Contenu connexe Similaire à JSON-B for CZJUG (20) Plus de Dmitry Kornilov (11) JSON-B for CZJUG1. Copyright © 2015, Oracle and/or its affiliates. All rights reserved.
JSONB introduction
and comparison with other frameworks
Dmitry Kornilov
JSON-B spec lead
@m0mus
Roman Grigoriadi
JSON-B RI lead engineer
@bravehorsie
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Safe Harbor Statement
The following is intended to outline our general product direction. It is intended for
information purposes only, and may not be incorporated into any contract. It is not a
commitment to deliver any material, code, or functionality, and should not be relied upon
in making purchasing decisions. The development, release, and timing of any features or
functionality described for Oracle’s products remains at the sole discretion of Oracle.
2
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Program Agenda
1. What is JSON-B
2. JSR-367 status
3. Default mapping
4. Customized mapping
5. Demo application
6. JSON-B RI
7. Q&A
4. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 4
• JSON Binding is a standard
• It’s about converting Java objects to and from JSON documents
• JSON Binding = JSON-B = JSONB = JSR 367
What is JSON Binding?
4
5. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 5
What is JSON Binding?
5
public class Customer {
public int id;
public String firstName;
public String lastName;
….
}
Customer e = new Customer();
e.id = 1;
e.firstName = “John”;
e.lastName = “Doe”;
{
"id": 1,
"firstName" : "John",
"lastName" : "Doe",
}
Java JSON
6. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 6
What is JSON Binding?
6
public class Customer {
public int id;
public String firstName;
public String lastName;
….
}
Customer e = new Customer();
e.id = 1;
e.firstName = “John”;
e.lastName = “Doe”;
{
"id": 1,
"firstName" : "John",
"lastName" : "Doe",
}
Java JSON
JSON-B
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• Genson
• Gson
• Jackson
• …
Alternatives
7
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JSON-B Standard
8
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Java Community Process
• JSR-367
• JSR status and updates
• Expert group
10. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 1010
Specification and API Project
• Hosted on java.net
• Spec in pdf format
• Git repository
• Wiki
• Bug tracker
• Mailing lists
11. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 1111
Participate!
users@jsonb-spec.java.net
12. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 1212
Reference Implementation
• eclipselink.org/jsonb
• Mirror on GitHub
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Summary
• JCP Page
https://www.jcp.org/en/jsr/detail?id=367
• Specification Project Home:
https://java.net/projects/jsonb-spec
• API sources & samples:
https://java.net/projects/jsonb-spec/sources/git/show/api
• Specification in pdf:
https://java.net/projects/jsonb-spec/sources/git/content/spec/spec.pdf
• Reference implementation:
http://eclipselink.org/jsonb
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JSON-B Default Mapping
14
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Default Mapping
• No configuration, no annotations
• The scope:
– Basic Types
– Specific JDK Types
– Dates
– Classes
– Collections/Arrays
– Enumerations
– JSON-P
import javax.json.bind.Jsonb;
import javax.json.bind.JsonbBuilder;
// Create with default config
Jsonb jsonb = JsonbBuilder.create();
16. Copyright © 2015, Oracle and/or its affiliates. All rights reserved.
• toJson(…)
• fromJson(…)
1616
JSON-B Engine
String toJson(Object object);
String toJson(Object object, Type runtimeType);
void toJson(Object object, Writer writer);
void toJson(Object object, Type runtimeType, Writer appendable);
void toJson(Object object, OutputStream stream);
void toJson(Object object, Type runtimeType, OutputStream stream);
<T> T fromJson(String str, Class<T> type);
<T> T fromJson(String str, Type runtimeType);
<T> T fromJson(Reader readable, Class<T> type);
<T> T fromJson(Reader readable, Type runtimeType);
<T> T fromJson(InputStream stream, Class<T> type);
<T> T fromJson(InputStream stream, Type runtimeType);
17. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 1717
Default Mapping – Basic Types
• java.lang.String
• java.lang.Character
• java.lang.Byte (byte)
• java.lang.Short (short)
• java.lang.Integer (int)
• java.lang.Long (long)
• java.lang.Float (float)
• java.lang.Double (double)
• java.lang.Boolean (boolean)
18. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 1818
Default Mapping – Basic Types
• java.lang.String
• java.lang.Character
• java.lang.Byte (byte)
• java.lang.Short (short)
• java.lang.Integer (int)
• java.lang.Long (long)
• java.lang.Float (float)
• java.lang.Double (double)
• java.lang.Boolean (boolean)
Serialization:
toString()
Deserialization:
parseXXX()
19. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 1919
• java.lang.String
• java.lang.Character
• java.lang.Byte (byte)
• java.lang.Short (short)
• java.lang.Integer (int)
• java.lang.Long (long)
• java.lang.Float (float)
• java.lang.Double (double)
• java.lang.Boolean (boolean)
Default Mapping – Basic Types
“string”
’u0041’
(byte) 1
(short) 1
(int) 1
1L
1.2f
1.2
true
“string”
“A”
