JAXB实例入门

JAXB（Java Architecture for XML Binding），JDK标准规范，Java对象和XML之间的转换，和SAX/DOM不同的是无需关注XML解析细节。

• Marshalling – 把Java对象转换成XML
• Unmarshalling – 把XML转换成Java对象

版本：
* JDK1.6开始提供JAXB 2.0（建议使用最新版JDK）
* 低于JDK1.6的版本需要下载jaxb-api.jar和jaxb-impl.jar
* JAXB还有JDK以外的很多第三方实现，比如：EclipseLink MOXy

以下代码都去掉了Bean的Setter/Getter，具体可执行的完整工程代码，可从附件下载。

(1) 基本

Java对象 -> XML

@XmlRootElement
public class Sample {
	private int id;
	private String name;
	private boolean flag;
}

		Sample s = new Sample();
		s.setId(101);
		s.setName("basicObj2XML");
		s.setFlag(false);
		
		StringWriter w = new StringWriter();
		// JAXB是JDK封装好的解析器
		JAXB.marshal(s, new StreamResult(w)); // 输出到字符串
		System.out.println(w.toString());

引用

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<sample>
    <flag>false</flag>
    <id>101</id>
    <name>basicObj2XML</name>
</sample>

转换后的XML内容可以直接输出到其他流（比如：控制台、文件等）

		Sample s = new Sample();
		s.setId(102);
		s.setName("basicObj2Output");
		s.setFlag(false);

		JAXB.marshal(s, System.out); // 输出到控制台
		JAXB.marshal(s, new File("d:\\jaxb_sample.xml")); // 输出到文件

XML -> Java对象

		String xml = "<?xml version=\"1.0\"?>" 
					+ "<sample>" 
					+ "  <id>103</id>" 
					+ "  <name>basicXML2Obj</name>" 
					+ "  <flag>false</flag>" 
					+ "</sample>";
		
		StringReader r = new StringReader(xml);
		Sample ss = JAXB.unmarshal(r, Sample.class);
		System.out.println(ss.toString());

(2) 通过JAXBContext创建解析器

创建Marshaller

		JAXBContext jaxbContext = JAXBContext.newInstance(Sample.class);
		Marshaller marshaller = jaxbContext.createMarshaller();
		marshaller.marshal(s, System.out);

创建Unmarshaller

		JAXBContext jaxbContext = JAXBContext.newInstance(Sample.class);
		Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
		StringReader r = new StringReader(xml);
		Sample sample = unmarshaller.unmarshal(new StreamSource(r), Sample.class).getValue();
		System.out.println(sample.toString());

设置Marshaller属性
marshaller.setProperty();

		JAXBContext jaxbContext = JAXBContext.newInstance(Sample.class);
		Marshaller marshaller = jaxbContext.createMarshaller();
		// 设置格式化后输出
		marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
		// 设置字符集
		marshaller.setProperty(Marshaller.JAXB_ENCODING, Charset.defaultCharset().name());
		marshaller.marshal(s, System.out);

(3) 采用EclipseLink MOXy作为JAXB provider
1）下载导入eclipselink.jar
2）在POJO的包下新建jaxb.properties

引用

#Sun JAXB
javax.xml.bind.context.factory=com.sun.xml.internal.bind.v2.ContextFactory
#Eclipse MOXy
#javax.xml.bind.context.factory=org.eclipse.persistence.jaxb.JAXBContextFactory

*** SUN的JAXB实现会在xml中添加属性standalone="yes"，而EclipseLink MOXy就不会。

(4) 监听器

marshaller.setListener();

Marshaller监听器

public class MarshallListener extends Marshaller.Listener {

	public void beforeMarshal(Object source) {
		System.out.println("BEFORE_MARSHAL fired");
	}

	public void afterMarshal(Object source) {
		System.out.println("AFTER_MARSHAL fired");
	}

