解决方案并不简单。
编组（对象到 XML）非常简单，当您必须解组（XML 到对象）时问题就来了。
发生的情况是，当 XStream 开始读取 XML 并找到 Product 标签时，它无法确定它是“Product”还是“OtherProduct”对象，因为标签名称相同。
因此，您必须教 XStream 向前看，并检查您所知道的使它们与众不同的东西。在这种情况下，内部属性“Name”和“Id”。
您可以教 XSTream 如何编写转换器。
上面的解决方案显示了如何解决问题。
产品类别：
@XStreamAlias("Product")
public class Product {
@XStreamAlias("Name")
private String name;
public Product() {
}
public Product(String name) {
this.name = name;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
其他产品类别：
@XStreamAlias("Product")
public class OtherProduct {
@XStreamAlias("Id")
private int id;
public OtherProduct() {
}
public OtherProduct(int id) {
this.id = id;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
}
组数据类：
@XStreamAlias("Groups")
public class GroupData {
@XStreamAlias("Products")
private List<Product> products = new ArrayList<>();
@XStreamAlias("OtherProducts")
private List<OtherProduct> otherProducts = new ArrayList<>();
public void add(Product product) {
getProducts().add(product);
}
public void add(OtherProduct otherProduct) {
getOtherProducts().add(otherProduct);
}
public List<Product> getProducts() {
return products;
}
public List<OtherProduct> getOtherProducts() {
return otherProducts;
}
}
产品转换器类：
public class ProductConverter implements Converter {
private ProductUnmarshaller productUnmarshaller = new ProductUnmarshaller();
@Override
public boolean canConvert(@SuppressWarnings("rawtypes") Class clazz) {
return clazz.equals(Product.class);
}
@Override
public void marshal(Object object, HierarchicalStreamWriter hsw, MarshallingContext mc) {
Product product = (Product) object;
hsw.startNode("Name");
hsw.setValue(product.getName());
hsw.endNode();
}
@Override
public Object unmarshal(HierarchicalStreamReader hsr, UnmarshallingContext uc) {
return productUnmarshaller.unmarshal(hsr, uc);
}
}
其他产品转换器类：
public class OtherProductConverter implements Converter {
private ProductUnmarshaller productUnmarshaller = new ProductUnmarshaller();
@Override
public boolean canConvert(@SuppressWarnings("rawtypes") Class clazz) {
return clazz.equals(OtherProduct.class);
}
@Override
public void marshal(Object object, HierarchicalStreamWriter hsw, MarshallingContext mc) {
OtherProduct otherProduct = (OtherProduct) object;
hsw.startNode("Id");
hsw.setValue(Integer.toString(otherProduct.getId()));
hsw.endNode();
}
@Override
public Object unmarshal(HierarchicalStreamReader hsr, UnmarshallingContext uc) {
return productUnmarshaller.unmarshal(hsr, uc);
}
}
ProductUnmarsheller 类：
public class ProductUnmarshaller {
public Object unmarshal(HierarchicalStreamReader hsr, UnmarshallingContext uc) {
hsr.moveDown();
String nodeName = hsr.getNodeName();
String nodeValue = hsr.getValue();
hsr.moveUp();
if ("Name".equals(nodeName)) {
return new Product(nodeValue);
} else if ("Id".equals(nodeName)) {
return new OtherProduct(Integer.parseInt(nodeValue));
} else {
return null;
}
}
}
最后，一个使用它的类：
public class ProductTest {
@Test
public void test() {
Product productOne = new Product("One");
Product productTwo = new Product("Two");
OtherProduct otherProduct1 = new OtherProduct(1);
OtherProduct otherProduct2 = new OtherProduct(2);
GroupData group = new GroupData();
group.add(productOne);
group.add(productTwo);
group.add(otherProduct1);
group.add(otherProduct2);
XStream xs = new XStream();
xs.processAnnotations(GroupData.class);
xs.processAnnotations(OtherProduct.class);
xs.processAnnotations(Product.class);
xs.registerConverter(new ProductConverter());
xs.registerConverter(new OtherProductConverter());
String xml = xs.toXML(group);
System.out.println(xml);
GroupData gd = (GroupData) xs.fromXML(xml);
for (Product product: gd.getProducts()) {
System.out.println(product.getName());
}
for (OtherProduct otherProduct: gd.getOtherProducts()) {
System.out.println(otherProduct.getId());
}
}
}