在 JAXB 中控制命名空间前缀 [英] Controlling namespace prefixes in JAXB

问题描述

jaxb 如何确定编组对象的命名空间前缀声明列表?我使用 xjc 为 ebics 编译 Java 类(ebics schema).当我为 ebicsRequest 创建实例时，它看起来像这样:

How does jaxb determine the list of namespace prefix declarations whem marshalling an object? I used xjc to compile java classes for ebics (ebics schema). When I create an instance for an ebicsRequest it looks like this:

<?xml version="1.0" encoding="UTF-16"?>
<ns2:ebicsRequest xmlns:ns2="http://www.ebics.org/H003" Revision="1" Version="H003" xmlns="http://www.ebics.org/H003" xmlns:ds="http://www.w3.org/2000/09/xmldsig#" xmlns:ns4="http://www.ebics.org/S001" xmlns:ns5="http://www.ebics.org/H000">
    <ns2:header authenticate="true">
        <ns2:static>
            <ns2:HostID>SIZBN001</ns2:HostID>
            <ns2:Nonce>A5488F43223063171CA0FA59ADC635F0</ns2:Nonce>
            <ns2:Timestamp>2009-08-04T08:41:56.967Z</ns2:Timestamp>
            <ns2:PartnerID>EBICS</ns2:PartnerID>
            <ns2:UserID>EBIX</ns2:UserID>
            <ns2:Product Language="de">EBICS-Kernel V2.0.4, SIZ/PPI</ns2:Product>
            <ns2:OrderDetails>
                <ns2:OrderType>FTB</ns2:OrderType>
                <ns2:OrderID>A037</ns2:OrderID>
                <ns2:OrderAttribute>OZHNN</ns2:OrderAttribute>
                <ns2:StandardOrderParams/>
            </ns2:OrderDetails>
            <ns2:BankPubKeyDigests>
                <ns2:Authentication Algorithm="RSA" Version="X002">...</ns2:Authentication>
                <ns2:Encryption Algorithm="RSA" Version="E002">...</ns2:Encryption>
            </ns2:BankPubKeyDigests>
            <ns2:SecurityMedium>0000</ns2:SecurityMedium>
            <ns2:NumSegments>1</ns2:NumSegments>
        </ns2:static>
        <ns2:mutable>
            <ns2:TransactionPhase>Initialisation</ns2:TransactionPhase>
        </ns2:mutable>
    </ns2:header>
    <ns2:AuthSignature>
        <ds:SignedInfo>
            <ds:CanonicalizationMethod Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315"/>
            <ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha256"/>
            <ds:Reference URI="#xpointer(//*[@authenticate='true'])">
                <ds:Transforms>
                    <ds:Transform Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315"/>
                </ds:Transforms>
                <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/>
                <ds:DigestValue>CSbjPbiNcFqSl6lCI1weK5x1nMeCH5bTQq5pedq5uI0=</ds:DigestValue>
            </ds:Reference>
        </ds:SignedInfo>
        <ds:SignatureValue>...</ds:SignatureValue>
    </ns2:AuthSignature>
    <ns2:body>
        <ns2:DataTransfer>
            <ns2:DataEncryptionInfo authenticate="true">
                <ns2:EncryptionPubKeyDigest Algorithm="http://www.w3.org/2001/04/xmlenc#sha256" Version="E002">dFAYe281vj9NB7w+VoWIdfHnjY9hNbZLbHsDOu76QAE=</ns2:EncryptionPubKeyDigest>
                <ns2:TransactionKey>...</ns2:TransactionKey>
            </ns2:DataEncryptionInfo>
            <ns2:SignatureData authenticate="true">...</ns2:SignatureData>
        </ns2:DataTransfer>
    </ns2:body>
</ns2:ebicsRequest>

我使用了自定义的 NamespacePrefixMapper 来声明 ds 和 xsi 的默认命名空间和前缀.对于命名空间 ds 它工作正常.但对于默认命名空间，它没有.它被声明两次，一次为 ns2，一次为"，后者来自我的自定义 NamespacePrefixMapper.getPreDeclaredNamespaceUris.我在这门课上玩了很多.我也尝试使用 package-info.java 但我无法让 jaxb 使用 "http://www.ebics.org/H003" 作为默认命名空间.我也不明白的是 ns4 和 ns5 的外观，它们根本不是 xml 文档的一部分.

I have used a custom NamespacePrefixMapper to declare the default namespace and prefixes for ds and xsi. For the namespace ds it works fine. But for the default namespace it does not. It is declared two times once as ns2 and once as "" the latter coming from my custom NamespacePrefixMapper.getPreDeclaredNamespaceUris. I have played around a lot with this class. Also I tried to use the package-info.java but I was not able to make jaxb use "http://www.ebics.org/H003" as default namespace. What I also do not understand is the appearance of ns4 and ns5 which are not at all part of the xml document.

我的 NamespacePrefixMapper 类看起来像

My NamespacePrefixMapper class looks like

public class NamespacePrefixMapperImpl extends NamespacePrefixMapper implements NamespaceContext {
    private static final String[] EMPTY_STRING = new String[0];

    private Map prefixToUri = null;
    private Map uriToPrefix = null;

    private void init(){
    prefixToUri = new HashMap();

    prefixToUri.put("", "http://www.ebics.org/H003" );
    prefixToUri.put("ds", "http://www.w3.org/2000/09/xmldsig#" );
    prefixToUri.put("xsi", "http://www.w3.org/2001/XMLSchema-instance" );
    prefixToUri.put(XMLConstants.XML_NS_PREFIX, XMLConstants.XML_NS_URI  );
    prefixToUri.put(XMLConstants.XMLNS_ATTRIBUTE , XMLConstants.XMLNS_ATTRIBUTE_NS_URI );

    uriToPrefix = new HashMap();
    for(String prefix : prefixToUri.keySet()){
        uriToPrefix.put(prefixToUri.get(prefix), prefix);
    }
    }

    @Override
    public String getPreferredPrefix(String namespaceUri, String suggestion, boolean requirePrefix) {
        if (uriToPrefix == null)
        init();

        if (uriToPrefix.containsKey(namespaceUri)){
            return uriToPrefix.get(namespaceUri);
        }

        return suggestion;
    }

    @Override
    public String[] getContextualNamespaceDecls() {
    // TODO Auto-generated method stub
    return EMPTY_STRING;
    }

    @Override
    public String[] getPreDeclaredNamespaceUris() {
    // TODO Auto-generated method stub
    return EMPTY_STRING;

    }

    @Override
    public String[] getPreDeclaredNamespaceUris2() {
    return new String [] {"", prefixToUri.get("")};

    }

    public String getNamespaceURI(String prefix) {
    if (prefixToUri == null)
            init();

    if (prefixToUri.containsKey(prefix)) {
        return prefixToUri.get(prefix);
    } else {
        return XMLConstants.NULL_NS_URI;
    }
    }

    public String getPrefix(String namespaceURI) {
    if (uriToPrefix == null)
            init();

        if (uriToPrefix.containsKey(namespaceURI)){
        return uriToPrefix.get(namespaceURI);
    } else {
        return null;
    }
    }

    public Iterator getPrefixes(String namespaceURI) {
    if (uriToPrefix == null)
            init();

    List prefixes = new LinkedList();

    if (uriToPrefix.containsKey(namespaceURI)){
        prefixes.add(uriToPrefix.get(namespaceURI));
    }
    return prefixes.iterator();
    }


