JSON:JsonMappingException同时尝试使用空值反序列化对象

Question

我尝试反序列化包含null属性的对象并具有JsonMappingException.

我所做的:

String actual = "{\"@class\" : \"PersonResponse\"," +
                "  \"id\" : \"PersonResponse\"," +
                "  \"result\" : \"Ok\"," +
                "  \"message\" : \"Send new person object to the client\"," +
                "  \"person\" : {" +
                "    \"id\" : 51," +
                "    \"firstName\" : null}}";
ObjectMapper mapper = new ObjectMapper();
mapper.readValue(new StringReader(json), PersonResponse.class); //EXCEPTION!

但是:如果扔掉"firstName = null"财产 - 一切正常!我的意思是传递下一个字符串:

String test = "{\"@class\" : \"PersonResponse\"," +
                "  \"id\" : \"PersonResponse\"," +
                "  \"result\" : \"Ok\"," +
                "  \"message\" : \"Send new person object to the client\"," +
                "  \"person\" : {" +
                "    \"id\" : 51}}";
ObjectMapper mapper = new ObjectMapper();
mapper.readValue(new StringReader(json), PersonResponse.class); //ALL WORKS FINE!

问题:如何避免此异常或承诺杰克逊在序列化期间忽略空值？

抛出:

信息:

com.fasterxml.jackson.databind.MessageJsonException:
 com.fasterxml.jackson.databind.JsonMappingException:
  N/A (through reference chain: person.Create["person"]->Person["firstName"])

原因:

com.fasterxml.jackson.databind.MessageJsonException:
 com.fasterxml.jackson.databind.JsonMappingException:
  N/A (through reference chain: prson.Create["person"]->Person["firstName"])

原因: java.lang.NullPointerException

Answer 1

有时在意外使用基本类型作为非原始字段的getter的返回类型时会出现此问题:

public class Item
{
    private Float value;

    public float getValue()
    {
        return value;
    }

    public void setValue(Float value)
    {
        this.value = value;
    }   
}

请注意getValue() - 方法的"float"而不是"Float",这可能会导致Null指针异常,即使您已添加

objectMapper.setSerializationInclusion(Include.NON_NULL);

Answer 2

如果您不想序列化null值,可以使用以下设置(在序列化期间):

objectMapper.setSerializationInclusion(Include.NON_NULL);

希望这能解决你的问题.

但是NullPointerException你在反序列化过程中得到的结果对我来说似乎很可疑(杰克逊理想情况下应该能够处理null序列化输出中的值).你能发布与PersonResponse班级相对应的代码吗？