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JSON Pointer and JSON Patch

JSON Pointer and JSON Patch. U pdates to Java API for JSON Processing. Kin-man Chung Oracle Corporation September 30, 2014. Program Agenda. 1. 2. 3. 4. 5. 6. JSON-P API Overview JSON Pointer JSON Patch JSON Editing/Transformation JSON Query with Java SE 8 Big JSON data.

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JSON Pointer and JSON Patch

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  1. JSON Pointer and JSON Patch Updates to Java API for JSON Processing Kin-man Chung Oracle Corporation September 30, 2014

  2. Program Agenda 1 2 3 4 5 6 JSON-P API Overview JSON Pointer JSON Patch JSON Editing/Transformation JSON Query with Java SE 8 Big JSON data

  3. Program Agenda 1 2 3 4 5 6 JSON-P Overview JSON Pointer JSON Patch JSON Editing/Transformation JSON Query with Java SE 8 Big JSON data

  4. JSON Object Model Overview JsonValue • An immutable representation of a JSON value • Represented by: • JsonObject • JsonArray • JsonNumber • JsonString • Literals • TRUE, FALSE, and NULL

  5. JSON Object Model Overview JsonObject • Represents a JSON object • java.util.Map<String, JsonValue> • Created with • JsonObjectBuilder • JsonObjectReader

  6. JSON Object Model Overview JsonArray • Represents a JSON array • java.util.List<JsonValue> • Created with • JsonArrayBuilder • JsonArrayReader

  7. JSON Object Model Overview Json • Factory class for creating JSON data • Plugin factories with service provider • API includes • createObjectBuilder() • createArrayBuilder()

  8. Example: contacts in JSON [ { "name": "Duke", "gender": "M", "phone": { "areacode": "650", "number": "234-5678"} }, { "name": "Jane", ”gender": "F", "phone": { "areacode": "777", "number": "999-5555"} }, { "name": "Amy", "gender": "F", "phone": { "areacode": "505" "number": "333-4444"} } ]

  9. Example: contacts in JSON object model JsonArray contacts = Json.createArrayBuilder() .add(Json.createObjectBuilder() .add("name", "Duke") .add("gender", "M") .add("phone", Json.createObjectBuilder() .add("areacode", "650") .add("number", "234-5678"))) .add(Json.createObjectBuilder() .add("name", "Jane") .add("gender", "F") .add("phone", Json.createObjectBuilder() .add("areacode", ”777") .add("number": "999-5555"))) .add(Json.createObjectBuilder() .add("name", “Amy") .add("gender", "F") .add("phone", Json.createObjectBuilder() .add("areacode", "505") .add("number", "333-4444"))) .build();

  10. Example: contacts in JSON object model JsonArray contacts = Json.createArrayBuilder() .add(Json.createObjectBuilder() .add("name", "Duke") .add("gender", "M") .add("phone", Json.createObjectBuilder() .add("areacode", "650") .add("number", "234-5678"))) .add(Json.createObjectBuilder() .add("name", "Jane") .add("gender", "F") .add("phone", Json.createObjectBuilder() .add("areacode", ”777") .add("number": "999-5555"))) .add(Json.createObjectBuilder() .add("name", “Amy") .add("gender", "F") .add("phone", Json.createObjectBuilder() .add("areacode", "505") .add("number", "333-4444"))) .build();

  11. Example: contacts in JSON object model JsonArray contacts = Json.createArrayBuilder() .add(Json.createObjectBuilder() .add("name", "Duke") .add("gender", "M") .add("phone", Json.createObjectBuilder() .add("areacode", "650") .add("number", "234-5678"))) .add(Json.createObjectBuilder() .add("name", "Jane") .add("gender", "F") .add("phone", Json.createObjectBuilder() .add("areacode", ”777") .add("number": "999-5555"))) .add(Json.createObjectBuilder() .add("name", “Amy") .add("gender", "F") .add("phone", Json.createObjectBuilder() .add("areacode", "505") .add("number", "333-4444"))) .build();

  12. JSON Streaming Model Overview JsonParser • Produces stream of parser events • Parser events • START_OBJECT, END_OBJECT, START_ARRAY, END_ARRAY • KEY_NAME, VALUE_STRING, VALUE_NUMBER • VALUE_TRUE, VALUE_FALSE, VALUE_NULL • Low level • Pull • Application controls accessing and advancing parser events • Suitable for processing big JSON data

