JAXB的XmlAttribute注解

• JAXB的XmlAttribute注解，将一个JavaBean属性映射到一个XML属性。

例如，下面的Java代码，将属性currency映射到了XML的属性currency：

package com.thb;import jakarta.xml.bind.annotation.XmlAttribute;
import jakarta.xml.bind.annotation.XmlRootElement;
import jakarta.xml.bind.annotation.XmlType;
import jakarta.xml.bind.annotation.XmlValue;@XmlRootElement
@XmlType(name = "", propOrder = {"value"})
public class Price {@XmlValuepublic String value;@XmlAttribute(name = "currency")public String currency;
}

生成的XML Schema：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<xs:schema version="1.0" xmlns:xs="http://www.w3.org/2001/XMLSchema"><xs:element name="price"><xs:complexType><xs:simpleContent><xs:extension base="xs:string"><xs:attribute name="currency" type="xs:string"/></xs:extension></xs:simpleContent></xs:complexType></xs:element>
</xs:schema>

• XmlAttribute的required属性指定被注解的属性是否必选。
  例如下面代码，Java属性currency用@XmlAttribute(name = "currency", required = true)注解，指明xml属性currency是必选的：

package com.thb;import jakarta.xml.bind.annotation.XmlAttribute;
import jakarta.xml.bind.annotation.XmlRootElement;
import jakarta.xml.bind.annotation.XmlType;
import jakarta.xml.bind.annotation.XmlValue;@XmlRootElement
@XmlType(name = "", propOrder = {"value"})
public class Price {@XmlValuepublic String value;@XmlAttribute(name = "currency", required = true)public String currency;
}

生成的XML Schema，属性currency中出现了use="required"：

 <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<xs:schema version="1.0" xmlns:xs="http://www.w3.org/2001/XMLSchema"><xs:element name="price"><xs:complexType><xs:simpleContent><xs:extension base="xs:string"><xs:attribute name="currency" type="xs:string" use="required"/></xs:extension></xs:simpleContent></xs:complexType></xs:element>
</xs:schema>