映射到“”而不是空Jackson

Question

XML示例：

<Example>
  <Object>
    <Member1><![CDATA[]]</Member1>
    <Member2><![CDATA[someText]]</Member2>
  </Object>
</Example>

然后我有POJO类，例如：（带有lombokgetter/setter/toString和jackson注释导入）

@Getter
@Setter
@ToString
@JacksonXMLRootElement(localName = "Example")
public class TXML {

  @JacksonXmlProperty(localName = "Object")
  private someObject object;
}

@Getter
@Setter
@ToString
public class someObject {

  @JacksonXmlProperty(localName = "Member1")
  private String member1;

  @JacksomXmlProperty(localName = "Member2")
  private String member2;
}

然后使用MappingJackson2XmlHttpMessageConverter获取对象映射器，并使用该映射器将XML字符串映射到示例类。

@Autowired ObjectMapper xmlMapper;
@Autowired
private MappingJackson2XmlHttpMessageConverter xmlConverter;
...
xmlMapper = xmlConverter.getObjectMapper();
Example example = xmlMapper.readValue(xmlString, Example.class);

这将产生一个具有以下内容的示例类：

Example
-> object
    -> member1 : ""
    -> member2 : "someText"

我希望member1为null，而不是空字符串。我怎样才能完成这件事呢？

Answer 1

您需要实现自己的com.fasterxml.jackson.databind.util.converter，它将在反序列化之后但在设置为必需的形式之前转换您的值。

示例实现：

class CDATAConverter implements Converter<String, String> {

    @Override
    public String convert(String value) {
        return (value == null || value.length() == 0) ? null : value;
    }

    @Override
    public JavaType getInputType(TypeFactory typeFactory) {
        return typeFactory.constructType(String.class);
    }

    @Override
    public JavaType getOutputType(TypeFactory typeFactory) {
        return typeFactory.constructType(String.class);
    }
}

您需要指示jackson使用它：

@Getter
@Setter
@ToString
class SomeObject {

    @JsonDeserialize(converter = CDATAConverter.class)
    @JacksonXmlProperty(localName = "Member1")
    private String member1;

    @JsonDeserialize(converter = CDATAConverter.class)
    @JacksonXmlProperty(localName = "Member2")
    private String member2;
}