上次已经完成了Android客户端向服务器端传值的功能，接下来的任务是服务器端通过连接数据库对传来的值进行判定，并将判定结果返回客户端。
对传来的数值进行判定的处理过程与web开发相同，比较简单。重点是将判定结果返回客户端的实现：
Servlet部分重点代码：
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/*** 功能：验证手机用户登录*/public void androidCheckUser(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {PrintWriter out = response.getWriter();String userName=request.getParameter("userName");String passWord=request.getParameter("passWord");//在服务器端解决中文乱码问题userName=NewString.getNewString(userName);passWord=NewString.getNewString(passWord);System.out.println("账号："+userName);System.out.println("密码："+passWord);//调用daoUserDao uDao=new UserDao();if(uDao.checkUser(userName, passWord)){ //得到登录用户的权限类型String type=uDao.getType(userName);if(type.equals("高级")){request.setAttribute("result","high");request.getRequestDispatcher("login.jsp").forward(request, response);}else if(type.equals("普通")){request.setAttribute("result","common");request.getRequestDispatcher("login.jsp").forward(request, response);}else if(type.equals("超级")){request.setAttribute("result","super");request.getRequestDispatcher("login.jsp").forward(request, response);}}else{request.setAttribute("result","false");request.getRequestDispatcher("login.jsp").forward(request, response);}}
如上所示，Servlet调用Dao进行判定，将判定标识写入XML格式的JSP页面中。
JSP页面结构：
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<%@ page language="java" import="java.util.*" contentType="text/xml; charset=UTF-8" pageEncoding="UTF-8"%><?xml version="1.0" encoding="UTF-8"?><%String result=(String)request.getAttribute("result");%><result><flag><%=result%></flag></result>
Android客户端解析XML格式的JSP页面，得到服务器端传来的判定结果，根据结果弹出提示框。
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/** * 验证用户登录是否合法 * 返回值：服务器端判断的标识 */public static String check(String name, String pass) throws XmlPullParserException, MalformedURLException, IOException {String path=":8080/lss/UserServlet?flag=androidCheck";//将用户名和密码放入HashMap中Map<String,String> params=new HashMap<String,String>();params.put("userName", name);params.put("passWord", pass);String checkr=uMethod.checkUser(path,params,"UTF-8");System.out.println("check"+checkr);return checkr;}
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//权限为高级用户//权限为普通用户//权限为超级用户//权限为超级用户//一定要加，不然报错Causedby:org.xmlpull.v1.XmlPullParserException:Prematureendofdocument.
public String checkUser(String path,Map<String, String> params,String encode) throws MalformedURLException, IOException, XmlPullParserException {StringBuilder url=new StringBuilder(path);url.append("&");for(Map.Entry<String, String> entry:params.entrySet()){url.append(entry.getKey()).append("=");url.append(URLEncoder.encode(entry.getValue(),encode));url.append("&");}//删掉最后一个&url.deleteCharAt(url.length()-1);HttpURLConnection conn=(HttpURLConnection)new URL(url.toString()).openConnection();conn.setConnectTimeout(5000);conn.setRequestMethod("GET");if(conn.getResponseCode()==200){InputStream inputStream=conn.getInputStream();System.out.println("准备解析！");String s=parseXML(inputStream);System.out.println("准备解析！"+s);//将得到的XML内容的解析if(s.equals("high")){ //权限为高级用户return "high";}else if(s.equals("common")){ //权限为普通用户return "common";}else if(s.equals("super")){ //权限为超级用户return "super";}else if(s.equals("false")){ //权限为超级用户return "false";}}return "false";}/*** 解析服务器端返回的XML*/public String parseXML(InputStream inputStream) throws XmlPullParserException, IOException {XmlPullParser parser=Xml.newPullParser();parser.setInput(inputStream,"UTF-8");String result=null;//得到开始文档事件int event=parser.getEventType();while(event!=XmlPullParser.END_DOCUMENT){switch(event){case XmlPullParser.START_TAG:if("flag".equals(parser.getName())){result=parser.nextText();System.out.println("flag"+result);}break;//一定要加，不然报错Caused by: org.xmlpull.v1.XmlPullParserException: Premature end of document.case XmlPullParser.END_TAG:break;}event = parser.next();}return result;}
运行效果：
总结：
服务器端将所传值写入XML格式的JSP页面中，，Android对XML进行解析，得到标识值
一定要成为你工作最大的资产。
