JSON

Spring Boot 提供与三个 JSON 映射库的集成：spring-doc.cadn.net.cn

Jackson

提供了 Jackson 的自动配置，Jackson 是spring-boot-starter-json. 当Jackson在班级路径上时，ObjectMapperbean 是自动配置的。提供了多个配置属性，用于自定义 ObjectMapper.spring-doc.cadn.net.cn

自定义序列化器和解串化器

如果您使用 Jackson 序列化和反序列化 JSON 数据，您可能需要编写自己的 JSON 数据JsonSerializer和JsonDeserializer类。自定义序列化器通常通过模块向 Jackson 注册，但 Spring Boot 提供了另一种选择@JsonComponent注释，使直接注册 Spring Bean 变得更加容易。spring-doc.cadn.net.cn

您可以使用@JsonComponent注释直接JsonSerializer,JsonDeserializer或KeyDeserializer实现。您还可以在包含序列化程序/反序列化程序作为内部类的类上使用它，如以下示例所示：spring-doc.cadn.net.cn

Javaspring-doc.cadn.net.cn
Kotlinspring-doc.cadn.net.cn

import java.io.IOException;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.ObjectCodec;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;

import org.springframework.boot.jackson.JsonComponent;

@JsonComponent
public class MyJsonComponent {

	public static class Serializer extends JsonSerializer<MyObject> {

		@Override
		public void serialize(MyObject value, JsonGenerator jgen, SerializerProvider serializers) throws IOException {
			jgen.writeStartObject();
			jgen.writeStringField("name", value.getName());
			jgen.writeNumberField("age", value.getAge());
			jgen.writeEndObject();
		}

	}

	public static class Deserializer extends JsonDeserializer<MyObject> {

		@Override
		public MyObject deserialize(JsonParser jsonParser, DeserializationContext ctxt) throws IOException {
			ObjectCodec codec = jsonParser.getCodec();
			JsonNode tree = codec.readTree(jsonParser);
			String name = tree.get("name").textValue();
			int age = tree.get("age").intValue();
			return new MyObject(name, age);
		}

	}

}

import com.fasterxml.jackson.core.JsonGenerator
import com.fasterxml.jackson.core.JsonParser
import com.fasterxml.jackson.core.JsonProcessingException
import com.fasterxml.jackson.databind.DeserializationContext
import com.fasterxml.jackson.databind.JsonDeserializer
import com.fasterxml.jackson.databind.JsonNode
import com.fasterxml.jackson.databind.JsonSerializer
import com.fasterxml.jackson.databind.SerializerProvider
import org.springframework.boot.jackson.JsonComponent
import java.io.IOException

@JsonComponent
class MyJsonComponent {

	class Serializer : JsonSerializer<MyObject>() {
		@Throws(IOException::class)
		override fun serialize(value: MyObject, jgen: JsonGenerator, serializers: SerializerProvider) {
			jgen.writeStartObject()
			jgen.writeStringField("name", value.name)
			jgen.writeNumberField("age", value.age)
			jgen.writeEndObject()
		}
	}

	class Deserializer : JsonDeserializer<MyObject>() {
		@Throws(IOException::class, JsonProcessingException::class)
		override fun deserialize(jsonParser: JsonParser, ctxt: DeserializationContext): MyObject {
			val codec = jsonParser.codec
			val tree = codec.readTree<JsonNode>(jsonParser)
			val name = tree["name"].textValue()
			val age = tree["age"].intValue()
			return MyObject(name, age)
		}
	}

}

都@JsonComponentbean 中的ApplicationContext自动在Jackson注册。因为@JsonComponent元注释为@Component，则适用通常的组件扫描规则。spring-doc.cadn.net.cn

Spring Boot 还提供了JsonObjectSerializer和JsonObjectDeserializer基类，在序列化对象时为标准 Jackson 版本提供有用的替代方法。看JsonObjectSerializer和JsonObjectDeserializer在 API 文档中了解详细信息。spring-doc.cadn.net.cn

上面的示例可以重写为JsonObjectSerializer和JsonObjectDeserializer如下：spring-doc.cadn.net.cn

Javaspring-doc.cadn.net.cn
Kotlinspring-doc.cadn.net.cn

import java.io.IOException;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.ObjectCodec;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.SerializerProvider;

import org.springframework.boot.jackson.JsonComponent;
import org.springframework.boot.jackson.JsonObjectDeserializer;
import org.springframework.boot.jackson.JsonObjectSerializer;

@JsonComponent
public class MyJsonComponent {

	public static class Serializer extends JsonObjectSerializer<MyObject> {

		@Override
		protected void serializeObject(MyObject value, JsonGenerator jgen, SerializerProvider provider)
				throws IOException {
			jgen.writeStringField("name", value.getName());
			jgen.writeNumberField("age", value.getAge());
		}

	}

	public static class Deserializer extends JsonObjectDeserializer<MyObject> {

		@Override
		protected MyObject deserializeObject(JsonParser jsonParser, DeserializationContext context, ObjectCodec codec,
				JsonNode tree) throws IOException {
			String name = nullSafeValue(tree.get("name"), String.class);
			int age = nullSafeValue(tree.get("age"), Integer.class);
			return new MyObject(name, age);
		}

	}

}

import com.fasterxml.jackson.core.JsonGenerator
import com.fasterxml.jackson.core.JsonParser
import com.fasterxml.jackson.core.ObjectCodec
import com.fasterxml.jackson.databind.DeserializationContext
import com.fasterxml.jackson.databind.JsonNode
import com.fasterxml.jackson.databind.SerializerProvider
import org.springframework.boot.jackson.JsonComponent
import org.springframework.boot.jackson.JsonObjectDeserializer
import org.springframework.boot.jackson.JsonObjectSerializer
import java.io.IOException

@JsonComponent
class MyJsonComponent {

	class Serializer : JsonObjectSerializer<MyObject>() {
		@Throws(IOException::class)
		override fun serializeObject(value: MyObject, jgen: JsonGenerator, provider: SerializerProvider) {
			jgen.writeStringField("name", value.name)
			jgen.writeNumberField("age", value.age)
		}
	}

	class Deserializer : JsonObjectDeserializer<MyObject>() {
		@Throws(IOException::class)
		override fun deserializeObject(jsonParser: JsonParser, context: DeserializationContext,
				codec: ObjectCodec, tree: JsonNode): MyObject {
			val name = nullSafeValue(tree["name"], String::class.java)
			val age = nullSafeValue(tree["age"], Int::class.java)
			return MyObject(name, age)
		}
	}

}

混合

Jackson 支持混合，可用于将其他注释混合到目标类上已声明的注释中。 Spring Boot 的 Jackson 自动配置将扫描应用程序的包以查找带有@JsonMixin并将它们注册到自动配置的ObjectMapper. 注册由 Spring Boot 的JsonMixinModule.spring-doc.cadn.net.cn

格森

提供 Gson 的自动配置。当 Gson 在类路径上时Gsonbean 是自动配置的。几个spring.gson.*提供了用于自定义配置的配置属性。要获得更多控制权，请GsonBuilderCustomizer可以使用豆子。spring-doc.cadn.net.cn

JSON-B

提供 JSON-B 的自动配置。当 JSON-B API 和实现位于类路径上时，aJsonbbean 将被自动配置。首选的 JSON-B 实现是 Eclipse Yasson，它提供了依赖管理。spring-doc.cadn.net.cn