当映射到 POJO 中的 Double 类型字段时，Jackson ObjectMapper 将 Integer 值转换为 null

Question

请多多包涵。我浏览了很多链接，但找不到适合我的案例的解决方案。我需要帮助。

注意：我无法更改 JSON 请求（在测试中表示为地图）

这是我的 POJO：

public class TestModelWithDoubleField {
    private Double frequency;

    public Double getFrequency(){
        return frequency;
    }

    /**
     * @param frequency the frequency to set
     */
    public void setFrequency(Double frequency) {
        this.frequency = frequency;
    }

    /**
     * @param frequency the frequency to set
     */
    @JsonIgnore
    public void setFrequency(Integer frequency) {
        if(frequency != null) {
            setFrequency(new Double(frequency));
        }
    }
}

这是失败的测试：

@Test
public void testWithIntegerValueConvertToDoubleFieldInPOJO() throws IOException {
    final Map<String, Integer> map = new HashMap<>();
    map.put("frequency", 900);
    TestModelWithDoubleField pojo = objectMapper.convertValue(map, TestModelWithDoubleField.class);
    Assert.assertNotNull(pojo);
    Assert.assertNotNull(pojo.getFrequency());   //-> This is giving output as null. Hence fails.
}

在Assert.assertNotNull(pojo.getFrequency()); 行中，频率为空。因此测试失败。

我希望它自动转换为 Double 类型。 将@JsonIgnore 放在另一个设置器上也不起作用。

从该地图中获取有效对象的任何方法都可以。

Answer 1

只需删除public void setFrequency(Integer frequency) 方法，它就会起作用：

public class TestModelWithDoubleField {
    private Double frequency;

    public Double getFrequency(){
        return frequency;
    }

    public void setFrequency(Double frequency){
        this.frequency = frequency;
    }
}

---

由于您不能删除public void setFrequency(Integer frequency) 方法，因此您可以使用@JsonProperty 注释另一个setter，将其定义为Jackson 使用的setter：

public class TestModelWithDoubleField {
    private Double frequency;

    public Double getFrequency(){
        return frequency;
    }

    @JsonProperty
    public void setFrequency(Double frequency) {
        this.frequency = frequency;
    }

    public void setFrequency(Integer frequency) {
        if(frequency != null) {
            setFrequency(new Double(frequency));
        }
    }
}

Answer 2

只需在所需的设置器上添加@JsonProperty("frequency")。你甚至不需要@JsonIgnore 另一个。

public static class TestModelWithDoubleField
{
  private Double frequency;

  public Double getFrequency()
  {
      return frequency;
  }

  /**
   * @param frequency the frequency to set
   */
  @JsonProperty("frequency")
  public void setFrequency(Double frequency)
  {
      this.frequency = frequency;
  }

  /**
   * @param frequency the frequency to set
   */
  public void setFrequency(Integer frequency)
  {
      if(frequency != null)
      {
          setFrequency(new Double(frequency));
      }
  }
}