反射的一点小应用

     今天工作中遇到这样一种情况，有一个父类，下面有非常多各种各样的子类，同时有这样一个总类，它包含了前面说的子类的所有属性，同时还拥有一个属性type标志它对应前面说的子类内容。这个总类实例要和前面的一堆子类实例进行比较，那堆子类是挂在List<父类>下的，比较时总类要根据type找到对应的子类对象，才可以比较。文字不好说明，看下面的代码（类似工作中遇到的情形）。

package com.fei;

import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class WifeFindHusband {

	public static void main(String[] args) {
		//TallHusband/FatHusband的父类是Husband
		List<Husband> husbands = new ArrayList<Husband>();
		//public TallHusband(String name, String secondName)
		husbands.add(new TallHusband("李明","狗娃"));
		//public FatHusband(String name, int age)
		husbands.add(new FatHusband("张华",18));
		
		//public Wife(String name, String husbandType, String husbandName,String husbandSecondName, int husbandAge)
		List<Wife> wifes = new ArrayList<Wife>();
		wifes.add(new Wife("陈红","tall","李明","狗娃",0));
		wifes.add(new Wife("林丽","fat","张华","",25));
		//妻子找丈夫，tall 对于 TallHusband,fat 对于 FatHusband
		//先判断丈夫类型，在详细比较
		find1(wifes,husbands);
		find2(wifes,husbands);
//		Husband h = new TallHusband("李明","狗娃");
//		TallHusband th = TallHusband.class.cast(h);
	}
	/**缺点： 如果丈夫类型有非常多（Husband的子类特别多），则if else if的判断会非常多
	 *有新类型的丈夫加入时，该方法需要修改它，多加else if判断
	 *优点：类型转换有保证，掉用CompatorHelper时，编译期就能准确知道调用哪个方法
	 */
	private static void find1( List<Wife> wifes ,List<Husband> husbands){
		for(Wife wife : wifes){
			boolean isFind = false;
			for(Husband husband : husbands){
				if("tall".equals(wife.getHusbandType()) && husband instanceof TallHusband){
					isFind =CompatorHelper. isCouple(wife,TallHusband.class.cast(husband));
				}else if("fat".equals(wife.getHusbandType()) && husband instanceof FatHusband){
					isFind = CompatorHelper.isCouple(wife,(FatHusband)husband);
				}
				if(isFind) break;
			}
			if(isFind){
				System.out.println("妻子"+wife.getName()+"找到丈夫了");
			}else{
				System.out.println("妻子"+wife.getName()+"没到丈夫了");
			}
				
		}
	}
	
	private static Map<String,Class<? extends Husband>> HUSBAND_TYPE;
	static{
		HUSBAND_TYPE = new HashMap<String,Class<? extends Husband>>();
		HUSBAND_TYPE.put("tall", TallHusband.class);
		HUSBAND_TYPE.put("fat", FatHusband.class);
	}
	/**
	 * 优点：当有新丈夫类型加入时，只需HUSBAND_TYPE中增加配置即可，不需要修改find2方
	 * 缺点：调用CompatorHelper中的方法时，无法在编译期就能检查到是否存在
	 */
	private static void find2( List<Wife> wifes ,List<Husband> husbands){
		for(Wife wife : wifes){
			boolean isFind = false;
			Class<? extends Husband> husbandType = HUSBAND_TYPE.get(wife.getHusbandType());
			if(husbandType != null){
				for(Husband husband : husbands){
					if(husbandType == husband.getClass()){
						//无法用这中形式，因为编译期无法确定husbandType.cast(husband)的具体类型，编译器报错
						//所以考虑用反射，突破编译器的约束
		//				isFind = CompatorHelper.isCouple(wife, husbandType.cast(husband));
						try {
						Method m=	CompatorHelper.class.getMethod("isCouple",wife.getClass(), husbandType);
						isFind =(boolean) m.invoke(null,wife,husband);
						} catch (Exception e) {
							e.printStackTrace();
							throw new RuntimeException("妻子找丈夫报错，CompatorHelper类isCouple方法无"+husbandType.getName()+"这种类型的丈夫");
						}
					}
					if(isFind) break;
				}
			}
			if(isFind){
				System.out.println("妻子"+wife.getName()+"找到丈夫了");
			}else{
				System.out.println("妻子"+wife.getName()+"没到丈夫了");
			}
				
		}
		
	}
	
}

package com.fei;

public class CompatorHelper {

	public static boolean isCouple(Wife wife ,TallHusband husband){
		if(wife.getHusbandName().equals(husband.getName())
				&& wife.getHusbandSecondName().equals(husband.getSecondName())){
			return true;
		}
		return false;
	}
	public static boolean isCouple(Wife wife ,FatHusband husband){
		if(wife.getHusbandName().equals(husband.getName())
				&& wife.getHusbandAge() == husband.getAge()){
			return true;
		}
		return false;
	}
}

      想了想，还是倾向于用find1方法，虽然会有很多if else if的判断，但是对CompatorHelper的调用可以在编译期就可以保证必须有对应的方法。如果用find2方法，由于哟哦那个了反射，如果CompatorHelper缺少了某些方法，在编译期也不报错，在运行期才会报错，风险较大，除非测试充分，把所有的丈夫类型都测试一遍。