Compensation Handler

Compensation Handler -

Compensation occurs when the BPEL process cannot complete a series of operations after some of them have already completed, and the BPEL process must backtrack and undo the previously completed transactions.

For example, if a BPEL process is designed to book a rental car, a hotel, and a flight, it may book the car and the hotel and then be unable to book a flight for the right day. In this case, the BPEL flow performs compensation by going back and unbooking the car and the hotel.

1)      Create  a Simple Bpel Code with below mentioned xsd parameters-

<?xml version="1.0" encoding="UTF-8"?>

<schema attributeFormDefault="unqualified"

                elementFormDefault="qualified"

                targetNamespace="http://xmlns.oracle.com/Application1/compensation_practice/Compensation_Practice"

                xmlns="http://www.w3.org/2001/XMLSchema">

                <element name="process">

                                <complexType>

                                                <sequence>

                                                                <element name="input" type="integer"/>

<element name="input1" type="integer"/>

                                                </sequence>

                                </complexType>

                </element>

                <element name="processResponse">

                                <complexType>

                                                <sequence>

                                                                <element name="addition" type="integer"/>

<element name="subtraction" type="integer"/>

<element name="multiplication" type="integer"/>

                                                </sequence>

                                </complexType>

                </element>

</schema>

2)      Below Is the complete bpel flow -

3)      How It Works ?-In this flow we will create a simple scope for addition and one for division. If input has 0 it will throw  an error and flow control will go to catch all block from where compensate will revert back all previous assigned values.

First -Create a scope for addition. Inside assign, logic will be –   [ input 1 + input 2 ] as shown below –

Next- Add compensation block  on the same scope by selecting arrow button  on left side,add assign activity and update  values as shown below  -

Create one more scope for division. Here logic is- if value for input1 is 0 it would throw an error and move to catch all block  as shown below –

Logic For Catch All Block –

Here in catch all- compensate activity will revert back all previous values and  assign  new one based on  logic written in compensation handler block within each scope.

Testing –

Provide the input parameters  as shown below –(positive test case) –

Response –

Compensation Test Case –

Provide 0 in input1 as shown below –

Response    ( It compensates the addition value and resets to 0 )