1
1
1
1
1.2
1.2
true
20. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 2020
Default Mapping – Specific Types
• java.math.BigInteger
• java.math.BigDecimal
• java.net.URL
• java.net.URI
• java.util.Optional
• java.util.OptionalInt
• java.util.OptionalLong
• java.util.OptionalDouble
21. Copyright © 2015, Oracle and/or its affiliates. All rights reserved.
• java.math.BigInteger
• java.math.BigDecimal
• java.net.URL
• java.net.URI
• java.util.Optional
• java.util.OptionalInt
• java.util.OptionalLong
• java.util.OptionalDouble
2121
Default Mapping – Specific Types
Serialization:
toString()
Deserialization:
Single argument constructor
22. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 2222
Default Mapping – Specific Types
• java.math.BigInteger
• java.math.BigDecimal
• java.net.URL
• java.net.URI
• java.util.Optional
• java.util.OptionalInt
• java.util.OptionalLong
• java.util.OptionalDouble
Serialization:
toString()
Deserialization:
Single argument constructor
• Represented by its value if not empty
• Considered null if empty
23. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 2323
Optional Types
OptionalInt.of(1)
OptionalInt.empty()
JSON-B 1
Genson {"asInt": 1, "present": true}
Gson {”value": 1, "present": true}
Jackson 1
JSON-B null
Genson -
Gson {”value": 0, "present": false}
Jackson null
24. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 2424
Default Mapping – Dates
java.util.Date ISO_DATE_TIME
java.util.Calendar, java.util.GregorianCalendar ISO_DATE if to time information present, otherwise ISO_DATE_TIME
Java.util.TimeZone, java.util.SimpleTimeZone NormalizedCustomId (see TimeZone javadoc)
java.time.Instant ISO_INSTANT
java.time.LocalDate ISO_LOCAL_DATE
java.time.LocalTime ISO_LOCAL_TIME
java.time.LocalDateTime ISO_LOCAL_DATE_TIME
java.time.ZonedDateTime ISO_ZONED_DATE_TIME
java.time.OffsetDateTime ISO_OFFSET_DATE_TIME
java.time.OffsetTime ISO_OFFSET_TIME
java.time.ZoneId NormalizedZoneId as specified in ZoneId javadoc
java.time.ZoneOffset NormalizedZoneId as specified in ZoneOffset javadoc
java.time.Duration ISO 8601 seconds based representation
java.time.Period ISO 8601 period representation
25. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 2525
SimpleDateFormat sdf =
new SimpleDateFormat("dd.MM.yyyy");
Date date = sdf.parse("08.03.2016");
Default Mapping – Date Sample
JSON-B “2016-03-08T00:00:00”
Genson 1457391600000
Gson "Mar 8, 2016 12:00:00 AM”
Jackson 1457391600000
26. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 2626
Default Mapping – Calendar Sample
Calendar cal = Calendar.getInstance();
cal.clear();
cal.set(2016, 3, 8);
JSON-B “2016-03-08”
Genson 1457391600000
Gson {"year":2016,
"month":3,
"dayOfMonth":8,
"hourOfDay":0,
"minute":0,
"second": 0}
Jackson 1457391600000
27. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 2727
Default Mapping – Classes
• Public and protected nested and static nested classes
• Anonymous classes (serialization only)
• Inheritance is supported
• Default no-argument constructor is required for deserialization
28. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 2828
Default Mapping – Fields
• Final fields are serialized
• Static fields are skipped
• Transient fields are skipped
• Null fields are skipped
• Lexicographical order
• Parent class fields are serialized before child class fields
29. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 2929
Fields Order Comparison
class Parent {
public int parentB = 2;
public int parentA = 1;
}
class Child extends Parent {
public int childB = 4;
public int childA = 3;
}
JSON-B {"parentA":1,"parentB":2,
"childA":3, "childB":4}
Genson {"childA":3, "childB":4,
"parentA":1,"parentB":2}
Gson {"childB":4, "childA":3,
"parentB":2,"parentA":1}
Jackson {"parentB":2,"parentA":1,
"childB":4, "childA":3}
30. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 3030
Default Mapping – Scope and Field Access Strategy
Serialization
• Existing fields with public getters
