在Java中使用Jackson处理JSON (反)序列化中的基元联合类型

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonValue;

public class UnionTypeExample {
    private final Object value;

    @JsonCreator
    public UnionTypeExample(Object value) {
        this.value = value;
    }

    @JsonValue
    public Object getValue() {
        return value;
    }

    public static void main(String[] args) throws JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();

        // 序列化
        UnionTypeExample example1 = new UnionTypeExample(123);
        String json1 = mapper.writeValueAsString(example1);
        System.out.println(json1); // 输出: {"value":123}

        UnionTypeExample example2 = new UnionTypeExample("unknown");
        String json2 = mapper.writeValueAsString(example2);
        System.out.println(json2); // 输出: {"value":"unknown"}

        // 反序列化
        String jsonInput = "{\"value\":\"free\"}";
        UnionTypeExample deserializedExample = mapper.readValue(jsonInput, UnionTypeExample.class);
        System.out.println(deserializedExample.getValue()); // 输出: free
    }
}

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.annotation.JsonDeserialize;

import java.io.IOException;

public class UnionTypeExample {
    @JsonDeserialize(using = UnionTypeDeserializer.class)
    private final Object value;

    // 构造函数和其他方法...

    static class UnionTypeDeserializer extends JsonDeserializer<Object> {
        @Override
        public Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOException, JsonProcessingException {
            if (p.isNumber()) {
                return p.getNumberValue();
            } else {
                return p.getText();
            }
        }
    }
}