JavaBean与xml互转的方法详解

2021-11-10 13:28:03

本文实例讲述了Jaxb2实现JavaBean与xml互转的方法。分享给大家供大家参考，具体如下：

一、简介

JAXB（Java Architecture for XML Binding) 是一个业界的标准，是一项可以根据XML Schema产生Java类的技术。该过程中，JAXB也提供了将XML实例文档反向生成Java对象树的方法，并能将Java对象树的内容重新写到 XML实例文档。

Jaxb 2.0是JDK 1.6的组成部分。我们不需要下载第三方jar包即可做到轻松转换。Jaxb2使用了JDK的新特性，如：Annotation、GenericType等，需要在即将转换的JavaBean中添加annotation注解。

二、重要概念

JAXBContext类，是应用的入口，用于管理XML/Java绑定信息。

Marshaller接口，将Java对象序列化为XML数据。

Unmarshaller接口，将XML数据反序列化为Java对象。

@XmlType，将Java类或枚举类型映射到XML模式类型

@XmlAccessorType(XmlAccessType.FIELD) ，控制字段或属性的序列化。FIELD表示JAXB将自动绑定Java类中的每个非静态的（static）、非瞬态的（由@XmlTransient标注）字段到XML。其他值还有XmlAccessType.PROPERTY和XmlAccessType.NONE。

@XmlAccessorOrder，控制JAXB 绑定类中属性和字段的排序。

@XmlJavaTypeAdapter，使用定制的适配器（即扩展抽象类XmlAdapter并覆盖marshal()和unmarshal()方法），以序列化Java类为XML。

@XmlElementWrapper ，对于数组或集合（即包含多个元素的成员变量），生成一个包装该数组或集合的XML元素（称为包装器）。

@XmlRootElement，将Java类或枚举类型映射到XML元素。

@XmlElement，将Java类的一个属性映射到与属性同名的一个XML元素。

@XmlAttribute，将Java类的一个属性映射到与属性同名的一个XML属性。

三、示例

1.工具类

package cn.om.utils;

import java.io.StringReader;
import java.io.StringWriter;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;

public class JaxbUtil {

/**
* JavaBean装换成xml
* 默认编码UTF-8
* @param obj
* @return
*/
public static String converTomXml(Object obj) {
return converToXml(obj,"UTF-8");

}
/**
* JavaBean装换成xml
* @param obj
* @param encoding
* @return
*/
private static String converToXml(Object obj, String encoding) {
String result = null;
try {
JAXBContext context = JAXBContext.newInstance(obj.getClass());
Marshaller marshaller = context.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT,true);
marshaller.setProperty(Marshaller.JAXB_ENCODING,encoding);
StringWriter writer = new StringWriter();
marshaller.marshal(obj,writer);
result =writer.toString();
} catch (Exception e) {
e.printStackTrace();
}
return result;
}

/**
* xml装换成JavaBean
* @param xml
* @param c
* @return
*/
@SuppressWarnings("unchecked")
public static<T> T converyToJavaBean(String xml,Class<T> c){
T t = null;
try {
JAXBContext context = JAXBContext.newInstance(c);
Unmarshaller unmarshaller = context.createUnmarshaller();
t = (T)unmarshaller.unmarshal(new StringReader(xml));
} catch (Exception e) {
e.printStackTrace();
}

return t;

}

需要注意的是

Marshaller.JAXB_FORMATTED_OUTPUT 决定是否在转换成xml时同时进行格式化（即按标签自动换行，否则即是一行的xml）

Marshaller.JAXB_ENCODING xml的编码方式

另外，Marshaller 还有其他Property可以设置，可以去查阅api。

2.转换

package cn.com.t1;

import java.util.Date;

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.XmlRootElement;
import javax.xml.bind.annotation.XmlType;

@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement
@XmlType(name = "book",propOrder = {"author","calendar","price","id"})
public class Book {
@XmlElement(required = true)
private String author;
@XmlElement(name = "price_1",required = true)
private float price;
@XmlElement
private Date calendar;
@XmlAttribute
private Integer id;

/**
*
* @return
*/
public String getAuthor() {
return author;
}
public void setAuthor(String author) {
this.author = author;
}
public float getPrice() {
return price;
}
public void setPrice(float price) {
this.price = price;
}
public Date getCalendar() {
return calendar;
}
public void setCalendar(Date calendar) {
this.calendar = calendar;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
@Override
public String toString() {
return "Book [author=" + author + ", price=" + price + ", calendar=" + calendar + ", id=" + id + "]";
}
}

package cn.com.t1;

import java.util.Date;
import org.junit.Test;
import javax.xml.bind.JAXBException;
import cn.om.utils.JaxbUtil;

