Siva's Blog

In ADF, often we see error saying ‘JBO-25014: Another user has changed the row with primary key oracle.jbo.Key’. The framework throws this error to make sure that none of the user changes are accidentally overwritten by another user and generally occurs when a user trying to modify record that has been just modified and committed by another user. In this post, we will see how to take care of this scenario using ADF BC REST services in context of HTTP PATCH.

ADF BC REST Services make use of attribute called changeIndicator  which can be observed in response of GET.

Follow the steps mentioned below to enable this in a resource:

• EO should have an attribute marked as Change Indicator and set Track Change History as shown below.

• Add this attribute in VO i.e to be exposed as REST resource.

Deploy your changes and issue GET to observe changeIndicator as below.

for e.g. changeIndicator for department 10 (resource instance):

ACED0005737200136A6176612E7574696C2E41727261794C6973747881D21D99C7619D0300014900047
3697A65787000000001770400000001737200116A6176612E6C616E672E496E746567657212E2A0A4F7
81873802000149000576616C7565787200106A6176612E6C616E672E4E756D62657286AC951D0B94E08
B02000078700000000178

Now update department 10 using following sql query to simulate the actual update.

update departments set department_name = ‘Administration-modified’, object_version_number = object_version_number+1
where department_id = 10

Issue GET again on same resource and observe the changeIndicator.

ACED0005737200136A6176612E7574696C2E41727261794C6973747881D21D99C7619D0300014900047
3697A65787000000001770400000001737200116A6176612E6C616E672E496E746567657212E2A0A4F7
81873802000149000576616C7565787200106A6176612E6C616E672E4E756D62657286AC951D0B94E08
B02000078700000000378

 

As observed above, the value of changeIndicator changes with each update and is calculated by RESTServlet registered in web.xml of RESTWebService project.

Here is an interesting observation and do issue issuing GET for department 10.

http://localhost:7001/departmentApi/rest/r1/departments/10

If we observe HTTP response headers, the value of ETag is same as that of changeIndicator. Hence changeIndicator works in similar lines of ETag defined in HTTP specification.

Now let us observe the behavior of REST resource when  ETag is used for If-Match/If-None-Match HTTP headers during GET and PATCH. Basically these HTTP headers tells server to do requested operation when sent Etag value matches or did not match respectively.

Make sure you enclose ETag value with “ (double quotes) as shown below.

If-None-Match:

Using GET:

• When resource is not modified, returns status code as 304.

• When resource is modified, returns response with new changeIndicator value.

Using PATCH:

• When resource is not modified, returns response status code as 412.

• When the resource is not modified, then returns response with new changeIndicator value after update.

If-None-Match	Modified	Not Modified
GET	Status:200 (Query Successful)	Status: 304
PATCH	Status: 200 (Update Successful)	Status: 412

If-Match:

Using GET:

• When resource is not modified, resource is returned.

• When resource is modified, expected response status code is 304 but shows 200 with junk response.

Using PATCH:

• When resource is not modified, returns response with new change Indicator value after update.

• When resource is modified, expected response status code is 412 but shows 200 with junk response. However you will observe that the actual update is not happening though it returns 200.

If-Match	Modified	Not Modified
GET	Status:304	Status:200 (Query Successful)
PATCH	Status:412	Status: 200 (Update Successful)

Note: As you observed above, ETag combination with If-Match header is not working as expected which is a bug in this release.

References:

http://docs.oracle.com/middleware/1221/adf/develop/GUID-589F3905-5A8D-402D-B2D2-3BEEB2D7DDD4.htm#ADFFD54158

In this blog post, We will see how to expose ADF VOs as REST resources. ADF has got native REST support in 12.2.1 release.

We will use Department, Employee VOs and following AM Data Model here.

Creating Release Version:

Creating a release version in adf-config.xml is the first step to be done before exposing any of the AM VOs as resource. Use the following steps to create one and you can follow your own conventions for versioning REST resources. Here I  have given the initial version as r1.

Expose VO as REST resources:

Open AM and navigate to Web Service –> REST and Click + icon.

Creation of REST resources create a new project RESTWebService.jpr in our workspace that can be deployed as WAR through which these REST services get deployed.

Give the resource name as shown below and click OK.

Observe the new RESTWebService project gets created.

Also observe other files related to REST resources that get created as shown below.

You can use the following tabs to choose the methods to be exposed and the attributes to be exposed to consumers.

When a VO has View Links the Resource Structure will show all these VOs as shown below. Check these VOs as shown below if it has to be exposed as child resource.

