Java对象和XML的相互转换化
https://blog.csdn.net/u010331823/article/details/78258311
写在前面：Jaxb是JavaEE的规范.全称Java Architecture for XML Binding. 可以根据XML Schema产生Java类的技术.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。JAXB 2.2.3是JDK 1.7的组成部分，在实际使用不需要引入新的jar.
1. 常用注解说明
常用的annotation有：
@XmlType
@XmlElement
@XmlRootElement
@XmlAttribute
@XmlAccessorType
@XmlAccessorOrder
@XmlTransient
@XmlJavaTypeAdapter
@Temporal(TemporalType.XXXX) -->JPA中的时间处理注解,非JAXB
@XmlElementWrapper
1.@XmlType
@XmlType用在class类的注解，常与@XmlRootElement，@XmlAccessorType一起使用。它有三个属性：name、propOrder、namespace，经常使用的只有前两个属性。如：
同时使用了@XmlType（propOrder={}）和@XmlAccessorOrder(XmlAccessOrder.ALPHABETICAL)的时候，生成的xml只按照propOrder定义的顺序生成元素
@XmlType(name = "basicStruct", propOrder = {
"intValue",
"stringArray",
"stringValue"
)
在使用@XmlType的propOrder 属性时，必须列出JavaBean对象中的所有属性，否则会报错。
2.@XmlRootElement
@XmlRootElement用于类级别的注解，对应xml的跟元素，常与 @XmlType 和 @XmlAccessorType一起使用。如：
@XmlType
@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement
public class Address {}
3.@XmlElement
@XmlElement将java对象的属性映射为xml的节点，在使用@XmlElement时，可通过name属性改变java对象属性在xml中显示的名称。如：
@XmlElement(name="Address")
private String yourAddress;
4.@XmlAttribute
@XmlAttribute用于把java对象的属性映射为xml的属性,并可通过name属性为生成的xml属性指定别名。如：
@XmlAttribute(name="Country")
private String state;
5.@XmlAccessorType
@XmlAccessorType用于指定由java对象生成xml文件时对java对象属性的访问方式。常与@XmlRootElement、@XmlType一起使用。它的属性值是XmlAccessType的4个枚举值，分别为:
XmlAccessType.FIELD:java对象中的所有成员变量
XmlAccessType.PROPERTY：java对象中所有通过getter/setter方式访问的成员变量
XmlAccessType.PUBLIC_MEMBER：java对象中所有的public访问权限的成员变量和通过getter/setter方式访问的成员变量
XmlAccessType.NONE:java对象的所有属性都不映射为xml的元素
注意：@XmlAccessorType的默认访问级别是XmlAccessType.PUBLIC_MEMBER，因此，如果java对象中的private成员变量设置了public权限的getter/setter方法，就不要在private变量上使用@XmlElement和@XmlAttribute注解，否则在由java对象生成xml时会报同一个属性在java类里存在两次的错误。同理，如果@XmlAccessorType的访问权限为XmlAccessType.NONE，如果在java的成员变量上使用了@XmlElement或@XmlAttribute注解，这些成员变量依然可以映射到xml文件。
注意：虽然@XmlAccessorType为XmlAccessType.NONE,但是在java类的私有属性上加了@XmlAttribute和@XmlElement注解后，这些私有成员会映射生成xml的元素
6.@XmlAccessorOrder
@XmlAccessorOrder用于对java对象生成的xml元素进行排序。它有两个属性值：
AccessorOrder.ALPHABETICAL：对生成的xml元素按字母书序排序
XmlAccessOrder.UNDEFINED:不排序
7.@XmlTransient
@XmlTransient用于标示在由java对象映射xml时，忽略此属性。即，在生成的xml文件中不出现此元素。
8.@XmlJavaTypeAdapter
@XmlJavaTypeAdapter常用在转换比较复杂的对象时，如map类型或者格式化日期等。使用此注解时，需要自己写一个adapter类继承XmlAdapter抽象类，并实现里面的方法。
@XmlJavaTypeAdapter(value=xxx.class),value为自己定义的adapter类
XmlAdapter 抽象接口如下：
public abstract class XmlAdapter<ValueType,BoundType> { // Do-nothing constructor for the derived classes.
protected XmlAdapter() {}
// Convert a value type to a bound type.
public abstract BoundType unmarshal(ValueType v);
// Convert a bound type to a value type.
