利用反射替代if-else

第一步：创建一个枚举类

MYSQL_DRIVER("mysql","optimization.ifelse.strategy.MySqlStrategy"),

ORCAL_DRIVER("orcal","optimization.ifelse.strategy.OrcalStrategy"),

SQLSERVER_DRIVER("sqlserver","optimization.ifelse.strategy.SqlServerStrategy"),

HBASE_DRIVER("hbase","optimization.ifelse.strategy.HbaseStrategy"),

MONGO_DRIVER("mogon","optimization.ifelse.strategy.MongoStrategy"),
;

private String type;
private String clazz;

private DbTypeEnum(String type,String clazz){
    this.type=type;
    this.clazz=clazz;
}

public String type() {
    return type;
}

public String clazz(){
    return  clazz;
}

第二步：

private static Map<String,String> strategyMap = new HashMap<>();

public static void excuteStrategy(String type){
    for (DbTypeEnum t : DbTypeEnum.values()) {
        strategyMap.put(t.type(), t.clazz());
    }
    String class_path=strategyMap.get(type);

    try {
        /*
         * 通过反射将RefelDbTypeEnum中映射的类实例化
         * */
        Class clazz=Class.forName(class_path);
        Method excute =clazz.getDeclaredMethod("excute");
        excute.invoke(clazz.newInstance());

    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    } catch (NoSuchMethodException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    } catch (InvocationTargetException e) {
        e.printStackTrace();
    } catch (InstantiationException e) {
        e.printStackTrace();
    }
}