New in Portal SP11: Dynamic System Resolution

The following is one in a series of weblogs on new features in SAP Enterprise Portal 6.0 SP11. 

In the past, whenever you created an iView that needed to connect to some back-end system, you provided a system alias. The alias was assigned to a specific system in the PCD, which was assigned to a specific back-end system.

Though an administrator could re-assign the alias to a different system during design time, during runtime the system was fixed. In other words, the back-end system for that iView was hardcoded and could not be changed during runtime.

SP11 now provides a mechanism — Dynamic System Resolution — that enables you to create a service that takes the alias and resolves it to a system during runtime. The logic for selecting the system is generally based on the current user, but could be based on any logic.

How Dynamic System Resolution Works

An iView that needs to connect to a back-end system contains a reference to a system alias. The iView — via the Connector Gateway or other service — calls the system landscape service method getSystemId() in order to resolve the alias to a specific system defined in the Portal Content Directory (PCD). By default, the system landscape service simply queries the PCD for the system that is associated with that alias, and returns the PCD path to that system.

In the PCD, a system alias is associated with only one system.

In order to resolve an alias to a different system, you can create a system resolving service for a specific alias. When an iView calls getSystemId() to resolve the alias, the system landscape service first checks if a custom service exists for the alias. If one exists, the system landscape service calls the resolving service — instead of querying the PCD — in order to get the corresponding system.

The resolving service — which receives from the system landscape service the name of the alias and a reference to the current user — can resolve the alias to any system based on any logic.

How to Create a System Resolving Service

A PAR file that defines a system resolving service must contain the following two parts:

• java class that implements the following interfaces:

• IService: The standard interface for all services
• IDynamicSystemService: The interface for a system resolving service. This interface exposes one method, getAlternateSystem(), which returns a string that represents the PCD path to a system defined in the PCD.

• A portalapp.xml file that defines the following:

  • The entries in the portal registry to create in order to indicate to the system landscape service the aliases for which to invoke this service.

    The following is an example that indicates to the portal that the service named System1Service should be used to resolve the alias named DynamicSystem1: 

    <registry>
    \
        <entry path="/runtime/alias.mappers/DynamicSystem1"
           name="System1Service" type="service"/>
    \
    </registry>
    \
    

  • The application properties that allow the service to function as a resolving service, such as the startup property (true) and the ServicesReference property com.sap.portal.ivs.api_dynamicSystemService).
  • The name of the resolving service and the class within the PAR that implements the service (as is required for any service that you implement)

Example of a Resolving Service

The following code sample shows the following methods:

• getAlternativeSystem(): You must implement this method, as required by the IDynamicSystemService interface.

• This method returns a string, which is the PCD address of a system.

• checkUser():

  This method is used for this example only, to separate the logic for choosing the system.

  This method uses the UME service to determine to which group the current user belongs. The system landscape service provides the current user as an IUser object passed into getAlternativeSystem().

  If the user is a member of Group1, then one system is  returned; if the user is a member of Group2, then a different system is returned.

\ public String getAlternativeSystem(IUser user, String alias) \ { \ \     String system = null; \ \     return (checkUser(user)); \ } \  \ public String checkUser(IUser user) { \  \ \     // Get Group1, Group2 groups \ \     IGroupFactory gfact = UMFactory.getGroupFactory(); \ \     IGroup group1 = null, group2 = null; \ \      \ \     try { \ \     \     group1 = gfact.getGroupByUniqueName(“Group1”); \ \     \     group2 = gfact.getGroupByUniqueName(“Group2”); \ \     } catch (UMException e) { } \  \ \     /* Check which group user is from */ \ \     if (user.isMemberOfGroup(group1.getUniqueID(), true)) \ \     \     return “pcd:portal_content/Systems/System1”; \ \     else if (user.isMemberOfGroup(group2.getUniqueID(), true)) \ \     \     return “pcd:portal_content/Systems/System2”; \ \     else \ \     \     return null; \ } \

The following is the entire sample java class for creating the system resolving service.

\ package com.sap.portal.dynamicsystem.sample; \   \ import com.sap.security.api.IGroup; \ import com.sap.security.api.IGroupFactory; \ import com.sap.security.api.IPrincipal; \ import com.sap.security.api.IRole; \ import com.sap.security.api.IRoleFactory; \ import com.sap.security.api.IUser; \ import com.sap.security.api.UMException; \ import com.sap.security.api.UMFactory; \ import com.sapportals.portal.prt.service.IServiceContext; \ import com.sapportals.portal.prt.service.IServiceConfiguration; \ import com.sapportals.portal.prt.service.IService; \  \ public class MyAliasMapping implements IMyAliasMapping, IService { \  \   private IServiceContext mm_serviceContext; \  \   /** \   * Generic init method of the service. Will be called by the portal runtime. \   * @param serviceContext \   */ \   public void init(IServiceContext serviceContext) \   { \     mm_serviceContext = serviceContext; \   } \  \   /** \   * This method is called after all services in the portal runtime \   * have already been initialized. \   */ \   public void afterInit() \   { \   } \  \   /** \   * configure the service \   * @param configuration \   */ \   public void configure(IServiceConfiguration configuration) \   { \   } \  \   /** \   * This method is called by the portal runtime \   * when the service is destroyed. \   */ \   public void destroy() \   { \   } \  \   /** \   * This method is called by the portal runtime \   * when the service is released. \   */ \   public void release() \   { \   } \  \   /** \   * @return the context of the service, which was previously set \   * by the portal runtime \   */ \   public IServiceContext getContext() \   { \     return mm_serviceContext; \   } \  \   /** \   * This method should return a string that is unique to this service amongst all \   * other services deployed in the portal runtime. \   * @return a unique key of the service \   */ \   public String getKey() \   { \     return KEY; \   } \   /** \   * The service must implement this method, which is called by the \   * System Landscape in order to get a system for the specified alias. \   *  \   * @param\     user\     the current user \   * \     \     alias\     the alias to resolve  \   * @return the PCD path to a system \   */ \  \   public String getAlternativeSystem(IUser user, String alias) \   { \ \     String system = null; \ \     return (checkUser(user)); \   } \   /** \   * This method is not part of the interface and is provided in order \   * to isolate the logic for selecting a system for a specific alias. This  \   * logic could have been placed in the getAlternateSystem() method. \   *  \   * @return\     the PCD path for a system, or null \   */ \  \   public String checkUser(IUser user) { \  \ \     // Get Group1, Group2 groups \ \     IGroupFactory gfact = UMFactory.getGroupFactory(); \ \     IGroup group1 = null, group2 = null; \ \      \ \     try { \ \     \     group1 = gfact.getGroupByUniqueName(“Group1”); \ \     \     group2 = gfact.getGroupByUniqueName(“Group2”); \ \     } catch (UMException e) { } \  \ \     /* Check which group user is from */ \ \     if (user.isMemberOfGroup(group1.getUniqueID(), true)) \ \     \     return “pcd:portal_content/Systems/System1”; \ \     else if (user.isMemberOfGroup(group2.getUniqueID(), true)) \ \     \     return “pcd:portal_content/Systems/System2”; \ \     else \ \     \     return null; \   } \  \ } \

For more information about Dynamic System Resolution, see Dynamic System Resolution in the Portal Developers’ Guide.

The articles in this series:

• What’s New in SAP Enterprise Portal SP11?
• New in Portal SP11: Content Administration
• New in Portal SP11: System Administration
• New in Portal SP11: Dynamic System Resolution