使用 Jackson 将 JSON 反序列化为具有重载方法的对象 [英] Deserializing JSON into object with overloaded methods using Jackson

问题描述

我正在尝试使用 Jackson 反序列化存储在 CouchDb 中的 JSON 对象.此对象需要反序列化为包含重载方法的 pojo.当我尝试从沙发上检索对象并进行反序列化时，出现以下异常:

I am attempting to deserialize a JSON object stored in CouchDb using Jackson. This object needs to deserialize into a pojo that contains overloaded methods. When I attempt to retrieve the object from couch and do the deserialization I get the following exception:

org.ektorp.DbAccessException:org.codehaus.jackson.map.JsonMappingException:冲突的 setter 定义属性乘数":com.db.commodities.framework.sdos.model.security.EqOpt#setMultiplier(1参数) vscom.db.commodities.framework.sdos.model.security.EqOpt#setMultiplier(1参数)

org.ektorp.DbAccessException: org.codehaus.jackson.map.JsonMappingException: Conflicting setter definitions for property "multiplier": com.db.commodities.framework.sdos.model.security.EqOpt#setMultiplier(1 params) vs com.db.commodities.framework.sdos.model.security.EqOpt#setMultiplier(1 params)

我试图注释我希望 Jackson 使用的 setter，但这似乎不起作用.

I tried to annotate the setter I would like Jackson to use, but that appears to not have worked.

@JsonProperty("multiplier")
public void setMultiplier(SDOSAttribute multiplier) {
     this.multiplier = multiplier;
}

public void setMultiplier(double multiplier) {
     this.multiplier.setValue(String.valueOf(multiplier));
}

如何配置 Jackson 以使用特定方法正确反序列化?还是我以错误的方式处理这个问题?

How do I configure Jackson to properly deserialize using a specific method? Or am I approaching this problem the wrong way?

我进行了以下更改.这似乎有效，但有点难看.如果有人有更好的方法来做到这一点，请随时分享，我很乐意接受.

I have made the following changes. This seems to work, but is a little uglier. If anyone has a better way to do this please feel free to share and I will gladly accept.

@JsonProperty("multiplier")
protected void setMultiplierAttribute(SDOSAttribute multiplier) {
    this.multiplier = multiplier;
}

@JsonIgnore
public void setMultiplier(double multiplier) {
    this.multiplier.setValue(String.valueOf(multiplier));
}

推荐答案

没有必要更改 setter 方法的名称以避免歧义.否则，您使用 @JsonIgnore 走在正确的轨道上.使用 @JsonIgnore 在所有要忽略的同名方法上，使用的方法不需要 @JsonProperty 注释.

It's not necessary to change the name of the setter method to avoid ambiguity. You're otherwise on the right track with @JsonIgnore. With @JsonIgnore on all of the same-named methods to be ignored, the one to use does not need the @JsonProperty annotation.

这是一个简单的例子来证明这一点.

Here's a simple example to demonstrate this point.

input.json: {"value":"四十二"}

Foo.java:

import java.io.File;

import org.codehaus.jackson.annotate.JsonIgnore;
import org.codehaus.jackson.map.ObjectMapper;

public class Foo
{
  String value;

  public String getValue() {return value;}
  public void setValue(String value) {this.value = value;}

  @JsonIgnore
  public void setValue(int value) {this.value = String.valueOf(value);}

  public static void main(String[] args) throws Exception
  {
    ObjectMapper mapper = new ObjectMapper();
    Foo foo = mapper.readValue(new File("input.json"), Foo.class);
    System.out.println(mapper.writeValueAsString(foo));
  }
}

如果您不想使用 Jackson 注释更改原始 POJO defs，那么您可以使用 MixIn.

If you don't want to alter the pristine POJO defs with a Jackson annotation, then you can use a MixIn.

import java.io.File;

import org.codehaus.jackson.annotate.JsonIgnore;
import org.codehaus.jackson.map.ObjectMapper;

public class Foo
{
  String value;

  public String getValue() {return value;}
  public void setValue(String value) {this.value = value;}
  public void setValue(int value) {this.value = String.valueOf(value);}

  public static void main(String[] args) throws Exception
  {
    ObjectMapper mapper = new ObjectMapper();
    mapper.getDeserializationConfig().addMixInAnnotations(Foo.class, IgnoreFooSetValueIntMixIn.class);
    Foo foo = mapper.readValue(new File("input.json"), Foo.class);
    System.out.println(mapper.writeValueAsString(foo));
  }
}

abstract class IgnoreFooSetValueIntMixIn
{
  @JsonIgnore public abstract void setValue(int value);
}

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