• Public fields with no getters
• Public getter/setter pair without a
corresponding field
Deserialization
• Existing fields with public setters
• Public fields with no setters
• Public getter/setter pair without a
corresponding field
31. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 3131
Scope and Field Access Strategy – JSON-B
public class Foo {
public final int publicFinalField;
private final int privateFinalField;
public static int publicStaticField;
public int publicWithNoGetter;
public int publicWithPrivateGetter;
public Integer publicNullField = null;
private int privateWithNoGetter;
private int privateWithPublicGetter;
public int getNoField() {};
public void setNoField(int value) {};
}
{
"publicFinalField": 1,
"publicWithNoGetter": 1,
"privateWithPublicGetter": 1,
"noField": 1
}
32. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 3232
Scope and Field Access Strategy – Genson
public class Foo {
public final int publicFinalField;
private final int privateFinalField;
public static int publicStaticField;
public int publicWithNoGetter;
public int publicWithPrivateGetter;
public Integer publicNullField = null;
private int privateWithNoGetter;
private int privateWithPublicGetter;
public int getNoField() {};
public void setNoField(int value) {};
}
{
"publicFinalField": 1,
"publicWithNoGetter": 1,
"publicWithPrivateGetter": 1,
"publicNullField": null,
"privateWithPublicGetter": 1,
"noField": 1
}
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Scope and Field Access Strategy – Gson
public class Foo {
public final int publicFinalField;
private final int privateFinalField;
public static int publicStaticField;
public int publicWithNoGetter;
public int publicWithPrivateGetter;
public Integer publicNullField = null;
private int privateWithNoGetter;
private int privateWithPublicGetter;
public int getNoField() {};
public void setNoField(int value) {};
}
{
"publicFinalField": 1,
"privateFinalField": 1,
"publicWithNoGetter": 1,
"publicWithPrivateGetter": 1,
"privateWithNoGetter": 1,
"privateWithPublicGetter": 1,
}
34. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 3434
Scope and Field Access Strategy – Jackson
public class Foo {
public final int publicFinalField;
private final int privateFinalField;
public static int publicStaticField;
public int publicWithNoGetter;
public int publicWithPrivateGetter;
public Integer publicNullField = null;
private int privateWithNoGetter;
private int privateWithPublicGetter;
public int getNoField() {};
public void setNoField(int value) {};
}
{
"publicFinalField": 1,
"publicWithNoGetter": 1,
"publicWithPrivateGetter": 1,
"publicNullField": null,
"privateWithPublicGetter": 1,
"noField": 1
}
35. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 3535
Scope and Field Access Strategy – Summary
Framework
Respects
getters/setters
Respects
getter/setter
visibility
Not public fields Virtual fields
JSON-B Yes Yes No Yes
Genson Yes No No Yes
Gson No No Yes No
Jackson Yes No No Yes
36. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 3636
// Array
int[] intArray = {1, 2, 3};
jsonb.toJson(intArray); // [1,2,3]
// Collection
Collection<Object> list = new ArrayList<>();
list.add(1);
list.add(2);
list.add(null);
jsonb.toJson(list); // [1,2,null]
// Map
Map<String, Object> map = new LinkedHashMap<>();
map.put("first", 1);
map.put("second", 2);
jsonb.toJson(map); // {"first":1,"second":2}
Arrays/Collections
• Collection
• Map
• Set
• HashSet
• NavigableSet
• SortedSet
• TreeSet
• LinkedHashSet
• TreeHashSet
• HashMap
• NavigableMap
• SortedMap
• TreeMap
• LinkedHashMap
• TreeHashMap
• List
• ArrayList
• LinkedList
• Deque
• ArrayDeque
• Queue
• PriorityQueue
• EnumSet
• EnumMap
37. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 3737
JSON-P Types
• javax.json.JsonArray
• javax.json.JsonStructure
• javax.json.JsonValue
• javax.json.JsonPointer
• javax.json.JsonString
• javax.json.JsonNumber
38. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 3838
JSON-P Types
• javax.json.JsonArray
• javax.json.JsonStructure
• javax.json.JsonValue
• javax.json.JsonPointer
• javax.json.JsonString
• javax.json.JsonNumber
Serialization:
javax.json.JsonWriter
Deserialization:
javax.json.JsonReader
39. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 3939
JsonBuilderFactory f =
Json.createBuilderFactory(null);
JsonObject jsonObject = f.createObjectBuilder()
.add(“name", "Jason")
.add(“city", "Prague")
.build();
JSON-P Sample
{
"name": "Jason",
”city": ”Prague"
}
40. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 4040
JSON-P Types Support in Other Frameworks
• Genson:
– Support added in JSR353Bundle
• Gson
– No JSON-P support
• Jackson
– Support added in JSR353Module
41. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. |
Customized Mapping
41
42. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 4242
JSON-B Engine Configuration
JsonbConfig config = new JsonbConfig()
.withFormatting(…)
.withNullValues(…)
.withEncoding(…)
.withStrictIJSON(…)
.withPropertyNamingStrategy(…)
.withPropertyOrderStrategy(…)
.withPropertyVisibilityStrategy(…)
.withAdapters(…)
.withBinaryDataStrategy(…);
Jsonb jsonb = JsonbBuilder.newBuilder()
.withConfig(…)
.withProvider(…)
.build();
• Annotations
• Runtime configuration
– JsonbConfig
– JsonbBuilder
43. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 4343
Customizations
• Property names
• Property order
• Ignoring properties
• Null handling
• Custom instantiation
• Fields visibility
• Adapters
• Date/Number Formats
• Binary Encoding
44. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 4444
Property Name Customization
• JSON-B:
– @JsonbProperty (Field, Method)
• Genson:
– @JsonProperty (Field, Method)
– Use GensonBuilder().rename() method
• Gson:
– @SerializedName (Field)
• Jackson:
– @JsonProperty (Field, Method)
45. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 4545
Custom Mapping - Property Names
public class Customer {
public int id;
public String firstName;
}
{
"id": 1,
"firstName": "Jason"
}
46. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 4646
Custom Mapping - Property Names
public class Customer {
private int id;
@JsonbProperty("name")
private String firstName;
}
public class Customer {
public int id;
public String firstName;
@JsonbProperty("name")
public String getFirstName() {
return firstName;
}
}
{
"id": 1,
"name": "Jason"
}
47. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 4747
Custom Mapping - Property Names
public class Customer {
public int id;
public String firstName;
@JsonbProperty(“getter-name")
String getFirstName() {
return firstName;
}
@JsonbProperty(“setter-name")
void setFirstName(String str) {
this.firstName = str;
}
}
Serialization:
{
"id": 1,
“getter-name": "Jason"
}
Deserialization:
{
"id": 1,
“setter-name": "Jason"
}
48. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 4848
Property Naming Strategy
• Supported naming strategies
– IDENTITY (myMixedCaseProperty)
– LOWER_CASE_WITH_DASHES (my-mixed-case-property)
– LOWER_CASE_WITH_UNDERSCORES (my_mixed_case_property)
– UPPER_CAMEL_CASE (MyMixedCaseProperty)
– UPPER_CAMEL_CASE_WITH_SPACES (My Mixed Case Property)
– CASE_INSENSITIVE (mYmIxEdCaSePrOpErTy)
– Or a custom implementation
• JsonbConfig().withPropertyNamingStrategy(…):
49. Copyright © 2015, Oracle and/or its affiliates. All rights reserved.
• Genson
– GensonBuilder.with(PropertyNameResolver… resolvers)
• Gson:
– GsonBuilder.setFieldNamingPolicy(FieldNamingPolicy policy)
• Jackson
– ObjectMapper.setPropertyNamingStrategy(PropertyNamingStrategy pns)
4949
Property Naming Strategy
50. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 5050
Property Order Strategy
• Strategies:
– LEXICOGRAPHICAL (A-Z)
– ANY
– REVERSE (Z-A)
• Compile Time:
– @JsonbPropertyOrder on class
• Runtime:
– withPropertyOrderStrategy(…)
@JsonbPropertyOrder(ANY)
public class Foo {
public int bar2;
public int bar1;
