我想基于xml解析出不同的类型，当header=1然后是User，header=2然后是Order等时，例如：
<entity>
<header>1</header>
<body>
<userId>1</userId>
<userName>jonh</userName>
...
<body>
</entity>
<entity>
<header>2</header>
<body>
<orderId>1</orderId>
<orderNo>20200101</orderNo>
...
<body>
</entity>
如何实现此功能？
Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
Object object = unmarshaller.unmarshal(xml);
我会尝试这样做：在解组时提供类型。所以，也许可以这样做：创建一个瞬态门面对象：
public class XmlEntityFacade {
private int header;
private Object body;
//getters and setters...
}
然后在解组时强制转换此类型：
...
XmlEntityFacade facade = (XmlEntityFacade) unmarshaller.unmarshal(xml);
然后，您可以通过调用.getHeader((和带有.getBody((的body(已提供XmlEntityFacade类的getter(来访问的值。然后根据值将所需的类型强制转换为Object。
public class TwiceUnmarshalTest {
@Data
@ToString
public static abstract class HeaderResponse {
private String header;
}
@XmlRootElement(name = "entity")
@XmlAccessorType(XmlAccessType.FIELD)
public static class XmlHeaderResponse extends HeaderResponse {
}
private final String xml = "<entity>" +
" <header>2</header>" +
" <body>" +
" <orderId>1</orderId>" +
" <orderNo>2020</orderNo>" +
" </body>" +
"</entity>";
@SuppressWarnings("unchecked")
public static <T> T unmarshal(Reader reader, Class<T> typeClass) throws Exception {
JAXBContext jaxbContext = JAXBContext.newInstance(typeClass);
Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
return (T) unmarshaller.unmarshal(reader);
}
@Test
public void headerResponse() throws Exception {
HeaderResponse response = unmarshal(new StringReader(xml), XmlHeaderResponse.class);
System.out.println(response);
}
@ToString(callSuper = true)
public static abstract class Response<T> extends HeaderResponse {
@XmlAnyElement(lax = true)
public T body;
}
@Data
@XmlRootElement(name = "body")
public static class Order {
private String orderId;
private String orderNo;
}
@XmlRootElement(name = "entity")
@XmlSeeAlso({Order.class})
public static class OrderResponse extends Response<Order> {
}
@Test
public void response() throws Exception {
XmlHeaderResponse response = unmarshal(new StringReader(xml), XmlHeaderResponse.class);
System.out.println(response);
//TwiceUnmarshalTest.HeaderResponse(header=2)
if (response.getHeader().equals("2")) {
OrderResponse orderResponse = unmarshal(new StringReader(xml), OrderResponse.class);
System.out.println(orderResponse);
//TwiceUnmarshalTest.Response(super=TwiceUnmarshalTest.HeaderResponse(header=2), body=TwiceUnmarshalTest.Order(orderId=1, orderNo=2020))
}
}
}
解组两次，只需先获取标头，然后获取实体。不是很好，但可以使用。