  13. JSON Streaming API Example: create a JsonArray JsonArrayBuilderarrayBuilder; JsonParserparser = Json.createParser(. . .); while (parser.hasNext()) { JsonParser.Eventevent = parser.next(); switch(event) { case START_ARRAY: arrayBuilder = Json.createArrayBuilder(); break; case VALUE_STRING: arrayBuilder.add(parser.getString()); break; case END_ARRAY: // do something with the array process(arrayBuilder.build()); break; case START_OBJECT: . . . } }

  14. Program Agenda 1 2 3 4 5 6 JSON-P API Overview JSON Pointer JSON Patch JSON Editing/Transformation JSON Query with Java SE 8 Big JSON data

  15. JSON Pointer • Specified in RFC 6901 • A string syntax for referencing a JSON value • Example • /0/phone/number • refers to the phone number of first person in the contacts

  16. JSON Pointer Proposed API JsonArray contacts = Json.createArrayBuilder().add(…).build(); // Create a JsonPointer JsonPointer p = Json.createPointer("/0/phone/number"); // Get the value at the referenced location in the target JsonValue v = p.getValue(contacts); // Replace a value at the referenced location, returning a new array // with the change JsonArray result = p.replace(contacts, "123-4567");

  17. JSON Pointer Methods in JsonPointer • getValue • Get the value at the referenced location • add • Add/insert a value at the referenced location • replace • Replace a value at the referenced location • remove • Remove a value at the referenced location

  18. JSON Pointer Operations in JsonPointer • An operation is applied to a JsonArray or JsonObject • Operations do not modify the target JsonArray or JsonObject • Operation add, replace, or remove returns a new JsonArray or JsonObjectcontaining the result • Transforms the target into the result

  19. Program Agenda 1 2 3 4 5 6 JSON-P API Overview JSON Pointer JSON Patch JSON Editing/Transformation JSON Query with Java SE 8 Big JSON data

  20. JSON Patch • Specified in RFC 6902 • Sequence of operations for modifying a JSON document • Operations specified in a JSON array • Suitable for use in http PATCH method

  21. JSON Patch Example [ {"op":"replace", "path":"/1/phone", "value": { "areacode": "111", "number": "222-3333"} } {"from":"/1/phone", "path": "/2", "op":"copy"} ]

  22. JSON Patch Operations • A JSON patch is an array of operations • An patch operation is a JSON object • Each operation must have an “op” field with a value of • “add”, “replace”, “remove”, “move”, “copy”, or “test” • Each operation must have a “path” field • A JSON Pointer specifying the target location • Other fields depending on “op”

  23. JSON Patch Proposed API // Create the target and the patch JsonArray target = Json.createArrayBuilder().add(…).build(); JsonArray patch = Json.createArrayBuilder()… .build(); // Create JsonPatch from patch JsonPatchjsonpatch= Json.createPatch(patch); // Apply the patch to the target and return the result JsonArray result = jsonpatch.apply(target);

  24. Program Agenda 1 2 3 4 5 6 JSON-P API Overview JSON Pointer JSON Patch JSON Editing/Transformation JSON Query with Java SE 8 Big JSON data

  25. JSON Editing/Transformation • A JSON Patch transforms a JSON target to a JSON result • Propose adding capability to edit a JsonArray or JsonObject • Use builder pattern: • Create builders with initial JsonArray or JsonObject • Add to ObjectBuilder • remove(name) • Add to ArrayBuilder • add(index, value), set(index, value), remove(index) • Builder returns immutable JsonArray or JsonObject from build()

  26. JSON Editing Proposed API // Create the target JsonArray target = Json.createArrayBuilder().add(…).build(); // Create a builder initialized with the target JsonArrayBuilder builder = Json.createArrayBuilder(target); // Creates a new object and insert it into the array JsonObjectjohn = Json.createObjectBuilder()… .build(); JsonArray result = builder.add(1, john) .build();

  27. Program Agenda 1 2 3 4 5 6 JSON=P API Overview JSON Pointer JSON Patch JSON Editing/Transformation JSON Query with Java SE 8 Big JSON data

  28. JSON Query with Java SE 8 • A JsonObject is a Map, and a JsonArray is a List, so queries can be implemented with Java’s stream operations, using Lambda expressions • Get concurrent processing for free • Example: Output names of contacts whose gender is F JsonArray contacts; contacts.getValuesAs(JsonObject.class).stream() .filter(x->"F".equals(x.getString("gender"))) .map(x->x.getString("name")) .forEach(System.out::println);

  29. JSON Query with Java SE 8 • Example: Collect query results in a List JsonArray contacts; List<String> names = contacts.getValuesAs(JsonObject.class).stream() .filter(x->"F".equals(x.getString("gender"))) .map(x->x.getString(“name”)) .collect(Collectors.toList());

  30. JSON Query with Java SE 8 Problem • Java Collectors return Lists or Maps. • We need collectors that return JsonArrays or JsonObjects

  31. JSON Query with Java SE 8 Proposed API • New helper class JsonCollectors that construct Collectors for JSON objects or arrays • toJsonArray: • Accumulates values in a JsonArray • toJsonObject: • Accumulates values in a JsonObject • groupBy • Implements “group by” operations on the values

  32. JSON Query with Java SE 8 Example • Collect the query result in a JsonArray JsonArray contacts; JsonArray names = contacts.getValuesAs(JsonObject.class).stream() .filter(x->"F".equals(x.getString("gender"))) .map(x->x.getString("name")) .collect(JsonCollectors.toJsonArray());

  33. JSON Query with Java SE 8 Example • Collect the query result in a JsonObject JsonArray contacts; JsonObjectnameToPhones = contacts.getValuesAs(JsonObject.class).stream() .filter(x->"F".equals(x.getString("gender"))) .collect(JsonCollectors.toJsonObject( x->x.getString("name"), x->x.getJsonObject("phone"));

  34. JSON Query with Java SE 8 Example • Group the contacts by gender JsonArray contacts; JsonObject groups = contacts.getValuesAs(JsonObject.class).stream() .collect(JsonCollectors.groupBy(x->getString("gender")));

  35. JSON Query with Java SE 8 Example: Putting it all together • Change the phone areacodes from “415” to “650” Static int index = -1; JsonArray patch =contacts.getValuesAs(JsonObject.class).stream() .peek(x->index++) .filter(x->x.getObject("phone").getString("areacode").equals("415")) .map(Json.createObjectBuilder() .add("op", "replace") .add("path", "/"+index+"/phone/areacode") .add("value", “650”) .build()) .collect(JsonCollectors.toJsonArray()); JsonArray result = Json.createPatch(patch).apply(contacts);

  36. Program Agenda 1 2 3 4 5 6 JSON-P API Overview JSON Pointer JSON Patch JSON Editing/Transformation JSON Query with Java SE 8 Big JSON data

  37. Support for big JSON data • Big JSON data • Cannot fit in memory • Generated dynamically • Potentially infinite • We already have a stream model, suitable for processing big data • Add API to make it more useful

  38. Support for big JSON data • Creating partial JSON data in JsonParser • Create an object at START_OBJECT • Create an array at START_ARRAY • Skipping values in JsonParser • Skip enclosing array • Skip enclosing object • Skip long string

  39. Support for big JSON data • Creating java.util.stream in JsonParser • For processing or querying of the created object or array • Create stream when creating objects or arrays • Lazy evaluation, as needed • Get optimization hints from the operation • Filter or short-circuit operations trigger skipping • Seamless integration with JsonParser event stream

  40. Summary • Support for JSON Pointer and JSON Patch • Add editing/transformations to JsonObject and JsonArray • Add helper classes/methods for JSON query • Add support for big JSON data • WARNING: The API changes are just proposals, are not final

  41. Status • Proposed JSR to be submitted • Watch https://www.jcp.org for announcement • Roadmap • Expert Group formed: 2014 • Public Review Draft: 2015 • Proposed Final Draft: 2015 • Final Release: 2016

  42. Reference Info • Questions and comments • users@json-processing-spec.java.net • Interested to join Expert Group • Nominate yourself at new JSR page (when approved) • Personal contact • kinman.chung@oracle.com

  43. Q & A

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