JAXB玩转命名空间

声明：如果你正在发愁xml命名空间及其前缀问题，那么请继续，否则请跳过

本文讲解使用jaxb结合dom4j的XMLFilterImpl过滤器实现序列化和反序列化的完全控制

主要实现以下功能

依赖的jar dom4j

 <dependency>            <groupId>dom4j</groupId>            <artifactId>dom4j</artifactId>            <version>1.6.1</version> </dependency>
主要原理就是在序列化和反序列化时通过XMLFilterImpl的匿名实现类实现命名空间及xml节点名称的控制，实现多样化需求，废话不多说直接上代码，有更多个性化需求的看官请自行扩展
package cn.lzrabbit.util;import java.io.StringReader;import java.io.StringWriter;import javax.xml.bind.*;import javax.xml.transform.sax.SAXSource;import org.dom4j.io.OutputFormat;import org.dom4j.io.XMLWriter;import org.xml.sax.Attributes;import org.xml.sax.InputSource;import org.xml.sax.SAXException;import org.xml.sax.XMLReader;import org.xml.sax.helpers.XMLFilterImpl;import org.xml.sax.helpers.XMLReaderFactory;public class XmlUtil {    public static String toXML(Object obj) {        try {            JAXBContext context = JAXBContext.newInstance(obj.getClass());            Marshaller marshaller = context.createMarshaller();            marshaller.setPRoperty(Marshaller.JAXB_ENCODING, "UTF-8");// //编码格式            marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);// 是否格式化生成的xml串            marshaller.setProperty(Marshaller.JAXB_FRAGMENT, false);// 是否省略xm头声明信息            StringWriter out = new StringWriter();            OutputFormat format = new OutputFormat();            format.setIndent(true);            format.setNewlines(true);            format.setNewLineAfterDeclaration(false);            XMLWriter writer = new XMLWriter(out, format);            XMLFilterImpl nsfFilter = new XMLFilterImpl() {                private boolean ignoreNamespace = false;                private String rootNamespace = null;                private boolean isRootElement = true;                @Override                public void startDocument() throws SAXException {                    super.startDocument();                }                @Override                public void startElement(String uri, String localName, String qName, Attributes atts) throws SAXException {                    if (this.ignoreNamespace) uri = "";                    if (this.isRootElement) this.isRootElement = false;                    else if (!uri.equals("") && !localName.contains("xmlns")) localName = localName + " xmlns=/"" + uri + "/"";                    super.startElement(uri, localName, localName, atts);                }                @Override                public void endElement(String uri, String localName, String qName) throws SAXException {                    if (this.ignoreNamespace) uri = "";                    super.endElement(uri, localName, localName);                }                @Override                public void startPrefixMapping(String prefix, String url) throws SAXException {                    if (this.rootNamespace != null) url = this.rootNamespace;                    if (!this.ignoreNamespace) super.startPrefixMapping("", url);                }            };            nsfFilter.setContentHandler(writer);            marshaller.marshal(obj, nsfFilter);            return out.toString();        } catch (Exception e) {            throw new RuntimeException(e);        }    }    public static <T> T fromXML(String xml, Class<T> valueType) {        try {            JAXBContext context = JAXBContext.newInstance(valueType);            Unmarshaller unmarshaller = context.createUnmarshaller();            // return (T) unmarshaller.unmarshal(new StringReader(xml));            SerializeUtil obj = new SerializeUtil();            XMLReader reader = XMLReaderFactory.createXMLReader();            XMLFilterImpl nsfFilter = new XMLFilterImpl() {                private boolean ignoreNamespace = false;                @Override                public void startDocument() throws SAXException {                    super.startDocument();                }                @Override                public void startElement(String uri, String localName, String qName, Attributes atts) throws SAXException {                    if (this.ignoreNamespace) uri = "";                    super.startElement(uri, localName, qName, atts);                }                @Override                public void endElement(String uri, String localName, String qName) throws SAXException {                    if (this.ignoreNamespace) uri = "";                    super.endElement(uri, localName, localName);                }                @Override                public void startPrefixMapping(String prefix, String url) throws SAXException {                    if (!this.ignoreNamespace) super.startPrefixMapping("", url);                }            };            nsfFilter.setParent(reader);            InputSource input = new InputSource(new StringReader(xml));            SAXSource source = new SAXSource(nsfFilter, input);            return (T) unmarshaller.unmarshal(source);        } catch (Exception e) {            throw new RuntimeException(e.getMessage());        }    }}
示例实体类
import javax.xml.bind.annotation.*;@XmlRootElement(namespace="http://www.lzrabbit.cn/")@XmlaccessorType(XmlAccessType.FIELD)public class ClassA {    private int classAId;        @XmlElement(name="ClassAName")    private String classAName;    @XmlElement(namespace="http://www.cnblogs.com/")    private ClassB classB;    public int getClassAId() {        return classAId;    }    public void setClassAId(int classAId) {        this.classAId = classAId;    }    public String getClassAName() {        return classAName;    }    public void setClassAName(String classAName) {        this.classAName = classAName;    }    public ClassB getClassB() {        return classB;    }    public void setClassB(ClassB classB) {        this.classB = classB;    }}import javax.xml.bind.annotation.*;@XmlAccessorType(XmlAccessType.FIELD)public class ClassB {    private int ClassBId;    private String ClassBName;    public int getClassBId() {        return ClassBId;    }    public void setClassBId(int classBId) {        this.ClassBId = classBId;    }    public String getClassBName() {        return ClassBName;    }    public void setClassBName(String classBName) {        this.ClassBName = classBName;    }}
调用
import cn.lzrabbit.util.XmlUtil;public class MainRun {    /**     * @param args     */    public static void main(String[] args) {        ClassB classB = new ClassB();        classB.setClassBId(22);        classB.setClassBName("B2");        ClassA classA = new ClassA();        classA.setClassAId(11);        classA.setClassAName("A1");        classA.setClassB(classB);        System.out.println(XmlUtil.toXML(classA));    }}
输出结果：
<?xml version="1.0" encoding="UTF-8"?><classA xmlns="http://www.lzrabbit.cn/">  <classAId>11</classAId>  <ClassAName>A1</ClassAName>  <classB xmlns="http://www.cnblogs.com/">    <ClassBId>22</ClassBId>    <ClassBName>B2</ClassBName>  </classB></classA>
可以看到输出的xml完全达到我们的预期
实现细节都在代码里面了，很简单，当遇到有特殊需求的xml命名空间问题时，再也不用愁了
 
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