JAXB编组XMPP节

Question

我正在尝试使用以下代码段整理邮件：        JAXBContext jContext = JAXBContext.newInstance(Iq.class);        Marshaller m = newJAXBContext.createMarshaller();        m.setProperty(Marshaller.JAXB_FRAGMENT, Boolean.TRUE);        m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);        Bind bind = new Bind();        bind.setResource("resource");        Iq iq = new Iq();        iq.setId(iqId);        iq.setType("set");        iq.getAnies().add(bind);        ByteArrayOutputStream baos = new ByteArrayOutputStream();        m.marshal(iq, baos);在此，Iq和Bind是由相关xmpp模式形成的对象。我的问题是，对于jaxb 2.0和更高版本，所有名称空间都在root元素中声明：<iq from='[e-mail]/balcony'     id='rg1'     type='get'  xmlns='jabber:client'  xmlns:ns1='urn:ietf:params:xml:ns:xmpp-bind'>     <ns1:bind>        <ns1:resource>resource</ns1:resource>    </ns1:bind></iq>但是，这里需要的是名称空间应占据适当的位置：<iq from='[e-mail]/balcony'     id="rg1"     type="get" xmlns="jabber:client">       <bind xmlns="urn:ietf:params:xml:ns:xmpp-bind">             <resource>resource</resource>       </bind></iq>有没有办法通过JAXB 2.0或更高版本在第二个xml节中封送xmpp节？长话短说，这里有两个问题：1.在适当的位置声明名称空间。2.删除我知道可以使用NamespacePrefixMapper删除的名称空间前缀吗？虽然不确定，但举个例子会很好。

Answer 1

怎么样？

创建一个自定义XMLStreamWriter，它将所有名称空间声明都视为默认名称空间，然后将其编组为：

ByteArrayOutputStream baos = new ByteArrayOutputStream();

XMLOutputFactory xof = XMLOutputFactory.newFactory();

XMLStreamWriter xsw = xof.createXMLStreamWriter(System.out);

xsw = new MyXMLStreamWriter(xsw);

m.marshal(iq, xsw);

xsw.close();

MyXMLStreamWriter

import java.util.Iterator;

import javax.xml.namespace.NamespaceContext;

import javax.xml.stream.XMLStreamException;

import javax.xml.stream.XMLStreamWriter;

public class MyXMLStreamWriter implements XMLStreamWriter {

    private XMLStreamWriter xsw;

    private MyNamespaceContext nc = new MyNamespaceContext();

    public MyXMLStreamWriter(XMLStreamWriter xsw) throws Exception {

        this.xsw = xsw;

        xsw.setNamespaceContext(nc);

    }

    public void close() throws XMLStreamException {

        xsw.close();

    }

    public void flush() throws XMLStreamException {

        xsw.flush();

    }

    public NamespaceContext getNamespaceContext() {

        return xsw.getNamespaceContext();

    }

    public String getPrefix(String arg0) throws XMLStreamException {

        return xsw.getPrefix(arg0);

    }

    public Object getProperty(String arg0) throws IllegalArgumentException {

        return xsw.getProperty(arg0);

    }

    public void setDefaultNamespace(String arg0) throws XMLStreamException {

        xsw.setDefaultNamespace(arg0);

    }

    public void setNamespaceContext(NamespaceContext arg0) throws XMLStreamException {

    }

    public void setPrefix(String arg0, String arg1) throws XMLStreamException {

        xsw.setPrefix(arg0, arg1);

    }

    public void writeAttribute(String arg0, String arg1) throws XMLStreamException {

        xsw.writeAttribute(arg0, arg1);

    }

    public void writeAttribute(String arg0, String arg1, String arg2) throws XMLStreamException {

        xsw.writeAttribute(arg0, arg1, arg2);

    }

    public void writeAttribute(String arg0, String arg1, String arg2, String arg3) throws XMLStreamException {

        xsw.writeAttribute(arg0, arg1, arg2, arg3);

    }

    public void writeCData(String arg0) throws XMLStreamException {

        xsw.writeCData(arg0);

    }

    public void writeCharacters(String arg0) throws XMLStreamException {

        xsw.writeCharacters(arg0);

