<form id="handleform">
    <!-- 根据学生id修改学生信息 -->
    <input type="hidden" name="student.stuid"/><!-- 隐藏学生id -->
    <div class="input-group el_modellist" role="toolbar">
     <span class="el_spans">要修改的班级：</span>
     <select class="selectpicker form-control" name="student.className" id="fmchechunit" title="请选择">
      <option value="0">--请选择班级--</option>
      <option value="1">软件一班</option>
      <option value="2">软件二班</option>
     </select>
    </div>
    <span class="el_spans">学生姓名：</span>
    <input type="text" id="student.name"/>
     <div class="input-group el_modellist" role="toolbar">
      <span class="el_spans">学生详细信息：</span>
      <textarea id="studentMsg" class="form-control texta" rows="10" name="student.msg"></textarea>
     </div>

     <div class="modal-footer">
      <button id="submitButton" onclick="saveButton()" type="button" class="btn btn-primary">更新</button>
     </div>
   </form>
   <script type="text/javascript">
    function saveButton(){
      //通过ajax异步将数据发送给action层
      $.ajax({
       url : '${pageContext.request.contextPath}/stu/stu_upstudent.action',//这里写上你的action路径
       data : $("#handleform").serialize(),//将你在form表单上提交的数据序列化
       type : 'POST', //提交方式
       dataType : 'json', //提交的数据类型
       async:true, //是否异步
       success : function(data) {//这是个回调函数 data表示从action中传过来的json数据
       //弹出从action层传过来的json格式的数据(用来显示是否更新成功)
       alert(data.result);
       }
      });
    }
   </script>

@Controller
@Scope("prototype")
// 控制层，多例模式
public class DangerAction extends ActionSupport {
 
 private Student student;
 public void setStudent(Student student){
  this.student = student;
 }
 public Student getStudent(){
  return this.student;
 }
 
 @Resource
 private StudentService studentService;
 public StudentService getStudentService() {
  return studentService;
 }
 public void setStudentService(StudentService studentService) {
  this.studentService = studentService;
 }
 public String updateStudent throws Exception{
  
  boolean flag = studentService.update(student);
  HttpServletResponse response = ServletActionContext.getResponse();
  
　　　　　//通过json对象将修改反馈信息响应给jsp
  JSONObject json = new JSONObject();
  if (flag) {
   System.out.println(flag);
   json.put("result", "修改成功");
  } else {
   System.out.println(flag);
   json.put("result", "修改失败");
  }
  System.out.println(json.toString());
  response.setContentType("text/html;charset=UTF-8");
  response.getWriter().write(json.toString());
  return null;//如果不需要跳转页面就写上null,如果要跳转页面就自己另外写上
 }
}

public class Student{
 private int stuid;
 private int className;
 private int name;
 private String studentMsg;
 public int getStuid() {
  return stuid;
 }
 public void setStuid(int stuid) {
  this.stuid = stuid;
 }
 public int getClassName() {
  return className;
 }
 public void setClassName(int className) {
  this.className = className;
 }
 public int getName() {
  return name;
 }
 public void setName(int name) {
  this.name = name;
 }
 public String getStudentMsg() {
  return studentMsg;
 }
 public void setStudentMsg(String studentMsg) {
  this.studentMsg = studentMsg;
 }
 
}