}

		JAXBContext jaxbContext = JAXBContext.newInstance(Sample.class);
		Marshaller marshaller = jaxbContext.createMarshaller();
		// 设置监听器（！！！Sun JAXB实现有Bug会被执行两次，而Eclipse MOXy能正确执行一次！！！）
		marshaller.setListener(new MarshallListener());
		marshaller.marshal(s, System.out);

Unmarshaller监听器

public class UnmarshallListener extends Unmarshaller.Listener {

	@Override
	public void beforeUnmarshal(Object target, Object parent) {
		System.out.println("BEFORE_UNMARSHAL fired");
	}

	@Override
	public void afterUnmarshal(Object target, Object parent) {
		System.out.println("AFTER_UNMARSHAL fired");
	}

}

		JAXBContext jaxbContext = JAXBContext.newInstance(Sample.class);
		Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
		// 设置监听器
		unmarshaller.setListener(new UnmarshallListener());
		StringReader r = new StringReader(xml);
		Sample sample = unmarshaller.unmarshal(new StreamSource(r), Sample.class).getValue();
		System.out.println(sample.toString());

(5) 注解

设置内部标签顺序（默认是按标签字母排序）
@XmlType(propOrder={"id", "name", "flag"})

@XmlRootElement
@XmlType(propOrder={"id", "name", "flag"})
public class SampleOrder {
	private int id;
	private String name;
	private boolean flag;
}

引用

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<sampleOrder>
    <id>501</id>
    <name>marshallerTagOrder</name>
    <flag>false</flag>
</sampleOrder>

把字段值作为属性（默认都是标签）
@XmlAttribute

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class SampleAttribute {
	@XmlAttribute
	private int id;
	private String name;
	private boolean flag;
}

引用

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<sampleAttribute id="502">
    <name>SampleAttribute</name>
    <flag>false</flag>
</sampleAttribute>

不输出某个字段值
@XmlTransient

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class SampleTransient {
	private int id;
	private String name;
	@XmlTransient
	private boolean flag;
}

引用

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<sampleTransient>
    <id>503</id>
    <name>SampleTransient</name>
</sampleTransient>

空值处理

@XmlElement(nillable = true)

		SampleEmpty s = new SampleEmpty();
		s.setId(504);
		s.setName("SampleEmpty");
		s.setFlag(false);
		s.setName1(null);
		s.setName2("");
		s.setName3(null);

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class SampleEmpty {
	private int id;
	private String name;
	private boolean flag;
	private String name1;
	private String name2;
	@XmlElement(nillable = true)
	private String name3;
}

引用

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<sampleEmpty>
    <id>504</id>
    <name>SampleEmpty</name>
    <flag>false</flag>
    <name2></name2>
    <name3 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:nil="true"/>
</sampleEmpty>

变更输出标签属性名称

@XmlRootElement(name="foobar-tag")
@XmlAttribute(name="foobar-id")
@XmlElement(name="foobar-value")

@XmlRootElement(name="foobar-tag")
@XmlAccessorType(XmlAccessType.FIELD)
public class SampleName {
	@XmlAttribute(name="foobar-id")
	private int id;
	@XmlElement(name="foobar-value")
	private String name;
	private boolean flag;
}

引用

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<foobar-tag foobar-id="505">
    <foobar-value>SampleName</foobar-value>
    <flag>false</flag>
</foobar-tag>

Bean类型

@XmlRootElement
public class SampleBeanNested {
	private int id;
	private String name;
	private boolean flag;
	private People people;
}

public class People {
	private int id;
	private String name;
}

引用

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<sampleBeanNested>
    <flag>false</flag>
    <id>506</id>
    <name>SampleBeanNested</name>
    <people>
        <id>100</id>
        <name>People</name>
    </people>
</sampleBeanNested>

List类型

【字符串】默认

@XmlRootElement
public class SampleStringList1 {
	private int id;
	private String name;
	private boolean flag;
	private List<String> emailAddresses;
}