    }

    public void writeCharacters(char[] arg0, int arg1, int arg2) throws XMLStreamException {

        xsw.writeCharacters(arg0, arg1, arg2);

    }

    public void writeComment(String arg0) throws XMLStreamException {

        xsw.writeComment(arg0);

    }

    public void writeDTD(String arg0) throws XMLStreamException {

        xsw.writeDTD(arg0);

    }

    public void writeDefaultNamespace(String arg0) throws XMLStreamException {

        xsw.writeDefaultNamespace(arg0);

    }

    public void writeEmptyElement(String arg0) throws XMLStreamException {

        xsw.writeEmptyElement(arg0);

    }

    public void writeEmptyElement(String arg0, String arg1) throws XMLStreamException {

        xsw.writeEmptyElement(arg0, arg1);

    }

    public void writeEmptyElement(String arg0, String arg1, String arg2) throws XMLStreamException {

        xsw.writeEmptyElement(arg0, arg1, arg2);

    }

    public void writeEndDocument() throws XMLStreamException {

        xsw.writeEndDocument();

    }

    public void writeEndElement() throws XMLStreamException {

        xsw.writeEndElement();

    }

    public void writeEntityRef(String arg0) throws XMLStreamException {

        xsw.writeEntityRef(arg0);

    }

    public void writeNamespace(String arg0, String arg1) throws XMLStreamException {

    }

    public void writeProcessingInstruction(String arg0) throws XMLStreamException {

        xsw.writeProcessingInstruction(arg0);

    }

    public void writeProcessingInstruction(String arg0, String arg1) throws XMLStreamException {

        xsw.writeProcessingInstruction(arg0, arg1);

    }

    public void writeStartDocument() throws XMLStreamException {

        xsw.writeStartDocument();

    }

    public void writeStartDocument(String arg0) throws XMLStreamException {

        xsw.writeStartDocument(arg0);

    }

    public void writeStartDocument(String arg0, String arg1) throws XMLStreamException {

        xsw.writeStartDocument(arg0, arg1);

    }

    public void writeStartElement(String arg0) throws XMLStreamException {

        xsw.writeStartElement(arg0);

    }

    public void writeStartElement(String arg0, String arg1) throws XMLStreamException {

        xsw.writeStartElement(arg0, arg1);

    }

    public void writeStartElement(String arg0, String arg1, String arg2) throws XMLStreamException {

        xsw.writeStartElement("", arg1, arg2);

        if(null != arg2 || arg2.length() > 0) {

            String currentDefaultNS = nc.getNamespaceURI("");

            if(!arg2.equals(currentDefaultNS)) {

                writeDefaultNamespace(arg2);

                nc.setDefaultNS(arg2);

            }

        }

     }

    private static class MyNamespaceContext implements NamespaceContext {

        private String defaultNS = "";

        public void setDefaultNS(String ns) {

            defaultNS = ns;

        }

        public String getNamespaceURI(String arg0) {

            if("".equals(arg0)) {

                return defaultNS;

            }

            return null;

        }

        public String getPrefix(String arg0) {

            return "";

        }

        public Iterator getPrefixes(String arg0) {

            return null;

        }

    }

}

Answer 2

如今，您还可以使用自定义映射器来控制前缀。

    NamespacePrefixMapper namespacePrefixMapper = new com.sun.xml.bind.marshaller.NamespacePrefixMapper() {

        private Map<String, String> prefixes;

        {

            prefixes = new HashMap<>(3);

            prefixes.put(XMLConstants.XML_NS_URI, XMLConstants.XML_NS_PREFIX);

            prefixes.put(XMLConstants.W3C_XML_SCHEMA_INSTANCE_NS_URI, "xsi");

            prefixes.put(XMLConstants.W3C_XML_SCHEMA_NS_URI, "xs");

            prefixes.put(WellKnownNamespace.XML_MIME_URI, "xmime");

        }

        @Override

        public String getPreferredPrefix(String namespaceUri, String suggestion,

            boolean requirePrefix) {

            String prefix = suggestion == null ? prefixes.get(namespaceUri)

                : suggestion;

            return prefix == null ? XMLConstants.DEFAULT_NS_PREFIX : prefix;

        }

    };

    marshaller.setProperty("com.sun.xml.bind.namespacePrefixMapper",

        namespacePrefixMapper);