JAXB：如何避免xmlns：xsi的重复命名空间定义 [英] JAXB: How to avoid repeated namespace definition for xmlns:xsi

问题描述

我有一个JAXB设置，我使用@XmlJavaTypeAdapter将 Person 类型的对象替换为类型 PersonRef 只包含该人的UUID。这完全没问题。但是，生成的XML每次使用时都会重新声明相同的命名空间（ xmlns：xsi =http://www.w3.org/2001/XMLSchema-instance）。虽然这通常没问题，但感觉不对。

I have a JAXB setup where I use a @XmlJavaTypeAdapter to replace objects of type Person with objects of type PersonRef that only contains the person's UUID. This works perfectly fine. However, the generated XML redeclares the same namespace (xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance") every time it's used. While this is generally okay, it just doesn't feel right.

如何配置JAXB以在文档的最开头声明xmlns：xsi？我可以手动将名称空间声明添加到根元素吗？

How can I configure JAXB to declare xmlns:xsi at the very beginning of the document? Can I manually add namespace declarations to the root element?

以下是我想要实现的示例：

Here's an example of what I want to achive:

当前：

<person uuid="6ec0cf24-e880-431b-ada0-a5835e2a565a">
    <relation type="CHILD"> 
        <to xsi:type="personRef" uuid="56a930c0-5499-467f-8263-c2a9f9ecc5a0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"/> 
    </relation> 
    <relation type="CHILD"> 
        <to xsi:type="personRef" uuid="6ec0cf24-e880-431b-ada0-a5835e2a565a" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"/> 
    </relation>
    <!-- SNIP: some more relations -->
</person>

通缉：

<person uuid="6ec0cf24-e880-431b-ada0-a5835e2a565a" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <relation type="CHILD"> 
        <to xsi:type="personRef" uuid="56a930c0-5499-467f-8263-c2a9f9ecc5a0"/> 
    </relation> 
    <relation type="CHILD"> 
        <to xsi:type="personRef" uuid="6ec0cf24-e880-431b-ada0-a5835e2a565a"/> 
    </relation>
    <!-- SNIP: some more relations -->
</person>

推荐答案

您可以使用以下代码执行此操作：

You can do it with the code:

marshaller.setProperty("com.sun.xml.bind.namespacePrefixMapper", new NamespacePrefixMapper() {
                @Override
                public String[] getPreDeclaredNamespaceUris() {
                    return new String[] { 
                        XMLConstants.W3C_XML_SCHEMA_INSTANCE_NS_URI
                    };
                }

                @Override
                public String getPreferredPrefix(String namespaceUri, String suggestion, boolean requirePrefix) {
                    if (namespaceUri.equals(XMLConstants.W3C_XML_SCHEMA_INSTANCE_NS_URI))
                        return "xsi";
                    if (namespaceUri.equals(XMLConstants.W3C_XML_SCHEMA_NS_URI))
                        return "xs";
                    if (namespaceUri.equals(WellKnownNamespace.XML_MIME_URI))
                        return "xmime";
                    return suggestion;

                }
            });

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