在反序列化时，添加一个条件，仅在已传递的值不为空时反序列化该值。

示例代码：

public class Person { private String name; private String age;

// getters and setters

@Override
public String toString() {
    return "Person{" +
            "name='" + name + '\'' +
            ", age='" + age + '\'' +
            '}';
}

}

// JSON字符串 String json = "{"name":"Tom"}";

// 反序列化Person对象 ObjectMapper mapper = new ObjectMapper(); Person person = mapper.readValue(json, Person.class);

// 输出结果 System.out.println(person); // 输出：Person{name='Tom', age='null'} (age未传递，反序列化为默认值null)

// 改进后的解决方法

public class Person { private String name; private String age;

// getters and setters

@Override
public String toString() {
    return "Person{" +
            "name='" + name + '\'' +
            ", age='" + age + '\'' +
            '}';
}

// 在setter中添加条件，仅在age不为空时设置age
public void setAge(String age) {
    if (age != null && !age.isEmpty()) {
        this.age = age;
    }
}

}

// JSON字符串 String json = "{"name":"Tom"}";

// 反序列化Person对象 ObjectMapper mapper = new ObjectMapper(); Person person = mapper.readValue(json, Person.class);

// 输出结果 System.out.println(person); // 输出：Person{name='Tom', age='null'} (age未传递，不会设置为null)