After completing this snippet you should be able to understand the following:
What is Internet Data Access Protocol?
Steps followed to perform Advanced Queuing operations using
Internet Data Access Protocol.
Notation
IDAP - Internet Data Access Protocol
AQ - Advanced Queuing
SOAP - Simple Object Access protocol
<oracle_home> - Folder where Oracle Database is installed
Introduction
IDAP is the SOAP specification for performing AQ operations.It enables advanced
queuing operations to be performed over HTTP and HTTPS using XML.
Pre-requisites
Oracle9i or higher version
Java and Servlets
Description
In IDAP the communication between the HTTP client and the database takes place
through a servlet called AQServlet. The basic steps required for communication
through IDAP are:
1) Create the AQServlet
First the AQServlet must be created and compiled. The steps for configuration
of AQServlet are mentioned here.
2) Authenticate the user
The AQServlet allows only authenticated users to access the servlet. So the
Web server must be configured to Authenticate the users.
3) Authorize the user
The users must be authorized to access the database from the AQServlet.
This is done by registering the user and mapping the user to the database. The
commands are:
where bob is the username used to authenticate the user.
4) Send IDAP request to AQServlet
Requests are sent to AQServlet using the POST method.
The body of the IDAP message depends on the type of the request made. For an
enqueue request the format of IDAP message is as given below:
If the message is enqueued to a topic of multiconsumer queue, instead of the
tag AQXmlSend you can use the AQXmlPublish
tag. Payload contains the actual data that is to be propagated. The structure
of message_payload depends on the payload that is specified in the queue
table. In this case the payload is:
CREATE OR REPLACE TYPE customerorders AS OBJECT
( customer_id VARCHAR2(40),
order_date DATE,
order_total NUMBER(8,2),
)
/
If the payload is an array of nested table created using the script mentioned
below, the corresponding payload will be in the following format:
Script
CREATE OR REPLACE TYPE purchased_products
AS OBJECT
(
product_id VARCHAR2(10),
manufacturer_id VARCHAR2(5),
quantity_ordered NUMBER(6)
)
/
CREATE TYPE products_table
AS TABLE OF purchased_products
/
CREATE OR REPLACE TYPE products_arr IS
VARRAY(1) OF products_table
/
CREATE OR REPLACE TYPE customerorders
AS OBJECT
( customer_id VARCHAR2(40),
order_date DATE,
order_total NUMBER(8,2),
orders_array products_arr
)
/
The response to the enqueue operation depends on the success or the failure
of the enqueue operation. The response will be in the following format:
If the messages are enqueued to a multiconsumer queue then the response tag
contains AQXmlPublish response instead of AQXmlSendResponse
and publish_result instead of send_result.
In a similar fashion messages can be dequeued using SOAP. In such case, a dequeue
request of the format given below must be sent to the AQServlet.
If the dequeue_mode is Remove, after dequeuing
the messages are removed from the queue. The dequeue_ mode can also be
Browse or Locked.
Along with these tags another tag that is significant is <transformation></transformation>.
This tag specifies the transformation function that is to be used before dequeuing.
If the dequeue operation is successful, the response will be of the form
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