JAXB XML和Bean互相转换
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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。是JDK的组成部分
JDK中JAXB相关的重要Class和Interface:
当使用 @XmlRootElement 注释对顶层类或枚举类型进行注释时,类型值被表示为 XML 文档中的 XML 元素。
JAXB Annotation
- @XmlRootElement // xml 文件的根元素 将Java类或枚举类型映射到XML元素(必须使用 指定xml跟元素)
- @XmlElement //将Java类的一个属性映射到与属性同名的一个XML元素
- @XmlAccessorType // 控制默认情况下是否对字段或 Javabean 属性进行系列化(必须使用 指定如何转化)。
- @XmlTransient
- @XmlJavaTypeAdaptor:参考Using JAXB 2.0\'s XmlJavaTypeAdapter
XmlAccessorType
默认规则:
默认情况下,如果包中不存在 @XmlAccessorType,那么假定使用以下包级别注释。
@XmlAccessorType(XmlAccessType.PUBLIC_MEMBER)
默认情况下,如果类中不存在 @XmlAccessorType,并且没有任何超类是使用 @XmlAccessorType 注释的,则假定在类中使用以下默认注释:
@XmlAccessorType(XmlAccessType.PUBLIC_MEMBER)
可能值:
FIELD: JAXB 绑定类中的每个非静态、非瞬态字段将会自动绑定到 XML,除非由 XmlTransient 注释。
NONE: 所有字段或属性都不能绑定到 XML,除非使用一些 JAXB 注释专门对它们进行注释。
PROPERTY: JAXB 绑定类中的每个获取方法/设置方法(get/set方法)对将会自动绑定到 XML,除非由 XmlTransient 注释。
PUBLIC_MEMBER:每个公共获取方法/设置方法对和每个公共字段将会自动绑定到 XML,除非由 XmlTransient 注释。
Java Bean转换成XML实例:
实体类:
@XmlRootElement(name = "person") @XmlAccessorType(XmlAccessType.FIELD) public class Person { private String name; private Integer age; public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } }
转换代码:
import javax.xml.bind.JAXBContext; import javax.xml.bind.JAXBException; import javax.xml.bind.Marshaller; import javax.xml.bind.Unmarshaller; public class JAXBTest { public static void main(String[] args) throws JAXBException { JAXBContext context = JAXBContext.newInstance(Person.class); Marshaller marshaller = context.createMarshaller(); Unmarshaller unmarshaller = context.createUnmarshaller(); Person person = new Person(); person.setAge(11); person.setName("测试"); marshaller.marshal(person, System.out); System.out.println(); } }
输出结果:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?><person><name>测试</name><age>11</age></person>
XML转换成Bean实例:
import javax.xml.bind.JAXBContext; import javax.xml.bind.JAXBException; import javax.xml.bind.Unmarshaller; import java.io.StringReader; public class JAXBTest { public static void main(String[] args) throws JAXBException { JAXBContext context = JAXBContext.newInstance(Person.class); Unmarshaller unmarshaller = context.createUnmarshaller(); String xml = "<person><age>11</age><name>测试</name></person>"; Person person = (Person) unmarshaller.unmarshal(new StringReader(xml)); System.out.println(person.getAge()); } }
XML转换成Bean是有命名空间的情况:
public class JAXBTest { public static void main(String[] args) throws JAXBException { JAXBContext context = JAXBContext.newInstance(Person.class); Unmarshaller unmarshaller = context.createUnmarshaller(); String xml = "<person xmlns=\\"http://test.org/\\"><age>11</age><name>测试</name></person>"; Person person = (Person) unmarshaller.unmarshal(new StringReader(xml)); System.out.println(person.getAge()); } }
会报错:
Exception in thread "main" javax.xml.bind.UnmarshalException: 意外的元素 (uri:"http://test.org/", local:"person")。所需元素为<{}person> at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.handleEvent(UnmarshallingContext.java:726) at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:247) at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:242) at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportUnexpectedChildElement(Loader.java:109) at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext$DefaultRootLoader.childElement(UnmarshallingContext.java:1131) at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext._startElement(UnmarshallingContext.java:556) at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.startElement(UnmarshallingContext.java:538) at com.sun.xml.internal.bind.v2.runtime.unmarshaller.SAXConnector.startElement(SAXConnector.java:153) at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXParser.java:509) at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.scanStartElement(XMLNSDocumentScannerImpl.java:374) at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl$NSContentDriver.scanRootElementHook(XMLNSDocumentScannerImpl.java:613) at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:3132) at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:852) at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:602) at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:112) at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:505) at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:841) at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:770) at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141) at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1213) at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:643) at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(UnmarshallerImpl.java:243) at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal(UnmarshallerImpl.java:214) at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:157) at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:214)
一种处理方法就是XML转换成Bean的时候忽略命名空间:
import org.xml.sax.InputSource; import org.xml.sax.SAXException; import org.xml.sax.XMLReader; import javax.xml.bind.JAXBContext; import javax.xml.bind.JAXBException; import javax.xml.bind.Unmarshaller; import javax.xml.parsers.ParserConfigurationException; import javax.xml.parsers.SAXParserFactory; import javax.xml.transform.Source; import javax.xml.transform.sax.SAXSource; import java.io.StringReader; public class JAXBTest { public static void main(String[] args) throws JAXBException, ParserConfigurationException, SAXException { JAXBContext jaxbContext = JAXBContext.newInstance(Person.class); Unmarshaller unmarshaller = jaxbContext.createUnmarshaller(); String xml = "<person xmlns=\\"http://test.org/\\"><age>11</age><name>测试</name></person>"; StringReader reader = new StringReader(xml); SAXParserFactory sax = SAXParserFactory.newInstance(); sax.setNamespaceAware(false);//设置忽略明明空间 XMLReader xmlReader = sax.newSAXParser().getXMLReader(); Source source = new SAXSource(xmlReader, new InputSource(reader)); Person person = (Person) unmarshaller.unmarshal(source); System.out.println(person.getAge()); } }
如果我们的根元素没有子元素并且里面有值 而且我们需要解析XML获取这个值的时候 一种解决办法:修改我们的Bean注解 这样就能正确转化成Bean
import javax.xml.bind.annotation.XmlRootElement; import javax.xml.bind.annotation.XmlValue; @XmlRootElement(name = "string") public class XMLToBeanlVo { private String stringValue; @XmlValue public String getStringValue() { return stringValue; } public void setStringValue(String stringValue) { this.stringValue = stringValue; } }
将xml中多个相同的元素解析成java中的list
<?xml version="1.0" encoding="GBK" ?> <reports> <report> <name>test</name> <mobile>13810000001</mobile> </report> <report> <name>test</name> <mobile>13810000002</mobile> </report> </reports>
java实体类:
@XmlAccessorType(XmlAccessType.FIELD) @XmlRootElement(name = "reports") public class XmlVo { @XmlElement(name = "report") private List<DetailXmlVo> report; public List<DetailXmlVo> getReport() { return report; } public void setReport(List<DetailXmlVo> report) { this.report = report; } }
public class DetailXmlVo { private String name; private String mobile; }
参考:https://www.cnblogs.com/Nouno/p/5728112.html
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