Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | JSON Pointer and JSON Patch Updates to Java API for JSON Processing Kin-man Chung Oracle Corporation September 30, 2014

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Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | Program Agenda JSON Object Model Overview JSON Pointer JSON Patch JSON Editing/Transformation JSON Query with Java SE 8 Big JSON data

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | Program Agenda JSON Object Model Overview JSON Pointer JSON Patch JSON Editing/Transformation JSON Query with Java SE 8 Big JSON data

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | JSON Object Model Overview An immutable representation of a JSON value Represented by: – JsonObject – JsonArray – JsonNumber – JsonString – Literals TRUE, FALSE, and NULL 6 JsonValue

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | JSON Object Model Overview Represents a JSON object java.util.Map Created with – JsonObjectBuilder – JsonObjectReader 7 JsonObject

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | JSON Object Model Overview Represents a JSON array java.util.List Created with – JsonArrayBuilder – JsonArrayReader 8 JsonArray

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | JSON Object Model Overview Factory class for creating JSON objects Plugin factories with service provider API includes – createObjectBuilder() – createArrayBuilder() 9 Json

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |10 [ { "name": "Duke", "gender": "M", "phone": { "areacode": "650", "number": " "} }, { "name": "Jane", ”gender": "F", "phone": { "areacode": "777", "number": " "} }, { "name": "Amy", "gender": "F", "phone": { "areacode": "505" "number": " "} } ] Example: contacts in JSON

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |11 JsonArray contacts = Json.createArrayBuilder().add(Json.createObjectBuilder().add("name", "Duke").add("gender", "M").add("phone", Json.createObjectBuilder().add("areacode", "650").add("number", " "))).add(Json.createObjectBuilder().add("name", "Jane").add("gender", "F").add("phone", Json.createObjectBuilder().add("areacode", ”777").add("number": " "))).add(Json.createObjectBuilder().add("name", “Amy").add("gender", "F").add("phone", Json.createObjectBuilder().add("areacode", "505").add("number", " "))).build(); Example: contacts in JSON object model

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | Program Agenda JSON Object Model Overview JSON Pointer JSON Patch JSON Editing/Transformation JSON Query with Java SE 8 Big JSON data

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | 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 13

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | JSON Pointer 14 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, " ");

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | JSON Pointer 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 15 Methods in JsonPointer

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | JSON Pointer 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 JsonObject containing the result – Transforms the target into the result 16 Operations in JsonPointer

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | Program Agenda JSON Object Model Overview JSON Pointer JSON Patch JSON Editing/Transformation JSON Query with Java SE 8 Big JSON data

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | 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 18

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | JSON Patch [ {"op":"replace", "path":"/1/phone", "value": { "areacode": "111", "number": " "} } {"from":"/1/phone", "path": "/2", "op":"copy"} ] 19 Example

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | JSON Patch An patch operation is a JSON object Must have an “op” field with a value of – “add”, “replace”, “remove”, “move”, “copy”, or “test” Must have a “path” field – A JSON Pointer specifying the target location Other fields depending on “op” 20 Operations

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | JSON Patch // Create the target and the patch JsonArray target = Json.createArrayBuilder().add(…).build(); JsonArray patch = Json.createArrayBuilder()….build(); // Create JsonPatch from patch JsonPatch jsonpatch = Json.createPatch(patch); // Apply the patch to the target and return the result JsonArray result = jsonpatch.apply(target); 21 Proposed API

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | Program Agenda JSON Object Model Overview JSON Pointer JSON Patch JSON Editing/Transformation JSON Query with Java SE 8 Big JSON data

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | 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 when done 23

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | JSON Editing // 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 JsonObject John = Json.createObjectBuilder()….build(); JsonArray result = builder.add(1, John).build(); 24 Proposed API

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | Program Agenda JSON Object Model Overview JSON Pointer JSON Patch JSON Editing/Transformation JSON Query with Java SE 8 Big JSON data

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | 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 Example: Output names of contacts whose gender is F 26 JsonArray contacts; contacts.getValuesAs(JsonObject.class).stream().filter(x->"F".equals(x.getString("gender"))).map(x->x.getString("name")).forEach(System.out::println);

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | JSON Query with Java SE 8 Example: Collect query results in a List 27 JsonArray contacts; List names = contacts.getValuesAs(JsonObject.class).stream().filter(x->"F".equals(x.getString("gender"))).map(x->x.getString(“name”)).collect(Collectors.toList());

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | JSON Query with Java SE 8 Java Collectors return Lists or Maps. We need collectors that returns JsonArrays or JsonObjects 28 Problem

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | JSON Query with Java SE 8 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 29 Proposed API

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | JSON Query with Java SE 8 Collect the query result in a JsonArray 30 Example JsonArray contacts; JsonArray names = contacts.getValuesAs(JsonObject.class).stream().filter(x->"F".equals(x.getString("gender"))).map(x->x.getString("name")).collect(JsonCollectors.toJsonArray());

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | JSON Query with Java SE 8 Collect the query result in a JsonObject 31 Example JsonArray contacts; JsonObject nameToPhones = contacts.getValuesAs(JsonObject.class).stream().filter(x->"F".equals(x.getString("gender"))).collect(JsonCollectors.toJsonObject( x->x.getString("name"), x->x.getJsonObject("phone"));

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | JSON Query with Java SE 8 Group the contacts by gender 32 Example JsonArray contacts; JsonObject groups = contacts.getValuesAs(JsonObject.class).stream().collect(JsonCollectors.groupBy(x->getString("gender")));

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | JSON Query with Java SE 8 Change the phone areacodes from “415” to “650” 33 Example: Putting it all together 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);

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | Program Agenda JSON Object Model Overview JSON Pointer JSON Patch JSON Editing/Transformation JSON Query with Java SE 8 Big JSON data

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | 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 35

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | Support for big JSON data Allow creation of partial JSON data in JsonParser – Add getJsonObject() at the beginning of an object – Add getJsonArray() at the beginning of an array Allow skipping values in JsonParser API for getting java.util.stream in JsonParser – Lazy evaluation, pull model – Low level: Stream of parse events – High level: Stream of JsonObject and JsonArray elements Performance matters 36

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | Summary Support for JSON Pointer and JSON Patch Add editing/transformation to JsonObject and JsonArray Add help class/method for JSON query Add support for big JSON data WARNING: The API changes are just proposals, are not final 37

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | Q & A 38

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |39