Jakarta Struts Cookbook

10.5. Decoupling Your Application from External Services

Problem

You want to decouple your Struts application from a specific implementation of an external business service.

Solution

Create an interface that provides an API for the business service. Then use a ServiceFactory class like the one shown in Example 10-13 to provide access to the service.

Example 10-13. Service factory

package com.oreilly.strutsckbk.ch10;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

public class ServiceFactory {

    private static Log log = LogFactory.getLog(ServiceFactory.class);
    
    public SecurityService createSecurityService( ) {
        SecurityService service = null;
        try {
            service = (SecurityService)
                Class.forName(securityServiceImpl).newInstance( );
        } catch (Exception e) {
            log.error(
               "Unable to create SecurityService for impl:"+
                    securityServiceImpl);
        }
        return service;
    }

    protected void setSecurityServiceImpl(String securityServiceImpl) {
        this.securityServiceImpl = securityServiceImpl;
    }
    private String securityServiceImpl;
}

You can use a Struts PlugIn, like the one shown in Example 10-14, to bind a service implementation to the interface, and store a reference to the service in the servlet context.

Example 10-14. Service factory plug-in

package com.oreilly.strutsckbk.ch10; import javax.servlet.ServletException; import org.apache.struts.action.ActionServlet; import org.apache.struts.action.PlugIn; import org.apache.struts.config.ModuleConfig; public class ServiceFactoryPlugin implements ...