Java Jackson

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Maven

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<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-core</artifactId>
    <version>2.9.2</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.9.2</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-annotations</artifactId>
    <version>2.9.2</version>
</dependency>

Object to Json

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ObjectMapper mapper = ObjectMapper()
String value = mapper.writeValueAsString(obj)

Json to Object

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ObjectMapper mapper = new ObjectMapper();
Obj value = mapper.readValue(json_str, Obj.class);

util

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object JsonUtil {
    private val mapper = ObjectMapper()

    fun toJson(obj: Any?): String {
        return mapper.writeValueAsString(obj)
    }

    fun <T> fromJson(obj: String?, clazz: Class<T>): T? {
        return mapper.readValue(obj, clazz)
    }
}

Anotation

@JsonProperty

Error solution

Jackson with JSON: Unrecognized field, not marked as ignorable

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@JsonIgnoreProperties(ignoreUnknown = true)
data class Obj {

}

data class

非Private可以直接生成Json字段，如果添加了Private，则无法生成Json字段，即使添加@JsonProperty也无效。

BigDecimal

必须设置浮点数使用BigDecimal类型

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ObjectMapper().enable(DeserializationFeature.USE_BIG_DECIMAL_FOR_FLOATS)

JsonDeserializer

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val mapper = JsonUtil.getMapper()
var module = SimpleModule()
module.addDeserializer(Order::class.java, OrdersDeserializer())
mapper.registerModule(module)
objectMapper.registerModule(module)