Jaxb:在同一包中使用多个命名空间解组 xml [英] Jaxb: Unmarshalling xml with multiple namespaces in same package

问题描述

我是在 xml 中使用命名空间的新手，所以我有点困惑，希望得到一些澄清.我有一个 java 服务，我在其中接收具有许多不同名称空间的 xml 文档，当我让它工作时，我觉得我一定做错了什么，所以我想检查一下.在我的 package-info.java 中，我有我的模式注释，例如:

I'm new to using namespaces in xml so I am kind of confused and would like some clarification. I have a java service where I am receiving xml documents with many different namespaces and while i got it working, I feel like I must have done something wrong so I want to check. In my package-info.java I have my schema annotation such as:

@javax.xml.bind.annotation.XmlSchema(
    xmlns={
        @javax.xml.bind.annotation.XmHS(prefix="train", namespaceURI="http://mycompany/train"), 
        @javax.xml.bind.annotation.XmHS(prefix="passenger", namespaceURI="http://mycompany/passenger")
    }, 
    elementFormDefault = javax.xml.bind.annotation.XmlNsForm=QUALIFIED
)

我在类级别注释了一个 Train.java:

I have a Train.java annotated on the class level with:

@XmlRootElement(name="Train", namespace="http://mycompany/train")

并且类中的每个字段都注释为:

and each field in the class annotated with:

@XmlElement(name="Color") for example

火车包含一个乘客列表，所以有一个属性

Train contains a List of Passenger(s) so there's a property

private Set<Passenger> passengers;

并且此集合注释为:

@XmlElementWrapper(name="Passengers")
@XmlElements(@XmlElement(name="Passenger", namespace="http://mycompany/passenger"))

然后在Passenger.java中，类本身被注释为:

Then within Passenger.java the class itself is annotated with:

@XmlElement(name="Passenger", namespace="http://mycompany/passenger")

最后，对于Passenger.java 中的各个字段，它们的注释如下:

Finally for individual fields within Passenger.java, they are annotated like this:

@XmlElement(name="TicketNumber", namespace="http://mycompany/passenger")

所以当我有一个如下所示的 xml 时:

So when I have an xml that looks like:

<train:Train>
   <train:Color>Red</train:Color>
   <train:Passengers>
       <train:Passenger>
           <passenger:TicketNumber>T101</passenger:TicketNumber>
       </train:Passenger>
   </train:Passengers>
</train:Train>

现在我解组收到的这个 xml，并设置了 Train 的 Color 属性并设置了 Passenger 的 TicketNumber 属性.但我不知道为什么我需要在 TicketNumber 的 XmlElement 注释上添加命名空间 url 才能工作，但我不需要为 Train 上的 Color 属性这样做.如果我从 TicketNumber 的 XmlElement 注释中删除命名空间属性，则 xml 中的值不会映射到对象，除非我也从 xml 请求中删除命名空间前缀.我觉得因为我已经在乘客的 XmlRootElement 上定义了命名空间属性，所以我不需要为类中的每个字段都这样做，就像我不必为 Train 那样做，所以我假设我一定是设置有问题.有人可以指出我正确的方向吗?谢谢！

Now I unmarshal this xml I received and Train's Color property is set and Passenger's TicketNumber property is set. But I don't know why I need to add the namespace url on the XmlElement annotation on TicketNumber for that to work but I didn't need to do so for the Color property on Train. If I remove the namespace attribute from the XmlElement annotation on TicketNumber, the value from the xml wont get mapped to the object unless I also remove the namespace prefix from the xml request. I feel like since I've got the namespace attribute defined on the XmlRootElement for Passenger, I shouldn't need to do that for every single field in the class as well just like I didn't have to for Train so I am assuming I must have setup something wrong. Can someone point me in the right direction? Thanks!

推荐答案

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)没有指定另一个命名空间.
• 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 注释上指定的 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

这篇关于Jaxb:在同一包中使用多个命名空间解组 xml的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！