引用

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<sampleStringList1>
    <emailAddresses>[e-mail]</emailAddresses>
    <emailAddresses>[e-mail]</emailAddresses>
    <emailAddresses>[e-mail]</emailAddresses>
    <flag>false</flag>
    <id>507</id>
    <name>SampleStringList1</name>
</sampleStringList1>

@XmlElementWrapper

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class SampleStringList2 {
	private int id;
	private String name;
	private boolean flag;
	@XmlElementWrapper(name="email-addresses")
	@XmlElement(name="email-address")
	private List<String> emailAddresses;
}

引用

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<sampleStringList2>
    <id>508</id>
    <name>SampleStringList2</name>
    <flag>false</flag>
    <email-addresses>
        <email-address>[e-mail]</email-address>
        <email-address>[e-mail]</email-address>
        <email-address>[e-mail]</email-address>
    </email-addresses>
</sampleStringList2>

@XmlList

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class SampleStringList3 {
	private int id;
	private String name;
	private boolean flag;
	@XmlList
	private List<String> emailAddresses;
}

引用

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<sampleStringList3>
    <id>509</id>
    <name>SampleStringList3</name>
    <flag>false</flag>
    <emailAddresses>[e-mail] [e-mail] [e-mail]</emailAddresses>
</sampleStringList3>

【Bean】默认

@XmlRootElement
public class SampleBeanList1 {
	private int id;
	private String name;
	private boolean flag;
	private List<People> peoples;
}

引用

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<sampleBeanList1>
    <flag>false</flag>
    <id>510</id>
    <name>SampleBeanList1</name>
    <peoples>
        <id>100</id>
        <name>People1</name>
    </peoples>
    <peoples>
        <id>200</id>
        <name>People2</name>
    </peoples>
    <peoples>
        <id>300</id>
        <name>People3</name>
    </peoples>
</sampleBeanList1>

@XmlElementWrapper

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class SampleBeanList2 {
	private int id;
	private String name;
	private boolean flag;
	@XmlElementWrapper(name="list")
	@XmlElement(name="people")
	private List<People> peoples;
}

引用

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<sampleBeanList2>
    <id>511</id>
    <name>SampleBeanList2</name>
    <flag>false</flag>
    <list>
        <people>
            <id>100</id>
            <name>People1</name>
        </people>
        <people>
            <id>200</id>
            <name>People2</name>
        </people>
        <people>
            <id>300</id>
            <name>People3</name>
        </people>
    </list>
</sampleBeanList2>

@XmlElements

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class SampleBeanList3 {
	private int id;
	private String name;
	private boolean flag;
	@XmlElementWrapper(name="list")
	@XmlElements( { 
    	@XmlElement(name = "man", type = Man.class),
		@XmlElement(name = "woman", type = Woman.class) 
	})
	private List<People> peoples;
}

引用

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<sampleBeanList3>
    <id>512</id>
    <name>SampleBeanLis3</name>
    <flag>false</flag>
    <list>
        <man>
            <id>100</id>
            <name>Man</name>
            <attr1>Attr1</attr1>
        </man>
        <woman>
            <id>200</id>
            <name>Woman</name>
            <attr2>Attr2</attr2>
        </woman>
    </list>
</sampleBeanList3>

枚举类型

@XmlEnum、@XmlEnumValue

@XmlEnum(Integer.class)
@XmlType
public enum BloodType {
    @XmlEnumValue("1") A,
    @XmlEnumValue("2") B,
    @XmlEnumValue("3") O,
    @XmlEnumValue("4") AB
}

@XmlRootElement
public class SampleEnum {
	private int id;
	private String name;
	private boolean flag;
	private BloodType bloodType;
}

引用

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<sampleEnum>
    <bloodType>2</bloodType>
    <flag>false</flag>
    <id>513</id>
    <name>SampleEnum</name>
</sampleEnum>

