idea的运行结果，查不出数据

运行结果

Person{id=null, name='null', age=null, sex='null', idCard=IdCard{id=2, code='null'}}

因果关系呢，这个是后台打印的吗

一般这种情况，先检查一下自己的Person类，如果用来private来修饰属性，是否有get set,toString方法，以及有无参构造函数
还有就是如果你用到了数据库，检查一下，有没有做好表字段和属性之间的映射关系，如果还没找到原因就把你的代码发出来

上代码

person类

public class Person {
    private Integer id;
    private String name;
    private Integer age;
    private String sex;
    private IdCard idCard;//个人关联的身份证实例

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public IdCard getIdCard() {
        return idCard;
    }

    public void setIdCard(IdCard idCard) {
        this.idCard = idCard;
    }

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

PersonMapper.xml

<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.gly.mybatis.mapper.PersonMapper">
    <resultMap id="personMap1"   type="Person">
        <id property="id" column=" id" />
        <result property="name" column=" name" />
        <result property="age" column=" age" />
        <result property="sex" column=" sex" />
        <!--嵌套查询-->
        <!--  一对一使用servlet属性应用另外一条sql语句-->
        <association property="idCard" column="card_id" javaType="idcard"
                     select="com.gly.mybatis.mapper.IdCardMapper.findCodeById"/>
    </resultMap>
    <select id="findPersonById" parameterType="Integer"  resultMap="personMap1">
    select * from t_person where id = #{id}
    </select>
    <!--嵌套结果-->
    <resultMap id="personmap2"   type="Person">
        <id property="id" column=" id" />
        <result property="name" column=" name" />
        <result property="age" column=" age" />
        <result property="sex" column=" sex" />
        <!--  一对一,使用嵌套结果-->
        <association property="idCard" javaType="idcard">
            <id property="id" column="card_id"/>
            <result property="code" column=" code" />
        </association>
    </resultMap>
    <select id="findPersonById2" parameterType="Integer"  resultMap="personmap2">
    select p.*,c.code from t_person p,t_idcard c where
    p.card_id = c.id and  p.id=#{id}
    </select>
</mapper>