JAXB

如果元素带有命名空间，那么处理方式与 JAXB - Hello World 会略有不同。

1. XML Schema:

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:jxb="http://java.sun.com/xml/ns/jaxb" xmlns:ns0="http://www.huey.com/hello/beans/" targetNamespace="http://www.huey.com/hello/beans/" jxb:version="2.0">
    <xsd:element name="Greetings" type="ns0:GreetingListType"/>
    <xsd:complexType name="GreetingListType">
        <xsd:sequence>
            <xsd:element name="Greeting" type="ns0:GreetingType" maxOccurs="unbounded"/>
        </xsd:sequence>
    </xsd:complexType>
    <xsd:complexType name="GreetingType">
        <xsd:sequence>
            <xsd:element name="Text" type="xsd:string"/>
        </xsd:sequence>
        <xsd:attribute name="language" type="xsd:language"/>
    </xsd:complexType>
</xsd:schema>

2. 编译 schema 生成 Java 类：

xjc hello.xsd    // 取默认的包路径，根据命名空间生成

3. 修改生成的 GreetingListType.java 文件，添加 @XmlRootElement，指定根元素的名称和命名空间：

package com.huey.hello.beans;

import java.util.ArrayList;
import java.util.List;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;


@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "GreetingListType", propOrder = {
    "greeting"
})
@XmlRootElement(namespace = "http://www.huey.com/hello/beans/", name = "Greetings")
public class GreetingListType {

    @XmlElement(name = "Greeting", required = true)
    protected List<GreetingType> greeting;

    public List<GreetingType> getGreeting() {
        if (greeting == null) {
            greeting = new ArrayList<GreetingType>();
        }
        return this.greeting;
    }

}

4. marshal:

public class JaxbUtils {

    // ...

    public static <T> String marshal(T obj) {
        StringWriter writer = new StringWriter();
        try {
            
            JAXBContext jc = JAXBContext.newInstance(obj.getClass());
            Marshaller m = jc.createMarshaller();
            m.setProperty( Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE );
            m.marshal(obj, writer);
        } catch (JAXBException jbe) {
            // ...
        }
        return writer.toString();
    }   
}

5. 测试 JaxbUtils.marshal 方法：

public class JaxbUtilsTest {
    @Test
    public void testMarshal() throws Exception {
        GreetingListType glt = new GreetingListType();
        GreetingType gt1 = new GreetingType();
        gt1.setLanguage("en");
        gt1.setText("Hello world");
        glt.getGreeting().add(gt1);
        GreetingType gt2 = new GreetingType();
        gt2.setLanguage("fr");
        gt2.setText("Bonjour, madame");
        glt.getGreeting().add(gt2);
        
        System.out.println(JaxbUtils.marshal(glt));
    }    
}

6. JaxbUtils.marshal 测试输出：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ns2:Greetings xmlns:ns2="http://www.huey.com/hello/beans/">
    <Greeting language="en">
        <Text>Hello world</Text>
    </Greeting>
    <Greeting language="fr">
        <Text>Bonjour, madame</Text>
    </Greeting>
</ns2:Greetings>

7. unmarshal:

public class JaxbUtils {

    // ...

    public static <T> T unmarshal(Class<T> docClass, InputStream inputStream) throws JAXBException {
        JAXBContext jc = JAXBContext.newInstance(docClass);
        Unmarshaller u = jc.createUnmarshaller();
        T obj = (T) u.unmarshal(inputStream);       
        return obj;
    }    
}

8. 以 JaxbUtils.marshal 的测试输出作为 JaxbUtils.unmarshal 的输入做测试：

public class JaxbUtilsTest {
    @Test
    public void testUnmarshal() throws Exception {
        String path = "/files/hello.xml";
        InputStream in = JaxbUtilsTest.class.getResourceAsStream(path);        
        try {
            GreetingListType greetingList = JaxbUtils.unmarshal(GreetingListType.class, in);
            List<GreetingType> greetings = greetingList.getGreeting();
            for (GreetingType greeting : greetings) {
                System.out.println(greeting.getLanguage() + ": " + greeting.getText());
            }
        } catch (JAXBException e) {
            e.printStackTrace();
        } finally {
            IOUtils.closeQuietly(in);
        }
    }
}

9. JaxbUtils.unmarshal 测试输出：

fr: Bonjour, madame
en: Hey, you

Namespace