XML 和 java对象相互转换

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下面使用的是JDK自带的类，没有引用任何第三方jar包。

Unmarshaller 类使客户端应用程序能够将 XML 数据转换为 Java 内容对象树。

备注：marshal(序列化、排列、整理)

Marshaller 类使客户端应用程序能够将 Java 内容树转换回 XML 数据。

package hb.jaxb;public class Classroom {private int id;private String name;private int grade;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getGrade() {return grade;}public void setGrade(int grade) {this.grade = grade;}public Classroom(int id, String name, int grade) {super();this.id = id;this.name = name;this.grade = grade;}public Classroom() {super();}}

package hb.jaxb;import javax.xml.bind.annotation.XmlRootElement;@XmlRootElementpublic class Student {private int id;private String name;private int age;private Classroom classroom;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public Classroom getClassroom() {return classroom;}public void setClassroom(Classroom classroom) {this.classroom = classroom;}public Student(int id, String name, int age, Classroom classroom) {super();this.id = id;this.name = name;this.age = age;this.classroom = classroom;}//无参够着函数一定需要，否则JXBContext无法正常解析。public Student() {super();}}

注意：

1、需要转换的model对象一定要添加@XmlRootElement注解，其里面的其他对象则不需要

2、需要转换的model对象一定要有不带参数的构造方法，包括该对象里面引用的对象。

package hb.jaxb;import java.io.StringReader;import javax.xml.bind.JAXBContext;import javax.xml.bind.JAXBException;import javax.xml.bind.Marshaller;import javax.xml.bind.Unmarshaller;import org.junit.Test;public class TestJaxb {@Testpublic void beanToXML() {Classroom classroom = new Classroom(1, "软件工程", 4);Student student = new Student(101, "张三", 22, classroom);try {JAXBContext context = JAXBContext.newInstance(Student.class);Marshaller marshaller = context.createMarshaller();marshaller.marshal(student, System.out);} catch (JAXBException e) {e.printStackTrace();}}@Testpublic void XMLStringToBean(){String xmlStr = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?><student><age>22</age><classroom><grade>4</grade><id>1</id><name>软件工程</name></classroom><id>101</id><name>张三</name></student>";try {JAXBContext context = JAXBContext.newInstance(Student.class);Unmarshaller unmarshaller = context.createUnmarshaller();Student student = (Student)unmarshaller.unmarshal(new StringReader(xmlStr));System.out.println(student.getAge());System.out.println(student.getClassroom().getName());} catch (JAXBException e) {e.printStackTrace();}}}

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。从另一方面来讲，JAXB提供了快速而简便的方法将XML模式绑定到Java表示，从而使得Java开发者在Java应用程序中能方便地结合XML数据和处理函数。

JAXBContext 类提供到 JAXB API 的客户端入口点。它提供了管理实现 JAXB 绑定框架操作所需的 XML/Java 绑定信息的抽象，这些操作包括：解组、编组和验证。

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