JAXB解析与生成XML

常用注解
@XmlRootElement(name = “report”)
将Java类或枚举类型映射成XML中根元素，设置name属性的值可指定义根元素名称，不设置则默认为类型首字母小写的名称。

@XmlType(propOrder = {“rmsId”, “department”, “userId”, “userName”,“reason”,“time”,“conclusion”,“attachList”})
将Java类后枚举类型映射到XML模式类型，设置propOrder可以指定生成XML中各元素的先后顺序。

@XmlElement(name=“attach”)
将JavaBean中的字段值映射到XML元素，设置name属性的值可指定XML元素的名称。

@XmlAttribute(name = “”, required = false)
将JavaBean中的字段映射到XML中元素的属性，设置name属性的值可指定xml中元素属性的名称；
至于required属性，官方文档是说指定 XML 模式属性是可选的还是必需的，不是特别理解。

@XmlElementWrapper(name=“attachList”)
为集合生成xml包装器元素，简单来讲就是使XML元素更有层次感，更美观，该注解只能用在集合上。
例子
1、类结构如下

AssistReportItem 与AssistReportMsg为映射对象；
JAXBUtils提供读写XML的方法；
JAXBXMLTest提供读写测试方法；

2、各个类如下
AssistReportItem 类
package cn.hb.jaxb1;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlRootElement;

/**

• @author:lwz

• @date:2019/10/16 20:07

• @description:

• @modefiled by:
  */
  @XmlAccessorType(XmlAccessType.FIELD)
  @XmlRootElement(name = “attach”)
  public class AssistReportItem {
  private String subjectId;
  private String subjectName;
  private String objectId;
  private String objectName;
  private String opName;
  private String opContent;
  private String opResult;
  private String logTime;
  private String category;
  private String remark;

  public String getSubjectId() {
  return subjectId;
  }

  public void setSubjectId(String subjectId) {
  this.subjectId = subjectId;
  }

  public String getSubjectName() {
  return subjectName;
  }

  public void setSubjectName(String subjectName) {
  this.subjectName = subjectName;
  }

  public String getObjectId() {
  return objectId;
  }

  public void setObjectId(String objectId) {
  this.objectId = objectId;
  }

  public String getObjectName() {
  return objectName;
  }

  public void setObjectName(String objectName) {
  this.objectName = objectName;
  }

  public String getOpName() {
  return opName;
  }

  public void setOpName(String opName) {
  this.opName = opName;
  }

  public String getOpContent() {
  return opContent;
  }

  public void setOpContent(String opContent) {
  this.opContent = opContent;
  }

  public String getOpResult() {
  return opResult;
  }

  public void setOpResult(String opResult) {
  this.opResult = opResult;
  }

  public String getLogTime() {
  return logTime;
  }

  public void setLogTime(String logTime) {
  this.logTime = logTime;
  }

  public String getCategory() {
  return category;
  }

  public void setCategory(String category) {
  this.category = category;
  }

  public String getRemark() {
  return remark;
  }

  public void setRemark(String remark) {
  this.remark = remark;
  }
  }

---

AssistReportMsg 类
package cn.hb.jaxb1;

import javax.xml.bind.annotation.*;
import java.util.List;

/**

• @author:lwz

• @date:2019/10/16 20:03

• @description:

• @modefiled by:
  */
  @XmlAccessorType(XmlAccessType.FIELD)
  @XmlType(propOrder = {“rmsId”, “department”, “userId”, “userName”,“reason”,“time”,“conclusion”,“attachList”})
  @XmlRootElement(name = “report”)
  public class AssistReportMsg {

  private String rmsId;
  private String department;
  private String userId;
  private String userName;
  private String reason;
  private String time;
  private String conclusion;

  @XmlElementWrapper(name=“attachList”)
  @XmlElement(name=“attach”)
  private List attachList;

  public List getAttachList() {
  return attachList;
  }

  public void setAttachList(List attachList) {
  this.attachList = attachList;
  }

  @Override
  public String toString() {
  return “AssistReportMsg{” +
  “rmsId=’” + rmsId + ‘’’ +
  “, department=’” + department + ‘’’ +
  “, userId=’” + userId + ‘’’ +
  “, userName=’” + userName + ‘’’ +
  “, reason=’” + reason + ‘’’ +
  “, time=’” + time + ‘’’ +
  “, conclusion=’” + conclusion + ‘’’ +
  ‘}’;
  }

