策略模式之if else代码优化

一、概念

  策略模式的用意是针对一组算法，将每一个算法封装到具有共同接口的独立类中，从而使得它们可以相互替换。策略模式使得算法可以在不影响到客户端的情况下发生变化。

• if else使用

  if (pageLevel = "1") {
  	// 发送get请求
  } else if(pageLevel = "2") {
  	// 发送post请求
  } else {
  	// 
  }
  

  这种if else代码块中，代码很难维护也很也不够美观，那么我们可以使用策略模式来处理这种情况。

二、案例

  简单来讲就是定义一个接口，然后有多个实现类，每种实现类封装了一种行为。然后根据条件的不同选择不同的实现类。

• 抽象业务接口

  public interface SendRequestCenter {
  
      public abstract void solve(String param);
  
      public abstract String[] supports();
  }
  

• 接口实现类，举例：一个发送get请求，一个发送post请求

  import org.springframework.stereotype.Component;
  
  @Component
  public class SendPostRequestSolver implements SendRequestCenter {
  
      @Override
      public void solve(String param) {
          System.out.println("参数是" + param + "的post请求已经发送了。。");
      }
  
      @Override
      public String[] supports() {
          return new String[]{RequestType.HTTP_POST};
      }
  }
  

  import org.springframework.stereotype.Component;
  
  @Component
  public class SendGetRequestSolver implements SendRequestCenter {
  
      @Override
      public void solve(String id) {
          System.out.println("参数是" + id + "的get请求已经发送了。。");
      }
  
      @Override
      public String[] supports() {
          return new String[]{RequestType.HTTP_GET};
      }
  }
  

• 常量类

  public class RequestType {
      public static String HTTP_GET = "1";
      public static String HTTP_POST = "2";
  }
  

• 将业务处理器和其支持处理的类型放到一个容器中，Map就是最常用的容器，使用spring的上下文存储信息

  import org.springframework.beans.BeansException;
  import org.springframework.context.ApplicationContext;
  import org.springframework.context.ApplicationContextAware;
  import org.springframework.stereotype.Component;
  
  import javax.annotation.PostConstruct;
  import java.util.HashMap;
  import java.util.Map;
  
  @Component
  public class RequestSolverChooser implements ApplicationContextAware {
  
      private ApplicationContext context;
      private Map<String, SendRequestCenter> chooseMap = new HashMap<>();
  
      public SendRequestCenter choose(String type) {
          return chooseMap.get(type);
      }
  
      //被@PostConstruct修饰的方法会在服务器加载Servlet的时候运行，并且只会被服务器调用一次，类似于Serclet的inti()方法。
      //被@PostConstruct修饰的方法会在构造函数之后，init()方法之前运行。
      @PostConstruct
      public void register() {
          Map<String, SendRequestCenter> solverMap = context.getBeansOfType(SendRequestCenter.class);
          for (SendRequestCenter solver : solverMap.values()) {
              for (String support : solver.supports()) {
                  chooseMap.put(support, solver);
              }
          }
      }
  
      @Override
      public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
          this.context = applicationContext;
      }
  }
  
  

• 另一种处理方式是使用工厂模式和策略模式相结合，工厂采用单例模式

  import java.util.HashMap;
  import java.util.Map;
  
  public class StrategyFactory {
  
      private static StrategyFactory factory = new StrategyFactory();
      private StrategyFactory(){
      }
      private static Map<String,SendRequestCenter> strategyMap = new HashMap<>();
      static{
          strategyMap.put(RequestType.HTTP_GET, new SendGetRequestSolver());
          strategyMap.put(RequestType.HTTP_POST, new SendPostRequestSolver());
      }
      public SendRequestCenter creator(String pType){
          return strategyMap.get(pType);
      }
      public static StrategyFactory getInstance(){
          return factory;
      }
  }
  

• 在单元测试中进行测试

  @Autowired
  private RequestSolverChooser chooser;
  //使用spring上下文测试
  @Test
  public void test() throws Exception {
  	//准备数据
  	String taskType = RequestType.HTTP_GET;
  	//获取任务类型对应的solver
  	SendRequestCenter solver = chooser.choose(taskType);
  	if (solver == null) {
  		throw new RuntimeException("任务类型暂时无法处理!");
  	}
  	//调用不同solver的方法进行处理
  	solver.solve("\"百度\"");
  }
  //使用工厂模式测试
  @Test
  public void test2() throws Exception {
  	String taskType = RequestType.HTTP_POST;
  	SendRequestCenter solver = StrategyFactory.getInstance().creator(taskType);
  	if (solver == null) {
  		throw new RuntimeException("任务类型暂时无法处理!");
  	}
  	//调用不同solver的方法进行处理
  	solver.solve("\"腾讯\"");
  }
  

• 测试结果1

  2020-01-15 15:25:46.752  INFO 2120 --- [           main] c.w.collection.DemoApplicationTests      : No active profile set, falling back to default profiles: default
  2020-01-15 15:25:47.574  INFO 2120 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
  2020-01-15 15:25:47.766  INFO 2120 --- [           main] c.w.collection.DemoApplicationTests      : Started DemoApplicationTests in 1.255 seconds (JVM running for 2.254)
  参数是"百度"的get请求已经发送了。。
  2020-01-15 15:25:47.923  INFO 2120 --- [extShutdownHook] o.s.s.concurrent.ThreadPoolTaskExecutor  : Shutting down ExecutorService 'applicationTaskExecutor'
  

• 测试结果2

  2020-01-15 15:26:30.860  INFO 4640 --- [           main] c.w.collection.DemoApplicationTests      : No active profile set, falling back to default profiles: default
  2020-01-15 15:26:31.689  INFO 4640 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
  2020-01-15 15:26:31.867  INFO 4640 --- [           main] c.w.collection.DemoApplicationTests      : Started DemoApplicationTests in 1.274 seconds (JVM running for 2.273)
  参数是"腾讯"的post请求已经发送了。。
  2020-01-15 15:26:32.013  INFO 4640 --- [extShutdownHook] o.s.s.concurrent.ThreadPoolTaskExecutor  : Shutting down ExecutorService 'applicationTaskExecutor'
  

参考博客：https://blog.csdn.net/qq_22343483/article/details/100195157

来源：CSDN

作者：wanglei_

链接：https://blog.csdn.net/qq_38932871/article/details/103995383