JAXB命名空间及前缀_动力节点Java学院整理

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

• 序列化及反序列化时忽略命名空间
• 序列化时使用@xmlrootelement(namespace="http://www.lzrabbit.cn")注解作为类的默认命名空间，彻底消除命名空间前缀
• 序列化时引用类有不同命名空间时也不会生成命名空间前缀，而是在具体的xml节点上添加相应的xmlns声明
• 其它的xml节点命名及命名空间需求
• 同一个包下有多个命名空间
• 自定义命名空间前缀

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 com.bjpowernode.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 com.bjpowernode.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

总结

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