About Blaise Doughan
Java will soon have a standard set of APIs for processing JSON as part of Java EE 7. This standard is being defined as JSR 353 – Java API for JSON Processing (JSON-P) and it is currently at the Final Approval Ballot. JSON-P offers both object oriented and stream based approaches, in this post I will introduce the stream APIs. You can get JSON-P reference implementation from the link below:
JsonGenerator (javax.json.stream)
JsonGenerator makes it very easy to create JSON. With its fluent API the code to produce the JSON very closely resembles the resulting JSON.
package blog.jsonp; import java.util.*;import javax.json.Json;import javax.json.stream.*; public class GeneratorDemo { public static void main(String[] args) { Map<String, Object> properties = new HashMap<String, Object>(1); properties.put(JsonGenerator.PRETTY_PRINTING, true); JsonGeneratorFactory jgf = Json.createGeneratorFactory(properties); JsonGenerator jg = jgf.createGenerator(System.out); jg.writeStartObject() // { .write("name", "Jane Doe") // "name":"Jane Doe", .writeStartObject("address") // "address":{ .write("type", 1) // "type":1, .write("street", "1 A Street") // "street":"1 A Street", .writeNull("city") // "city":null, .write("verified", false) // "verified":false .writeEnd() // }, .writeStartArray("phone-numbers") // "phone-numbers":[ .writeStartObject() // { .write("number", "555-1111") // "number":"555-1111", .write("extension", "123") // "extension":"123" .writeEnd() // }, .writeStartObject() // { .write("number", "555-2222") // "number":"555-2222", .writeNull("extension") // "extension":null .writeEnd() // } .writeEnd() // ] .writeEnd() // } .close(); } } Output
Below is the output from running the GeneratorDemo.
{ "name":"Jane Doe", "address":{ "type":1, "street":"1 A Street", "city":null, "verified":false }, "phone-numbers":[ { "number":"555-1111", "extension":"123" }, { "number":"555-2222", "extension":null } ]} JsonParser (javax.json.stream)
Using JsonParser we will parse the output of the previous example to get the address information. JSON parser provides a depth first traversal of events corresponding to the JSON structure. Different data can be obtained from the JsonParser depending on the type of the event.
package blog.jsonp; import java.io.FileInputStream;import javax.json.Json;import javax.json.stream.JsonParser;import javax.json.stream.JsonParser.Event; public class ParserDemo { public static void main(String[] args) throws Exception { try (FileInputStream json = new FileInputStream("src/blog/jsonp/input.json")) { JsonParser jr = Json.createParser(json); Event event = null; // Advance to "address" key while(jr.hasNext()) { event = jr.next(); if(event == Event.KEY_NAME && "address".equals(jr.getString())) { event = jr.next(); break; } } // Output contents of "address" object while(event != Event.END_OBJECT) { switch(event) { case KEY_NAME: { System.out.print(jr.getString()); System.out.print(" = "); break; } case VALUE_FALSE: { System.out.println(false); break; } case VALUE_NULL: { System.out.println("null"); break; } case VALUE_NUMBER: { if(jr.isIntegralNumber()) { System.out.println(jr.getInt()); } else { System.out.println(jr.getBigDecimal()); } break; } case VALUE_STRING: { System.out.println(jr.getString()); break; } case VALUE_TRUE: { System.out.println(true); break; } default: { } } event = jr.next(); } } } } Output
Below is the output from running the ParserDemo.
type = 1street = 1 A Streetcity = nullverified = false
MOXy and the Java API for JSON Processing (JSR-353)
Mapping your JSON to domain objects is still the easiest way to interact with JSON. Now that JSR-353 is finalizing we will integrating it into MOXy’s JSON-binding. You can track our progress on this using the following link:
Source : http://www.javacodegeeks.com/2013/04/java-api-for-json-processing-jsr-353-stream-apis.html
