JAXB转换对象到XML前缀ns2:的问题解决方案

最新推荐文章于 2024-04-18 17:52:08 发布

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#xsd #xml #序列化

本文探讨了在使用JAXB进行对象到XML转换时，如何避免生成不必要的命名空间前缀如ns2。介绍了两种方法：一是通过pack-info.java配置文件，二是直接在JAXB实体类中指定命名空间，并使用NamespacePrefixMapper进行前缀设置。

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项目在使用JAXB转换对象到xml文件是总是莫名其妙的生成ns2的前缀，经过查询资料总结出两种方式：不清楚注解作用的转这里：
https://blog.youkuaiyun.com/lhzjj/article/details/11796713
（1）pack-info.java方式
在要转换对象目录下新建pack-info.java并进行相关配置即可：以下是demo

package com.cn.rcp.xsdtest;
import java.io.StringWriter;
import java.util.Date;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlTransient;
import javax.xml.bind.annotation.XmlType;



import com.cn.rcp.xsdtest.EnvelopInfo;
import com.sun.xml.internal.bind.marshaller.NamespacePrefixMapper;

public class Root {
public static void main(String[] args) {
	RootClass rc = new RootClass();
	EleClassA a = new EleClassA();
	EleClassB b = new EleClassB();
	
	a.setAttrC("attrc");
	a.setEleA("eleA");
	a.setEleB("eleB");
	
	b.setAttrPassword("attrPassword");
	b.setAttrUserName("attrUsrName");
    b.setEleCode("eleCode");

	rc.setA(a);
	rc.setB(b);
	rc.setRoot("root");
	rc.setRootA("rootA");
	
		
	JAXBContext context;
	try {
		context = JAXBContext.newInstance(RootClass.class);
		Marshaller mar = context.createMarshaller();
		mar.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
		mar.setProperty(Marshaller.JAXB_ENCODING, "UTF-8");
		//mar.setProperty(Marshaller.JAXB_NO_NAMESPACE_SCHEMA_LOCATION, value);
		//mar.setProperty(Marshaller.JAXB_SCHEMA_LOCATION, "http://www.w3.orgxxx#");
		
		StringWriter writer = new StringWriter();
		
		mar.marshal(rc, writer);
		
		System.out.println(writer.toString());
	} catch (JAXBException e) {
		e.printStackTrace();
	}
	
}
}



@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name="rootcfsdf")
class RootClass {


private EleClassA a;

private EleClassB b;

private String root;

private String rootA;


public EleClassA getA() {
	return a;
}
public void setA(EleClassA a) {
	this.a = a;
}

public EleClassB getB() {
	return b;
}
public void setB(EleClassB b) {
	this.b = b;
}

public String getRoot() {
	return root;
}
public void setRoot(String root) {
	this.root = root;
}

public String getRootA() {
	return rootA;
}
public void setRootA(String rootA) {
	this.rootA = rootA;
    }	
}

@XmlAccessorType(XmlAccessType.PROPERTY)
class EleClassA {

private String eleA;
private String eleB;

private String attrC;


public String getEleA() {
	return eleA;
}

public void setEleA(String eleA) {
	this.eleA = eleA;
}

@XmlElement(name="elebnewname")
public String getEleB() {
	return eleB;
}

public void setEleB(String eleB) {
    this.eleB = eleB;
}

//@XmlAttribute()
@XmlTransient
public String getAttrC() {
	return attrC;
}

public void setAttrC(String attrC) {
	this.attrC = attrC;
}
	
}




class EleClassB {
private String attrUserName;
private String attrPassword;

private String eleCode;

@XmlAttribute
public String getAttrUserName() {
	return attrUserName;
}
public void setAttrUserName(String attrUserName) {
	this.attrUserName = attrUserName;
}
@XmlAttribute(name="password")
public String getAttrPassword() {
	return attrPassword;
}
public void setAttrPassword(String attrPassword) {
	this.attrPassword = attrPassword;
}

public String getEleCode() {
	return eleCode;
}
public void setEleCode(String eleCode) {
	this.eleCode = eleCode;
}


	
}

pack-info.java:

@javax.xml.bind.annotation.XmlSchema(namespace = "http://www.w3.org/2000/09/xmldsig#",
xmlns={@javax.xml.bind.annotation.XmlNs(prefix="xsd",namespaceURI="http://www.sdeport.gov.cn/xsd/ArrivalSchema.xsd"),
@javax.xml.bind.annotation.XmlNs(prefix="",namespaceURI="http://www.w3.org/2000/09/xmldsig#")}
, elementFormDefault = javax.xml.bind.annotation.XmlNsForm.QUALIFIED)
package com.cn.rcp.xsdtest;

结果：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<rootcfsdf xmlns="http://www.w3.org/2000/09/xmldsig#" xmlns:xsd="http://www.sdeport.gov.cn/xsd/ArrivalSchema.xsd">
    <a>
        <eleA>eleA</eleA>
        <elebnewname>eleB</elebnewname>
    </a>
    <b password="attrPassword" attrUserName="attrUsrName">
        <eleCode>eleCode</eleCode>
    </b>
    <root>root</root>
    <rootA>rootA</rootA>
</rootcfsdf>

（2）

不用pack-info.java

package com.cn.rcp.xsd;
import java.io.StringWriter;
import java.util.Date;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlTransient;
import javax.xml.bind.annotation.XmlType;



import com.cn.rcp.xsdtest.EnvelopInfo;
import com.sun.xml.internal.bind.marshaller.NamespacePrefixMapper;

public class Root {

public static void main(String[] args) {
	RootClass rc = new RootClass();
	EleClassA a = new EleClassA();
	EleClassB b = new EleClassB();
	
	a.setAttrC("attrc");
	a.setEleA("eleA");
	a.setEleB("eleB");
	
	b.setAttrPassword("attrPassword");
	b.setAttrUserName("attrUsrName");
    b.setEleCode("eleCode");

	rc.setA(a);
	rc.setB(b);
	rc.setRoot("root");
	rc.setRootA("rootA");
	
