create or replace package body chat_mgr
as
c_im_destination CONSTANT varchar2(100):= 'im_account';
c_im_service_base_url CONSTANT varchar2(100):= 'http://host/service?';
c_amp constant varchar2(5) := chr(38);
procedure send_im_message( p_msg in varchar2) is
l_response varchar2(32000);
begin
l_response:= utl_http.request
( c_im_service_base_url
||'imDestination='||c_im_destination
||c_amp||'msgBody='||replace(p_msg,' ', '%20')
, null
);
end send_im_message;
end chat_mgr;

Emp Informer
create or replace trigger mananager_sal_update_watcher
before insert or update of sal
on emp
for each row
when (new.job ='MANAGER'
and new.sal > 4000
and new.sal > nvl(old.sal,0))
declare
l_msg varchar2(32000);
begin
l_msg:= 'Selfenrichment '
||'Salary of '||:new.ename
||' ( manager in Department '||:new.deptno||') '
||'is changed to '||:new.sal
;
chat_mgr.send_im_message
( p_msg => l_msg
);
end;

RESTful WebServices
• Simple, stateless, light weight, http-based
message exchange protocol
– Use standard get, put, post, delete operations
– Use URL to pass resource reference
• Small, easy-to-understand messages
• Typically XML or JSON based
• Not using SOAP, or the WS*-stack
• Often used directly from User Interface –
(AJAX enabled) JavaScript

RESTful architecture
RESTful PL/SQL API
exposed through dbms_epg

Publish REST-ful HTTP API –
directly on top of the RDBMS

Consuming REST-ful services
• Invoking a REST-ful service is simply
making an HTTP request to some URL
• Can be done through:
– utl_http
– httpuritype
– Stored Java
• Result can be processed as just a string or
as XML, JSON or other format
– Libraries can help with special formats

Calling ‘formal’ WS* and
SOAP based Web Services
• Invoking a SOAP WS* service is making
an HTTP request to some URL
• Can be done through:
– utl_http
– Stored Java
• Request and Response
are both SOAP-wrapped XML messages
– Using XMLDB functionality including XML Type these
can easily by composed, transformed, validated and
parsed

(Expose) Native WebServices
• Publish and PL/SQL Package as externally
available WebService
– WSDL is auto-generated
– SOAP calls over http and https are supported

Reaching Out From PL/SQL (OPP 2010)

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