Library

A library is a project that is used to store resources and artifacts, so that the resources or artifacts can be shared by multiple modules defined in the library. The usage of libraries is good practice where interfaces are shared across multiple mediation modules.

Unlike modules or mediation modules, library projects can share resources. The resources or artifacts that are defined in the library are:

Business objects
Interfaces
Mediation subflow
Datamap
Relationship
Binding resource

There are two kinds of sharing:

Sharing of artifacts for development
Sharing of artifacts within the solution at run time

For a module or mediation module to use the resources from a library at run time, you must add a dependency, indicating that the module is dependent on the library. You can add a library to the module and select to deploy it with the module. You can also add library dependencies to a library; for example, if one library uses resources in another library, then you must add the library dependency.

Artifacts in a library are public, and they can be shared across modules. Artifacts in a module are private. WebSphere® ESB integration developers should organize artifacts by taking into consideration logical function and visibility. For example, related data types that are used by various pieces of a system should be placed into a library. Other modules can then easily reuse this library. Only one copy of each element needs to be created and maintained using this method. Likewise, related business logic features of the application should be grouped into modules. Structuring an application in this way will yield a more flexible, easily maintained application. It will also be easier to add new features to the application.

Business objects and interfaces

Business objects are containers for application data, such as customer details or an invoice. Data is exchanged between components by way of business objects. When using imports and exports in assembly diagrams, it is good practice to put the business objects and interfaces that are used by the import and exports into a library so that they can be shared. Then, add a dependency on the library to all of the modules that use these common resources. Avoid copying the same business objects and interfaces into different modules to use them.

Mediation subflows

If you have mediation logic that you want to reuse across mediation flows you can define a mediation subflow within a library. Mediation flows cannot be placed in a library.

Library resources that are shared

If you choose to deploy a library with a module, which is the default setting, a copy of the library is made for each module when the module is deployed. After deployment, if shared resources change in the library, all modules using the resources have to be updated. For example, two modules share some resources in a library. The applications are deployed. One of the modules has to be updated, resulting in changes to some of the shared resources in the library. In this case, the second module also needs to be updated to reflect the changes in the shared resources.