Customizing REST services to support new custom response formats

JSON and XML formats are supported by default by the WebSphere Commerce REST framework. You can extend the default JAX-RS resource handlers to customize REST services to support new custom response formats.

Before you begin

You must install the following WebSphere Application Server interim fix APAR #PM59223This APAR fixes issues where empty pages might appear from customized JSP files.

Ensure that you are aware of the following assumptions for this customization scenario:

The new custom response format is of type application/custom+xml for the default com.ibm.commerce.rest.search.handler.ProductViewHandler resource handler class.
The following URL pattern is used:
- store/storeID/productview/partNumber
For example, http://host_name/wcs/resources/store/10101/productview/MW-0090
The application/custom+xml response format is the same as the custom XML format. However, for the purposes of this customization scenario, it is referred to as the custom response format.

The following sample code archive illustrates the tasks described in this topic CustomEntityProvider_Sample_Assets. The sample code archive contains the following directory structure:
Sample archive directory structure

Procedure

Open WebSphere Commerce Developer and switch to the Enterprise Explorer view.
Add an entity provider to support the custom response format:

Each entity provider formats an entity into a specific response format. Since the customization is about adding a response format, a new entity provider must be added to format the entity in the new custom response format.
1. In the WebSphereCommerceServerExtensionsLogic project, create a class that is called com.mycompany.commerce.foundation.rest.providers.CustomXMLEntityProvider that extends com.ibm.commerce.foundation.rest.providers.AbstractEntityProvider.
2. Add the following annotation in the entity class to register the entity provider for the application/custom+xml response format in the JAX-RS run time:
```
@Produces(value = { "application/custom+xml" })
```
  For more information, see the provided sample class. The sample class contains inline comments to help you implement the entity provider.
3. Save your changes and close the file.
4. Add the entity provider class name in the Rest/WebContent/WEB-INF/config/providers-ext.properties file to register the new entity provider.
5. Save your changes and close the file.
Add a response format shortcut for the custom response format or use Accept HTTP request header:

Response format shortcuts are requested media type shortcuts that can be easily specified by a client in the request URL as a query parameter. You add a response format shortcut for your new custom response format application/custom+xml, by creating the file if it does not exist. Otherwise, you add the custom format shortcut.
1. Create the following file Rest/WebContent/WEB-INF/config/com.ibm.commerce.rest-ext/wc-rest-responseformat.xml
2. Add a shortcut for the "application/custom+xml" response format to the file as shown in the following code snippet.
```
<responseFormatMappings>

  
  
  

  <formatMapping responseFormat="custom" mediaType="application/custom+xml"/>
    
</responseFormatMappings>
```
3. Save your changes and close the file.
If a response format shortcut is not specified, you can specify the response format that uses the Accept HTTP request header, instead of using the responseFormat query parameter. In the Accept request header, you must specify the response format in the full form, for example application/custom+xml. However, using Accept request header requires the following steps to extend the existing REST resource handler. To simplify the procedure, it is recommended that you add a custom response format shortcut to wc-rest-responseFormat.xml so that a client can use the responseFormat query parameter to get the custom response format:
1. In the WebSphereCommerceServerExtensionsLogic project, create a new com.mycompany.commerce.rest.catalog.handler.ProductViewHandlerExt class that extends com.ibm.commerce.rest.search.handler.ProductViewHandler.
2. In the ProductViewHandlerExt class, ensure that you add the same Path annotation that exists in the super class. This ensures that when the default URL is invoked, the custom resource handler ProductViewHandlerExt is used instead of the default resource handler. Overwrite the findProductByPartNumber super class method with the following content:
```
@GET
@Path("{partNumber}")
@Produces( { "application/json", "application/xml", "application/custom+xml" })// additionally add custom response format
@Override
public Response findProductByPartNumber(
@PathParam("storeId") String storeId,
@PathParam("partNumber") String partNumber,
@QueryParam(value = "responseFormat") String responseFormat)
{
// write custom logic here
return super.findProductByPartNumber(storeId, partNumber, responseFormat);
}
```
  For more information, see the sample class provided in the CustomEntityProvider_Sample_Assets archive. The sample class contains inline comments that help you extend the default resource handler.
Implement a new JSP file to format the data objects into the custom response format:
JSP files can be used to format an entity. See com.ibm.commerce.foundation.rest.providers.AbstractEntityProvider for more information. In this customization, JSP files are used due to the dynamic nature of the custom XML format.
1. Create a new JSP file to format the data object in the following location:
  - Rest/WebContent/jsp/commerce/catalog/custom/SerializeShowCatalogNavigationViewDataAreaTypeCustom.jsp
  The JSP file coding guideline is identical to the storefront JSP files that format a data object. The JSP file can include other JSP fragments, such as SerializeShowCatalogEntryViewCustom.jspf, which formats parts of the noun in the data object. See the provided sample JSP files for more information.
2. Save your changes and close the file.
3. Add a struts action in the Rest/WebContent/WEB-INF/struts-extension.xml struts file to register the JSP.
  For example:
```
<action path="/ShowCatalogNavigationViewCustom/0" 
forward="/jsp/commerce/catalog/custom/SerializeShowCatalogNavigationViewDataAreaTypeCustom.jsp"/>
```
  Note: The struts action format must match the formatting group name that is returned in the custom ProductViewHandlerExt resource handler. See the IResourceHandler interface for more information.
  When you launch the default URL indicating the application/custom+xml custom response format:
  - http://localhost/wcs/resources/store/10101/productview/MW-0090?responseFormat=custom
  It runs /jsp/commerce/catalog/custom/SerializeShowCatalogNavigationViewDataAreaTypeCustom.jspWhich formats the ShowCatalogNavigationViewDataAreaType data object in the application/custom+xml custom format.
4. Save your changes and close the file.
Implement a new error JSP file for the custom response format:
In case of any errors, the REST framework runs an error JSP file specific to the response format, passing the error parameters.
1. Create a JSP file to format the error response in the following location Rest/WebContent/jsp/commerce/foundation/custom/Error.jsp
2. Save your changes and close the file.
3. Add a struts action in the Rest/WebContent/WEB-INF/struts-extension.xml struts file to register the JSP.
```
<action path="/ErrorCustom/0" forward="/jsp/commerce/foundation/custom/Error.jsp"/>
```
  Note: The struts action format must match the formatting group name that is returned in the custom ProductViewHandlerExt resource handler.
  When you launch the default URL indicating the application/custom+xml custom response format:
  - http://localhost/wcs/resources/store/10101/productview/MW-0090?responseFormat=custom
  It runs:
  - /Rest/WebContent/jsp/commerce/foundation/custom/Error.jsp in the case of any errors or exceptions.
  Which formats the Error parameters that are passed to the error JSP file in the application/custom+xml custom format.
Verify your customization by restarting the WebSphere Commerce server and starting the URLs created in this task.