Jackson定制注释用于自定义值序列化 [英] Jackson custom annotation for custom value serialization
本文介绍了Jackson定制注释用于自定义值序列化的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我正在尝试创建会影响序列化值的自定义jackson注释。
I'm trying to create custom jackson annotation that would affect serialization value.
含义:
class X {
@Unit("mm") int lenght;
...
}
现在序列化对象X(10)会导致in:
Now serializaling object X(10) would result in:
{
"lenght" : "10 mm"
}
我如何实现这一目标?
推荐答案
import com.fasterxml.jackson.core.JsonGenerationException;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;
import com.fasterxml.jackson.databind.ser.ContextualSerializer;
import com.fasterxml.jackson.databind.ser.std.StdSerializer;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import java.io.IOException;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
// Create own annotation storing your unit value
@Target({ ElementType.FIELD })
@Retention(RetentionPolicy.RUNTIME)
@interface Unit {
String value();
}
// Create custom serializer checking @Unit annotation
class UnitSerializer extends StdSerializer<Integer> implements ContextualSerializer {
private String unit;
public UnitSerializer() {
super(Integer.class);
}
public UnitSerializer(String unit) {
super(Integer.class);
this.unit = unit;
}
@Override
public void serialize(Integer value, JsonGenerator jgen, SerializerProvider provider) throws IOException {
jgen.writeString(String.format("%d %s", value, unit));
}
@Override
public JsonSerializer<?> createContextual(SerializerProvider prov, BeanProperty property) throws JsonMappingException {
String unit = null;
Unit ann = null;
if (property != null) {
ann = property.getAnnotation(Unit.class);
}
if (ann != null) {
unit = ann.value();
}
return new UnitSerializer(unit);
}
}
@NoArgsConstructor
@AllArgsConstructor
@Data
class X {
@JsonSerialize(using = UnitSerializer.class)
@Unit("mm")
private int length;
}
public class Runner {
public static void main(String[] args) throws JsonProcessingException {
X x = new X(10);
ObjectMapper objectMapper = new ObjectMapper();
System.out.println(objectMapper.writeValueAsString(x));
}
}
结果:
{"length":"10 mm"}
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