20221116 ObjectMapper

概述

com.fasterxml.jackson.databind.ObjectMapper

门面类，提供几乎所有的 JSON 操作方法

databind 模块中的类

线程安全，前提是不修改对象映射器的配置

公共方法

模块（Module）

Module registration, discovery

  • registerModule

  • registerModules

  • getRegisteredModuleIds

  • findModules

  • findAndRegisterModules

创建 JsonGenerator 工厂方法

Factory methods for creating JsonGenerators

  • createGenerator

创建 JsonParser 工厂方法

Factory methods for creating JsonParsers

  • createParser

  • createNonBlockingByteArrayParser

配置：对象访问

Configuration: main config object access

  • getSerializationConfig

  • getDeserializationConfig

  • getDeserializationContext

配置：序列化、反序列化工厂

Configuration: ser/deser factory, provider access

  • setSerializerFactory

  • getSerializerFactory

  • setSerializerProvider

  • getSerializerProvider

  • getSerializerProviderInstance

配置：混合注解

Configuration: mix-in annotations

  • setMixIns

  • addMixIn

  • setMixInResolver

  • findMixInClassFor

  • mixInCount

配置：自省

Configuration, introspection

  • getVisibilityChecker

  • setVisibility

  • setVisibility

  • getSubtypeResolver

  • setSubtypeResolver

  • setAnnotationIntrospector

  • setAnnotationIntrospectors

  • setPropertyNamingStrategy

  • getPropertyNamingStrategy

  • setAccessorNaming

  • setDefaultPrettyPrinter

  • setPolymorphicTypeValidator

  • getPolymorphicTypeValidator

配置：全局默认配置

Configuration: global-default/per-type override settings

  • setSerializationInclusion

  • setDefaultPropertyInclusion

  • setDefaultSetterInfo

  • setDefaultVisibility

  • setDefaultMergeable

  • setDefaultLeniency

子类型注册

Subtype registration

  • registerSubtypes

默认类型

Default typing (automatic polymorphic types): current (2.10)

  • activateDefaultTyping

  • activateDefaultTypingAsProperty

  • deactivateDefaultTyping

  • setDefaultTyping

配置：强制配置

Configuration, config, coercion overrides

  • configOverride

  • coercionConfigDefaults

  • coercionConfigFor

配置：基本类型处理

Configuration, basic type handling

  • getTypeFactory

  • setTypeFactory

  • constructType

配置：反序列化

Configuration, deserialization

  • getNodeFactory

  • setNodeFactory

  • setConstructorDetector

  • addHandler

  • clearProblemHandlers

  • setConfig

配置：序列化

Configuration, serialization

  • setFilters

  • setFilterProvider

  • setBase64Variant

  • setConfig

配置：其他

Configuration, other

  • tokenStreamFactory

  • getFactory

  • setDateFormat

  • getDateFormat

  • setHandlerInstantiator

  • setInjectableValues

  • getInjectableValues

  • setLocale

  • setTimeZone

  • setDefaultAttributes

配置：简单特征 Feature

Configuration, simple features:

MapperFeature、SerializationFeature、DeserializationFeature、JsonParser.Feature、JsonGenerator.Feature、JsonFactory.Feature、StreamReadFeature、StreamWriteFeature

  • isEnabled

  • configure

  • enable

  • disable

公共 API （来自 ObjectCodec ）：反序列化

Public API (from ObjectCodec): deserialization

(mapping from JSON to Java types); main methods

  • readValue

公共 API （不在 ObjectCodec ）：反序列化

Public API not included in ObjectCodec: deserialization

(mapping from JSON to Java types)

  • readTree

公共 API （来自 ObjectCodec ）：序列化

Public API (from ObjectCodec): serialization

(mapping from Java types to Json)

  • writeValue

公共 API（来自 TreeCodec）：树模型支持

Public API (from TreeCodec via ObjectCodec): Tree Model support

  • writeTree

  • createObjectNode

  • createArrayNode

  • missingNode

  • nullNode

  • treeAsTokens

  • treeToValue

  • valueToTree

扩展公共 API：存取器

Extended Public API, accessors

  • canSerialize

  • canDeserialize

扩展公共 API：反序列化

Extended Public API, deserialization,

convenience methods

  • readValue

扩展公共 API：序列化

Extended Public API: serialization

(mapping from Java types to JSON)

  • writeValue

  • writeValueAsString

  • writeValueAsBytes

扩展公共 API：构造 ObjectWriter

Extended Public API: constructing ObjectWriters

for more advanced configuration

  • writer

  • writerWithView

  • writerFor

  • writerWithDefaultPrettyPrinter

扩展公共 API：构造 ObjectReader

Extended Public API: constructing ObjectReaders

for more advanced configuration

  • reader

  • readerForUpdating

  • readerFor

  • readerForArrayOf

  • readerForListOf

  • readerForMapOf

  • readerWithView

扩展公共 API：便捷类型转换

Extended Public API: convenience type conversion

  • convertValue

  • updateValue

扩展公共 API：JSON Schema 生成

  • acceptJsonFormatVisitor

基本用法

ObjectMapper 相关方法：

  • readValue

  • writeValue

转对象

// 序列化
String jsonString = objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(user);
System.out.println(jsonString);