@SuppressWarnings("unused")
public class JaxbTest1 {
/**
* @throws JAXBException
*/
@Test
public void showMarshaller(){
Book book = new Book();
book.setId(100);
book.setAuthor("lin");
book.setCalendar(new Date());
book.setPrice(23.56f);
String str = JaxbUtil.converTomXml(book);
System.out.println(str);

}

/**
* @throws JAXBException
*/
@Test
public void showUnMarshaller(){
String str = "<?xml version =\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>"+
"<book id =\"100\">"+
"<author>lin</author>" +
"<calendar>2018-9-3T11:58.006</calendar>"+
"<price_1>23.56</price_1>"+
"</book>";
Book book = JaxbUtil.converyToJavaBean(str,Book.class);
System.out.println(book);
}
}

输出结果:

3、类中包含复杂对象的转换

3.1

package cn.com.t2;

@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name = "student")
@XmlType(propOrder = {})
public class Student {
@XmlAttribute
private Integer id;
@XmlElement
private String name;
@XmlElement(name = "role")
private Role role;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Role getRole() {
return role;
}
public void setRole(Role role) {
this.role = role;
}
@Override
public String toString() {
return "Student [id=" + id + ", name=" + name + ", role=" + role + "]";
}
}

3.2

package cn.com.t2;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlType;

@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(propOrder = {"name","desc"})
public class Role {
@XmlElement
private String name;
@XmlElement
private String desc;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDesc() {
return desc;
}
public void setDesc(String desc) {
this.desc = desc;
}
@Override
public String toString() {
return "Role [name="+name+",desc="+desc+"]";
}
}

3.3

package cn.com.t2;

import org.junit.Test;

import cn.om.utils.JaxbUtil;

public class JaxbTest2 {
@Test
public void showMarshaller(){
Student student = new Student();
student.setId(12);
student.setName("nihao");
Role role = new Role();
role.setDesc("管理");
role.setName("班长");
student.setRole(role);
String str = JaxbUtil.converTomXml(student);
System.out.println(str);

}
@Test
public void showUnMarshaller(){
String str = "<?xml version =\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>"+
"<student id =\"12\">"+
"<name>nihao</name>" +
"<role>"+
"<desc>管理</desc>"+
"<name>班长</name>"+
"</role>"+
"</student>";
Student student = JaxbUtil.converyToJavaBean(str, Student.class);
System.out.println(student);
}
}

输出结果

4、集合对象的转换（同样适用于Set）

4.1

package cn.com.t3;

import java.util.List;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElementWrapper;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;

@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name = "country")
@XmlType(propOrder = {"name","provinceList"})
public class Country {
@XmlElement(name = "country_name")
private String name;

@XmlElementWrapper(name = "provinces")
@XmlElement(name = "province")
private List<Province> provinceList;

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public List<Province> getProvinceList() {
return provinceList;
}

public void setProvinceList(List<Province> provinceList) {
this.provinceList = provinceList;
}
@Override
public String toString(){
return "Country [name = "+ name +",provinceList" + provinceList + "]";
}

}

4.2

package cn.com.t3;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlType;

@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(propOrder = {"name","provCity"})
public class Province {
@XmlElement(name = "province_name")
private String name;
@XmlElement(name = "prov_city")
private String provCity;

public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getProvCity() {
return provCity;
}
public void setProvCity(String provCity) {
this.provCity = provCity;
}

@Override
public String toString(){
return "Province [name=" + name +", provCity=" + provCity + "]";
}
}

4.3

package cn.com.t3;

import java.util.List;
import java.util.ArrayList;

import org.junit.Test;

import cn.om.utils.JaxbUtil;

public class JaxbTest3 {

@Test
public void showShaller(){
Country country = new Country();
country.setName("中国");
List<Province> list = new ArrayList<Province>();
Province province = new Province();
province.setName("辽宁省");
province.setProvCity("大连市");
Province province2 = new Province();
province2.setName("黑龙江省");
province2.setProvCity("哈尔滨市");
list.add(province);
list.add(province2);
country.setProvinceList(list);
String str = JaxbUtil.converTomXml(country);
System.out.println(str);
}

@Test
public void showUnShaller(){
String str = "<?xml version =\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>"+
"<country>"+
"<country_name>中国</country_name>"+
"<provinces>"+
"<province>"+
"<province_name>辽宁省</province_name>"+
"<prov_city>大连市</prov_city>"+
"</province>"+
"<province>"+
"<province_name>黑龙江省</province_name>"+
"<prov_city>哈尔滨市</prov_city>"+
"</province>"+
"</provinces>"+
"</country>";
Country country = JaxbUtil.converyToJavaBean(str, Country.class);
System.out.println(country);
}
}

输出结果:

其中运行后错误:

红框处province少写一个n,获取不到省份信息

红框处prov_city没有和前面的匹配上,所以获取不到任何的值

尽量手敲这个代码,不要复制!!!

参考文章:

https://blog.csdn.net/u010502101/article/details/79586834

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