data-dismiss="modal"

提交按钮不加：

 加上则不会出现提示，直接关闭弹出框

<div class="modal fade" id="myModal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel">
    <div class="modal-dialog " role="document">
        <div class="modal-content">
            <div class="modal-header" style="background-color: #dedede">
                <button type="button" class="close" data-dismiss="modal" aria-label="Close"><span aria-hidden="true">&times;</span></button>
                <h4 class="modal-title" id="myModalLabel">ADD</h4>
                <div class="modal-body">
                    <form id="addForm" onsubmit="return false" action="#" method="post" style="width: 70%">
                        <div class="form-group">
                            <label for="Provider" class="form-inline" style="font-weight:normal">Provider
                                <input type="text" name="UserName" id="Provider" style="width:14.2em;" class="form-control" required="required" placeholder="NOT NULL" onblur="checkIsNull(this)checkName()">
                                <div id="roName" style="color: #843534;display: inline;"></div>
                            </label>
                        </div>
                        <div class="form-group">
                            <label for="Status"  class="form-inline" style="font-weight:normal">&nbsp;&nbsp;&ensp;Status
                                <select id="Status" class="form-control"  style="width:14.2em;">
                                    <option th:each="status : ${statusList}" th:text="${status.name}" th:value="${status.value}"></option>
                                </select>
                            </label>
                        </div>
                        <div class="modal-footer">
                            <button type="submit" id="btn_submit" onclick="addRole()" class="btn btn-success"
                                    >Ok
                            </button>
                            <button type="button" class="btn btn-danger" data-dismiss="modal">Close
                            </button>
                        </div>
                    </form>
                </div>
            </div>
        </div>
    </div>
</div>