	
	
	JAXBContext context;
	try {
		context = JAXBContext.newInstance(RootClass.class);
		Marshaller mar = context.createMarshaller();
		mar.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
		mar.setProperty(Marshaller.JAXB_ENCODING, "UTF-8");
		//mar.setProperty(Marshaller.JAXB_NO_NAMESPACE_SCHEMA_LOCATION, value);
		//mar.setProperty(Marshaller.JAXB_SCHEMA_LOCATION, "http://www.w3.orgxxx#");
			
		
		mar.setProperty("com.sun.xml.internal.bind.namespacePrefixMapper", new NamespacePrefixMapper() {	
			@Override
			public String getPreferredPrefix(String namespaceUri,
					String suggestion, boolean requirePrefix) {
				if (namespaceUri.equals("http://www.w3.org/2000/09/xmldsig#")) {
					
					return "";
				}
				if (namespaceUri.equals("http://www.w3.org")){
					
					return "org";
				}
				return suggestion;
			}
		});
		
		StringWriter writer = new StringWriter();
		
		mar.marshal(rc, writer);
		
		System.out.println(writer.toString());
	} catch (JAXBException e) {
		e.printStackTrace();
	}
	
}
}



@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name="rootclass" , namespace="http://www.w3.org/2000/09/xmldsig#")
class RootClass {
	
@XmlElement(namespace="http://www.w3.org/2000/09/xmldsig#")  
private EleClassA a;
@XmlElement(namespace="http://www.w3.org/2000/09/xmldsig#")  
private EleClassB b;
@XmlElement(namespace="http://www.w3.org")  
private String root;
@XmlElement(namespace="http://www.w3.org/2000/09/xmldsig#")  
private String rootA;


public EleClassA getA() {
	return a;
}
public void setA(EleClassA a) {
	this.a = a;
}

public EleClassB getB() {
	return b;
}
public void setB(EleClassB b) {
	this.b = b;
}

public String getRoot() {
	return root;
}
public void setRoot(String root) {
	this.root = root;
}

public String getRootA() {
	return rootA;
}
public void setRootA(String rootA) {
	this.rootA = rootA;
}
	
}




@XmlAccessorType(XmlAccessType.PROPERTY)
class EleClassA {
    
private String eleA;
private String eleB;

private String attrC;

@XmlElement(namespace="http://www.w3.org/2000/09/xmldsig#")
public String getEleA() {
	return eleA;
}

public void setEleA(String eleA) {
	this.eleA = eleA;
}

@XmlElement(name="elebnewname",namespace="http://www.w3.org/2000/09/xmldsig#")
public String getEleB() {
	return eleB;
}

public void setEleB(String eleB) {
    this.eleB = eleB;
}

//@XmlAttribute()
@XmlTransient
public String getAttrC() {
	return attrC;
}

public void setAttrC(String attrC) {
	this.attrC = attrC;
}
	
}




class EleClassB {
private String attrUserName;
private String attrPassword;

private String eleCode;

@XmlAttribute
public String getAttrUserName() {
	return attrUserName;
}
public void setAttrUserName(String attrUserName) {
	this.attrUserName = attrUserName;
}
@XmlAttribute(name="password")
public String getAttrPassword() {
	return attrPassword;
}
public void setAttrPassword(String attrPassword) {
	this.attrPassword = attrPassword;
}
@XmlElement(namespace="http://www.w3.org/2000/09/xmldsig#")
public String getEleCode() {
	return eleCode;
}
public void setEleCode(String eleCode) {
	this.eleCode = eleCode;
}



}

结果：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<rootclass xmlns="http://www.w3.org/2000/09/xmldsig#" xmlns:org="http://www.w3.org">
    <a>
        <eleA>eleA</eleA>
        <elebnewname>eleB</elebnewname>
    </a>
    <b password="attrPassword" attrUserName="attrUsrName">
        <eleCode>eleCode</eleCode>
    </b>
    <org:root>root</org:root>
    <rootA>rootA</rootA>
</rootclass>

总结：
以上两种方式其实都是将所有元素ElEMENT都加上namespace的方法实现的，只是pack-info.java中的namespace = "http://www.w3.org/2000/09/xmldsig#"是将同级包目录下所有的jaxb实体都增加上来namespace，然后用XmlNs的方式设置前缀，而不用pack-info.java的第二种方式其实是手动给所有jaxb实体的ELEMENT上添加了namespace，然后用匿名内部类NamespacePrefixMapper的方式进行前缀设置，两种方式都可以实现表空间前缀的设置，之所以你的代码转换的时候出现ns2是因为ns2所在的那个元素ELEMENT上没有指定namespace，那在转换的时候未定义命名空间的那个ELEMENT就会被认为是默认的命名空间下的元素，所以下面 <a> 节点没有前缀，一个xml只能有一个默认的命名空间，所以再用匿名内部类NamespacePrefixMapper的方式进行前缀设置的时候

if(namespaceUri.equals("http://www.w3.org/2000/09/xmldsig#")) {return "";}

返回的这个“”就和<a>节点冲突了，这种情况下就会默认生成一个前缀就是这个ns2.
在这里插入图片描述
也就是说ns2其实是Marshaller 在转换的时候为未定义的ELEMENT自动生成的一个前缀，因为xml文件里面每一个节点都需要有明确的命名空间，也就是定义这个节点的xsd，否则就像类没有所属的jar包一样没有明确的意义。