Web在线聊天室(7) --- 查询频道列表

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查询频道列表接口

接口设计文档

请求:
GET /channel
响应:
HTTP/1.1 200 OK
[ok:truereason:xxxdata{channelId: 1,channelName: xxx}
]

编写前端ajax回调函数

	   getChannels() {$.ajax({type: "get",url: "channel",success: function(body, status) {if(body.ok) {app.channels = body.data;}else {alert(body.reason)}}})}

编写servlet实现doget方法

@WebServlet("/channel")@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {req.setCharacterEncoding("UTF-8");resp.setCharacterEncoding("UTF-8");resp.setContentType("applicaation/json");Response response = new Response();try {//查询所有频道列表返回List<Channel> list = ChannelDao.query();response.setOk(true);response.setData(list);//ok:true,data[{},{}]}catch (Exception e) {e.printStackTrace();//目前，前端的实现，在后端报错，要返回空的list//改造前端为解析ok，reason//参考LoginServlet改造response.setReason(e.getMessage());//ok:false,reason:""}resp.getWriter().println(Util.serialize(response));}

编写操作数据库方法

    /*** 查询频道列表*/public static List<Channel> query() {Connection connection = null;PreparedStatement statement = null;ResultSet resultSet = null;//定义返回数据List<Channel> list = new ArrayList<>();try {//1. 获取数据库连接Connectionconnection = Util.getConnection();//2. 通过Connection+sql 创建操作命令对象StatementString sql = "select channelId,channelName from channel";statement = connection.prepareStatement(sql);//3. 执行sql：执行前替换占位符resultSet = statement.executeQuery();//如果是查询操作，处理结果集while (resultSet.next()) {//移动到下一行，有数据返回trueChannel channel = new Channel();//设置属性channel.setChannelId(resultSet.getInt("channelId"));channel.setChannelName(resultSet.getString("channelName"));list.add(channel);}return list;}catch (Exception e) {throw new AppException("查询频道列表出错", e);}finally {//释放资源Util.close(connection,statement,resultSet);}}