Servlet不向android返回JSON
Servlet不向android返回JSON
提问于 2014-12-23 14:50:31
我正在尝试从android客户端向servlet发送图像。我使用JSON在servlet中发送编码图像和解码。
当我在eclipse中运行servlet时，我在tomcat服务器控制台上得到'null‘。当我尝试将printf语句用于测试时，也会得到相同的响应。
我的servlet代码是：
protected void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException
{
try
{
res.setContentType("application/json");
res.setHeader("Cache-Control", "nocache");
res.setCharacterEncoding("utf-8");
PrintWriter out = res.getWriter();
JSONObject json = new JSONObject();
String jsonString = json.getString("image");
byte[] decodedString = Base64.decodeBase64(jsonString.getBytes());//, Base64.DEFAULT);
FileOutputStream fos = new FileOutputStream("C:\\Users\\OWNER\\Desktop\\image.jpg");
try {
fos.write(decodedString);
}
finally {
fos.close();
}
// finally output the JSON with 1 for success
JSONObject response=new JSONObject();
out.println(response.put("result", 1).toString());
}
catch(Exception e){e.printStackTrace();}
}android代码是：
class ImageUploadTask extends AsyncTask<Void, Void, String> {
@Override
protected String doInBackground(Void... unsued) {
try {
HttpClient httpClient = new DefaultHttpClient();
HttpContext localContext = new BasicHttpContext();
HttpPost httpPost = new HttpPost(URL);
MultipartEntity entity = new MultipartEntity(
HttpMultipartMode.BROWSER_COMPATIBLE);
HttpEntity res;
ByteArrayOutputStream bos = new ByteArrayOutputStream();
// Compress to jpg and convert to byte[]:
bitmap.compress(CompressFormat.JPEG, 100, bos);
byte[] data = bos.toByteArray();
String imgData= Base64.encodeToString(data, Base64.DEFAULT);
String img=imgData.replace("\n", "%20");
//add fields in JSON:
JSONObject jsonObject= new JSONObject();
jsonObject.put("img",data);
httpPost.setEntity(new ByteArrayEntity(jsonObject.toString().getBytes("UTF8")));
HttpResponse response = httpClient.execute(httpPost);
BufferedReader reader = new BufferedReader(
new InputStreamReader(
response.getEntity().getContent(), "UTF-8"));
String sResponse = reader.readLine();
return sResponse;
} catch (Exception e) {
if (dialog.isShowing())
dialog.dismiss();
Toast.makeText(getApplicationContext(),
e.getMessage(),
Toast.LENGTH_LONG).show();
Log.e(e.getClass().getName(), e.getMessage(), e);
return null;
}
}
@Override
protected void onPostExecute(String sResponse) {
try {
if (dialog.isShowing())
dialog.dismiss();
if (sResponse != null) {
JSONObject JResponse = new JSONObject(sResponse);
int success = JResponse.getInt("result");
if (success == 1) {
Toast.makeText(getApplicationContext(),
"Photo uploaded successfully",
Toast.LENGTH_SHORT).show();
caption.setText("");
} else {
Toast.makeText(getApplicationContext(), "Error",
Toast.LENGTH_LONG).show();
}
}
} catch (Exception e) {
Toast.makeText(getApplicationContext(),
e.getMessage(),
Toast.LENGTH_LONG).show();
Log.e(e.getClass().getName(), e.getMessage(), e);
}
}
}web.xml：
<servlet>
<servlet-name>q</servlet-name>
<servlet-class>Server1</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>q</servlet-name>
<url-pattern>/P4</url-pattern>
</servlet-mapping>在android设备上启动app后，按下upload按钮，没有响应。在tomcat服务器上，我得到了'null‘。
我怎么才能让它工作呢？谢谢!
回答 1
Stack Overflow用户
发布于 2014-12-23 21:02:33
如果您的客户端工作正常：
您应该根据请求创建json对象：
BufferedReader br = new BufferedReader(new InputStreamReader(req.getInputStream()));
String jsonStr = "";
if(br != null)
jsonStr = br.readLine();
JSONObject json = new JSONObject(jsonStr); 使用img而不是image
String jsonString = json.getString("img");servlet编辑servlet:要调试您的程序，首先要编写一个简单的示例:一个，它只返回一个简单的结果。使用firebug和firefox测试此servlet。然后添加一个调用此servlet的android程序。如果这个简单的程序工作正常，那么一步一步地添加程序的其他方面，并在每一步测试您的程序。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/27615430
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