// 反序列化
user = objectMapper.readValue(jsonString, User.class);
System.out.println(user);

/*
    {
      "name" : "张三",
      "age" : 18,
      "birthDate" : 949494020000,
      "likes" : [ "sing", "dance", "read" ]
    }
    User(name=张三, age=18, birthDate=Wed Feb 02 20:20:20 CST 2000, likes=[sing, dance, read])
*/

转对象 List

List<User> userList = CollUtil.toList(getUser(), getUser());

String jsonStr = objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(userList);
System.out.println(jsonStr);

List<User> users = objectMapper.readValue(jsonStr, new TypeReference<List<User>>() {
});
System.out.println(users);

/*
[ {
    "name" : "张三",
    "age" : 18,
    "birthDate" : 949494020000,
    "likes" : [ "sing", "dance", "read" ]
}, {
    "name" : "张三",
    "age" : 18,
    "birthDate" : 949494020000,
    "likes" : [ "sing", "dance", "read" ]
} ]
[User(name=张三, age=18, birthDate=Wed Feb 02 20:20:20 CST 2000, likes=[sing, dance, read]), User(name=张三, age=18, birthDate=Wed Feb 02 20:20:20 CST 2000, likes=[sing, dance, read])]
*/

转 Map

Map<String, User> userMap = MapUtil.ofEntries(MapUtil.entry("1", getUser()), MapUtil.entry("2", getUser()));
String jsonStr = objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(userMap);
System.out.println(jsonStr);

Map<String, User> map = objectMapper.readValue(jsonStr, new TypeReference<Map<String, User>>() {
});
System.out.println(map);
/*
    {
      "1" : {
        "name" : "张三",
        "age" : 18,
        "birthDate" : 949494020000,
        "likes" : [ "sing", "dance", "read" ]
      },
      "2" : {
        "name" : "张三",
        "age" : 18,
        "birthDate" : 949494020000,
        "likes" : [ "sing", "dance", "read" ]
      }
    }
    {1=User(name=张三, age=18, birthDate=Wed Feb 02 20:20:20 CST 2000, likes=[sing, dance, read]), 2=User(name=张三, age=18, birthDate=Wed Feb 02 20:20:20 CST 2000, likes=[sing, dance, read])}
 */

常用方法

时间格式设置

  • setDateFormat

  • getDateFormat

objectMapper.setDateFormat(DateUtil.newSimpleFormat(DatePattern.NORM_DATETIME_PATTERN));

配置 Feature

  • isEnabled

  • configure

  • enable

  • disable

// 按字母表顺序序列化字段（若false，按字段声明的顺序）
boolean enabled = objectMapper.isEnabled(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY);
objectMapper.enable(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY);

读写 JSON

  • readValue

  • writeValue

  • writeValueAsString

参考【基本用法】

树模型

  • readTree

  • writeTree

ObjectReader 和 ObjectWriter

  • 不可变对象，更轻量，可重用，如果需要多次创建对象，应该使用这两个类

  • 可以通过 ObjectMapper 的工厂方法创建，也可以通过构造器创建

  • 具有和 ObjectMapper 相同的常用方法

SerializationConfig 、DeserializationConfig

ObjectMapper 属性

protected SerializationConfig _serializationConfig;
protected DeserializationConfig _deserializationConfig;

关联 SerializationFeature 和 DeserializationFeature

JsonSerializer 和 JsonDeserializer

ObjectMapper 属性

protected DefaultSerializerProvider _serializerProvider;
protected SerializerFactory _serializerFactory;

protected DeserializationConfig _deserializationConfig;
protected DefaultDeserializationContext _deserializationContext;

配合 @JsonSerialize 和 @JsonDeserialize 一起使用

JsonMapper

com.fasterxml.jackson.databind.json.JsonMapper

ObjectMapper 的子类

从 2.10 版本开始出现

处理 JSON 时，更应该使用 JsonMapper ，就像处理 XML 时，使用 XmlMapper

目前和 ObjectMapper 在功能上几乎没有区别

推测是在未来的定位上，ObjectMapper 将作为基类，而在实际处理不同数据格式时，选用不同的实现

证据包括对 Feature 的处理上，JsonReadFeature 、JsonWriteFeature 、StreamReadFeature 、StreamWriteFeature 这四个细分的 Feature 也是从 2.10 版本开始出现，为了取代 JsonParser.Feature 、JsonGenerator.Feature

支持 Builder 模式创建对象

配置 Feature

支持 JsonReadFeature 、JsonWriteFeature

posted @ 2022-11-21 16:03  流星<。)#)))≦  阅读(365)  评论(0)  编辑  收藏  举报