java - 将参数传递给 doGet() servlet

Question

我在尝试通过 Servlet 从 Android 访问 MySQL 时遇到了一些问题。我想做的是通过将一些值传递给 servlet 类来检查事件是否存在于数据库中。如果没有现有记录，则执行数据库插入。

    public void createEvent(Event event) {
    String page;
    JSONArray jsonArray;
    try {
        HttpClient client = new DefaultHttpClient();
        HttpGet request = new HttpGet(ENeighbourhoodActivity.URL + "checkEventExist");
        List<NameValuePair> checkExistnvp = new ArrayList<NameValuePair>(3);
        checkExistnvp.add(new BasicNameValuePair("eventName", event.getEventName()));
        checkExistnvp.add(new BasicNameValuePair("eventX", event.getEventX()));
        checkExistnvp.add(new BasicNameValuePair("eventY", event.getEventY()));

        try {
            post.setEntity(new UrlEncodedFormEntity(checkExistnvp));
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }

        HttpResponse response = client.execute(request);
        HttpEntity entity = response.getEntity();
        String responseString = EntityUtils.toString(entity, "UTF-8");
        page = "{\'Events\':" + responseString + "}";
        try {
            JSONObject jsonObject = new JSONObject(page);
            jsonArray = jsonObject.getJSONArray("Events");
            int length = jsonArray.length();
            if(length == 0){
                // If no existing record, then perform DB insertion
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }
    } catch (IOException e) {
        e.printStackTrace();
    }

}

在我的 servlet 中:

protected void doGet(HttpServletRequest request,
        HttpServletResponse response) throws ServletException, IOException {
    JSONArray jsonArray = new JSONArray();
    PrintWriter out = response.getWriter();
    if (request.getParameter("checkEventExist") != null) {
        String eventX = request.getParameter("eventX");
        String eventY = request.getParameter("eventY");
        String eventName = request.getParameter("eventName");
        try {
            Class.forName("com.mysql.jdbc.Driver");
            Connection con = DriverManager.getConnection(
                    "jdbc:mysql://localhost/mydb", "root", "root");

            PreparedStatement statement = con
                    .prepareStatement("SELECT * FROM event WHERE eventName = '" + eventName + "' AND eventX = '" + eventX + "' AND eventY = '"+ eventY + "'");
            ResultSet result = statement.executeQuery();
            while (result.next()) {
                JSONObject eventInfo = new JSONObject();
                eventInfo.put("eventName", result.getString("eventName"));
                eventInfo.put("eventX", result.getString("eventX"));
                eventInfo.put("eventY", result.getString("eventY"));
                jsonArray.put(eventInfo);
            }
        }

        catch (JSONException je) {
            System.out.println(je.getMessage());
        } catch (Exception exc) {
            System.out.println(exc.getMessage());
        }
        out.println(jsonArray.toString());
    }

}

我不确定我应该如何将名称/值对传递并获取到 servlet 中的 doGet() 中。用这一行:

post.setEntity(new UrlEncodedFormEntity(checkExistnvp));

这就是我将值传递给 doPost() 的方式。但我需要将它传递给 doGet() 。有什么指南吗？

提前致谢。

Answer 1

您应该使用查询参数，因为 HTTP GET 不允许在 HTTP 正文中发送实体。

为了发送 HTTP GET 的参数，你应该准备一个像这样的 URL:

HttpGet request = new HttpGet(ENeighbourhoodActivity.URL + "checkEventExist?" + 
    "eventName=<eventName>&"+
    "eventX=<eventX>&"+
    "eventY=<eventY>");
HttpResponse response = client.execute(request);

而且你不应该在请求中添加任何NameValuePair