Read embedded object in Jackson

To deal with an "embedded" object you should use @JsonUnwrapped — it's an equivalent of the Hibernate's @Embeddable/@Embedded.

class Item {    private String title;    @JsonProperty("date")    private Date createdAt;    // How to map this?    @JsonUnwrapped    private Author author;}

I would deserialize the original JSON to a single, flat object first (kind of like an adapter), then create your own domain objects.

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.

 //... 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);

Your Item class could only be automatically deserialized from the following form:

{    "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.

Note: I'm the EclipseLink JAXB (MOXy) lead and a member of the JAXB 2 (JSR-222) expert group.

I'm not sure if Jackson supports this use case, but below is an example of how you can leverage MOXy's @XmlPath extension to meet your requirements. Note you will need to use an EclipseLink 2.4.0 nightly label from April 7, 2012 or newer.

• http://www.eclipse.org/eclipselink/downloads/nightly.php

Item

The author property on Item is mapped with @XmlPath('.'). This means that the content of Author is pulled up to the same level as the content for Item. I also needed to use an XmlAdapter for the Date property as the format you are using doesn't match MOXy's default representation.

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

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

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

A file called jaxb.properties with the following entry must be placed in the same package as the domain classes to specify MOXy as the JAXB (JSR-222) provider.

javax.xml.bind.context.factory = org.eclipse.persistence.jaxb.JAXBContextFactory

input.json/Output

{   "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"}

For More Information

• http://blog.bdoughan.com/2010/07/xpath-based-mapping.html
• http://blog.bdoughan.com/2011/08/json-binding-with-eclipselink-moxy.html
• http://blog.bdoughan.com/2011/08/binding-to-json-xml-geocode-example.html