}
51. Copyright © 2015, Oracle and/or its affiliates. All rights reserved.
• Compile Time:
– Transient modifier
– @JsonbTransient annotation
– PropertyVisibilityStrategy interface
– @JsonbVisibility annotation
• Runtime:
– withPropertyVisibilityStrategy(…)
5151
Ignoring Properties and Visibility Customization
public class Foo {
public transient int skipped;
@JsonbTransient
public int alsoSkipped;
}
@JsonbVisibility(MyStrategy.class)
public class Bar {
private int field1;
private int field2;
}
52. Copyright © 2015, Oracle and/or its affiliates. All rights reserved.
• Genson
– @JsonIgnore annotation
– Include(…) and exclude(…) methods in GensonBuilder class
• Gson:
– @Exposed annotation
– ExclusionStrategy interface
• Jackson
– @JsonIgnore annotation on field
– @JsonIgnoreProperties annotation on class
– Filters and mix-ins
5252
Ignoring Properties in Other Frameworks
53. Copyright © 2015, Oracle and/or its affiliates. All rights reserved.
• Null fields are skipped by default
• Compile Time:
– @JsonbNillable annotation
• Runtime:
– JsonbConfig().withNullValues(true)
5353
Null Handling
public class Customer {
public int id = 1;
@JsonbNillable
public String name = null;
}
54. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 5454
Null Handling in Other Frameworks
Framework
Serializes
nulls by
default
Null Handling
JSON-B No @JsonbNillable
Genson Yes GensonBuilder.setSkipNull(true)
Gson No GsonBuilder.serializeNulls()
Jackson Yes @JsonInclude(JsonInclude.Include.NON_NULL)
ObjectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
55. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 5555
Custom Instantiation
public class Customer {
public int id;
public String name;
@JsonbCreator
public static Customer getFromDb(int id) {
return CustomerDao.getByPrimaryKey(id);
}
}
public class Order {
public int id;
public Customer customer;
}
{
"id": 1,
"customer": {
"id": 2 }
}
56. Copyright © 2015, Oracle and/or its affiliates. All rights reserved.
• JAXB inspired JsonbAdapter interface
• @JsonbTypeAdapter annotation
• JsonbConfig().withAdapters(JsonbAdapter… adapters);
5656
Adapters
57. Copyright © 2015, Oracle and/or its affiliates. All rights reserved.
• Genson
– Converter interface
– JAXB adapters support with JAXBBundle
• Gson:
– TypeAdapter interface
• Jackson
– External serializers
– Mix-In annotations
5757
Adapters in Other Frameworks
58. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 5858
Date/Number Format
public class FormatTest {
public Date defaultDate;
@JsonbDateFormat("dd.MM.yyyy")
public Date formattedDate;
public BigDecimal defaultNumber;
@JsonbNumberFormat(“#0.00")
public BigDecimal formattedNumber;
}
{
“defaultDate”: “2015-07-26T23:00:00",
“formattedDate”: ”26.07.2015",
“defaultNumber": 1.2,
“formattedNumber": 1.20
}
59. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. |
Date/Number Formats in other Frameworks
• Genson
– @JsonDateFormat annotation
– GensonBuilder.setDateFormat(dateFormat)
• Gson:
– GsonBuilder.setDateFormat
• Jackson
– @JsonFormat annotation
– objectMapper.setDateFormat(myDateFormat);
60. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 6060
Binary Data Encoding
• BYTE (default)
• BASE_64
• BASE_64_URL
JsonbConfig config = new JsonbConfig()
.withBinaryDataStrategy(BinaryDataStrategy.BASE_64);
Jsonb jsonb = JsonbBuilder.create(config);
String json = jsonb.toJson(obj);
61. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 6161
I-JSON
• I-JSON (”Internet JSON”) is a restricted profile of JSON
– https://tools.ietf.org/html/draft-ietf-json-i-json-06
• JSON-B fully supports I-JSON by default with three exceptions:
– JSON Binding does not restrict the serialization of top-level JSON texts that are
neither objects nor arrays. The restriction should happen at application level.
– JSON Binding does not serialize binary data with base64url encoding.
– JSON Binding does not enforce additional restrictions on dates/times/duration.
