Java 如何在Jackson中反序列化嵌套的包装字符串?
我有一个JSON字符串,它包含一个嵌套和包装的JSON字符串。我想用Jackson反序列化这个,但我不确定怎么做。下面是一个示例bean:Java 如何在Jackson中反序列化嵌套的包装字符串?,java,jackson,jackson2,mongo-jackson-mapper,Java,Jackson,Jackson2,Mongo Jackson Mapper,我有一个JSON字符串,它包含一个嵌套和包装的JSON字符串。我想用Jackson反序列化这个,但我不确定怎么做。下面是一个示例bean: @JsonIgnoreProperties(ignoreUnknown = true) public class SomePerson { public final String ssn; public final String birthday; public final Address address; @JsonCr
@JsonIgnoreProperties(ignoreUnknown = true)
public class SomePerson {
public final String ssn;
public final String birthday;
public final Address address;
@JsonCreator
public SomePerson(
@JsonProperty("ssn") String ssn,
@JsonProperty("birthday") String birthday,
@JsonProperty("data") Address address,
@JsonProperty("related") List<String> related) {
this.ssn = ssn;
this.birthday = birthday;
this.address = address;
}
@JsonIgnoreProperties(ignoreUnknown = true)
public static class Address {
public final String city;
public final String country;
@JsonCreator
public Address(
@JsonProperty("city") String city,
@JsonProperty("country") String country) {
this.city = city;
this.country = country;
}
}
}
虽然我以前反序列化过nsted对象,但当对象是包装字符串时,我不知道如何进行反序列化。应该可以:
Address addObject = mapper.readValue(root.getString("address"), Address.class);
其中
root
是您的主JSONObject
当内部对象被转义JSON字符串时,我们需要“两次”反序列化它。第一次是在rootJSON对象
被反序列化时运行,第二次需要手动运行。为此,我们需要实现自定义反序列化程序,该程序实现com.fasterxml.jackson.databind.deser.ContextualDeserializer
接口。它可能是这样的:
class FromStringJsonDeserializer<T> extends StdDeserializer<T> implements ContextualDeserializer {
/**
* Required by library to instantiate base instance
* */
public FromStringJsonDeserializer() {
super(Object.class);
}
public FromStringJsonDeserializer(JavaType type) {
super(type);
}
@Override
public T deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
String value = p.getValueAsString();
return ((ObjectMapper) p.getCodec()).readValue(value, _valueType);
}
@Override
public JsonDeserializer<?> createContextual(DeserializationContext ctxt, BeanProperty property) {
return new FromStringJsonDeserializer<>(property.getType());
}
}
从现在起,您应该能够将上面的JSON
负载反序列化到您的POJO
模型
另见:
为什么“地址”在您的模型中是一个字符串?它应该是地址类型的一个实例。对不起,我的错。那是个打字错误。你看到我的答案了吗?另请看:
class FromStringJsonDeserializer<T> extends StdDeserializer<T> implements ContextualDeserializer {
/**
* Required by library to instantiate base instance
* */
public FromStringJsonDeserializer() {
super(Object.class);
}
public FromStringJsonDeserializer(JavaType type) {
super(type);
}
@Override
public T deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
String value = p.getValueAsString();
return ((ObjectMapper) p.getCodec()).readValue(value, _valueType);
}
@Override
public JsonDeserializer<?> createContextual(DeserializationContext ctxt, BeanProperty property) {
return new FromStringJsonDeserializer<>(property.getType());
}
}
@JsonDeserialize(using = FromStringJsonDeserializer.class)
public final Address address;