Java Web服务器向Android客户端返回数据（服务器端）

来源：互联网发布：神之浩劫ps4港服网络编辑：程序博客网时间：2024/05/21 02:51

结合我之前的文章 Android Java Web实现登录注册（一）——客户端点击打开链接

Android Java Web实现登录注册（二）——服务器端点击打开链接

Android客户端通过post方法调用web服务器的Servlet，post方法包含请求信息request和回答信息response，在服务器端Servlet的post方法中更新response，以达到向客户端返回信息的效果。

以下代码为客户端传来用户ID，服务器端返回用户信息（ID，用户名，密码）的示例，（服务器端）使用到 net.sf.json jar包中所有的.jar文件进行数据处理和传递，下载地址点击打开链接

UserInfoServlet.java（服务器端）

public class UserInfoServlet extends HttpServlet {    private static final long serialVersionUID = 1L;    public UserInfoServlet() {        super();    }    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        doPost(request, response);        response.getWriter().append("Served at: ").append(request.getContextPath());    }    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        // 输出流          PrintWriter out = response.getWriter();        // 设置编码形式          request.setCharacterEncoding("utf-8");        response.setCharacterEncoding("utf-8");        // 获取传入的数据          String id = request.getParameter("id");        System.out.println("UserInfoServlet: id = " + id);        ArrayList<User> user_list =                new ArrayList<User>(new UserService().getInfo(id));        if(user_list.size() == 0){            out.print("NO_SUCH_USER");        }else{            JSONObject json = new JSONObject();            JSONArray jarray_u = new JSONArray();            try {                for(User user : user_list)                {                    JSONObject user1 = new JSONObject();                    user1.put("id", user.getId());                    //解决中文乱码问题，服务器端加密，客户端解密                      user1.put("username", URLEncoder.encode(user.getUsername(), "utf-8"));                    user1.put("password", user.getPassword());jarray_u.add(user1);                }                json.put("users",jarray_u);            } catch (JSONException e) {                e.printStackTrace();            }            out.print(json.toString());            System.out.println("UserInfoServlet:" + json.toString());        }        out.flush();        out.close();    }}

UserService.java（节选，服务器端）

 //根据id获取用户用户名、密码 public ArrayList<User> getInfo(String id) { // 创建User对象数组 ArrayList<User> list= null; list = new ArrayList <User>(); // SQL 语句：根据id查询 String sql = "select * from user_list where id = "+ id;try {// 获得数据库连接Connection con = DBManager.getConnection();// 获得语句对象preparedStatement = con.prepareStatement(sql);// 执行语句resultSet = preparedStatement.executeQuery();// 获取下一条记录while (resultSet.next()){System.out.println("UserService getInfo found");User user = new User();user.setId(resultSet.getString("id"));user.setUsername(resultSet.getString("username"));user.setPassword(resultSet.getString("password"));list.add(user);}// 关闭结果resultSet.close();// 释放语句对象preparedStatement.close();// 关闭数据库连接con.close();} catch (SQLException e) {e.printStackTrace();} return list; }

启动Thread调用服务器端方法（节选，客户端）

// 访问数据库，通过id获取用户信息    public void getUserInfo(final String id) {        // 新建一个用于网络连接的线程，获取用户详细信息Thread        Log.i("tag", "getUserInfo");        new Thread() {            @Override            public void run() {                // Sevice传回Long                String responseMsg = "FAIL";                // 要发送的数据                List<NameValuePair> params = new ArrayList<NameValuePair>();                params.add(new BasicNameValuePair("id", id));                responseMsg = UserInfoPostService.send(params);                Log.i("tag", "MainAcitivity responseMsg : " + responseMsg);                // 准备发送消息                Message msg = handler.obtainMessage();                // 设置消息默认值                msg.what = 100;                if (responseMsg.equals("NO_SUCH_USER")) {                    msg.obj = "用户不存在";                } else if (responseMsg.equals("FAIL")) {                    msg.obj = "连接服务器失败";                } else {                    // 解析JSON数据，存入本地数据库                    try{                        JSONObject jsonobject = new JSONObject(responseMsg.toString());                        JSONArray ja_g = jsonobject.getJSONArray("users");                        for (int i = 0; i < ja_g.length(); i++) {                            JSONObject jsonobject2 = ja_g.getJSONObject(i);                            UserItem user = new UserItem(jsonobject2.getString("id"),                                    jsonobject2.getString("username").toString(),                                    jsonobject2.getString("password").toString());                            Message msg1 = handler.obtainMessage();                            msg1.what = 333;                            msg1.obj = user;                            handler.sendMessage(msg1);                        }                    }catch(JSONException e){                        e.printStackTrace();                    }                }                handler.sendMessage(msg);            }        }.start();    }

处理Thread返回的消息（节选，客户端）

handler = new Handler() {            @Override            public void handleMessage(Message msg) {                if (msg.what == 333) {//得到详细用户信息                    username = ((UserItem) msg.obj).getUsername();                    Log.i("tag", "username: " + username);                } else {// 提示信息                    //Toast.makeText(getApplicationContext(),(String)msg.obj,Toast.LENGTH_SHORT).show();                }            }        };

MyHttpPost.java (客户端)

和之前的代码相比，加上了解密的过程，解决中文乱码问题

public class MyHttpPost {    // 服务器地址    private static String SERVER = "http://123.207.3.202:8080";    // 项目地址    private static String PROJECT = "/SeeTogetherServer/";    // 请求超时    private static final int REQUEST_TIMEOUT = 0;    // 读取超时    private static final int SO_TIMEOUT = 0;    // 通过 POST 方式获取HTTP服务器数据    public static String executeHttpPost(String servlet, List<NameValuePair> params) {        String baseURL = SERVER + PROJECT + servlet;        String responseMsg = "FAILED";        try {            //连接到服务器端相应的Servlet            HttpPost request = new HttpPost(baseURL);            //request.addHeader("Content-Type", "application/json; charset=utf-8");            request.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));            BasicHttpParams httpParams = new BasicHttpParams();            HttpConnectionParams.setConnectionTimeout(httpParams, REQUEST_TIMEOUT);            HttpConnectionParams.setSoTimeout(httpParams, SO_TIMEOUT);            HttpClient client = new DefaultHttpClient(httpParams);            //client.getParams().setParameter("http.protocol.content-charset", "UTF-8");            HttpResponse response = client.execute(request);            if(response.getStatusLine().getStatusCode()==200)//是否成功收取信息                responseMsg = EntityUtils.toString(response.getEntity(), HTTP.UTF_8);        } catch (Exception e) {            e.printStackTrace();        }        Log.i("tag", "server" + SERVER);        try {//解密            Log.i("tag", "1 HttpPost: responseMsg = " + URLDecoder.decode(responseMsg,"utf-8"));            return URLDecoder.decode(responseMsg,"utf-8");        } catch (UnsupportedEncodingException e) {            e.printStackTrace();        }        Log.i("tag", "2 HttpPost: responseMsg = " + responseMsg);        return responseMsg;    }}

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