设置JSON自定义反序列化器 [英] Setting up JSON custom deserializer
问题描述
我正在尝试设置Jackson JSON自定义反序列化器以将JSON值转换为Long对象。
我按照本网站上的说明操作: http://wiki.fasterxml.com/JacksonHowToCustomDeserializers 设置自定义反序列化器。
I am trying to setup Jackson JSON custom deserializer to convert JSON values into Long object. I followed the instructions on this site : http://wiki.fasterxml.com/JacksonHowToCustomDeserializers to setup the custom deserializer.
但是,要启动自定义反序列化器,我必须每次都注释
例如
However, for the custom deserializer to kick in, I have to always annotate each time e.g.
public class TestBean {
Long value;
@JsonDeserialize(using=LongJsonDeserializer.class)
public void setValue(Long value) {
this.value = value;
}
}
有没有办法告诉杰克逊总是使用自定义反序列化器反序列化Long而不必每次都使用@JsonDeserialize(using = LongJsonDeserializer.class)注释?
Is there a way to tell Jackson to always use the custom deserializer to deserialize Long without having to use @JsonDeserialize(using=LongJsonDeserializer.class) annotation each time?
推荐答案
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Jackson的最新版本,也可能与Jackson版本一起回溯到1.7。
Here's a full demo application. This works with the latest release of Jackson, and probably also with Jackson versions going back to 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;
}
}
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