在开发过程中,许多的业务场景都用到了条件分支,即如果...就....,否则....就等场景。if...else是Java提供的传统的处理分支的实现方式。比如,以一个加减乘除作为案例,传统写法是这样的:
public void arithmetic(@RequestParam(value = "arithmeticType") String arithmeticType,
@RequestParam(value = "startNum") int startNum,
@RequestParam(value = "endNum") int endNum) {
double result = 0.0;
if (arithmeticType.equals("addition")) {
result = startNum + endNum;
} else if (arithmeticType.equals("subtraction")) {
result = startNum - endNum;
} else if (arithmeticType.equals("multiplication")) {
result = startNum * endNum;
} else {
result = startNum / endNum;
}
System.out.println("====================>" + result);
}
但是实际的业务场景肯定不止这四种,随着条件越来也来,代码就显得非常的臃肿和难以维护。
这种方式也不符合开闭原则。
重构:下面使用策略模式,对代码进行重构
创建一个接口类:BaseHandler
import org.springframework.stereotype.Component;
@Component
public interface BaseHandler {
double arithmetic(int startNum, int endNum);
}
创建加减乘法四种业务对应的接口实现类
/*加法*/
@Component("addition")
public class AdditionHandler implements BaseHandler {
@Override
public double arithmetic(int startNum, int endNum) {
return startNum + endNum;
}
}
/*减法*/
@Component("division")
public class DivisionHandler implements BaseHandler {
@Override
public double arithmetic(int startNum, int endNum) {
return startNum / endNum;
}
}
/*乘法*/
@Component("multiplication")
public class multiplicationHandler implements BaseHandler {
@Override
public double arithmetic(int startNum, int endNum) {
return startNum * endNum;
}
}
/*除法*/
@Component("subtraction")
public class SubtractionHandler implements BaseHandler {
@Override
public double arithmetic(int startNum, int endNum) {
return startNum - endNum;
}
}
Controller类代码,使用@Autowired将BaseHandler注入
@RestController
@RequestMapping("action")
public class SpringTestController {
@Autowired
private Map<String, BaseHandler> handlerMap;
@GetMapping("/handler")
public void arithmetic(@RequestParam(value = "arithmeticType") String arithmeticType,
@RequestParam(value = "startNum") int startNum,
@RequestParam(value = "endNum") int endNum){
BaseHandler baseHandler = handlerMap.get(arithmeticType);
double result = baseHandler.arithmetic(startNum, endNum);
System.out.println("===========>" + result);
}
}
@component注解会把普通pojo实例化到spring容器中,相当于配置文件中的<bean id="",class=""/>,启动项目时加载到handlerMap中。
总结
@component将所有的bean实例化到Spring中,是一个map格式,@component注解的属性值就是map的key。
使用设计模式完全避免了大量的if...else,代码看起来简洁,便于后期扩展和维护。
后期新增业务只需关注自己的业务点,不需要新增逻辑判断。
缺点就是需要创建很多的实现类。
参考链接:https://blog.csdn.net/XIAO_4510123/article/details/105272695?spm=1001.2101.3001.6650.12&utm_medium=distribute.pc_relevant.none-task-blog-2%7Edefault%7ECTRLIST%7ERate-12-105272695-blog-116993087.pc_relevant_3mothn_strategy_and_data_recovery&depth_1-utm_source=distribute.pc_relevant.none-task-blog-2%7Edefault%7ECTRLIST%7ERate-12-105272695-blog-116993087.pc_relevant_3mothn_strategy_and_data_recovery&utm_relevant_index=20