public abstract ValueType marshal(BoundType v);
}
下面举一个简单的例子:
1.School类 一些基本的属性，包含Student集合
package com.gs.mountain.test.xml;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import java.util.ArrayList;
import java.util.List;
@XmlRootElement(name="list")
public class School {
private String name;
private String address;
private String level;
private long popular;
private List<Student> students=new ArrayList<Student>();
@XmlElement(name = "name")
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@XmlElement(name = "address")
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@XmlElement(name = "level")
public String getLevel() {
return level;
}
public void setLevel(String level) {
this.level = level;
}
@XmlElement(name = "popular")
public long getPopular() {
return popular;
}
public void setPopular(long popular) {
this.popular = popular;
}
@XmlElement(name = "Student")
public List<Student> getStudents() {
return students;
}
public void setStudents(List<Student> students) {
this.students = students;
}
}
2.Student类，包含爱好集合和一些基本的属性
package com.gs.mountain.test.xml;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElementWrapper;
import java.util.List;
public class Student {
String name; //姓名
String sex; //性别
int number; //学号
String className; //班级
List<String> hobby; //爱好
public Student(){
}
public Student(String name,String sex,int number,
String className,List<String> hobby) {
this.name = name;
this.sex = sex;
this.number = number;
this.className = className;
this.hobby = hobby;
}
@XmlAttribute(name="name")
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@XmlAttribute(name="sex")
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
@XmlAttribute(name="number")
public int getNumber() {
return number;
}
public void setNumber(int number) {
this.number = number;
}
@XmlElement(name="className")
public String getClassName() {
return className;
}
public void setClassName(String className) {
this.className = className;
}
@XmlElementWrapper(name="hobbys")
@XmlElement(name = "hobby")
public List<String> getHobby() {
return hobby;
}
public void setHobby(List<String> hobby) {
this.hobby = hobby;
}
}
3.工具类，提供xml到javaBean的相互转换 由 valvin大神提供，很好用(自己看其中的方法，说不定有你需要的)
/**
* Copyright (c) 2005-2012 springside.org.cn
*/
package com.gs.mountain.common.mapper;
import java.io.StringReader;
import java.io.StringWriter;
import java.util.Collection;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBElement;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
import javax.xml.bind.annotation.XmlAnyElement;
import javax.xml.namespace.QName;
import com.gs.mountain.common.utils.StringUtils;
import org.springframework.http.converter.HttpMessageConversionException;
import org.springframework.util.Assert;
import com.gs.mountain.common.utils.Exceptions;
import com.gs.mountain.common.utils.Reflections;
/**
* 使用Jaxb2.0实现XML<->Java Object的Mapper.
*
* 在创建时需要设定所有需要序列化的Root对象的Class.
* 特别支持Root对象是Collection的情形.
*
* @author calvin
* @version 2013-01-15
*/
@SuppressWarnings("rawtypes")
public class JaxbMapper {
private static ConcurrentMap<Class, JAXBContext> jaxbContexts = new ConcurrentHashMap<Class, JAXBContext>();
/**
* Java Object->Xml without encoding.
*/
public static String toXml(Object root) {
Class clazz = Reflections.getUserClass(root);
return toXml(root, clazz, null);
}
/**
* Java Object->Xml with encoding.
*/
public static String toXml(Object root, String encoding) {
Class clazz = Reflections.getUserClass(root);
return toXml(root, clazz, encoding);
}
/**
* Java Object->Xml with encoding.
*/
public static String toXml(Object root, Class clazz, String encoding) {
try {
StringWriter writer = new StringWriter();
createMarshaller(clazz, encoding).marshal(root, writer);
return writer.toString();
} catch (JAXBException e) {
throw Exceptions.unchecked(e);
}
}
/**
* Java Collection->Xml without encoding, 特别支持Root Element是Collection的情形.
*/
public static String toXml(Collection<?> root, String rootName, Class clazz) {
return toXml(root, rootName, clazz, null);
}
/**
* Java Collection->Xml with encoding, 特别支持Root Element是Collection的情形.
*/
public static String toXml(Collection<?> root, String rootName, Class clazz, String encoding) {
try {
CollectionWrapper wrapper = new CollectionWrapper();
wrapper.collection = root;
JAXBElement<CollectionWrapper> wrapperElement = new JAXBElement<CollectionWrapper>(new QName(rootName),
CollectionWrapper.class, wrapper);
StringWriter writer = new StringWriter();
createMarshaller(clazz, encoding).marshal(wrapperElement, writer);
return writer.toString();
} catch (JAXBException e) {
throw Exceptions.unchecked(e);
}
}
/**
* Xml->Java Object.
*/
@SuppressWarnings("unchecked")
public static <T> T fromXml(String xml, Class<T> clazz) {
try {
StringReader reader = new StringReader(xml);
return (T) createUnmarshaller(clazz).unmarshal(reader);
} catch (JAXBException e) {
throw Exceptions.unchecked(e);
}
}
/**
* 创建Marshaller并设定encoding(可为null).
* 线程不安全，需要每次创建或pooling。
*/
public static Marshaller createMarshaller(Class clazz, String encoding) {
try {
JAXBContext jaxbContext = getJaxbContext(clazz);
Marshaller marshaller = jaxbContext.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
if (StringUtils.isNotBlank(encoding)) {
marshaller.setProperty(Marshaller.JAXB_ENCODING, encoding);
}
return marshaller;
} catch (JAXBException e) {
throw Exceptions.unchecked(e);
}
}
/**
* 创建UnMarshaller.
