解析JSON对象时遇‘End of input at character 0’错误求助

我来帮你拆解下遇到的问题，逐个解决：

1. 服务器返回的JSON格式不合法 #

你贴出的服务器响应内容是多个JSONObject直接用逗号拼接，但没有用[]包裹，这不是合法的JSON数组格式。正确的合法格式应该是：

[{"id":"16165","sensorid":"cc3200_8A7F30","pm1":"0.22","pm25":"0.23","pm10":"0.41","timestamp":"2018-01-30 12:28:56.000"},{"id":"16166","sensorid":"cc3200_E271A6","pm1":"0","pm25":"0.02","pm10":"0.46","timestamp":"2018-01-30 12:30:15.000"},{"id":"16167","sensorid":"cc3200_8A7F30","pm1":"0.09","pm25":"0.09","pm10":"0.58","timestamp":"2018-01-30 12:30:56.000"},{"id":"16168","sensorid":"cc3200_E271A6","pm1":"0.07","pm25":"0.07","pm10":"0.26","timestamp":"2018-01-30 12:32:15.000"}]

如果没法要求服务器修改返回格式，你可以在客户端手动给响应内容前后加上[]，把它转换成合法的JSONArray。

2. 网络请求代码的错误导致空响应 #

你的sendGet方法里有两个明显的问题，这也是你出现End of input at character 0的直接原因：

• 你先获取了InputStream inputStr = con.getInputStream();但没有使用，之后又再次调用con.getInputStream()创建BufferedReader。一个HttpURLConnection的输入流只能被读取一次，第二次获取的流是空的；
• con.setRequestProperty("api-key");和con.setRequestProperty("api-code");写法错误，该方法需要传入键值对，比如con.setRequestProperty("api-key", "你的key值");，否则请求可能不被服务器正确处理，返回空内容。

修正后的sendGet方法示例：

private String sendGet() throws Exception {
    String url = "myUrl";
    URL obj = new URL(url);
    HttpURLConnection con = (HttpURLConnection) obj.openConnection();
    con.setRequestMethod("GET");
    con.setRequestProperty("User-Agent", USER_AGENT);
    // 修正请求头写法，传入键和对应的值
    con.setRequestProperty("api-key", "你的API_KEY");
    con.setRequestProperty("api-code", "你的API_CODE");

    int responseCode = con.getResponseCode();
    System.out.println("\nSending 'GET' request to URL : " + url);
    System.out.println("Response Code : " + responseCode);

    if (responseCode == 200) {
        // 只获取一次输入流
        BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream(), "UTF-8"));
        String inputLine;
        StringBuffer response = new StringBuffer();

        while ((inputLine = in.readLine()) != null) {
            response.append(inputLine);
        }
        in.close();
        // 返回响应内容
        return response.toString();
    } else {
        // 处理非200响应，读取错误流排查问题
        BufferedReader errorIn = new BufferedReader(new InputStreamReader(con.getErrorStream(), "UTF-8"));
        String inputLine;
        StringBuffer errorResponse = new StringBuffer();
        while ((inputLine = errorIn.readLine()) != null) {
            errorResponse.append(inputLine);
        }
        errorIn.close();
        System.err.println("Error response: " + errorResponse.toString());
        return null;
    }
}

3. JSON解析逻辑错误 #

你的解析代码试图从JSONObject里获取名为particles的数组，但服务器返回的内容（修正格式后）本身就是一个JSONArray，根本没有particles这个键。你需要直接把响应字符串转换成JSONArray，而不是先转成JSONObject。

修正后的解析代码：

@Override
protected Void doInBackground(Void... voids) {
    HttpHandler sh = new HttpHandler();
    String jsonString = sh.makeServiceCall(url);
    Log.e(TAG, "Response from url: " + jsonString);
    System.out.println("jsonstring: " + jsonString);

    if (jsonString != null && !jsonString.isEmpty()) {
        // 手动修正服务器返回的非法JSON格式：前后加[]
        if (!jsonString.startsWith("[") && !jsonString.endsWith("]")) {
            jsonString = "[" + jsonString + "]";
        }

        try {
            // 直接解析成JSONArray
            JSONArray particles = new JSONArray(jsonString);
            for (int i = 0; i < particles.length(); i++) {
                JSONObject c = particles.getJSONObject(i);
                String id = c.getString("id");
                String sensorid = c.getString("sensorid");
                String pm1 = c.getString("pm1");
                String pm25 = c.getString("pm25");
                String pm10 = c.getString("pm10");
                String timestamp = c.getString("timestamp");

                HashMap<String, String> particle = new HashMap<>();
                particle.put("id", id);
                particle.put("sensorid", sensorid);
                particle.put("pm1", pm1);
                particle.put("pm25", pm25);
                particle.put("pm10", pm10);
                particle.put("timestamp", timestamp);

                // 记得把particle添加到你的数据列表中，比如mParticleList.add(particle);
            }
        } catch (final JSONException e) {
            Log.e(TAG, "Json Parsing error: " + e.getMessage());
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    Toast.makeText(getApplicationContext(), "Json Parsing error: " + e.getMessage(), Toast.LENGTH_LONG).show();
                }
            });
        }
    } else {
        Log.e(TAG, "Couldn't get json from server.");
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                Toast.makeText(getApplicationContext(), "Couldn't get json from server. Check LogCat for possible errors!", Toast.LENGTH_LONG)
                        .show();
            }
        });
    }
    return null;
}

总结解决步骤 #

1. 修复网络请求代码中的输入流重复获取问题，以及请求头的正确写法；
2. 修正服务器返回的非法JSON格式（服务器不能改则客户端手动加[]）；
3. 调整解析逻辑，直接解析JSONArray而不是寻找不存在的particles键。

内容的提问来源于stack exchange，提问作者Kkona