• Configuration: withStrictIJSONSerializationCompliance
62. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. |
JSON-B RI
62
63. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. |
JSON-B Demo Application
• https://github.com/bravehorsie/jsonb-demo.git
• Client server web application
• Subject is JSON object, constructed and managed in JavaScript
• Demonstrates:
–Default and customized mappings
–@JsonbProperty annotation
–Adapters
–Virtual properties handling
64. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 6464
JSON-B Demo Model
public class Hero {
@JsonbProperty("hero_name")
private String name;
@JsonbProperty("hero_class")
private HeroClass heroClass;
@JsonbTypeAdapter(ItemsAdapter.class)
@JsonbProperty("hero_items")
private Map<ItemSlot, Item> items = new HashMap<>();
@JsonbProperty("total_strength")
public Long getTotalStrength() {
return getTotalStat("strength");
}
@JsonbProperty("total_vitality")
public Long getTotalVitality() {
return getTotalStat("vitality");
}
…
}
public class ItemSlot {
private final Long id;
// Head, Shoulders, Chest, Boots, etc.
private final String name;
}
public class Item {
// Tyrael's might, Butcher's Carver
private String name;
private List<Stat> stats;
...
}
public class Stat {
// Strength, Vitality
private String name;
private Integer value;
...
}
65. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 6565
JSON-B Demo Servlet
@Override
protected void doPost(HttpServletRequest httpRequest, HttpServletResponse httpResponse) throws ServletException, IOException {
// Unmarshall json to Request object with Hero inside.
Request request = jsonb.fromJson(httpRequest.getInputStream(), Request.class);
Hero hero = request.getHero();
// Generate combat log and loot.
CombatLog combatLog = combatEngine.generateCombatLog(hero);
combatEngine.generateLoot(hero);
// Marshall our hero back to JSON object.
jsonb.toJson(new Response(hero, combatLog), Response.class, httpResponse.getOutputStream());
}
66. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. |
JSON-B Scope and Concurrency
• Thread safe
• Optimal when instance is
created per “class model”
or per configuration.
public class MyRestWsDao {
private final Jsonb jsonb;
public MyRestWsDao() {
JsonbBuilder.create(config);
}
public Response callBusiness(Request req) {
String reqPayload = jsonb.toJson(req);
String respPayload = transport.send(reqPayload);
return jsonb.fromJson(
respPayload, Response.class);
}
}
67. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. |
Type Resolution and Generics
• There is no type info in JSON document.
• Type resolution by field / method type declaration
{ ”fileld1": ”value1", “field2": ”value2” }
jsonb.fromJson(json, Pojo.class);
public class Pojo {
private Box box;
}
68. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. |
Type Resolution and Generics
• Generic types are resolved by field bounds
// Example 1
private List<Box> boxList;
// Example 2
public class Pojo<X> {
private GenericPojo<Integer> integerGenericPojo;
}
public class GenericPojo<X> {
private List<X> x;
}
69. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. |
Type Resolution and Generics
• Generic types for root type must be passed to JSONB
• Deserialization into interfaces is not supported
(besides known types as Map, List, Set, etc..)
public class GenericBox<X> {
private List<X> xList;
private X x;
}
jsonb.fromJson(json, new GenericBox<BigDecimal>() {}.getClass());
public class IncompatibleClass {
public Serializable something;
}
70. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. |
JSON-B Adapters
• JSON-B runtime conversion of one type to another (in addition to pre-
process conversion)
• Customizing types, which you can’t modify (don’t own sources)
• Conversion is needed for just a part of domain model
• Inspired by JAXB XmlAdapter
71. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 7171
JSON-B Adapter Sample
public class User {
private Long id;
private String email;
private String userName;
private String firstName;
private String surName;
}
{
“email”: ”f.pokorny@centrum.cz",
“firstName": “Frantisek",
“id”: 123,
“userName": “frantaUser",
“surName”: ”Pokorny"
}
72. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 7272
JSON-B Adapter Sample
public class AdaptedUser {
@JsonbProperty("USER_ID")
private Long id;
}
{
“USER_ID”: 123
}
73. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 7373
JSON-B Adapter Sample
public class UserAdapter implements JsonbAdapter<User, AdaptedUser> {
@Inject
private UserService userService;
@Override
public AdaptedUser adaptToJson(User obj) throws Exception {
return new AdaptedUser(obj.getId());
}
@Override
public User adaptFromJson(AdaptedUser obj) throws Exception {
User user = userService.findById(obj.getId());
return user;
}
}
74. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 7474
JSON-B Adapter Sample
public class Hero {
...
