@Getter@Setter@NoArgsConstructor@AllArgsConstructor@XmlAccessorType(XmlAccessType.FIELD)@XmlRootElement(name="root")public static class TNode {@XmlElement(name="key", required = true)private String key;@XmlElement(name="value", required = true)private String value;}public static void main(String[] args) {TNode obj = new TNode("key_1", "val_1");try {JAXBContext jc = JAXBContext.newInstance(TNode.class);Marshaller marshaller = jc.createMarshaller();marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);marshaller.setProperty(Marshaller.JAXB_ENCODING, "UTF-8");StringWriter writer = new StringWriter();marshaller.marshal(obj, writer);System.out.println(writer.toString());} catch (JAXBException e) {e.printStackTrace();}}

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<root><key>key_1</key><value>val_1</value>
</root>

public interface Marshaller {// *) 指定编码模式public static final String JAXB_ENCODING = "jaxb.encoding";// *) 指定输出时, 是否支持缩进和换行public static final String JAXB_FORMATTED_OUTPUT = "jaxb.formatted.output";/*** The name of the property used to specify the xsi:schemaLocation* attribute value to place in the marshalled XML output.*/public static final String JAXB_SCHEMA_LOCATION = "jaxb.schemaLocation";/*** The name of the property used to specify the* xsi:noNamespaceSchemaLocation attribute value to place in the marshalled* XML output.*/public static final String JAXB_NO_NAMESPACE_SCHEMA_LOCATION = "jaxb.noNamespaceSchemaLocation";// *) 是否生成报文头public static final String JAXB_FRAGMENT = "jaxb.fragment";}

    public static void main(String[] args) {TNode obj = new TNode("key_1", "val_1");try {JAXBContext jc = JAXBContext.newInstance(TNode.class);Marshaller marshaller = jc.createMarshaller();marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);marshaller.setProperty(Marshaller.JAXB_ENCODING, "UTF-8");// 1) 隐去报文头的生成, Marshaller.JAXB_FRAGMENT默认为falsemarshaller.setProperty(Marshaller.JAXB_FRAGMENT, true);StringWriter writer = new StringWriter();// 2) 自定义生成writer.write("<?xml version=\"1.0\" encoding=\"UTF-8\" ?>\n");marshaller.marshal(obj, writer);System.out.println(writer.toString());} catch (JAXBException e) {e.printStackTrace();}}

<?xml version="1.0" encoding="UTF-8" ?>
<root><key>key_1</key><value>val_1</value>
</root>