@XmlSchema(namespace = "http://www.lzrabbit.cn")
package com.bjpowernode.test;

import javax.xml.bind.annotation.XmlSchema;

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ns2:classA xmlns:ns2="http://www.lzrabbit.cn">
  <classAId>11</classAId>
  <ClassAName>A1</ClassAName>
  <classB>
    <ClassBId>22</ClassBId>
    <ClassBName>B2</ClassBName>
  </classB>
</ns2:classA>

@XmlSchema( xmlns = { @XmlNs(namespaceURI = "http://www.lzrabbit.cn", prefix = "rabbit"), @XmlNs(namespaceURI = "http://www.cnblogs.com", prefix = "blog")})

package com.bjpowernode.test;
import javax.xml.bind.annotation.XmlSchema;
import javax.xml.bind.annotation.XmlNs;

Package com.bjpowernode.test;

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;

  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;
  }
}

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<rabbit:classA xmlns:rabbit="http://www.lzrabbit.cn" xmlns:blog="http://www.cnblogs.com">
  <classAId>11</classAId>
  <ClassAName>A1</ClassAName>
  <classB>
    <ClassBId>22</ClassBId>
    <ClassBName>B2</ClassBName>
  </classB>
</rabbit:classA>

marshaller.setProperty("com.sun.xml.bind.namespacePrefixMapper", new NamespacePrefixMapper() {
        @Override
        public String getPreferredPrefix(String namespaceUri, String suggestion, boolean requirePrefix) {
          if (namespaceUri.equals("http://www.lzrabbit.cn")) return "abc";
          return suggestion;
        }
      });

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<abc:classA xmlns:abc="http://www.lzrabbit.cn">
  <classAId>11</classAId>
  <ClassAName>A1</ClassAName>
  <classB>
    <ClassBId>22</ClassBId>
    <ClassBName>B2</ClassBName>
  </classB>
</abc:classA>

package com.bjpowernode.test;

import java.io.StringReader;
import java.io.StringWriter;

import javax.xml.bind.*;

import com.sun.xml.bind.marshaller.NamespacePrefixMapper;
import com.sun.xml.bind.v2.WellKnownNamespace;

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

      marshaller.setProperty("com.sun.xml.bind.namespacePrefixMapper", new NamespacePrefixMapper() {
        @Override
        public String getPreferredPrefix(String namespaceUri, String suggestion, boolean requirePrefix) {
          if (namespaceUri.equals("http://www.lzrabbit.cn")) return "abc";
          if (namespaceUri.contains("http://www.cnblogs.com")) return "blog";
          return suggestion;
        }
      });

      StringWriter writer = new StringWriter();
      marshaller.marshal(obj, writer);
      return writer.toString();
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }

  @SuppressWarnings("unchecked")
  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));
    } catch (Exception e) {
      throw new RuntimeException(e.getMessage());
    }
  }
}

<dependency>
 <groupId>com.sun.xml.bind</groupId>
 <artifactId>jaxb-core</artifactId>
 <version>2.2.7</version>
</dependency>

<dependency>
 <groupId>com.sun.xml.bind</groupId>
 <artifactId>jaxb-impl</artifactId>
 <version>2.2.7</version>
</dependency>