}

我正在使用

Manifest-Version: 1.0
Ant-Version: Apache Ant 1.6.5
Created-By: 1.5.0-b64 (Sun Microsystems Inc.)
Specification-Title: Java Architecture for XML Binding
Specification-Version: 2.0
Specification-Vendor: Sun Microsystems, Inc.
Implementation-Title: JAXB Reference Implementation 
Implementation-Version: 2.0.2
Implementation-Vendor: Sun Microsystems, Inc.
Implementation-Vendor-Id: com.sun
Extension-Name: com.sun.xml.bind
Build-Id: b01
Class-Path: jaxb-api.jar activation.jar jsr173_1.0_api.jar jaxb1-impl.
 jar

Name: com.sun.xml.bind.v2.runtime
Implementation-Version: 2.0.2-b01-fcs

推荐答案

出于性能原因，JAXB 总是将 JAXBContext 已知的所有命名空间添加到 XML 文档的根元素.有关详细信息，请参阅 Kohsuke 对 JAXB-103 的评论.

JAXB always adds all namespaces that are known by the JAXBContext to the root element of the XML document for performance reasons. See this comment by Kohsuke on JAXB-103 for more information.

我发现处理此问题的唯一方法是在使用 JAXB 创建文档后自己遍历文档，并使用以下帮助程序类删除所有未使用的命名空间:

The only way I found to deal with this, is to traverse the document myself after it has been created with JAXB and remove all unused namespaces using the following helper class:

public class RemoveUnusedNamespaces {

    private static final String XML_NAMESPACE_SCHEMA_INSTANCE = "http://www.w3.org/2001/XMLSchema-instance";

    private static final String XML_NAMESPACE_NAMESPACE = "http://www.w3.org/2000/xmlns/";

    private interface ElementVisitor {

        void visit(Element element);

    }

    public void process(Document document) {
        final Set<String> namespaces = new HashSet<String>();

        Element element = document.getDocumentElement();
        traverse(element, new ElementVisitor() {

            public void visit(Element element) {
                String namespace = element.getNamespaceURI();
                if (namespace == null)
                    namespace = "";
                namespaces.add(namespace);
                NamedNodeMap attributes = element.getAttributes();
                for (int i = 0; i < attributes.getLength(); i++) {
                    Node node = attributes.item(i);
                    if (XML_NAMESPACE_NAMESPACE.equals(node.getNamespaceURI()))
                        continue;
                    String prefix;
                    if (XML_NAMESPACE_SCHEMA_INSTANCE.equals(node.getNamespaceURI())) {
                        if ("type".equals(node.getLocalName())) {
                            String value = node.getNodeValue();
                            if (value.contains(":"))
                                prefix = value.substring(0, value.indexOf(":"));
                            else
                                prefix = null;
                        } else {
                            continue;
                        }
                    } else {
                        prefix = node.getPrefix();
                    }
                    namespace = element.lookupNamespaceURI(prefix);
                    if (namespace == null)
                        namespace = "";
                    namespaces.add(namespace);
                }
            }

        });
        traverse(element, new ElementVisitor() {

            public void visit(Element element) {
                Set<String> removeLocalNames = new HashSet<String>();
                NamedNodeMap attributes = element.getAttributes();
                for (int i = 0; i < attributes.getLength(); i++) {
                    Node node = attributes.item(i);
                    if (!XML_NAMESPACE_NAMESPACE.equals(node.getNamespaceURI()))
                        continue;
                    if (namespaces.contains(node.getNodeValue()))
                        continue;
                    removeLocalNames.add(node.getLocalName());
                }
                for (String localName : removeLocalNames)
                    element.removeAttributeNS(XML_NAMESPACE_NAMESPACE, localName);
            }

        });
    }

    private final void traverse(Element element, ElementVisitor visitor) {
        visitor.visit(element);
        NodeList children = element.getChildNodes();
        for (int i = 0; i < children.getLength(); i++) {
            Node node = children.item(i);
            if (node.getNodeType() != Node.ELEMENT_NODE)
                continue;
            traverse((Element) node, visitor);
        }
    }

}

这篇关于在 JAXB 中控制命名空间前缀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！