(6) 适配器

@XmlJavaTypeAdapter

public class DateAdapter extends XmlAdapter<String, Date> {

	private static final SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd hh:mm:ss");

	public Date unmarshal(String v) throws Exception {
		return dateFormat.parse(v);
	}

	public String marshal(Date v) throws Exception {
		return dateFormat.format(v);
	}

}

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class SampleDateAdapter {
	private int id;
	private String name;
	private boolean flag;
	@XmlJavaTypeAdapter(DateAdapter.class)
	private Date date;
}

引用

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<sampleDateAdapter>
    <id>601</id>
    <name>SampleDateAdapter</name>
    <flag>false</flag>
    <date>2017/06/09 09:52:26</date>
</sampleDateAdapter>

(7) Schema检验

SampleSchema.xsd

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
     
    <xs:element name="SampleSchema">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="name" type="xs:string"  />
                <xs:element name="flag" type="xs:boolean" />
            </xs:sequence>
            <xs:attribute name="id" type="xs:int" />
        </xs:complexType>
    </xs:element> 
    
</xs:schema>

marshaller.setSchema();

@XmlRootElement(name="SampleSchema")
@XmlAccessorType(XmlAccessType.FIELD)
public class SampleSchema {
	@XmlAttribute
	private int id;
	private String name;
	private boolean flag;
}

		SampleSchema s = new SampleSchema();
		s.setId(701);
		s.setName("SampleSchema");
		s.setFlag(false);
		
		ClassLoader classLoader = new Main().getClass().getClassLoader();
        File schemaFile = new File(classLoader.getResource("SampleSchema.xsd").getFile());
		
		SchemaFactory sf = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
		Schema schema = sf.newSchema(schemaFile);

		JAXBContext jaxbContext = JAXBContext.newInstance(SampleSchema.class);
		Marshaller marshaller = jaxbContext.createMarshaller();
		marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
		// 设置Schema
		marshaller.setSchema(schema);
		marshaller.marshal(s, System.out);

引用

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<SampleSchema id="701">
    <name>SampleSchema</name>
    <flag>false</flag>
</SampleSchema>

validator.validate(source);

		SampleSchema s = new SampleSchema();
		s.setId(702);
		s.setName("marshallerValidator");
		s.setFlag(false);

		ClassLoader classLoader = new Main().getClass().getClassLoader();
        File schemaFile = new File(classLoader.getResource("SampleSchema.xsd").getFile());
        
		SchemaFactory sf = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
		Schema schema = sf.newSchema(schemaFile);

		JAXBContext jaxbContext = JAXBContext.newInstance(SampleSchema.class);
		
		// 校验XML
		JAXBSource source = new JAXBSource(jaxbContext, s);
        Validator validator = schema.newValidator();
        validator.setErrorHandler(new CustomValidationErrorHandler());
        validator.validate(source);

		Marshaller marshaller = jaxbContext.createMarshaller();
		marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
		marshaller.marshal(s, System.out);

(8) 捕获事件

marshaller.setEventHandler();

public class CustomEventHandler implements ValidationEventHandler {

	@Override
	public boolean handleEvent(ValidationEvent event) {
		System.out.println(event.getSeverity());

		if (event.getSeverity() == ValidationEvent.ERROR
				|| event.getSeverity() == ValidationEvent.FATAL_ERROR) {
			ValidationEventLocator locator = event.getLocator();
			System.out.println("Line:Col[" + locator.getLineNumber() + ":" + locator.getColumnNumber() + "]");
			throw new RuntimeException(event.getMessage(), event.getLinkedException());
		}
		return true;
	}

}

		JAXBContext jaxbContext = JAXBContext.newInstance(Sample.class);
		Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
		// 设置事件处理器
		unmarshaller.setEventHandler(new CustomEventHandler());
		StringReader r = new StringReader(xml);
		Sample sample = unmarshaller.unmarshal(new StreamSource(r), Sample.class).getValue();
		System.out.println(sample.toString());