@JsonbTypeAdapter(ItemsAdapter.class)
private Map<ItemSlot, Item> items = new HashMap<>();
...
}
public class ItemSlot {
private final Long id;
private final String name;
...
}
public class Item {
private String name;
private List<Stat> stats;
...
}
75. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. 7575
JSON-B Adapter Sample
public class ItemsAdapter implements JsonbAdapter<Map<ItemSlot, Item>, Map<String, Item>> {
@Override
public Map<String, Item> adaptToJson(Map<ItemSlot, Item> obj) throws Exception {
final Map<String, Item> result = new HashMap<>();
for (Map.Entry<ItemSlot, Item> entry : obj.entrySet()) {
result.put(entry.getKey().getName(), entry.getValue());
}
return result;
}
@Override
public Map<ItemSlot, Item> adaptFromJson(Map<String, Item> obj) throws Exception {
final Map<ItemSlot, Item> result = new HashMap<>();
for (Map.Entry<String, Item> entry : obj.entrySet()) {
ItemSlotEnum slotEnum = ItemSlotEnum.valueOf(entry.getKey());
result.put(new ItemSlot(slotEnum.getId(), slotEnum.name()), entry.getValue());
}
return result;
}
}
76. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. |
What’s Next
• Serializers / Deserializers with access to low level JSON-P API
• Polymorphism (@JsonbPolymorphic / PolymorphicAdapter)
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Participate!
users@jsonb-spec.java.net
Notes de l'éditeur Here is some legal stuff. What I will present now could be not be included in the final version of the product. So the text basically says that you shouldn't trust me. Trust no one. I will start with defining and explaining what JSON-B is.
After that we will go through JSR status and progress.
Next I will show you what is in the spec. Why do we need a standard? Native JSON Binding frameworks
Not comparing with JAXB inspired frameworks
Goal of standardizing.
Experts group OK. Now lets talk about the specification. Current state – Early Draft
Now it’s time to see what’s in the spec. We will start with default mapping.
The first question comes is what is default mapping?
JSONB engine with default mapping sample
We go though all these items later What is JSON-B engine? Lets take a look how default mapping works. Here is a list of all basic types handled by JSON-B specification. It includes all basic types and the corresponding primitives. The rules are simple: toString() method is used for serialization and the corresponding parse() method for deserialization. Here is a sample. All frameworks handle it the same way, so no comparison here. Specific types. The specific types are JDK types specified in JSON-B spec which are not basic. It includes… For Big and URL types toString() method is used for serialization the same as for basic types. For deserialization (here comes the difference) default constructor with String argument is used. Optional types were introduced in Java 8. Optional can be empty or contains a value. If it does have a value it gets represented by it. The value is processed instead of Optional type. If it’s empty it’s precessed as null. Not all frameworks handle optional types the same way. Calendar with no time Calendar with no time portion. Now lets talk about classes. The specification strictly defines what kind of classes are supported. Specification is also clear about what types of fields are supported and in which order fields are serialized. Respect getters/setters
Respect getters/setters visibility
Respect property visibility
Support virtual fields Jackson has the same results as Genson. Here is a summary table. Arrays and Collections. Here is a list of officially supported types. Sample is on the right side. Nothing much to say here. Just important to mention that null elements are not skipped here as in case of class fields and always serialized. JSON-P types. JSON-P is used by JSON-B as a parser. The following JSON-P types are supported. The rules are simple. JsonWriter from jsonp is used for serialization and JsonReader for deserialization. Here is a sample. As you see, JSON-P class is serialized as a normal Java class. There are Genson and Jackson modules to support JSON-P types. Gson doesn’t have a special JSONP types support. But it can be added by creating a custom serializer there. This is it about defaults. Now lets talk about how mapping can be customized. There are 2 types of configuration: Compile type and Runtime.
