Question

我正在尝试使用以下代码段对邮件进行编组：

        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);

这里，Iq和Bind是由相关的xmpp模式组成的对象。我的问题是，使用jaxb 2.0及更高版本，所有命名空间都在根元素中声明：

<iq from='juliet@example.com/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该占据适当的位置：

<iq from='juliet@example.com/balcony'
     id="rg1"
     type="get" xmlns="jabber:client">
       <bind xmlns="urn:ietf:params:xml:ns:xmpp-bind">
             <resource>resource</resource>
       </bind>
</iq>

是否可以通过JAXB 2.0或更高版本在第二个xml节中看到它们来编组xmpp节？

长话短说，我有两个问题： 1.在适当的位置声明命名空间。 2.删除我理解的名称空间前缀可以使用NamespacePrefixMapper删除？但不确定，一个例子会很棒。

Answer 1

以下情况如何？：

创建一个自定义XMLStreamWriter，它将所有名称空间声明视为默认名称空间，然后编组为：

ByteArrayOutputStream baos = new ByteArrayOutputStream();
XMLOutputFactory xof = XMLOutputFactory.newFactory();
XMLStreamWriter xsw = xof.createXMLStreamWriter(System.out);
xsw = new MyXMLStreamWriter(xsw);
m.marshal(iq, xsw);
xsw.close();

<强> 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

您现在也可以使用自定义映射器控制前缀。

    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);

JAXB编组XMPP节

2 个答案: