為什么我的服務器運行出現 http 500 的錯誤啊 ?跟著老師的打的

求高手來解救下，架包用的gson-2.2.2.jar

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
?this.doPost(request, response);
?}

?/**
? * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
? */
?protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
??response.setContentType("text/html;charset=utf-8");
??
??PrintWriter out=response.getWriter();
??
??data data = new data();

??ArrayList<Person> personslist = new ArrayList<Person>();
??ArrayList<schoolinfor> schoolinforslist = new ArrayList<schoolinfor>();

??// 寫入json數據
??Person person1 = new Person();
??person1.setName("小華");
??person1.setAddress("新華街22號");

??schoolinfor schoolinfor1 = new schoolinfor();
??schoolinfor1.setMiddleSchool("第一初中");
??schoolinfor1.setCollege("清華大學");

??person1.setSchoolinfor(schoolinfor1);
??personslist.add(person1);
??schoolinforslist.add(schoolinfor1);
??// **************************************************************
??Person person2 = new Person();
??person2.setName("小明");
??person2.setAddress("中華街22號");

??schoolinfor schoolinfor2 = new schoolinfor();
??schoolinfor2.setMiddleSchool("第二初中");
??schoolinfor2.setCollege("北京大學");

??person2.setSchoolinfor(schoolinfor2);
??personslist.add(person2);
??schoolinforslist.add(schoolinfor2);

??data.setPersonlist(personslist);
??data.setSchoollist(schoolinforslist);
??// 轉為json數據格式
??Gson gson=new Gson();
??out.println(gson.toJson(data));
?}

}