com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: 无法识别的字段 "Symbol"

Question

我正在尝试拍摄一些看起来像这样的 JSON（来自 AlphaVantage）：

{
    "Symbol": "IBM",
    "AssetType": "Common Stock",
    "Name": "International Business Machines Corporation",
... more properties
}

并使用 Jackson (& Ebeans) 解析它：

  ObjectMapper objectMapper = new ObjectMapper();
  String json = response.body().string();
  Stock stock = objectMapper.readValue(json, Stock.class);
  stock.save();

我的库存 class 看起来像这样：

@Entity
@Table(name = "stock")
public class Stock extends Model {

@Id
private Long id;
private String Symbol;
private String AssetType;
private String Name;
... other properties

public Long getId() {
    return this.id;
}

public void setId(Long id) {
    this.id = id;
}

public String getSymbol() {
    return this.Symbol;
}
public void setSymbol(String Symbol) {
    this.Symbol = Symbol;
}

... other setters/getters

}

相反，我收到以下错误：

com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "Symbol" (class com.myprojectname.Stock), not marked as ignorable (60 known properties: "ebitda", "sharesOutstanding", "bookValue", ....more fields

为什么 Jackson 在连接到我的 Stock class 时遇到问题？如何将 JSON 中的符号连接到股票 class 中的符号？

编辑：如果我将符号更改为小写，我会收到相同的错误消息：

@Entity
@Table(name = "stock")
public class Stock extends Model {

@Id
private Long id;
private String symbol;

public String getSymbol() {
    return this.symbol;
 }
public void setSymbol(String symbol) {
    this.symbol = symbol;
 }
}

Answer 1

将属性的名称从 Symbol 更改为 symbol 无济于事，因为 json 文件中仍然有 "Symbol"。

您可以尝试使用@JsonProperty注解like in the example。对于 "Symbol" json 字段，它可能如下所示：

//...
    private String Symbol;

    @JsonProperty("Symbol")
    public String getSymbol() {
        return this.Symbol;
    }

    @JsonProperty("Symbol")
    public void setSymbol(String symbol) {
        this.Symbol = symbol;
    }
// ...

这种方法也适用于与 json 对应的大写/小写字母不同的其他字段。

编辑：就像我上面评论中链接的问题 the answer 一样 - 解释一下：

Since your setter method is named setSymbol() Jackson assumes the variable is named symbol because of the Java naming conventions (variables should start with lower case letters).

edit(2)：其他选项将利用 the object mapper configuration. So instead of the annotations approach you could use the approach from here 并使映射器不区分大小写：

objectMapper.configure(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES, true);

其他属性我觉得有用的是：

objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

在上面链接的 Baeldung 文章中有描述

Answer 2

您还可以将 ObjectMapper 配置为仅检查字段并忽略 getter：

JsonMapper mapper = JsonMapper.builder()
        .visibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY)
        .visibility(PropertyAccessor.GETTER, JsonAutoDetect.Visibility.NONE)
        .build();

How to specify jackson to only use fields - preferably globally

com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: 无法识别的字段 "Symbol"

com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "Symbol"

java

json

jackson

ebean