I did a http client and I'm getting a response. I am using a JSONObject to parse the data and when I execute the code below it prints out all of the JSON just fine
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
if(entity!=null){
try(InputStream instream = entity.getContent()) {
String responseString = readInputStream(instream);
JSONObject job = new JSONObject(responseString);
statusLabel.setText("Command Result: " + job.toString());
Here is the readInputSream function:
static private String readInputStream(InputStream inputStream) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(
inputStream, "UTF-8"));
String tmp;
StringBuilder sb = new StringBuilder();
while ((tmp = reader.readLine()) != null) {
sb.append(tmp).append("\n");
}
if (sb.length() > 0 && sb.charAt(sb.length() - 1) == '\n') {
sb.setLength(sb.length() - 1);
}
reader.close();
return sb.toString();
}
If I change it from job.toString() to:
statusLabel.setText("Command Result: " + job.get("result"));
it prints a 1 which is correct, it works all the way up to my_list. I'm not sure how to parse the list. I put a snippet of the response below. Ive tried "my_list", "my_list[]", my_list[0]" which none have worked. I get JSONObject "blank" not found
{"result":1, "ver":1,"total":2,"catch":true,"my_list":[{"id":3,"mid":0,"format":3,"user":4,"property":1,"type":0,"title":"hello","start":146,"end":1464,"hid":3,"bid":1,"reason":1,"time":0,"creator":"1","hello":0,"my":0,"year":"0","ggg":614,"name":"","ch":"0","attr":0,"type":1,"vtype":1,"tm_log": {"fr":4,"action":0,"vr":"82","started":1,"av_ended":2,"tr":1}}
The element you trying to retrieve is parsed into a JSONArray, not a JSONObject. Try:
JSONArray my_list = job.getJSONArray("my_list");
Assuming that you are using json parser project JSON-java to parse your JSON you need to retrieve a JSONArray instance - this is how arrays are storred in JSONObject. so do the following: JSONArray my_list = job.getJSONArray("my_list"); and then use methods of JSONArray class to access your array. The Javadoc to JSON-java package can be found here: http://stleary.github.io/JSON-java/index.html. Also note that JSON-java is very simple and easy to use JSON parser project but it is not very efficient for any serious project. Common recommendation for commercial use is Jackson JSON Processor which is one of the fastest and powerful JSON parsers. Here are some links to read about it: https://github.com/FasterXML/jackson, http://wiki.fasterxml.com/JacksonHome
Related
I am using the following code to retreive information from API
HttpURLConnection connection;
..
reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
while ((line = reader.readLine()) != null) {
responseContent.append(line);
}
reader.close();
Then I convert the reponse to string
String responseBody = responseContent.toString();
After that I use org.json library to parse the information
JSONObject ob = new JSONObject(responseBody);
JSONArray Information = ob.getJSONArray("info");
for (int i = 0; i < Information.length(); i++) {
JSONObject data= Information.getJSONObject(i);
String dataName= data.getString("data_name");
}
As result I obtained some texts with html tags when I print dataName values, for example:
content name<sup></sup>
Solved
I used the Java Jsoup library to read the HTML tags.
Best regards.
Forgive me if this is too broad a question, shout at me if so.
I'm retrieving data from a rest API in java. I then want to be able to search through the JSON data for a particular key-value pair. As far as I'm aware, a JSONObject from org.json is a good way of doing this. So far I have:
URL url = new URL("api string");
HttpURLConnection connnection = (HttpURLConnection)url.openConnection();
BufferedReader br = new BufferedReader(new InputStreamReader(connection.getInputStream()));
String input;
StringBuffer sb = new StringBuffer();
while ((input = br.readLine()) != null){
sb.append(input);
}
br.close();
returnedJSON = new JSONObject(sb.toString());
So fairly standard get request code.
Firstly, I can't tell if I need a JSONObject or JSONArray. Everything I've researched uses JSONObjects for writing to from an API, but I'll be retrieving JSON that is in the following form:
[ { x:y, a:b, foo:bar }, { x:y, a:b, foo:bar }, ... , ... ]
So there's multiple JSON "entries" if that makes sense, and I'd like to look through the entire JSON string to see if two pieces of data exist in the same record. Ex: Is the value of 'foo' the expected value for the record where the value of 'x' is 'y'?
I'm unclear on how to proceed here as it is the first time I've properly used JSON.
