Java从Map中获取多层级的key技巧

实现方式一：

/**
 * 从map中获取多层级的key 如：parentKey.childKey...
 * @param map
 * @param key
 * @return 从map中获取的value<br   />
 * Map {"parentKey":{"childKey":"value"}}<br/>
 * getValueFromMapWithMultiLevel(map, "parentKey.childKey") 返回 value
 */
public static Object getValueFromMapMultiLevel(Map<String, Object> map, String key){
  if (key.contains(".")) {
    String[] keys = key.split("\\.");
    for (int i = 0; i < keys.length - 1; i++) {
      Object tmpMap = map.get(keys[i]);
      if (tmpMap instanceof Map) {
        map = (Map<String, Object>) tmpMap;
      } else {
        return null;
      }
    }
    return map.get(keys[keys.length - 1]);
  } else {
    return map.get(key);
  }
}

实现方式一：

/**
 * 从map中获取多层级key的值 如： parentKey.childKey...
 */
public static Object getValueFromMapMultiLevel2(Map<String,Object>  map, String key){
  return getValueFromMultiLevel(map, key, Object.class);
}

/**
 * 从map中获取多层级key的值，返回值为clazz类型
 */
public static <T> T getValueFromMultiLevel(Map<String,Object>  map, String key, Class<T> clazz) {
  if (map == null) {
    return null;
  }
  StringTokenizer s = new StringTokenizer(key, ".");
  T result;
  try {
    Object temp = map;
    while (s.hasMoreElements()) {
      String tempKey = (String) s.nextElement();
      if (temp instanceof Map) {
        temp = org.apache.commons.collections.MapUtils.MapUtils.getObject((Map) temp, tempKey);
      } else {
        Class tempClazz = temp.getClass();
        Field field = tempClazz.getDeclaredField(tempKey);
        field.setAccessible(true);
        temp = field.get(temp);
      }
    }
    result = com.alibaba.fastjson.util.TypeUtils.cast(temp, clazz, null);
  } catch (Exception e) {
    return null;
  }
  return result;
}

测试效果

public static void main(String[] args) {
  Map a = new HashMap();
  Map b = new HashMap();
  b.put("b","ab");
  a.put("a",b);

  System.out.println(getValueFromMapMultiLevel(a, "a.b"));
  System.out.println(getValueFromMapMultiLevel2(a, "a.b"));
}