一个div里面包含两个div,第二个子div有一个<a>标签，让这个<a>标签在第一个大的DIV垂直居中有哪些办法？

  <div class="user">
            <div class="user_head">
                
            </div>
            <div class="user_name">
                <a href="#">ABC123</a>
            </div>
        </div>


 .user{
    width: 260px;
    height: 100px;
    background-color: gray;
}

.user_head{ 
width: 60px;
height: 60px;
background-color: #b9babe;

margin: 20px 10px 20px 40px;
display: inline-block;

border-radius: 50%;
box-shadow: 0 0 0 5px #2b2e3d inset;
border: 2px solid #b9babe;       
}


   .user_name{
display: inline-block;
height: 100px;
width: 60px;
background-color: yellow;
text-align: center;
}
.user_name a{
line-height: 100px;
text-align: center;
}