First of all you should use JSONArray instead of JSONObject because it's a array of object that you receive from API Response..
Now iterate this array and grab each of the JSONObject , which actually received in a form of HashMap (key-value pair).
Now you can get each element of JSONObject by accessing their keys..
Having received the following response from Foursquare, when I try to parse it, I get the error below:
Response:
{"meta":{"code":200},"response":{"venues":[{"id":"4b1c3ce9f964a520d60424e3","name":"Folsom Lake Bowl","contact":{},"location":{"address":"511 East Bidwell","lat":38.67291745,"lng":-121.165447,"distance":39,"postalCode":"95630","city":"Folsom","state":"CA"},"categories":[{"id":"4bf58dd8d48988d1e4931735","name":"Bowling Alley","pluralName":"Bowling Alleys","shortName":"Bowling Alley","icon":{"prefix":"https://foursquare.com/img/categories/arts_entertainment/bowling_","sizes":[32,44,64,88,256],"name":".png"},"primary":true}],"verified":false,"stats":{"checkinsCount":592,"usersCount":284,"tipCount":2},"hereNow":{"count":0}}]}}
Error:
Exception in thread "main" org.codehaus.jettison.json.JSONException: JSONObject["groups"] not found.
at org.codehaus.jettison.json.JSONObject.get(JSONObject.java:360)
at org.codehaus.jettison.json.JSONObject.getJSONArray(JSONObject.java:436)
at playaround.FoursquareAPI.get(FoursquareAPI.java:56)
at playaround.FoursquareAPI.main(FoursquareAPI.java:31)
Code:
StringBuilder sb = new StringBuilder();
BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
for (String line; null != (line = reader.readLine());) {
sb.append(line);
}
String output = sb.toString();
JSONObject json = new JSONObject(output);
JSONArray venues = json.getJSONObject("response").getJSONArray("groups").getJSONObject(0).getJSONArray("items");
System.out.println(venues.length());
All I want is to read the response from Foursquare as JSONObject in Java. Any help?
Reading that stack trace, the JSON is being parsed just fine.
The problem is that you are trying to read a property that doesn't exist -- "groups"
From my experience, if you get the JSON object - such as the problem I had ;parsing a returned LOCATION field. I started with the following code:
JSONObject jsonObjLoc = new JSONObject(myLocation);
If you can get the Object, then simply refer to "has" parameter like:
if(jsonObjLoc.has("myAddress")) { // name of field to look for
myTextAddress = jsonObjLoc.getString("address");
}
I use has to protect against the empty or null field not being returned.
I used cURL to get some twitter feeds in the form of a json file ("twitter-feed.json"). I want to convert this json file to a JSONArray object. How do I do it?
I am new to Java and json. Your suggestions are most welcome.
FileInputStream infile = new FileInputStream("input/twitter-feed.json");
// parse JSON
JSONArray jsonArray = new JSONArray(string);
// use
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObject = jsonArray.getJSONObject(i);
System.out.println(jsonObject.getString("id"));
System.out.println(jsonObject.getString("text"));
System.out.println(jsonObject.getString("created_at"));
}
Thanks,
PD.
You need to read the file first, convert it to String then feed it to the JSONArray (I am assuming that you are using the JSON-Java Project. The code below illustrates how to read the file and set it to JSONArray
// read the source file, source comes from streaming API delimited by newline
// done by curl https://stream.twitter.com/1/statuses/sample.json?delimited=newline -utwitterUsername:twitterPasswd
// > /Projects/StackOverflow/src/so7655570/twitter.json
FileReader f = new FileReader("/Projects/StackOverflow/src/so7655570/twitter.json");
BufferedReader br = new BufferedReader(f);
ArrayList jsonObjectArray = new ArrayList();
String currentJSONString = "";
// read the file, since I ask for newline separation, it's easier for BufferedReader
// to separate each String
while( (currentJSONString = br.readLine()) != null ) {
// create new JSONObject
JSONObject currentObject = new JSONObject(currentJSONString);
// there are more than one way to do this, right now what I am doing is adding
// each JSONObject to an ArrayList
jsonObjectArray.add(currentObject);
}
for (int i = 0; i < jsonObjectArray.size(); i++) {
JSONObject jsonObject = jsonObjectArray.get(i);
// check if it has valid ID as delete won't have one
// sample of JSON for delete :
// {"delete":{"status":{"user_id_str":"50269460","id_str":"121202089660661760","id":121202089660661760,"user_id":50269460}}}
if(jsonObject.has("id")) {
System.out.println(jsonObject.getInt("id"));
System.out.println(jsonObject.getString("text"));
System.out.println(jsonObject.getString("created_at") + "\n");
}
}
Steps explanation :
Stream API does not provide valid JSON as a whole but rather a valid one specified by the delimited field. Which is why, you can't just parse the entire result as is.
