Hi i have multiple data in my database with map.
i want to get only unique keys of all the objects of map.
my data is like this.
map values are like Map<String, Object> attributes:
[ { 用户名：abc， 属性：{ “ a”：“ 1”， “ b”：“ 2”， “ c”：“ 3” } }， { 用户名：xyz， 属性：{ “ a”：“ 1”， “ d”：“ 2”， “ e”：“ 3” } }， { 用户名：qwe， 属性：{ “ w”：“ 1”， “ s”：“ 2”， “ c”：“ 3” } }]