以下解释了 JAXB (JSR-222) 基于您的模型.

Below is an explanation of how namespaces work in JAXB (JSR-222) based on your model.

Java 模型

包信息

以下是您的 @XmlSchema 注释的修改版本.它包含一些关键信息:

Below is a modified version of your @XmlSchema annotation. It contains some key information:

• namespace - 将用于限定全局元素的默认命名空间(对应于 @XmlRootElement 和 @XmlElementDecl 注释(和本地基于 elementFormDefault 值的元素)没有指定其他命名空间.
• elementFormDefault 默认情况下，只有全局元素是命名空间限定的，但是通过将值设置为 XmlNsForm.QUALIFIED，所有没有指定显式命名空间的元素都将使用 命名空间值.
• xmlns 是 JAXB impl 应该用于这些命名空间的首选前缀集(尽管它们可能使用其他前缀).

• namespace - The default namespace that will be used to qualify global elements (those corresponding to @XmlRootElement and @XmlElementDecl annotations (and local elements based on the elementFormDefault value) that don't have another namespace specified.
• elementFormDefault by default only global elements are namespace qualified but by setting the value to be XmlNsForm.QUALIFIED all elements without an explicit namespace specified will be qualified with the namespace value.
• xmlns is the preferred set of prefixes that a JAXB impl should use for those namespaces (although they may use other prefixes).

@XmlSchema(
    namespace="http://mycompany/train",
    elementFormDefault = XmlNsForm.QUALIFIED,
    xmlns={
       @XmlNs(prefix="train", namespaceURI="http://mycompany/train"), 
       @XmlNs(prefix="passenger", namespaceURI="http://mycompany/passenger")
   }
)
package forum15772478;

import javax.xml.bind.annotation.*;

训练

由于Train类对应的所有元素都对应于@XmlSchema注解上指定的namespace，所以我们不需要指定任何命名空间信息.

Since all the elements corresponding to the Train class correspond to the namespace specified on the @XmlSchema annotation, we don't need to specify any namespace info.

• 全局元素 - @XmlRootElement 注释对应于一个全局元素.
• 本地元素 - @XmlElementWrapper 和 @XmlElement 注释对应于本地元素.

• Global Elements - The @XmlRootElement annotation corresponds to a global element.
• Local Elements - The @XmlElementWrapper and @XmlElement annotations correspond to local elements.

package forum15772478;

import java.util.List;
import javax.xml.bind.annotation.*;

@XmlRootElement(name="Train")
public class Train {

    private List<Passenger> passengers;

    @XmlElementWrapper(name="Passengers")
    @XmlElement(name="Passenger")
    public List<Passenger> getPassengers() {
        return passengers;
    }

    public void setPassengers(List<Passenger> passengers) {
        this.passengers = passengers;
    }

}

乘客

如果 Passenger 类上的属性对应的所有元素都在 http://mycompany/passenger 命名空间中，那么您可以使用 @XmlType 注释以覆盖 @XmlSchema 注释中的 namespace.

If all the elements corresponding to properties on the Passenger class will be in the http://mycompany/passenger namespace, then you can use the @XmlType annotation to override the namespace from the @XmlSchema annotation.

package forum15772478;

import javax.xml.bind.annotation.*;

@XmlType(namespace="http://mycompany/passenger")
public class Passenger {

    private String ticketNumber;

    @XmlElement(name="TicketNumber")
    public String getTicketNumber() {
        return ticketNumber;
    }

    public void setTicketNumber(String ticketNumber) {
        this.ticketNumber = ticketNumber;
    }

}

或者，您可以在属性级别覆盖命名空间.

Alternatively you can override the namespace at the property level.

package forum15772478;

import javax.xml.bind.annotation.*;

public class Passenger {

    private String ticketNumber;

    @XmlElement(
        namespace="http://mycompany/passenger",
        name="TicketNumber")
    public String getTicketNumber() {
        return ticketNumber;
    }

    public void setTicketNumber(String ticketNumber) {
        this.ticketNumber = ticketNumber;
    }

}

演示代码

可以运行以下演示代码来证明一切正常:

The following demo code can be run to prove that everything works:

演示

package forum15772478;

import java.io.File;
import javax.xml.bind.*;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Train.class);

        Unmarshaller unmarshaller = jc.createUnmarshaller();
        File xml = new File("src/forum15772478/input.xml");
        Train train = (Train) unmarshaller.unmarshal(xml);

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.marshal(train, System.out);
    }

}

input.xml/输出

在下面的 XML 中，我添加了您问题中 XML 文档中缺少的必要命名空间声明.

In the XML below I have added the necessary namespace declarations that were missing from the XML document in your question.

<train:Train 
   xmlns:train="http://mycompany/train" 
   xmlns:passenger="http://mycompany/passenger">
   <train:Color>Red</train:Color>
   <train:Passengers>
       <train:Passenger>
           <passenger:TicketNumber>T101</passenger:TicketNumber>
       </train:Passenger>
   </train:Passengers>
</train:Train>

了解更多信息

• http://blog.bdoughan.com/2010/08/jaxb-命名空间.html