In order to parse the JSON, I use the delimited to use newline since BufferedReader has a method readLine that we could directly use to get each JSONObject
Once I get each valid JSON from each line, I create JSONObject and add it to the ArrayList
I then iterate each JSONObject in the ArrayList and print out the result. Note that if you want to use the result immediately and don't have the need to use it later, you can do the processing itself in while loop without storing them in the ArrayList which change the code to:
// read the source file, source comes from streaming API
// done by curl https://stream.twitter.com/1/statuses/sample.json?delimited=newline -utwitterUsername:twitterPasswd
// > /Projects/StackOverflow/src/so7655570/twitter.json
FileReader f = new FileReader("/Projects/StackOverflow/src/so7655570/twitter.json");
BufferedReader br = new BufferedReader(f);
String currentJSONString = "";
// read the file, since I ask for newline separation, it's easier for BufferedReader
// to separate each String
while( (currentJSONString = br.readLine()) != null ) {
// create new JSONObject
JSONObject currentObject = new JSONObject(currentJSONString);
// check if it has valid ID as delete status won't have one
if(currentObject.has("id")) {
System.out.println(currentObject.getInt("id"));
System.out.println(currentObject.getString("text"));
System.out.println(currentObject.getString("created_at") + "\n");
}
}
You may try Gson:
For just arrays you can use:
Gson gson = new Gson();
//(Deserialization)
int[] ints2 = gson.fromJson("[1,2,3,4,5]", int[].class);
To deserialize an array of objects, you can just do:
Container container = new Gson().fromJson(json, Container.class);
As shown here
Use ObjectMapper Class from jackson library like this :
//JSON from file to Object
Staff obj = mapper.readValue(new File("c:\\file.json"), Staff.class);
//JSON from URL to Object
Staff obj = mapper.readValue(new URL("http://mkyong.com/api/staff.json"), Staff.class);
//JSON from String to Object
Staff obj = mapper.readValue(jsonInString, Staff.class);
I want to make an Http request and store the result in a JSONObject. I haven't worked much with servlets, so I am unsure as to whether I am 1) Making the request properly, and 2) supposed to create the JSONObject. I have imported the JSONObject and JSONArray classes, but I don't know where I ought to use them. Here's what I have:
public void doGet(HttpServletRequest req, HttpServletResponse resp)
throws IOException {
//create URL
try {
// With a single string.
URL url = new URL(FEED_URL);
// Read all the text returned by the server
BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
String str;
while ((str = in.readLine()) != null) {
// str is one line of text; readLine() strips the newline character(s)
}
in.close();
} catch (MalformedURLException e) {
}
catch (IOException e) {
}
My FEED_URL is already written so that it will return a feed formatted for JSON.
This has been getting to me for hours. Thank you very much, you guys are an invaluable resource!
First gather the response into a String:
BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
StringBuilder fullResponse = new StringBuilder();
String str;
while ((str = in.readLine()) != null) {
fullResponse.append(str);
}
Then, if the string starts with "{", you can use:
JSONObject obj = new JSONObject(fullResponse.toString()); //[1]
and if it starts with "[", you can use:
JSONArray arr = new JSONArray(fullResponse.toStrin()); //[2]
[1] http://json.org/javadoc/org/json/JSONObject.html#JSONObject%28java.lang.String%29
[2] http://json.org/javadoc/org/json/JSONArray.html#JSONArray%28java.lang.String%29
Firstly, this is actually not a servlet problem. You don't have any problems with javax.servlet API. You just have problems with java.net API and the JSON API.
For parsing and formatting JSON strings, I would recommend to use Gson (Google JSON) instead of the legacy JSON API's. It has much better support for generics and nested properties and can convert a JSON string to a fullworthy javabean in a single call.
I've posted a complete code example before here. Hope you find it useful.