设计模式学习笔记--服务定位器模式

三十二、服务定位器模式

服务定位器模式(Service Locator Pattern)，主要用在JDNI中，充分利用缓存来快速定位使用服务service，来提高效率。

实现

创建service接口，以及接口的实现类，也就是具体的service，然后创建服务定位器，和缓存对象类。在创建一个初始化条件类。

• Service接口

  IService.java

  package patterns.service;
  
  /**
  * Created by lenovo on 2016/12/12 0012.
  * 服务接口
  */
  public interface IService {
    public String getName();
    public void execute();
  }

• 接口实现类

  Service1.java

  package patterns.service;
  
  /**
  * Created by lenovo on 2016/12/12 0012.
  * Service 接口实现类
  */
  public class Service1 implements IService {
    @Override
    public String getName() {
        return "Service1";
    }
  
    @Override
    public void execute() {
  System.out.println("执行服务，1#服务");
    }
  }

  Service2.java

  package patterns.service;
  
  /**
  * Created by lenovo on 2016/12/12 0012.
  * Service 接口实现类
  */
  public class Service2 implements IService {
    @Override
    public String getName() {
        return "Service2";
    }
  
    @Override
    public void execute() {
  System.out.println("执行服务，2#服务");
    }
  }

• 目标程序类

  Target.java

  package patterns.intercepting;
  
  /**
  * Created by lenovo on 2016/12/12 0012.
  * 目标程序类
  */
  public class Target {
    public void execute(String request){
        System.out.println("执行处理请求 "+request);
    }
  }

• 缓存类

  Cache.java

  package patterns.service;
  
  import java.util.ArrayList;
  import java.util.List;
  
  /**
  * Created by lenovo on 2016/12/12 0012.
  * 缓存类
  */
  public class Cache {
    private List<IService> services;
  
    public Cache() {
        services = new ArrayList<>();
    }
  
    public List<IService> getServices() {
        return services;
    }
  
    public void addServices(IService service) {
        boolean exists = false;
        for (IService s : services) {
            if (s.getName().equalsIgnoreCase(service.getName())) {
                exists = true;
            }
        }
        if (!exists) {
            services.add(service);
        }
    }
  
    public IService getService(String serviceName) {
        for (IService s : services) {
            if (s.getName().equalsIgnoreCase(serviceName)) {
                return s;
            }
        }
        return null;
    }
  }

• 初始化类

  InitialContext.java

  package patterns.service;
  
  /**
  * Created by lenovo on 2016/12/12 0012.
  * 针对JNDI而创建的初始化类
  */
  public class InitialContext {
    public Object lookup(String jndiName) {
        if (jndiName.equalsIgnoreCase("Service1")) {
            System.out.println("Looking up and creating a new Service1 object");
            return new Service1();
        } else if (jndiName.equalsIgnoreCase("Service2")) {
            System.out.println("Looking up and creating a new Service1 object");
            return new Service2();
        }
        return null;
    }
  }
  

• 定位器端

  ServiceLocator.java

  package patterns.service;
  
  /**
  * Created by lenovo on 2016/12/12 0012.
  * 服务定位器
  */
  public class ServiceLocator {
    private static Cache cache;
  
    static {
        cache = new Cache();
    }
  
    public static IService getService(String jndiName) {
        IService service = cache.getService(jndiName);
        if (service != null) {
            return service;
        }
        InitialContext context = new InitialContext();
        IService service1 = (IService) context.lookup(jndiName);
        cache.addServices(service1);
        return service1;
    }
  }

• 演示

  InterceptingFilterPatternDemo.java

  package patterns.service;
  
  /**
  * Created by lenovo on 2016/12/12 0012.
  * 演示
  */
  public class ServiceLocatorPatternDemo {
    public static void main(String[] args){
        //service都是新建
        IService service = ServiceLocator.getService("service1");
        service.execute();
  
        service = ServiceLocator.getService("service2");
        service.execute();
  
        //service开始使用缓存
        service = ServiceLocator.getService("service1");
        service.execute();
        service = ServiceLocator.getService("service2");
        service.execute();
    }
  }

  ​

• 输出

  Looking up and creating a new Service1 object
  执行服务，1#服务
  Looking up and creating a new Service1 object
  执行服务，2#服务
  执行服务，1#服务
  执行服务，2#服务