java设计模式进阶_service-locator

//////  Generated by StarUML(tm) Java Add-In////  @ Project : Untitled//  @ File Name : Service.java//  @ Date : 2016/9/2//  @ Author : /////** * This is going to be the parent service interface which we will * use to create out services.All services will have a * <li>service name</li> * <li>unique id</li> * <li>execution work flow</li> * */public interface Service {    /**     * the human readable name of the service     * @return     */    public String getName();    /**     * Unique ID of the particular service     * @return     */    public int getId();    /**     * the workflow method that defines what this service does     */    public void execute();}//////  Generated by StarUML(tm) Java Add-In////  @ Project : Untitled//  @ File Name : ServiceImpl.java//  @ Date : 2016/9/2//  @ Author : /////** * This is a single service implementation of a sample service.This is the actual * service that will process the request.The reference for this service is to * be looked upon in the JNDI server that can be set in the web.xml deployment descriptor * */public class ServiceImpl implements Service {    private final String serviceName;    private final int id;    public ServiceImpl(String serviceName) {        //set the service name        this.serviceName = serviceName;        //Generate a random id the this ervice object        this.id = (int)Math.floor(Math.random()*1000) + 1;    }    public String getName() {        return serviceName;    }    public int getId() {        return id;    }    public void execute() {        System.out.println("Service " + getName() + " is now executing with id " + getId());    }}import java.util.HashMap;import java.util.Map;//////  Generated by StarUML(tm) Java Add-In////  @ Project : Untitled//  @ File Name : ServiceCache.java//  @ Date : 2016/9/2//  @ Author : /////** * The service cache implementation which will cache services that are being created. * On first hit,the cache will be empty and thus any service that is being requested,will be * created fresh and the placed into the cache map.On next hit,if same service name will * be requested,it will be returned from the cache * */public class ServiceCache {    private final Map<String,Service> serviceCache;    public ServiceCache() {        serviceCache = new HashMap<String,Service>();    }    /**     * Get the service from the cache.null if no service is found matching the name     *      */    public Service getService(String serviceName) {        Service cachedService = null;        for(String serviceJndiName : serviceCache.keySet())         {            if(serviceJndiName.equals(serviceName))            {                cachedService = serviceCache.get(serviceJndiName);                System.out.println("(cache call) Fetched service " + cachedService.getName() + "(" + cachedService.getId() + ") from cache... !");            }        }        return cachedService;    }    /**     * Adds the service into the cache map     * @param service     */    public void addService(Service service) {        serviceCache.put(service.getName(),service);    }}//////  Generated by StarUML(tm) Java Add-In////  @ Project : Untitled//  @ File Name : ServiceLocator.java//  @ Date : 2016/9/2//  @ Author : /////** * The service locator module. * Will fetch service from cache,otherwise creates a fresh service and update cache * */public class ServiceLocator {    private static ServiceCache serviceCache = new ServiceCache();    /**     * Fetch the service with the name param from the cache first,     * if no service is found,lookup the service from the InitContext and     * then add the newly created service into the cache map for future requests.     *      * @param serviceName     * @return     */    public static Service getService(String serviceName) {        Service serviceObj = serviceCache.getService(serviceName);        if(serviceObj != null)            return serviceObj;        else{            /**             * If we are unable to retrive anything from cache,then             * lookup the service and add it in the cache map             */            InitContext ctx = new InitContext();            serviceObj = (Service)ctx.lookup(serviceName);            serviceCache.addService(serviceObj);;            return serviceObj;        }    }}//////  Generated by StarUML(tm) Java Add-In////  @ Project : Untitled//  @ File Name : InitContext.java//  @ Date : 2016/9/2//  @ Author : /////** * For JNDI lookup of services from the web.xml Will match name of the service name that * is being requested and return a newly created service object with the name * */public class InitContext {    /**     * Perform the lookup based on the service name.The returned object will need to be     * casted into a Service     * @param serviceName     * @return     */    public Object lookup(String serviceName) {        if (serviceName.equals("jndi/serviceA")) {            return new ServiceImpl("jndi/serviceA");        } else if (serviceName.equals("jndi/serviceB")) {            return new ServiceImpl("jndi/serviceB");        } else {            return null;        }    }}/** * Service locator pattern,used to lookup jndi services * and cache them for subsequent requests. * @author Administrator * */public class App {    public static void main(String[] args) {        Service service = ServiceLocator.getService("jndi/serviceA");        service.execute();        service = ServiceLocator.getService("jndi/serviceB");        service.execute();        service = ServiceLocator.getService("jndi/serviceA");        service.execute();        service = ServiceLocator.getService("jndi/serviceA");        service.execute();    }}/*Service jndi/serviceA is now executing with id 908Service jndi/serviceB is now executing with id 893(cache call) Fetched service jndi/serviceA(908) from cache... !Service jndi/serviceA is now executing with id 908(cache call) Fetched service jndi/serviceA(908) from cache... !Service jndi/serviceA is now executing with id 908*/