.file_box{
float: right;
width: 1035px;
border: 1px solid #999;
height: 32px;
line-height: 35px;
padding-left: 10px;
margin-right: 25px;
}
.file{
float: right;
outline: none;
border:none;
background: #67BEF4;
border-radius: 4px;
padding: 4px 12px;
cursor:pointer;
color: #fff;
font-size:18px;
line-height: 20px;
vertical-align: middle;
margin: 2px;
}

<div class="file_box">
<button type="button" class="file" id="select_file" onclick="file1.click();" > 选择附件</button>
<input type="file" id="file1" name="PXXA_APPENDIX" style="width:250px;display: none;" onchange="setfile_tmp()";>
<input type="text" id="file2" readonly="readonly" th:value="${map.PXXA_APPENDIX}" onclick="file1.click(); ">
</div>

function setfile_tmp(){

var file11 = $("#file1")[0].value;
var arrays1 = file11.split("\\");
var name1 = arrays1[arrays1.length-1];
name1=name1.toLowerCase();
$("#file2")[0].value=name1;
}