与Jackson重复的JSON字段

Question

我正在使用Jackson与Spring一起进行JSON(de)序列化.但是,在某些情况下,我遇到了两次字段的问题.

我有一个抽象类:

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "mimeType")
@JsonSubTypes({
    @JsonSubTypes.Type(value = ImageBookmarkJsonModel.class, name = "image/jpeg"),
    @JsonSubTypes.Type(value = EpubBookmarkJsonModel.class, name = "application/epub+zip")
})
public abstract class AbstractBookmarkJsonModel extends AbstractJsonModel {
    protected String mimeType;
    // Removed other fields for brevity

    public String getMimeType() {
        return mimeType;
    }

    public void setMimeType(String mimeType) {
        this.mimeType = mimeType;
    }

    @Override
    public String toString() {
        ObjectMapper mapper = new ObjectMapper();

        try {
            return mapper.writeValueAsString(this);
        } catch (IOException e) {
            throw new IllegalStateException("Cannot convert object of type " + this.getClass().toString() + " to JSON", e);
        }
    }
}

一个具体的类扩展了抽象:

public class EpubBookmarkJsonModel extends AbstractBookmarkJsonModel {
    private static final long serialVersionUID = 1L;
    // Removed other fields for brevity

    public EpubBookmarkJsonModel() {
        this.mimeType = "application/epub+zip";
    }
}

问题是当我序列化这个JSON时,我得到一个重复的mimeType字段:

{
  "mimeType": "application/epub+zip",
  "mimeType": "application/epub+zip",
  "userId": 24,
  "acid": "ACID-000000000029087",
  "added": "2013-08-14T12:02:17Z",
  "epubBookmarkId": 34,
  "cfi": "epubcfi(/6/4!/2/68)",
  "context": "CONTEXT"
}

我已经尝试使用先前 答案的建议来使用@JsonAutoDetect注释来指定只应使用类上的字段以及设置相同的字段ObjectMapper,但这不能解决问题.

注解:

@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY, getterVisibility = JsonAutoDetect.Visibility.NONE,
        setterVisibility = JsonAutoDetect.Visibility.NONE, creatorVisibility = JsonAutoDetect.Visibility.NONE,
        isGetterVisibility = JsonAutoDetect.Visibility.NONE)

ObjectMapper:

    ObjectMapper mapper = new ObjectMapper();
    mapper.getSerializationConfig().getDefaultVisibilityChecker()
            .withFieldVisibility(JsonAutoDetect.Visibility.ANY)
            .withGetterVisibility(JsonAutoDetect.Visibility.NONE)
            .withSetterVisibility(JsonAutoDetect.Visibility.NONE)
            .withCreatorVisibility(JsonAutoDetect.Visibility.NONE);

Answer 1

我通过使用JsonTypeInfo.As.EXISTING_PROPERTY@JsonTypeInfo注释来解决这个问题.

该项目是开源的,请在此处查看:ANS.java

Answer 2

此行为是由类上的注释引起的AbstractBookmarkJsonModel:

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "mimeType")
@JsonSubTypes({
    @JsonSubTypes.Type(value = ImageBookmarkJsonModel.class, name = "image/jpeg"),
    @JsonSubTypes.Type(value = EpubBookmarkJsonModel.class, name = "application/epub+zip")
})

@JsonTypeInfo告诉Jackson将逻辑类型name(JsonTypeInfo.Id.NAME)序列化为JsonTypeInfo.As.PROPERTY带有name mimeType(property = "mimeType")的property ().随着@JsonSubTypes.Type分配的逻辑名称application/epub+zip 来EpubBookmarkJsonModel.

在序列化方面,Jackson将逻辑名称序列化为属性,mimeType = "application/epub+zip"然后将mimeType其中的对象属性序列化,这些属性 恰好与逻辑名称application/epub+zip(在构造函数中分配)具有相同的值.

我认为mimeType应该objectType在@JsonTypeInfo注释中更改或甚至更好地删除该mimeType字段,因为杰克逊将通过类型信息序列化来处理.

Answer 3

重复输出我遇到了同样的问题.我找到了一个不涉及其他财产的解决方案,并允许我不删除原始财产.首先,我将JsonTypeInfo的visible标志设置为true.然后,我在属性声明和getter(但不是setter)中添加了JsonIgnore注释.到目前为止,只使用type属性的一个键正确输出JSON.

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, visible = true, property = "mimeType")
@JsonSubTypes({
    @JsonSubTypes.Type(value = ImageBookmarkJsonModel.class, name = "image/jpeg"),
    @JsonSubTypes.Type(value = EpubBookmarkJsonModel.class, name = "application/epub+zip")
})
public abstract class AbstractBookmarkJsonModel extends AbstractJsonModel {
    @JsonIgnore
    @JsonProperty("mimeType")
    protected String mimeType;

    @JsonIgnore
    @JsonProperty("mimeType")
    public String getMimeType() {
        return mimeType;
    }

    @JsonProperty("mimeType")
    public void setMimeType(String mimeType) {
        this.mimeType = mimeType;
    }

}

需要注意的是,这是使用fastxml jackson jackson-databind 2.1.1

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.1.1</version>
</dependency>