无法使用 Jackson 解析 JSON（映射不起作用）

Question

I am trying to use Jackson to parse sample json as demonstrated below. However, I the parsing doesn't work (fails without any exceptions - as I get an empty string for event.getAccountId(); What could I be doing wrong? Thanks!

        ObjectMapper om = new ObjectMapper();
    String json = "{\"_procurementEvent\" : [{ \"accountId\" : \"3243234\",\"procurementType\" : \"view\"," +
            "\"_procurementSubType\" : \"Standard Connector\",\"_quantity\" : \"4\", \"_pricePerMonth\" : \"100.00\"" +
            ",\"_annualPrice\" : \"1200.00\"}]}";
    ProcurementEvent event = om.readValue(json, ProcurementEvent.class);

    event.getAccountId(); // returns null    

   @JsonIgnoreProperties(ignoreUnknown = true)
    private static class ProcurementEvent {
        private String _accountId;
        private String _procurementType;
        private String _quantity;
        private String _pricePerMonth;
        private String _annualPrice;

        @JsonProperty("accountId")
        public String getAccountId() {
            return _accountId;
        }

        public void setAccountId(String accountId) {
            _accountId = accountId;
        }

        @JsonProperty("procurementType")
        public String getProcurementType() {
            return _procurementType;
        }

        public void setProcurementType(String procurementType) {
            _procurementType = procurementType;
        }

        @JsonProperty("_quantity")
        public String getQuantity() {
            return _quantity;
        }

        public void setQuantity(String quantity) {
            _quantity = quantity;
        }

        @JsonProperty("_pricePerMonth")
        public String getPricePerMonth() {
            return _pricePerMonth;
        }

        public void setPricePerMonth(String pricePerMonth) {
            _pricePerMonth = pricePerMonth;
        }

        @JsonProperty("_annualPrice")
        public String getAnnualPrice() {
            return _annualPrice;
        }

        public void setAnnualPrice(String annualPrice) {
            _annualPrice = annualPrice;
        }
    }

Answer 1

In the question, try the following approach:

class ProcurementEvents {
  private List<ProcurementEvent> _procurementEvent; // + annotations like @JsonIgnoreProperties, getters/ setters, etc.
}

// json from your example
ProcurementEvents events = om.readValue(json, ProcurementEvents.class);
events.get(0).getAccountId();

Answer 2

Your code deserializes an instance of ProcurementEvent from a json representation. The problem there is that your json represents a mapping string=>list of object representation . You can have the code work without changes but you need to edit the Json data; the example will work when the json contains the object representation only.

Modify the json data as:

String json = "{ \"accountId\" : \"3243234\",\"procurementType\" : \"view\","
    + "\"_procurementSubType\" : \"Standard Connector\",\"_quantity\" : \"4\", "
    + "\"_pricePerMonth\" : \"100.00\",\"_annualPrice\" : \"1200.00\"}";

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