Convert InputStream into JSON

Question

I am using json-rpc-1.0.jar.Below is my code. I need to convert InputStream object into JSON since the response is in JSON.

I did verify the json response obtained from Zappos API. It is valid.

PrintWriter out = resp.getWriter(); String jsonString = null; URL url = new URL("http://api.zappos.com/Search?term=boots&key=my_key"); InputStream inputStream = url.openConnection().getInputStream(); resp.setContentType("application/json"); JSONSerializer jsonSerializer = new JSONSerializer(); try { jsonString = jsonSerializer.toJSON(inputStream); } catch (MarshallException e) { e.printStackTrace(); } out.print(jsonString);

I get the below mentioned exception:

com.metaparadigm.jsonrpc.MarshallException: can't marshall sun.net.www.protocol.http.HttpURLConnection$HttpInputStream at com.metaparadigm.jsonrpc.JSONSerializer.marshall(JSONSerializer.java:251) at com.metaparadigm.jsonrpc.JSONSerializer.toJSON(JSONSerializer.java:259) at Communicator.doGet(Communicator.java:33) at javax.servlet.http.HttpServlet.service(HttpServlet.java:740) at javax.servlet.http.HttpServlet.service(HttpServlet.java:853) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193) at filters.ExampleFilter.doFilter(ExampleFilter.java:149)

First of all, setContentType() should be called before you send the request, ie. before getInputStream(). — Sotirios Delimanolis
– Sotirios Delimanolis, Commented Sep 13, 2013 at 20:09
Might be better to convert InputStream to Stream<JsonNode>. stackoverflow.com/questions/36047907/… — Alex
– Alex, Commented Nov 24, 2019 at 0:10

Vishal Pawale · Accepted Answer · 2013-09-13 20:49:27Z

86

Make use of Jackson JSON parser.

Refer - Jackson Home

The only thing you need to do -

ObjectMapper mapper = new ObjectMapper(); Map<String, Object> jsonMap = mapper.readValue(inputStream, Map.class);

Now jsonMap will contain the JSON.

answered Sep 13, 2013 at 20:49

Vishal Pawale

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4 Comments

Margi Over a year ago

Ok. Looks like the Jackson Home page you asked to refer to, is OLD Jackson Java JSON-processor Home Page. I have downloaded jackson-core-2.2.3.jar. It does not seem to have ObjectMapper Class.

Vishal Pawale Over a year ago

Yes..They have shifted to fasterxml.com. BTW you need to download Core, Annotation & Databind jars.

Margi Over a year ago

Compilation error is : Bad class file ..ObjectMapper.class. Class file has wrong version 50.0,should be 48.0.Tomcat server is running java version 1.4.2_13. I have two options now. 1.Change java version on Tomcat. 2. Look for any other compatible json library. Which one should I go for. Its really a small application.

Vishal Pawale Over a year ago

I think you should change JAVA version, 1.4 is really too old, and I think you should update it.And as far as my opinion is concerned, Jackson is better that all the others.

Philip Rego · Accepted Answer · 2018-07-04 03:49:41Z

ObjectMapper.readTree(InputStream) easily let's you get nested JSON with JsonNodes.

public void testMakeCall() throws IOException { URL url = new URL("https://api.coindesk.com/v1/bpi/historical/close.json?start=2010-07-17&end=2018-07-03"); HttpURLConnection httpcon = (HttpURLConnection) url.openConnection(); httpcon.addRequestProperty("User-Agent", "Mozilla/4.0"); InputStream is = httpcon.getInputStream(); try { ObjectMapper mapper = new ObjectMapper(); JsonNode jsonMap = mapper.readTree(is); JsonNode bpi = jsonMap.get("bpi"); JsonNode day1 = bpi.get("2010-07-18"); System.out.println(bpi.toString()); System.out.println(day1.toString()); } finally { is.close(); } }

Result:

{"2010-07-18":0.0858,"2010-07-19":0.0808,...}

0.0858

Alex · Accepted Answer · 2019-11-24 00:19:58Z

Better to save memory by having output as Stream<JsonNode>

 private fun InputStream.toJsonNodeStream(): Stream<JsonNode> { return StreamSupport.stream( Spliterators.spliteratorUnknownSize(this.toJsonNodeIterator(), Spliterator.ORDERED), false ) } private fun InputStream.toJsonNodeIterator(): Iterator<JsonNode> { val jsonParser = objectMapper.factory.createParser(this) return object: Iterator<JsonNode> { override fun hasNext(): Boolean { var token = jsonParser.nextToken() while (token != null) { if (token == JsonToken.START_OBJECT) { return true } token = jsonParser.nextToken() } return false } override fun next(): JsonNode { return jsonParser.readValueAsTree() } } }

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