* 线程不安全，需要每次创建或pooling。
*/
public static Unmarshaller createUnmarshaller(Class clazz) {
try {
JAXBContext jaxbContext = getJaxbContext(clazz);
return jaxbContext.createUnmarshaller();
} catch (JAXBException e) {
throw Exceptions.unchecked(e);
}
}
protected static JAXBContext getJaxbContext(Class clazz) {
Assert.notNull(clazz, "'clazz' must not be null");
JAXBContext jaxbContext = jaxbContexts.get(clazz);
if (jaxbContext == null) {
try {
jaxbContext = JAXBContext.newInstance(clazz, CollectionWrapper.class);
jaxbContexts.putIfAbsent(clazz, jaxbContext);
} catch (JAXBException ex) {
throw new HttpMessageConversionException("Could not instantiate JAXBContext for class [" + clazz
+ "]: " + ex.getMessage(), ex);
}
}
return jaxbContext;
}
/**
* 封装Root Element 是 Collection的情况.
*/
public static class CollectionWrapper {
@XmlAnyElement
protected Collection<?> collection;
}
}
4.下面是测试的代码，结果很棒，so easy!
package com.gs.mountain.test.xml;
import com.gs.mountain.common.mapper.JaxbMapper;
import javax.xml.bind.JAXBException;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
public class BeanToXml {
public static void main(String[] args) throws JAXBException, IOException {
List<String> hobby = new ArrayList();
hobby.add("篮球");
hobby.add("音乐");
hobby.add("乒乓球");
List<Student> studentList = new ArrayList();
Student st = new Student("张三","男",10001,"尖子班",hobby);
studentList.add(st);
Student st1 = new Student("李四","男",10002,"普通班",hobby);
studentList.add(st1);
Student st2 = new Student("莉莉","女",10003,"普通班",hobby);
studentList.add(st2);
School school = new School();
School school1 ;
School school2 ;
school.setAddress("成都市武侯区天府五街");
school.setLevel("高级中学");
school.setName("华阳中学");
school.setPopular(5000L);
school.setStudents(studentList);
school1=school;
school2=school;
List<School> listSchool=new ArrayList<School>();
listSchool.add(school);
listSchool.add(school1);
listSchool.add(school2);
String str = JaxbMapper.toXml(listSchool,"schoolList",School.class);
//写入到xml文件中
String xmlPath = "D:/testConfig.xml";
BufferedWriter bfw = new BufferedWriter(new FileWriter(new File(xmlPath)));
bfw.write(str);
bfw.close();
}
}
下面是由listSchool转化成的xml文件，内容如下：
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<schoolList>
<list>
<address>成都市武侯区天府五街</address>
<level>高级中学</level>
<name>华阳中学</name>
<popular>5000</popular>
<Student name="张三" number="10001" sex="男">
<className>尖子班</className>
<hobbys>
<hobby>篮球</hobby>
<hobby>音乐</hobby>
<hobby>乒乓球</hobby>
</hobbys>
</Student>
<Student name="李四" number="10002" sex="男">
<className>普通班</className>
<hobbys>
<hobby>篮球</hobby>
<hobby>音乐</hobby>
<hobby>乒乓球</hobby>
</hobbys>
</Student>
<Student name="莉莉" number="10003" sex="女">
<className>普通班</className>
<hobbys>
<hobby>篮球</hobby>
<hobby>音乐</hobby>
<hobby>乒乓球</hobby>
</hobbys>
</Student>
</list>
<list>
<address>成都市武侯区天府五街</address>
<level>高级中学</level>
<name>华阳中学</name>
<popular>5000</popular>
<Student name="张三" number="10001" sex="男">
<className>尖子班</className>
<hobbys>
<hobby>篮球</hobby>
<hobby>音乐</hobby>
<hobby>乒乓球</hobby>
</hobbys>
</Student>
<Student name="李四" number="10002" sex="男">
<className>普通班</className>
<hobbys>
<hobby>篮球</hobby>
<hobby>音乐</hobby>
<hobby>乒乓球</hobby>
</hobbys>
</Student>
<Student name="莉莉" number="10003" sex="女">
<className>普通班</className>
<hobbys>
<hobby>篮球</hobby>
<hobby>音乐</hobby>
<hobby>乒乓球</hobby>
</hobbys>
</Student>
</list>
<list>
<address>成都市武侯区天府五街</address>
<level>高级中学</level>
<name>华阳中学</name>
<popular>5000</popular>
<Student name="张三" number="10001" sex="男">
<className>尖子班</className>
<hobbys>
<hobby>篮球</hobby>
<hobby>音乐</hobby>
<hobby>乒乓球</hobby>
</hobbys>
</Student>
<Student name="李四" number="10002" sex="男">
<className>普通班</className>
<hobbys>
<hobby>篮球</hobby>
<hobby>音乐</hobby>
<hobby>乒乓球</hobby>
</hobbys>
</Student>
<Student name="莉莉" number="10003" sex="女">
<className>普通班</className>
<hobbys>
<hobby>篮球</hobby>
<hobby>音乐</hobby>
<hobby>乒乓球</hobby>
</hobbys>
</Student>
</list>
</schoolList>
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版权声明：本文为CSDN博主「mountainGS」的原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/u010331823/java/article/details/78258311