  public String getRmsId() {
  return rmsId;
  }

  public void setRmsId(String rmsId) {
  this.rmsId = rmsId;
  }

  public String getDepartment() {
  return department;
  }

  public void setDepartment(String department) {
  this.department = department;
  }

  public String getUserId() {
  return userId;
  }

  public void setUserId(String userId) {
  this.userId = userId;
  }

  public String getUserName() {
  return userName;
  }

  public void setUserName(String userName) {
  this.userName = userName;
  }

  public String getReason() {
  return reason;
  }

  public void setReason(String reason) {
  this.reason = reason;
  }

  public String getTime() {
  return time;
  }

  public void setTime(String time) {
  this.time = time;
  }

  public String getConclusion() {
  return conclusion;
  }

  public void setConclusion(String conclusion) {
  this.conclusion = conclusion;
  }
  }
  JAXBUtils 类
  package cn.hb.jaxb;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
import java.io.File;

/**

• @author:lwz

• @date:2019/10/16 19:43

• @description:

• JAXBUtils提供读写XML的方法；

• @modefiled by:
  */
  public class JAXBUtils {

  public static void writeXML(Object obj, File path, Class… clazz) throws JAXBException {
  JAXBContext jctx = JAXBContext.newInstance(clazz);
  Marshaller marshaller = jctx.createMarshaller();
  // 格式化输出，设置换行和缩进，不设置则会显示在一行
  marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
  marshaller.marshal(obj, path);
  // 设置控制台输出
  marshaller.marshal(obj, System.out);
  }

  public static Object readXML(File path, Class… clazz) throws JAXBException {
  JAXBContext jctx = JAXBContext.newInstance(clazz);
  Unmarshaller unMarshaller = jctx.createUnmarshaller();
  Object obj = unMarshaller.unmarshal(path);

   return obj;
  

  }

}

JAXBXMLTest 类
package cn.hb.jaxb;

import javax.xml.bind.JAXBException;
import java.io.File;
import java.time.LocalDate;
import java.util.ArrayList;

/**

• @author:lwz

• @date:2019/10/16 19:45

• @description:

• JAXBXMLTest提供读写测试方法；

• @modefiled by:
  */
  public class JAXBXMLTest {
  private static final String XML_PATH_COUNTRY = “./Country.xml”;
  private static final String XML_PATH_COUNTRIES = “./Countries.xml”;

  public static void main(String[] args) throws JAXBException {
  Country china = new Country();
  china.setName(“中国”);
  china.setCapital(“北京”);
  china.setPopulation(1400000000);
  china.setRank(25);
  String fTimeChina = LocalDate.of(1949, 10, 1).toString();
  china.setFoundationTime(fTimeChina);

   Country america = new Country();
   america.setName("United States of America");
   america.setCapital("New York");
   america.setPopulation(300000000);
   america.setRank(11);
   String fTimeAmerica = LocalDate.of(1776, 7, 4).toString();
   america.setFoundationTime(fTimeAmerica);
  
   File xmlFile = new File(XML_PATH_COUNTRY);
   File xmlFile1 = new File(XML_PATH_COUNTRIES);
  
   System.out.println("\n【写入到" + XML_PATH_COUNTRY + "】");
   JAXBUtils.writeXML(china, xmlFile, Country.class);
  
   System.out.println("\n【写入list到" + XML_PATH_COUNTRIES + "】");
   Countries countries = new Countries();
   ArrayList<Country> list = new ArrayList<>();
   list.add(china);
   list.add(america);
   countries.setCountries(list);
   JAXBUtils.writeXML(countries, xmlFile1, Countries.class);
  
   System.out.println("\n【从" + XML_PATH_COUNTRIES + "中读取】");
   Countries countriesRead = (Countries) JAXBUtils.readXML(xmlFile1, Countries.class, Country.class);
   System.out.println(countriesRead);
  
   System.out.println("\n【从" + XML_PATH_COUNTRY + "中读取】");
   Country countryRead = (Country) JAXBUtils.readXML(xmlFile, Country.class);
   System.out.println(countryRead);
  

  }

}
运行测试类，结果如下：
遇到的问题：
解决方法：
在类上添加这个注解
@XmlAccessorType(XmlAccessType.FIELD)

表示使用这个类中的 private 非静态字段作为 xml 的序列化的属性或者元素。这里还可以选择属性，也就是使用 set/get 方法来序列化属性或者元素