让 Jackson 在任何地方都使用自定义反序列化程序（对于不是我的类型）

json deserialization java jackson

2022-09-03 10:38:04

我正在尝试设置Jackson JSON自定义反序列化程序以将JSON值转换为对象。我按照此站点上的说明进行操作：http://wiki.fasterxml.com/JacksonHowToCustomDeserializers 设置自定义解串器。Long

但是，要启动自定义反序列化程序，我必须始终在每次都进行注释，例如

public class TestBean {
    Long value;

    @JsonDeserialize(using=LongJsonDeserializer.class)
    public void setValue(Long value) {
       this.value = value;
     }
 }

有没有办法告诉 Jackson 始终使用自定义反序列化程序来反序列化所有属性，而不必每次都使用注释？Long@JsonDeserialize(using=LongJsonDeserializer.class)

答案 1

LongJsonDeserializer deserializer = new LongJsonDeserializer();

SimpleModule module =
  new SimpleModule("LongDeserializerModule",
      new Version(1, 0, 0, null, null, null));
module.addDeserializer(Long.class, deserializer);

ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(module);

这是一个完整的演示应用程序。这适用于最新版本的Jackson，也可能适用于Jackson版本，可以追溯到1.7。

import java.io.IOException;

import org.codehaus.jackson.JsonParser;
import org.codehaus.jackson.JsonProcessingException;
import org.codehaus.jackson.Version;
import org.codehaus.jackson.map.DeserializationContext;
import org.codehaus.jackson.map.JsonDeserializer;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.module.SimpleModule;

public class Foo
{
  public static void main(String[] args) throws Exception
  {
    TestBean bean = new TestBean();
    bean.value = 42L;

    ObjectMapper mapper = new ObjectMapper();

    String beanJson = mapper.writeValueAsString(bean);
    System.out.println(beanJson);
    // output: {"value":42}

    TestBean beanCopy1 = mapper.readValue(beanJson, TestBean.class);
    System.out.println(beanCopy1.value);
    // output: 42

    SimpleModule module =
      new SimpleModule("LongDeserializerModule",
          new Version(1, 0, 0, null));
    module.addDeserializer(Long.class, new LongJsonDeserializer());

    mapper = new ObjectMapper();
    mapper.registerModule(module);

    TestBean beanCopy2 = mapper.readValue(beanJson, TestBean.class);
    System.out.println(beanCopy2.value);
    // output: 126
  }
}

class TestBean
{
  Long value;
  public Long getValue() {return value;}
  public void setValue(Long value) {this.value = value;}
}

class LongJsonDeserializer extends JsonDeserializer<Long>
{
  @Override
  public Long deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException
  {
    Long value = jp.getLongValue();
    return value * 3;
  }
}

答案 2