Updates to the java api for json processing for java ee 8

Updates to the Java API
for JSON Processing for
Java EE 8
Alex Soto & Mite Mitreski
#JSON #JAVAEE

Mite Mitreski
Software engineer

JSON-P 1.0
● JSR-353
● javax.json
○ Json, JsonReader,JsonWriter JsonString, JsonNumber...
● Implementations
○ RI in GlassFish
○ Jonzon
○ Genson
<dependency>
<groupId>org.glassfish</groupId>
<artifactId>javax.json</artifactId>
<version>1.0.4</version>
</dependency>

Agenda
● IETF RFC 7159 aka new JSON
● JsonArray and JsonObject transformations
● JSON Pointer
● JSON Patch, JSON Merge Patch
● JSON Queries
● Big JSON Processing
● Alignment with JSON-B
● Alignment with JAX-RS

RFC - 4627 - JSON - The application/json
Media Type for JavaScript Object
Notation
July 2006 JSON.org
On the 8th day, Douglas Crockford introduced JSON. And he saw that it was good.

IETF RFC 7159
The JavaScript Object Notation (JSON)
Data Interchange Format
Tim Bray - Google
2014 - Old new JSON

JSON-P 1.1
IETF RFC 7159 – New API
● Json
○ public static JsonString createValue(String value)
○ public static JsonNumber createValue(int value)
○ Similarly for long, double, BigInteger, and BigDecimal
● JsonReader
○ default JsonValue readValue()
● JsonWriter
○ default void write(JsonValue value)

JsonArray and
JsonObject
Transformations

JSON-P 1.1
● Transformation on immutable JsonArray and JsonObject
● Low level operations used in JsonPatch
● Use builder pattern
○ Create builders with initial JsonArray or JsonObject
○ Add editing operations to builders
○ Builder returns immutable JsonArray or JsonObject when done
JsonArray and JsonObject Transformations

Example : JSON array transformation
// Create the target
JsonArray target = Json.createArrayBuilder().add(…).build();
// Create a builder initialized with the target
JsonArrayBuilder builder = Json.createArrayBuilder(target);
// Operations on the array
JsonArray result = builder.add(99, "john")
.set(100, 1234)
.remove(3)
.build();

JSON Pointer
IETF RFC 6901
● String syntax for identifying a specific value
○ /author/name
○ /parents/0
● ‘/’ —> ‘~1’
● ‘~’ —> ‘~0’
● Absolute

JSON Pointer
JsonStructure beer = reader.read();
JsonPointer p = new JsonPointer("/brewery/key");
JsonValue name = p.getValue(beer);
{
"key":"guinness",
"title":"Guinness",
"brewery": {
"key": "guinness",
"title": "St. James's Gate Brewery"
}
}

JSON Pointer
● Apply operations to a pointer
○ add(JsonStructure, JsonValue)
○ replace(JsonStructure, JsonValue)
○ remove(JsonStructure)

JSON Pointer extra operations
JsonPointer p = new JsonPointer("/brewery/key");
JsonStructure bewBeer = p.replace(beer, Json.createValue("GuinnessBrewery"));
"title":"Guinness",
"brewery": {
"key": "guinness"
}
"title":"Guinness",
"brewery": {
"key": "GuinessBrewery"
}

JSON-P 1.1 JSON PATCH
● Standardise Update operation
● Sequence of modifications
○ test, remove, add, replace, move, copy
● JSON PATCH is a document
● HTTP PATCH method (application/json-patch+json)

JSON-PATCH — IETF RFC 6902
[
{"op":"replace", "path":"/brewery/key", “value”:"GuinessBrewery"},
{"op":"remove", "path": "/title"}
]
"title":"Guinness",
"brewery": {
"key": "guinness"
}
"brewery": {
"key": "GuinessBrewery"
}

JsonArrayBuilder patchExpression = Json.createArrayBuilder();
//creates operation
JsonObjectBuilder patch = Json.createObjectBuilder()
.add("op", "replace")
.add("path", "/brewery/key")
.add("value", “GuinessBrewery");
patchExpression.add(patch);
JsonPatch jsonPatch = new JsonPatch(patchExpression.build());
JsonStructure newBeer = jsonPatch.apply(beer);

