java 将对象序列化为 XML 时如何添加 XML 命名空间 (xmlns)
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How to add an XML namespace (xmlns) when serializing an object to XML
提问by Ingo Fischer
I'm serializing Objects to XML with the help of XStream. How do I tell XStream to insert an xmlns to the XML output of my object?
我在 XStream 的帮助下将对象序列化为 XML。如何告诉 XStream 将 xmlns 插入到我的对象的 XML 输出中？
As an example, I have this simple object I want to serialize:
例如，我有一个要序列化的简单对象：
@XStreamAlias(value="domain")
public class Domain
{
@XStreamAsAttribute
private String type;
private String os;
(...)
}
How do I achieve exactlythe following output with XStream?
如何使用 XStream准确实现以下输出？
<domain type="kvm" xmlns:qemu="http://libvirt.org/schemas/domain/qemu/1.0">
<os>linux</os>
</domain>
采纳答案by bdoughan
Alternatively, this use case could be handled quite easily with a JAXB implementation (Metro, EclipseLink MOXy, Apache JaxMe, etc):
或者，可以使用 JAXB 实现（Metro、EclipseLink MOXy、Apache JaxMe等）轻松处理此用例：
Domain
领域
package com.example;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlRootElement;
@XmlRootElement
public class Domain
{
private String type;
private String os;
@XmlAttribute
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public String getOs() {
return os;
}
public void setOs(String os) {
this.os = os;
}
}
package-info
包信息
@XmlSchema(xmlns={
@XmlNs(
prefix="qemu",
namespaceURI="http://libvirt.org/schemas/domain/qemu/1.0")
})
package com.example;
import javax.xml.bind.annotation.XmlNs;
import javax.xml.bind.annotation.XmlSchema;
Demo
演示
package com.example;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
public class Demo {
public static void main(String[] args) throws JAXBException {
JAXBContext jc = JAXBContext.newInstance(Domain.class);
Domain domain = new Domain();
domain.setType("kvm");
domain.setOs("linux");
Marshaller marshaller = jc.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.marshal(domain, System.out);
}
}
Output
输出
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<domain xmlns:qemu="http://libvirt.org/schemas/domain/qemu/1.0" type="kvm">
<os>linux</os>
</domain>
For More Information
想要查询更多的信息
回答by dogbane
XStream doesn't support namespaces but the StaxDriverit uses, does. You need to set the details of your namespace into a QNameMapand pass that into the StaxDriver:
XStream 不支持命名空间，但StaxDriver它使用的支持。您需要将命名空间的详细信息设置为 aQNameMap并将其传递到StaxDriver：
QNameMap qmap = new QNameMap();
qmap.setDefaultNamespace("http://libvirt.org/schemas/domain/qemu/1.0");
qmap.setDefaultPrefix("qemu");
StaxDriver staxDriver = new StaxDriver(qmap);
XStream xstream = new XStream(staxDriver);
xstream.autodetectAnnotations(true);
xstream.alias("domain", Domain.class);
Domain d = new Domain("kvm","linux");
String xml = xstream.toXML(d);
Output:
输出：
<qemu:domain type="kvm" xmlns:qemu="http://libvirt.org/schemas/domain/qemu/1.0">
<qemu:os>linux</qemu:os>
</qemu:domain>
回答by z0r
This is a bit of a hack, but it's quick and easy: add a field to your class called xmlns, and only have it non-null during serialisation. To continue your example:
这有点小技巧，但它既快捷又简单：向名为 的类添加一个字段xmlns，并且仅在序列化期间将其设为非空。继续你的例子：
@XStreamAlias(value="domain")
public class Domain
{
@XStreamAsAttribute
private String type;
private String os;
(...)
@XStreamAsAttribute
@XStreamAlias("xmlns:qemu")
String xmlns;
public void serialise(File path) {
XStream xstream = new XStream(new DomDriver());
xstream.processAnnotations(Domain.class);
(...)
PrintWriter out = new PrintWriter(new FileWriter(path.toFile()));
xmlns = "http://libvirt.org/schemas/domain/qemu/1.0";
xstream.toXML(this, out);
xmlns = null;
}
}
To be complete, setting xmlns = nullshould be in a finallyclause. Using a PrintWriteralso allows you to insert an XML declaration at the start of the output, if you like.
为了完整起见，设置xmlns = null应该在finally子句中。PrintWriter如果您愿意，还可以使用 a在输出的开头插入 XML 声明。
