Java 使用 Jackson 复制 JSON 字段
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Duplicate JSON Field with Hymanson
提问by
I am using Hymanson for JSON (de)serialization in conjunction with Spring. However I am having an issue with a field being twice in some cases.
我正在使用 Hymanson 与 Spring 结合进行 JSON（反）序列化。但是，在某些情况下，我遇到了一个字段是两次的问题。
I have an abstract class:
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);
}
}
}
And a concrete class extend the abstract:
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";
}
}
The problem is that when I serialize this JSON, I get a duplicate mimeTypefield:
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"
}
I have tried using the recommendation of previousanswersto use the @JsonAutoDetectannotation to specify that only fields on a class should be used as well as setting the same on the ObjectMapper, however this does not fix the problem.
我曾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在 上设置相同的字段ObjectMapper，但这并不能解决问题。
Annotation:
注解：
@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY, getterVisibility = JsonAutoDetect.Visibility.NONE,
setterVisibility = JsonAutoDetect.Visibility.NONE, creatorVisibility = JsonAutoDetect.Visibility.NONE,
isGetterVisibility = JsonAutoDetect.Visibility.NONE)
ObjectMapper:
对象映射器：
ObjectMapper mapper = new ObjectMapper();
mapper.getSerializationConfig().getDefaultVisibilityChecker()
.withFieldVisibility(JsonAutoDetect.Visibility.ANY)
.withGetterVisibility(JsonAutoDetect.Visibility.NONE)
.withSetterVisibility(JsonAutoDetect.Visibility.NONE)
.withCreatorVisibility(JsonAutoDetect.Visibility.NONE);
回答by Katona
This behaviour is caused by the annotations placed on class AbstractBookmarkJsonModel:
此行为是由放置在 class 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")
})
@JsonTypeInfotells Hymanson to serialize the logical type name (JsonTypeInfo.Id.NAME) as a property (JsonTypeInfo.As.PROPERTY) with name mimeType(property = "mimeType"). With @JsonSubTypes.Typeyou assign the logical name application/epub+zipto EpubBookmarkJsonModel.
@JsonTypeInfo告诉Hyman逊序列化的逻辑类型名称（JsonTypeInfo.Id.NAME）作为属性（JsonTypeInfo.As.PROPERTY）与名称mimeType（property = "mimeType"）。随着@JsonSubTypes.Type分配的逻辑名称application/epub+zip来EpubBookmarkJsonModel。
When it comes to serialization, Hymanson serializes the logical name as a property mimeType = "application/epub+zip"then the properties of the object among them
mimeTypewhich happens to have the same value as the logical name application/epub+zip(assigned in the constructor).
在序列化方面，Hymanson 将逻辑名称序列化为一个属性，mimeType = "application/epub+zip"然后将mimeType其中的对象的属性
序列化为与逻辑名称application/epub+zip（在构造函数中分配）相同的值。
I think mimeTypeshould be changed to objectTypein the @JsonTypeInfoannotation or even better to remove the mimeTypefield since Hymanson will take care of that through type info serialization.
我认为mimeType应该objectType在@JsonTypeInfo注释中更改为，甚至更好地删除该mimeType字段，因为 Hymanson 将通过类型信息序列化来处理该问题。
回答by ZacharyP
I was having this exact same problem with the duplicate output. I found a solution that did not involve another property, and allowed me to not remove the original property. First, I set the visible flag to true for JsonTypeInfo. Then, I added a JsonIgnore annotation to the property declaration and the getter (but not the setter). This is so far outputting the JSON correctly with only one key for the type property.
我在重复输出时遇到了完全相同的问题。我找到了一个不涉及其他属性的解决方案，并且允许我不删除原始属性。首先，我将 JsonTypeInfo 的可见标志设置为 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，只有一个用于 type 属性的键才能正确输出 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;
}
}
To note, this is with fasterxml Hymanson Hymanson-databind 2.1.1
请注意，这是使用 fastxml Hymanson Hymanson-databind 2.1.1
<dependency>
<groupId>com.fasterxml.Hymanson.core</groupId>
<artifactId>Hymanson-databind</artifactId>
<version>2.1.1</version>
</dependency>
