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此文转载自：https://blog.csdn.net/yqq962464/article/details/110228633

基于反射的工厂模式

基础枚举类：

/**
 *  @author: yangyahui
 *  @Date: 2020/11/11 9:52 上午
 *  @Description: 惠农业务品种
 */
public enum BusinessTypeEnum {

    CHD("12020020140","彩虹贷"),
    JQD("12020020130","金秋贷"),
    NXD("16020040400","农兴贷"),
    ZND_JY("12020020020","助农贷（农户经营"),
    ZND_XF("12020010050","助农贷（农户消费"),
    XMD("12020020030","农户畜牧业养殖贷款");

    private String code;
    private String desc;

    BusinessTypeEnum(String code,String desc){
        this.code = code;
        this.desc = desc;
    }

    public String getCode() {
        return code;
    }

    public String getDesc() {
        return desc;
    }

    public static BusinessTypeEnum getType(String code){
        for (BusinessTypeEnum typeEnum : values()){
            if (typeEnum.getCode().equals(code)){
                return typeEnum;
            }
        }
        return null;
    }
}

 简单工厂类：

public static FreeBaseDetailVO buildFreeObj(String businessType){
        FreeBaseDetailVO freeBaseDetailVO = null;
        switch (BusinessTypeEnum.getType(businessType)) {
            case CHD:
                freeBaseDetailVO = new FreeCHDDetailVO();
                break;
            case JQD:
                freeBaseDetailVO = new FreeJQDDetailVO();
                break;
            case NXD:
                freeBaseDetailVO = new FreeNXDDetailVO();
                break;
            case ZND_JY:
                freeBaseDetailVO = new FreeZNDJYDetailVO();
                break;
            case ZND_XF:
                freeBaseDetailVO = new FreeZNDXFDetailVO();
                break;
            case XMD:
                freeBaseDetailVO = new FreeXMDDetailVO();
                break;
            default:
                throw new RuntimeException("全流程返回业务品种码值错误:" + businessType);
        }
        return freeBaseDetailVO;
    }

改造：由于不满足“开闭原则”，所以对工厂类进行改造，通过引入配置文件和反射，使之满足“开闭原则”。

/**
 *  @author: yangyahui
 *  @Date: 2020/11/27 10:52 上午
 *  @Description: 读取配置文件参数工具类
 */
public class PropertiesUtil {
    private static Map<String, Properties> cacheMap = new HashMap<String, Properties>();

    public static String get(String fileName, String key){
        return (String) getProperties(fileName).get(key);
    }

    private static Properties getProperties(String fileName){

        if (cacheMap.get(fileName) != null){
            return cacheMap.get(fileName);
        }

        InputStream is = PropertiesUtil.class.getResourceAsStream(fileName);
        Properties properties = new Properties();
        try {
            properties.load(is);
        } catch (IOException e) {
            e.printStackTrace();
        }
        cacheMap.put(fileName,properties);
        return properties;
    }
}

/**
 *  @author: yangyahui
 *  @Date: 2020/11/27 11:02 上午
 *  @Description: 工厂类
 */
public class Factory {
    public static FreeBaseDetailVO getObj(String fileName,String key){
        FreeBaseDetailVO freeBaseDetailVO = null;
        String classPath;
        try {
            classPath = PropertiesUtil.get(fileName, key);  //获取配置文件中的类路径
            if (StringUtils.isNotBlank(classPath)){
                freeBaseDetailVO = (FreeBaseDetailVO) Class.forName(classPath).newInstance();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return freeBaseDetailVO;
    }
}

配置文件配置信息application.properties 

CHD = com.hrbank.entity.vo.freenong.FreeCHDDetailVO