WebSphere® eXtreme Scale: Retrieve mediation primitive

Introduction

You can use the eXtreme Scale Retrieve mediation primitive to retrieve information from a eXtreme Scale cache. By combining the eXtreme Scale Store and Retrieve mediation primitives you can cache the response from a back-end system, which means future requests do not require access to that back-end system.

The eXtreme Scale Retrieve mediation primitive has an input terminal (in), two output terminals (out and notFound), and a fail terminal (fail) terminal. The in terminal is wired to accept a message and the other terminals are wired to propagate a message. The out terminal is used if the key results in information being returned from the cache. In this case, the information obtained from the cache is stored in the message and the updated message is propagated. The notFound terminal is used if the key results in no information being returned by the cache. In this case, the original message is propagated unchanged. If an exception occurs during the processing of the input message, the fail terminal propagates the original message, together with any exception information.

If no connection to WebSphere eXtreme Scale can be found, the fail terminal is fired.

Details

The eXtreme Scale Retrieve mediation primitive looks up values in the cache and stores them as elements in the message using a key.

If the key is an XSD primitive type, such as xsd:string, xsd:int or xsd:float, then the corresponding Java object type is used to retrieve from the cache. If the key is a business object, then this (key) is converted to an XML String representation (without any namespaces or prefixes) to look up from the eXtreme Scale cache.

The information obtained from the cache should be of the same type specified by the XPath of the data to store the result from the cache property. If the data type obtained from the cache is assigned to a string then a string representation of that information will be used, where possible. If the information obtained from the cache cannot be converted to the type expected by the message, an exception occurs.

Usage

You can use the eXtreme Scale Retrieve mediation primitive to add information to a message, using a key contained within that message.

By combining the eXtreme Scale Store and Retrieve mediation primitives you can cache the response from a back-end system, which means future requests do not require access to that back-end system.