java 在 Jackson 中读取嵌入的对象
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Read embedded object in Hymanson
提问by Crozin
I'm trying to read a legacy JSON code using Hymanson 2.0-RC3, however I'm stuck with an "embedded" object.
我正在尝试使用 Hymanson 2.0-RC3 读取旧的 JSON 代码，但是我遇到了“嵌入式”对象。
Given a following JSON:
给定以下 JSON：
{
"title": "Hello world!",
"date": "2012-02-02 12:23:34".
"author": "username",
"author_avatar": "http://.../",
"author_group": 123,
"author_prop": "value"
}
How can I map it into the following structure:
如何将其映射到以下结构中：
class Author {
@JsonPropery("author")
private String name;
@JsonPropery("author_avatar")
private URL avatar;
@JsonProperty("author_group")
private Integer group;
...
}
class Item {
private String title;
@JsonProperty("date")
private Date createdAt;
// How to map this?
private Author author;
}
I was trying to do that with @JsonDeserializebut it seems that I'd have to map the entire Itemobject that way.
我试图这样做，@JsonDeserialize但似乎我必须以Item这种方式映射整个对象。
回答by Bruno Hansen
To deal with an "embedded" object you should use @JsonUnwrapped— it's an equivalent of the Hibernate's @Embeddable/@Embedded.
要处理您应该使用的“嵌入式”对象@JsonUnwrapped——它相当于 Hibernate 的@Embeddable/ @Embedded。
class Item {
private String title;
@JsonProperty("date")
private Date createdAt;
// How to map this?
@JsonUnwrapped
private Author author;
}
回答by c_maker
I would deserialize the original JSON to a single, flat object first (kind of like an adapter), then create your own domain objects.
我会首先将原始 JSON 反序列化为单个平面对象（有点像适配器），然后创建您自己的域对象。
class ItemLegacy {
private String title;
@JsonProperty("date")
private Date createdAt;
@JsonPropery("author")
private String name;
@JsonPropery("author_avatar")
private URL avatar;
@JsonProperty("author_group")
private Integer group;
@JsonProperty("author_prop")
private Integer group;
}
Then use this object to fill out your Item and Author objects and create the correct relationships.
然后使用此对象填写您的 Item 和 Author 对象并创建正确的关系。
//... the deserialized original JSON
ItemLegacy legacy ...
// create an author
Author author = new Author();
author.setName(legacy.getName());
author.setGroup(legacy.getGroup());
...
// create an item
Item item = new Item();
item.setTitle(legacy.getTitle());
...
// finally set the author... and you should have the desired structure
item.setAuthor(author);
YourItemclass could only be automatically deserialized fromthe following form:
您的Item类只能从以下形式自动反序列化：
{
"title": "Hello world!",
"date": "2012-02-02 12:23:34".
"author": {
"name": "username",
"author_avatar": "http://...",
"author_group": "123",
"author_prop": "value"
}
}
You might be able to do something with custom deserialization, but it would not be the simpler solution for sure.
您也许可以使用自定义反序列化来做一些事情，但这肯定不是更简单的解决方案。
回答by bdoughan
Note:I'm the EclipseLink JAXB (MOXy)lead and a member of the JAXB 2 (JSR-222)expert group.
注意：我是EclipseLink JAXB (MOXy) 的负责人和JAXB 2 (JSR-222)专家组的成员。
I'm not sure if Hymanson supports this use case, but below is an example of how you can leverage MOXy's @XmlPathextension to meet your requirements. Note you will need to use an EclipseLink 2.4.0 nightly label from April 7, 2012 or newer.
我不确定 Hymanson 是否支持这个用例，但下面是一个示例，说明如何利用 MOXy 的@XmlPath扩展来满足您的要求。请注意，您需要使用 2012 年 4 月 7 日或更新版本的 EclipseLink 2.4.0 nightly 标签。
Item
物品
The authorproperty on Itemis mapped with @XmlPath('.'). This means that the content of Authoris pulled up to the same level as the content for Item. I also needed to use an XmlAdapterfor the Dateproperty as the format you are using doesn't match MOXy's default representation.
该author物业上Item映射有@XmlPath('.')。这意味着 的内容Author被上拉到与 的内容相同的级别Item。我还需要XmlAdapter为Date属性使用 ，因为您使用的格式与 MOXy 的默认表示不匹配。
package forum10036530;
import java.util.Date;
import javax.xml.bind.annotation.*;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
import org.eclipse.persistence.oxm.annotations.XmlPath;
@XmlAccessorType(XmlAccessType.FIELD)
class Item {
private String title;
@XmlElement(name="date")
@XmlJavaTypeAdapter(DateAdapter.class)
private Date createdAt;
@XmlPath(".")
private Author author;
}
Author
作者
package forum10036530;
import java.net.URL;
import javax.xml.bind.annotation.*;
@XmlAccessorType(XmlAccessType.FIELD)
class Author {
@XmlElement(name="author")
private String name;
@XmlElement(name="author_avatar")
private URL avatar;
@XmlElement(name="author_group")
private Integer group;
@XmlElement(name="author_prop")
private String prop;
}
DateAdapter
日期适配器
package forum10036530;
import java.text.SimpleDateFormat;
import java.util.Date;
import javax.xml.bind.annotation.adapters.XmlAdapter;
public class DateAdapter extends XmlAdapter<String, Date> {
private SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
@Override
public Date unmarshal(String string) throws Exception {
return dateFormat.parse(string);
}
@Override
public String marshal(Date date) throws Exception {
return dateFormat.format(date);
}
}
jaxb.properties
jaxb.properties
A file called jaxb.propertieswith the following entry must be placed in the same package as the domain classes to specify MOXy as the JAXB (JSR-222) provider.
jaxb.properties必须将使用以下条目调用的文件与域类放在同一个包中，以将 MOXy 指定为 JAXB (JSR-222) 提供程序。
javax.xml.bind.context.factory = org.eclipse.persistence.jaxb.JAXBContextFactory
input.json/Output
输入.json/输出
{
"title" : "Hello world!",
"date" : "2012-02-02 12:23:34",
"author" : "username",
"author_avatar" : "http://www.example.com/foo.png",
"author_group" : 123,
"author_prop" : "value"
}
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