Question

Maven依赖关系-Eclipse IDE

<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
        <dependency>
                <groupId>com.fasterxml.jackson.core</groupId>
                <artifactId>jackson-databind</artifactId>
                <version>2.9.8</version>
        </dependency>

没有任何注释，我得到了

控制台错误

com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException：无法识别的字段“ id”（类com.optimight.prakash.general.Employee），未标记为可忽略（0个已知属性：]）在[来源：（String）“ {” id“：1，” name“：” Lokesh Gupta“，” age“：34，” location“：” India“}”;行：1，列：8]（通过参考链：com.optimight.prakash.general.Employee [“ id”]）在com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException.from（UnrecognizedPropertyException.java:61）在com.fasterxml.jackson.databind.DeserializationContext.handleUnknownProperty（DeserializationContext.java:823）在com.fasterxml.jackson.databind.deser.std.StdDeserializer.handleUnknownProperty（StdDeserializer.java:1153）在com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownProperty（BeanDeserializerBase.java:1589）在com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownVanilla（BeanDeserializerBase.java:1567）在com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize（BeanDeserializer.java:294）在com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize（BeanDeserializer.java:151）在com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose（ObjectMapper.java:4013）在com.fasterxml.jackson.databind.ObjectMapper.readValue（ObjectMapper.java:3004）在com.optimight.prakash.general.JSONtoJavaPOJO.main（JSONtoJavaPOJO.java:18）

带有注释：@JsonIgnoreProperties（ignoreUnknown = true）

在Employe课堂上，然后我得到了

员工[id = null，name = null，age = null，location = null]

应用程序类-主要方法

    import java.io.IOException;
    import com.fasterxml.jackson.core.JsonGenerationException;
    import com.fasterxml.jackson.databind.JsonMappingException;
    import com.fasterxml.jackson.databind.ObjectMapper;

public class JSONtoJavaPOJO {
public static void main(String[] args) {
    String json = "{\"id\":1,\"name\":\"Lokesh Gupta\",\"age\":34,\"location\":\"India\"}";

    ObjectMapper mapper = new ObjectMapper();
    try
    {
        Employee emp = mapper.readValue(json, Employee.class);

        System.out.println(emp);
    }
    catch (JsonGenerationException e)
    {
        e.printStackTrace();
    } catch (JsonMappingException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

}

员工类别

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;



//@JsonIgnoreProperties(ignoreUnknown = true)
public class Employee
{
    private Integer id;
    private String name;
    private Integer age;
    private String location;



    public Employee() {
    }


    public Employee(Integer id, String name, Integer age, String location) {
        super();
        this.id = id;
        this.name = name;
        this.age = age;
        this.location = location;
    }



    @Override
    public String toString() {
        return "Employee [id=" + id + ", name=" + name + ", age=" + age
                + ", location=" + location + "]";
    }
}

Answer 1

将setter和getter添加到Employee类。

尝试将JSON字符串转换为JavaPOJO时遇到奇怪的问题