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 = 1 street = 1 A Street city = null verified = 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:
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