通过 Jettison 将 Java 对象（不带 @XmlRootElement）编组到 JSON
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Marshalling the Java objects (without @XmlRootElement) to JSON via Jettison
提问by Arun
I have done the marshalling of an JAXB object (Which contains @XmlRootElement) to JSON using Jettison. But I can not convert a simple java object which has no annotations like @XmlRootElement to JSON. I would like to know "Is it mandatory to have that @XmlRootElement to marshall an object to JSON?"
我已经使用 Jettison 将 JAXB 对象（其中包含 @XmlRootElement）编组到 JSON。但是我无法将没有像@XmlRootElement 这样的注释的简单 java 对象转换为 JSON。我想知道“是否必须让 @XmlRootElement 将对象编组为 JSON？”
I am getting the following Exception when I try to marshall the java object to Json
当我尝试将 java 对象编组到 Json 时，出现以下异常
com.sun.istack.SAXException2: unable to marshal type "simpleDetail" as an element because it is missing an @XmlRootElement annotation
What could be the issue?
可能是什么问题？
采纳答案by bdoughan
Note:I'm the EclipseLink JAXB (MOXy)lead and a member of the JAXB (JSR-222)expert group.
注意：我是EclipseLink JAXB (MOXy) 的负责人，也是JAXB (JSR-222)专家组的成员。
The JAXB (JSR-222) specification does not cover JSON-binding. Instead of using a JAXB implementation with the Jettison library, you could use EclipseLink JAXB (MOXy) that offers native JSON-binding. Below is an example.
JAXB (JSR-222) 规范不包括 JSON 绑定。您可以使用提供原生 JSON 绑定的 EclipseLink JAXB (MOXy)，而不是将 JAXB 实现与 Jettison 库一起使用。下面是一个例子。
JAVA MODEL
爪哇模型
Foo
富
import java.util.List;
import javax.xml.bind.annotation.*;
@XmlAccessorType(XmlAccessType.FIELD)
public class Foo {
private List<Bar> mylist;
}
Bar
酒吧
import javax.xml.bind.annotation.*;
@XmlAccessorType(XmlAccessType.FIELD)
public class Bar {
private int id;
private String name;
}
jaxb.properties
jaxb.properties
To specify MOXy as your JAXB provider you need to include a file called jaxb.propertiesin the same package as your domain model with the following entry (see: http://blog.bdoughan.com/2011/05/specifying-eclipselink-moxy-as-your.html):
要将 MOXy 指定为您的 JAXB 提供程序，您需要包含一个jaxb.properties在与域模型相同的包中调用的文件，其中包含以下条目（请参阅：http: //blog.bdoughan.com/2011/05/specifying-eclipselink-moxy-as -your.html):
javax.xml.bind.context.factory=org.eclipse.persistence.jaxb.JAXBContextFactory
DEMO CODE
演示代码
Demo
演示
MOXy does not require the @XmlRootElementannotation, and you can use the JSON_INCLUDE_ROOTproperty to tell MOXy to ignore the presence of any @XmlRootElementannotations. When the root element is ignored you need to use an unmarshalmethod that takes a class parameter to specify the type you are unmarshalling.
MOXy 不需要@XmlRootElement注释，您可以使用该JSON_INCLUDE_ROOT属性告诉 MOXy 忽略任何@XmlRootElement注释的存在。当根元素被忽略时，您需要使用一个unmarshal带有类参数的方法来指定您要解组的类型。
import java.util.*;
import javax.xml.bind.*;
import javax.xml.transform.stream.StreamSource;
import org.eclipse.persistence.jaxb.JAXBContextProperties;
public class Demo {
public static void main(String[] args) throws Exception {
Map<String, Object> properties = new HashMap<String, Object>(2);
properties.put(JAXBContextProperties.MEDIA_TYPE, "application/json");
properties.put(JAXBContextProperties.JSON_INCLUDE_ROOT, false);
JAXBContext jc = JAXBContext.newInstance(new Class[] {Foo.class}, properties);
Unmarshaller unmarshaller = jc.createUnmarshaller();
StreamSource json = new StreamSource("src/forum15404528/input.json");
Foo foo = unmarshaller.unmarshal(json, Foo.class).getValue();
Marshaller marshaller = jc.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.marshal(foo, System.out);
}
}
input.json/Output
输入.json/输出
We see that no root element is present in the input or output.
我们看到输入或输出中不存在根元素。
{
"mylist" : [ {
"id" : 104,
"name" : "Only one found"
} ]
}
ADDITIONAL INFORMATION
附加信息
回答by Jeevan Patil
Just read that @XmlRootElementis not necessary always. Please read this blog, at the bottom you will find how it's done without @XmlRootElement.
Also go through the answers in the post No @XmlRootElement generated by JAXB.
只是阅读这@XmlRootElement并不总是必要的。请阅读此博客，在底部您会发现没有@XmlRootElement. 还请查看由 JAXB 生成的 No @XmlRootElement帖子中的答案。
