Spring项目中干掉if-elese，写出优雅代码

1.背景：

在项目经常会遇到因为不同的条件执行不同的方法，当类型比较多的情况下，代码维护起来比较痛苦，并且会有大量的if-else判断。这样不管是后期的需求迭代还是别人接手代码，那都是相当的自闭。。。

2.反面教材：

首先我们先看下面一段代码，这边采用大量的状态if else 判定

 if ("AType".equals(tier)) {
	Map<String, Object> mapPar = new HashMap<String, Object>();
	mapPar.put("tier", tier);
	mapPar.put("tierStr", "");
	mapPar.put("tierStrOther", "");
	ApiResponse<List<Govdep>> govdepListApi = accountClient.getGovdepList(mapPar);
	if (govdepListApi.getStatus() == 200) {
		govdepList = govdepListApi.getBody();
	}
	return govdepList;
} else if ("AType".equals(tier)) {
	Map<String, Object> mapPar = new HashMap<String, Object>();
	mapPar.put("tier", "");
	mapPar.put("tierStr", tier);
	mapPar.put("tierStrOther", "");
	ApiResponse<List<Govdep>> govdepListApi = accountClient.getGovdepList(mapPar);
	if (govdepListApi.getStatus() == 200) {
		govdepList = govdepListApi.getBody();
	}
	return govdepList;
} else {
	Map<String, Object> mapPar = new HashMap<String, Object>();
	mapPar.put("tier", "");
	mapPar.put("tierStr", "");
	mapPar.put("tierStrOther", tier);
	ApiResponse<List<Govdep>> govdepListApi = accountClient.getGovdepList(mapPar);
	if (govdepListApi.getStatus() == 200) {
		govdepList = govdepListApi.getBody();
	}
	return govdepList;
}

3.优雅写法

• 策略枚举

  public enum TypeEnum {
      A {
          @Override
          public Class acquireStrategy() {
              return ATypeStrategy.class;
          }
      },
      B {
          @Override
          public Class acquireStrategy() {
              return BTypeStrategy.class;
          }
      };
  
      public abstract Class<TypeStrategy> acquireStrategy();
  }
  

• 抽象接口定义

  /**
   * 抽象接口
   */
  public interface TypeStrategy {
  
      void execute(String requestParam);
  
  }
  

• 抽象接口实现

  @Component
  public class ATypeStrategy implements TypeStrategy {
  
      @Override
      public void execute(String requestParam) {
          System.out.println("执行A策略的业务代码");
      }
  }
  
  

  @Component
  public class BTypeStrategy implements TypeStrategy {
  
      @Override
      public void execute(String requestParam) {
          System.out.println("执行B的业务代码");
      }
  }
  

• 具体业务使用

  /**
   * @title: BusinissessService
   * @description: 执行业务代码
   * @date 2020/12/27 7:24 下午
   */
  @Service
  public class BusinessService implements ApplicationContextAware {
  
      private ApplicationContext applicationContext;
  
      public void business(String requestParam, String type) {
          // 策略选取执行
          TypeStrategy typeStrategy = applicationContext.getBean(TypeEnum.valueOf(type).acquireStrategy());
          // 执策略方法
          typeStrategy.execute(requestParam);
      }
  	//此处利用了Spring声明周期中的特性, Spring 自动注入 ApplicationContext
      @Override
      public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
          this.applicationContext = applicationContext;
      }
  }