How do I parse JSON from a Java HTTPResponse?
JavaAndroidJsonJava Problem Overview
I have an HttpResponse object for a web request I just made. The response is in the JSON format, so I need to parse it. I can do it in an absurdly complex way, but it seems like there must be a better way.
Is this really the best I can do?
HttpResponse response; // some response object
Reader in = new BufferedReader(
new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
StringBuilder builder= new StringBuilder();
char[] buf = new char[1000];
int l = 0;
while (l >= 0) {
builder.append(buf, 0, l);
l = in.read(buf);
}
JSONTokener tokener = new JSONTokener( builder.toString() );
JSONArray finalResult = new JSONArray( tokener );
I'm on Android if that makes any difference.
Java Solutions
Solution 1 - Java
Two things which can be done more efficiently:
- Use
StringBuilder
instead ofStringBuffer
since it's the faster and younger brother. - Use
BufferedReader#readLine()
to read it line by line instead of reading it char by char.
HttpResponse response; // some response object
BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
StringBuilder builder = new StringBuilder();
for (String line = null; (line = reader.readLine()) != null;) {
builder.append(line).append("\n");
}
JSONTokener tokener = new JSONTokener(builder.toString());
JSONArray finalResult = new JSONArray(tokener);
If the JSON is actually a single line, then you can also remove the loop and builder.
HttpResponse response; // some response object
BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
String json = reader.readLine();
JSONTokener tokener = new JSONTokener(json);
JSONArray finalResult = new JSONArray(tokener);
Solution 2 - Java
Use JSON Simple,
http://code.google.com/p/json-simple/
Which has a small foot-print, no dependencies so it's perfect for Android.
You can do something like this,
Object obj=JSONValue.parse(buffer.tString());
JSONArray finalResult=(JSONArray)obj;
Solution 3 - Java
You can use the Gson library for parsing
void getJson() throws IOException {
HttpClient httpClient = new DefaultHttpClient();
HttpGet httpGet = new HttpGet("some url of json");
HttpResponse httpResponse = httpClient.execute(httpGet);
String response = EntityUtils.toString(httpResponse.getEntity());
Gson gson = new Gson();
MyClass myClassObj = gson.fromJson(response, MyClass.class);
}
here is sample json file which is fetchd from server
{
"id":5,
"name":"kitkat",
"version":"4.4"
}
here is my class
class MyClass{
int id;
String name;
String version;
}
refer this
Solution 4 - Java
Jackson appears to support some amount of JSON parsing straight from an InputStream
. My understanding is that it runs on Android and is fairly quick. On the other hand, it is an extra JAR to include with your app, increasing download and on-flash size.
Solution 5 - Java
Instead of doing
Reader in = new BufferedReader(
new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
StringBuilder builder= new StringBuilder();
char[] buf = new char[1000];
int l = 0;
while (l >= 0) {
builder.append(buf, 0, l);
l = in.read(buf);
}
JSONTokener tokener = new JSONTokener( builder.toString() );
You can do:
JSONTokener tokener = new JSONTokener(
IOUtils.toString(response.getEntity().getContent()) );
where IOUtils is from the commons IO library.
Solution 6 - Java
For Android, and using Apache's Commons IO Library for IOUtils
:
// connection is a HttpURLConnection
InputStream inputStream = connection.getInputStream()
ByteArrayOutputStream baos = new ByteArrayOutputStream();
IOUtils.copy(inputStream, baos);
JSONObject jsonObject = new JSONObject(baos.toString()); // JSONObject is part of Android library
Solution 7 - Java
There is no need to do the reader loop yourself. The JsonTokener has this built in. E.g.
ttpResponse response; // some response object
BufferedReader reader = new BufferedReader(new
JSONTokener tokener = new JSONTokener(reader);
JSONArray finalResult = new JSONArray(tokener);