Deployment:

Modify context root of RESTWebService project as shown below representing the purpose of your REST API.

Optionally, we can modify URL pattern in web.xml as shown below.

Integrated WLS:

Select RESTWebservice project and do Run on right click as shown below.

Standalone WLS:

Create EAR profile for ADF application and include RESTWebService project as shown below and deploy this EAR to standalone WLS.

Once the deployment is done, you can access the REST resource using url like:

http://<<host>&gt;:<<port>>/<<ContextRoot>>/<<url pattern>>/<<version>>/<<resource name>>

For e.g.: http://localhost:7001/departmentApi/rest/r1/departments

We can also use latest keyword to access the latest version of the resource.

For e.g.: http://localhost:7001/departmentApi/rest/latest/departments

You can use any REST client to try out POST, DELETE, PUT, PATCH depending on the operations you exposed on REST resource.

Describing Resource – GET:

URI: http://localhost:7001/departmentApi/rest/r1/departments/describe

Describing Resource Instance – GET:

URI: http://localhost:7001/departmentApi/rest/r1/departments/10/describe

 

Querying Departments – GET:

URI: http://localhost:7001/departmentApi/rest/r1/departments

Querying a particular Department – GET:

URI: http://localhost:7001/departmentApi/rest/r1/departments/{id}

Creating Department – POST:

URI: http://localhost:7001/departmentApi/rest/r1/departments

Content-Type: application/vnd.oracle.adf.resourceitem+json

Body:

{
“DepartmentId”: 1000,
“DepartmentName”: “Administration”,
“ManagerId”: 200,
“LocationId”: 1700
}

Deleting a Department – DELETE:

URI: http://localhost:7001/departmentApi/rest/r1/departments/{id}

Updating a Department – POST:

URI: http://localhost:7001/departmentApi/rest/r1/departments/{id}

Content-Type: application/vnd.oracle.adf.resourceitem+json

X-HTTP-Method-Override: PATCH

Body: (contains only fields to be modified)

{
“DepartmentName”: “Administration-Modified”
}

Replacing a Department – PUT:

URI: http://localhost:7001/departmentApi/rest/r1/departments/{id}

Content-Type: application/vnd.oracle.adf.resourceitem+json

Body: (Values not sent in body will be set to null)

{
“DepartmentId”:10,

“DepartmentName”: “Administration-Replace”,
“ManagerId”: 100
}

Querying Department for a few fields – GET:

URI: http://localhost:7001/departmentApi/rest/r1/departments?fields=DepartmentName,ManagerId

Querying a Department using an attribute – GET:

URI: http://localhost:7001/departmentApi/rest/r1/departments/{id}?q=DepartmentName=Administration

Querying a Department for only Data – GET:

URI: http://localhost:7001/departmentApi/rest/r1/departments?onlyData=true

Will not fetch any links or  metadata for resource instances in response.

Sorting Departments – GET:

URI: http://localhost:7001/departmentApi/rest/r1/departments?orderBy=DepartmentName:asc

URI: http://localhost:7001/departmentApi/rest/r1/departments?orderBy=DepartmentName: desc

Limiting the records in Querying Departments – GET:

URI: http://localhost:7001/departmentApi/rest/r1/departments?limit=2

Fetches only 2 records.

Querying Departments from a particular record– GET:

URI: http://localhost:7001/departmentApi/rest/r1/departments?offset=2

Fetches only 2 records.

URI: http://localhost:7001/departmentApi/rest/r1/departments?offset=2&limit=5

Fetches 5 records starting from 2nd record.

Expanding a Child Resource – GET:

URI: http://localhost:7001/departmentApi/rest/r1/departments?expand=Employee (Child Resource Name)

Querying Child Resource – GET:

URI: http://localhost:7001/departmentApi/rest/r1/departments/{id}/child/Employee

Querying a particular Child Resource – GET:

URI: http://localhost:7001/departmentApi/rest/r1/departments/{id}/child/Employee/{Child Resource Id}

Querying a Child Resource using an attribute – GET:

URI: http://localhost:7001/departmentApi/rest/r1/departments/{id}/child/Employee?q=FirstName=Jennifer

References:

http://docs.oracle.com/middleware/1221/adf/develop/GUID-8F85F6FA-1A13-4111-BBDB-1195445CB630.htm#ADFFD589

http://docs.oracle.com/middleware/1221/adf/develop/GUID-589F3905-5A8D-402D-B2D2-3BEEB2D7DDD4.htm#ADFFD54082