使用反射API获取列表对象值

Question

我有一个XML解析的pojo，如下

@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "", propOrder = {
    "activity",
    "orderDetails"
})
@XmlRootElement(name = "GxML")
public class GxML {
    @XmlElement(name = "Activity", required = true)
    public String activity;
    @XmlElement(name = "OrderDetails", required = true)
    public GxML.OrderDetails orderDetails;
   //get set
    @XmlAccessorType(XmlAccessType.FIELD)
    @XmlType(name = "", propOrder = {
        "initiatorRole",
        "productDetails"
    })
    public static class OrderDetails {
        @XmlElement(name = "InitiatorRole", required = true)
        public String initiatorRole;
        //get set
        @XmlAccessorType(XmlAccessType.FIELD)
        @XmlType(name = "", propOrder = {
            "product"
        })
        public static class ProductDetails {
            @XmlElement(name = "Product", required = true)
            public List<GxML.OrderDetails.ProductDetails.Product> product;
            public List<GxML.OrderDetails.ProductDetails.Product> getProduct() {
                if (product == null) {
                    product = new ArrayList<GxML.OrderDetails.ProductDetails.Product>();
                }
                return this.product;
            }
            @XmlAccessorType(XmlAccessType.FIELD)
            @XmlType(name = "", propOrder = {
               "quantity",
                "commodity"
            })
            public static class Product {
            @XmlElement(name = "Quantity", required = true)
                public BigDecimal quantity;
                @XmlElement(name = "Commodity", required = true)
                public String commodity;
                //get set
            }}}}

我需要使用Java反射获取所有字段名称及其相应的值

Class c1 = gXml.getClass();    
Field[] valueObjFields = c1.getDeclaredFields()[1].getType().getDeclaredFields();   
for (int i = 0; i < valueObjFields.length; i++)      {     
String fieldName = valueObjFields[i].getName();     
valueObjFields[i].setAccessible(true);    
Object newObj = valueObjFields[i].get(gXml.getOrderDetails());     
orderMap.put(valueObjFields[i].getAnnotation(XmlElement.class).name(), newObj);   
if("productDetails".equalsIgnoreCase(fieldName)){
Class c2 = gXml.getOrderDetails().getProductDetails().getProduct().get(0).getClass();  
Field[] valueObjFields1 = c2.getDeclaredFields();   
for (int j = 0; j < valueObjFields1.length; j++)      {     
String fieldName2 = valueObjFields1[j].getName();     
valueObjFields1[j].setAccessible(true);    
Object newObj2 = valueObjFields1[j].get(gXml.getOrderDetails().getProductDetails().getProduct());  
orderMap.put(valueObjFields1[j].getAnnotation(XmlElement.class).name(), newObj2);   
} } }  

对于订单详细信息，它运行良好，但在获取数量和商品的产品详细信息中，它在
处给出了非法参数异常对象newObj2=valueObjFields1[j].get（gXml.getOrderDetails（）.getProductDetails（）.getProduct（））；

如何使用反射获取列表值。

Answer 1

您可以从getProduct().get(0)类（看起来像列表的成员）中获得字段

Class c2 = gXml.getOrderDetails().getProductDetails().getProduct().get(0).getClass();  
Field[] valueObjFields1 = c2.getDeclaredFields();

但是尝试从集合本身读取值（而不是获取（0）元素）

valueObjFields1[j].get(gXml.getOrderDetails().getProductDetails().getProduct());