JsonbBuilder.withProvider() On this slide a summarized all customizations provided by JSONB. Other frameworks do have it as well. Some them offer much more complicated customizations. Lets quickly go throw these customizations in details. Sometimes we need to have a field name in JSON document different than in Java class. This is a common use case. JSONB offers JsonbProperty annotation to do it. Other frameworks have it the similar way but annotation is named differently. Here is a sample. We have a Customer class which serializes to this JSON document by default. We want to serialize firstName field as name. In order to do it we put JsonbProperty on firstName field with different name specified. Alternatively JsonbProperty annotation can be placed on a getter. We actually can use different property names for serialization and for deserialization as this sample shows. Strange use case, is it? Property naming strategy is a way to change property names globally. By default field is serialized with a name as it is defined in a class. If this is not a desired behavior JSONB supports 6 predefined strategies or a custom one can be created. Naming strategy is specified at runtime using withPropertyNamingStrategy of JsonbConfig class. All other frameworks have a similar feature. ANY - performance Here is how other frameworks handle ignoring properties. Different frameworks handle nulls different way. Here is a comparison table. Sometimes we need to customize a way how class instance is created. For example if class is created by a static factory method instead of a default constructor. In this case this method has to be annotated with JsonbCreator annotation and it will be called to make an instance of a class instead of a default constructor. Parameters are also supported. Take a look at the sample. Order class has a field customer. Customer class has a method annotated with JsonbCreator annotation. During unmarshalling this method is called and ‘two’ is passed as a parameter. Tokenizers, Readers All other frameworks have similar features. All of them allow you to define classes with custom logic used to control binding process. Genson actually supports JAXB annotations in JAXBBundle. Jackson has a very powerfull and simple mix-ins mechanism. Again. All other frameworks have a similar feature. If binary data is processed it has to be encoded. JSONB supports 3 types of binary encoding: byte, base_64 and base_64_url. Encoding is specified as part of runtime configuration using withBinaryDataStrategy method of JsonbConfig class. I-JSON (”Internet JSON”) is a restricted profile of JSON. It’s a standard draft.
JSON-B fully supports I-JSON by default with three exceptions:
It is possible to switch a full support mode in runtime config using withStrictIJSONSerializationCompliance method of JsonbConfig class. This is it about defaults. Now lets talk about how mapping can be customized. Deserializer doesn’t know the root type, so it must be passed
In case of generic type variables, an extension or anonymous class must be passed to Jsonb.
Considering using TypeToken which is popular in other frameworks.
If generic variable type cannot be resolved it is treated as Object – HashMap is used to populate it.
Interface and abstract types cannot be resolved by default. (with exception to known interfaces like Map/List). Supposed to be created per “class model” or configuration.
JSONP Generator/Parser instances created and closed inside JSONB each toJson / fromJson call Deserializer doesn’t know the root type, so it must be passed
In case of generic type variables, an extension or anonymous class must be passed to Jsonb.
Considering using TypeToken which is popular in other frameworks.
If generic variable type cannot be resolved it is treated as Object – HashMap is used to populate it.
Interface and abstract types cannot be resolved by default. (with exception to known interfaces like Map/List). Deserializer doesn’t know the root type, so it must be passed
In case of generic type variables, an extension or anonymous class must be passed to Jsonb.
Considering using TypeToken which is popular in other frameworks.
If generic variable type cannot be resolved it is treated as Object – HashMap is used to populate it.
Interface and abstract types cannot be resolved by default. (with exception to known interfaces like Map/List). Deserializer doesn’t know the root type, so it must be passed
In case of generic type variables, an extension or anonymous class must be passed to Jsonb.
Considering using TypeToken which is popular in other frameworks.
If generic variable type cannot be resolved it is treated as Object – HashMap is used to populate it.
Interface and abstract types cannot be resolved by default. (with exception to known interfaces like Map/List). Deserializer doesn’t know the root type, so it must be passed
In case of generic type variables, an extension or anonymous class must be passed to Jsonb.
Considering using TypeToken which is popular in other frameworks.
If generic variable type cannot be resolved it is treated as Object – HashMap is used to populate it.
Interface and abstract types cannot be resolved by default. (with exception to known interfaces like Map/List). Deserializer doesn’t know the root type, so it must be passed
In case of generic type variables, an extension or anonymous class must be passed to Jsonb.
Considering using TypeToken which is popular in other frameworks.
If generic variable type cannot be resolved it is treated as Object – HashMap is used to populate it.
Interface and abstract types cannot be resolved by default. (with exception to known interfaces like Map/List).