JsonPatchBuilder patchBuilder = new JsonPatchBuilder();
JsonStructure newBeer = patchBuilder
.replace("/brewery/key", "GuinessBrewery")
.remove("/title")
.apply(commit);

JSON-PATCH — extra operations
● Diff between two documents
○ Reverse operation
● Useful in case of conflicts

JSON-PATCH — extra operations
JsonArray diff = JsonPatch.diff(beer1, beer2);
[
{"op":"replace", "path":"/brewery/key", “value”:"GuinessBrewery"},
{"op":"remove", "path": "/title"}
]

JSON Merge Patch
IETF RFC 7386

JSON Merge patch
● Standardise Update operation
● Syntax that closely mimics the document being modified
● null value to delete
● JSON PATCH is a document
● HTTP PATCH method (application/json-patch+json)

JSON Merge patch
"title":"Guinness",
"brewery": {
"key": "guinness"
}
{"title":null}
"brewery": {
"key": "guinness"
}

JSON Merge patch
JsonObject removeTitle = Json.createObjectBuilder()
.add("title", JsonValue.NULL)
.build();
JsonValue newBeer = JsonMergePatch.mergePatch(beer, removeTitle);

JSON Merge patch
● Diff between two documents
○ Reverse operation
● Useful in case of conflicts

JSON Merge patch
JsonValue diff = JsonMergePatch.diff(beer, newBeer);
{"title": null}

JSON Queries
Working with java.util.Stream

JSON queries
● 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
● We need collectors that return JsonArray or JsonObject
instead of List or Map.

JSON queries
● toJsonArray
○ Accumulates values in a JsonArray
● toJsonObject
○ Accumulates values in a JsonObject
● groupBy
○ Implements “group by” operations on the values

BIG JSON Data
JSON processing of large objects

JSON-P 1.1 Big JSON
● Too big to build data model in memory
● Dynamically generated JSON
● Usually interested only small fraction of data

JSON-P 1.1 Big JSON
● JsonParser parses JSON using streaming model
● Pull model, under user control
● Efficient in execution and memory usage
● Low level, token based

JSON-P 1.1 Big JSON
● skipArray
○ Skip tokens and advance the parser to END_ARRAY
● skipObject
○ Skip tokens and advance the parser to END_OBJECT

Alignment
with JSON-B and JAX-RS

JSON-B
● API to marshal/unmarshal Java objects to/from JSON
● From best practices of existing JSON binders
a. Gson, Jackson, Johnzon, ...
● Implementations compete on common ground
● MUST support binding of the JSON Processing API

JSON-B
Jsonb jsonb = JsonbBuilder.create();
// Unmarshal
Book book = jsonb.fromJson(new File(“book.json”), Book.class);
// Marshal
jsonb.toJson(book, new File(“book.json”));

JAX-RS
@Patch
@Consumes(MediaType.APPLICATION_JSON_PATCH)
public Response updateBook(..., JsonPatch patch){}
● integration with JSON-B
● Integration with JSON-P PATCH

JSON-P 1.1 Current status
● Early Draft Review
○ http://download.oracle.com/otndocs/jcp/json_p-1_1-edr-spec/index.html
● Roadmap
○ Q1 2016 Public Review
○ Q3 2016 Proposed Final Draft
○ H1 2017 Final Release

JSON-P 1.1 Expert Group
● Public Project Page
○ https://java.net/projects/json-processing-spec
● Public Communications
○ https://java.net/projects/json-processing-spec/lists
● Issue Tracking
○ https://java.net/jira/browse/JSON_PROCESSING_SPEC

JSON-P 1.1 Reference Implementation
● Public Project Page
○ https://java.net/projects/jsonp
○ https://jsonp.java.net/
● Source Code Repository
○ git://java.net/jsonp~git
○ https://github.com/json-processing-inofficial
● Issue Tracking
○ https://java.net/jira/browse/JSONP

QUESTIONS ?
● Alex Soto
○ @alexsotob
● Mite Mitreski
○ @mitemitreski

Updates to the java api for json processing for java ee 8

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