我有一個以下形式的簡單 Json：{ "products": [ { "id": 1, "productSku": "123", "productInventory": "24" }, { "id": 2, "productSku": "12350", "productInventory": "22" }, { "id": 3, "productSku": "12351", "productInventory": "19" } ]}我正在通過 localhost URL 獲取此 Json，并嘗試將其映射到在不同端口上運行的不同 Spring Boot 應用程序中的 POJO 類。上述Json對應的POJO類為：@JsonIgnoreProperties(ignoreUnknown = true)@JsonRootName(value = "products")public class Product { private Integer id; private String productSku; private String productInventory; //getters and setters omitted}以下是我處理映射和綁定的控制器：@ResponseBody @GetMapping("index") public String getIndex() throws JsonParseException, JsonMappingException, IOException { URL ApiUrlJson = new URL("http://localhost:1990/product"); ObjectMapper mapper = new ObjectMapper(); Product product = mapper.readValue(ApiUrlJson, Product.class); System.out.println(product.getProductInventory()); return "Processed!"; }當我運行應用程序并訪問索引以獲取某個變量的值時，輸出始終為空，我不確定我缺少什么？
3 回答
瀟湘沐
TA貢獻1816條經驗 獲得超6個贊
您的 JSON 文件中有一個產品列表。您正在反序列化一個具有 3 個字段的對象。這些字段都不是在產品下，但您忽略了缺少的字段。
嘗試反序列化為包含 Product 列表的新類。刪除 @JsonRootName
侃侃無極
TA貢獻2051條經驗 獲得超10個贊
您正在嘗試反序列化 JSON 數組。也不要省略 setter，因為這個變量的訪問是私有的。你可以參考下面的代碼。我已經檢查過了，我能夠正確地反序列化它。
@JsonIgnoreProperties(ignoreUnknown = true)
class Product {
private Integer id;
private String productSku;
private String productInventory;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getProductSku() {
return productSku;
}
public void setProductSku(String productSku) {
this.productSku = productSku;
}
public String getProductInventory() {
return productInventory;
}
public void setProductInventory(String productInventory) {
this.productInventory = productInventory;
}
}
class Products{
private List<Product> products;
public List<Product> getProducts() {
return products;
}
public void setProducts(List<Product> products) {
this.products = products;
}
}
public class Main{
public static void main(String[] args) throws Exception{
String jsonString =
"{\n"
+ " \"products\": [\n"
+ " {\n"
+ " \"id\": 1,\n"
+ " \"productSku\": \"123\",\n"
+ " \"productInventory\": \"24\"\n"
+ " },\n"
+ " {\n"
+ " \"id\": 2,\n"
+ " \"productSku\": \"12350\",\n"
+ " \"productInventory\": \"22\"\n"
+ " },\n"
+ " {\n"
+ " \"id\": 3,\n"
+ " \"productSku\": \"12351\",\n"
+ " \"productInventory\": \"19\"\n"
+ " }\n"
+ " ]\n"
+ "}";
ObjectMapper mapper = new ObjectMapper();
Products products = mapper.readValue(jsonString, Products.class);
// To just access list of ids
List<Product> productsList= products.getProducts();
List<Integer> productIds = new ArrayList<>();
for(Product product : productsList){
productIds.add(product.getId());
}
System.out.println(productIds);
}
}
慕姐8265434
TA貢獻1813條經驗 獲得超2個贊
您有一個對象，該對象內部是一個對象列表。IE
@JsonIgnoreProperties(ignoreUnknown = true)
@JsonRootName(value = "products")
public class Products {
private List<Product> products;
public List<Product> getProducts() {
return products;
}
public void setProducts(final List<Product> products) {
this.products = products;
}
}
public class Product{
.....
}
ObjectMapper objectMapper = new ObjectMapper();
Products product = objectMapper.readValue("json here....", Products.class);
System.out.println(product.getProducts().size());
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