JAXB 问题（一）

1. 从XML读取数据时，找不到相应的标签类。

1. person.xsd文件

   <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
   <xs:schema version="1.0"
       targetNamespace="http://xml.javainthebox.net"
       xmlns:tns="http://xml.javainthebox.net"
       xmlns:xs="http://www.w3.org/2001/XMLSchema">
     <xs:element name="persons">
       <xs:complexType>
         <xs:sequence>
           <xs:element ref="tns:person"
                       minOccurs="0" maxOccurs="unbounded"/>
         </xs:sequence>
       </xs:complexType>
     </xs:element>
     <xs:element name="person">
       <xs:complexType>
         <xs:attribute name="name" type="xs:string"/>
         <xs:attribute name="age" type="xs:int"/>
         <xs:attribute name="sex" type="tns:sex"/>
       </xs:complexType>
     </xs:element>
     <xs:simpleType name="sex">
       <xs:restriction base="xs:string">
         <xs:enumeration value="MALE"/>
         <xs:enumeration value="FEMALE"/>
       </xs:restriction>
     </xs:simpleType>
   </xs:schema>
   

2. artists.xml文件

   <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
   <persons>
     <person name="Neil Young" age="62" sex="MALE" />
     <person name="Bob Dylan" age="67" sex="MALE" />
     <person name="Joni Mitchell" age="65" sex="FEMALE" />
   </persons>
   

3. UnmarshallerSample.java文件

   import java.io.File;
   import javax.xml.bind.JAXBContext;
   import javax.xml.bind.JAXBException;
   import javax.xml.bind.Unmarshaller;
   import net.javainthebox.xml.Persons;
   import net.javainthebox.xml.Person;
   public class UnmarshallerSample {
       public UnmarshallerSample() {
           try {
               JAXBContext context
                   = JAXBContext.newInstance("net.javainthebox.xml");
               Unmarshaller unmarshaller = context.createUnmarshaller();
               File file = new File("artists.xml");
               Object obj = unmarshaller.unmarshal(file);
               Persons artists = (Persons)obj;
               java.util.List<Person> p = artists.getPerson();
               for (Person person: artists.getPerson()) {
                   System.out.printf("%s\tAge: %2d Sex: %s%n",
                                     person.getName(),
                                     person.getAge(),
                                     person.getSex());
               }
           } catch (JAXBException ex) {
               System.out.println(ex.getMessage());
           }
       }
       public static void main(String[] args) {
           new UnmarshallerSample();
       }
   }
   

   按顺序执行：

   C:\jaxb>xjc persons.xsd
   C:\jaxb>javac net\javainthebox\xml\ObjectFactory.java
   C:\jaxb>javac net\javainthebox\xml\package-info.java
   C:\jaxb>javac UnmarshallerSample.java
   C:\jaxb>java UnmarshallerSample
   

   执行完后，出现下面错误：

   没有预期的元素(URI:””、ローカル:”persons”)。预期的元素是{http://xml.javainthebox.net}person,{http://xml.javainthebox.net}persons。

   解决方法：修改artists.xml
   修改前：

   <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
   <persons>
     <person name="Neil Young" age="62" sex="MALE" />
     <person name="Bob Dylan" age="67" sex="MALE" />
     <person name="Joni Mitchell" age="65" sex="FEMALE" />
   </persons>
   

   修改后：

   <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
   <persons xmlns="http://xml.javainthebox.net" >
     <person name="Neil Young" age="62" sex="MALE" />
     <person name="Bob Dylan" age="67" sex="MALE" />
     <person name="Joni Mitchell" age="65" sex="FEMALE" />
   </persons>