创建表t_emp

定义实体类

package org.example.entity;

public class Emp {
private Integer empId;
private String empName;
private Integer age;
private String gender;
private Integer deptId;

public Emp() {  
}

public Emp(Integer empId, String empName, Integer age, String gender, Integer deptId) {  
    this.empId = empId;  
    this.empName = empName;  
    this.age = age;  
    this.gender = gender;  
    this.deptId = deptId;  
}

public Integer getEmpId() {  
    return empId;  
}

public void setEmpId(Integer empId) {  
    this.empId = empId;  
}

public String getEmpName() {  
    return empName;  
}

public void setEmpName(String empName) {  
    this.empName = empName;  
}

public Integer getAge() {  
    return age;  
}

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

public String getGender() {  
    return gender;  
}

public void setGender(String gender) {  
    this.gender = gender;  
}

public Integer getDeptId() {  
    return deptId;  
}

public void setDeptId(Integer deptId) {  
    this.deptId = deptId;  
}

@Override  
public String toString() {  
    return "Emp{" +  
            "empId=" + empId +  
            ", empName='" + empName + '\\'' +  
            ", age=" + age +  
            ", gender='" + gender + '\\'' +  
            ", deptId=" + deptId +  
            '}';  
}  

}

mapper接口

public interface EmpMapper {

public Emp queryEmpById(@Param("id") int id);
}

EmpMapper.xml

<!--  
    resultMap：设置自定义映射关系  
    id：唯一标识  
    type：处理映射关系的实体类的类型  
    常用的标签：  
    id：处理主键和实体类中属性的映射关系  
    result：处理普通字段实体类中属性的映射关系  
    column：设置映射关系中的字段名，必须是sql查询出的某个字段  
    property：设置映射关系中的属性的属性名，必须是处理的实体类类型中的属性名  
-->  
<resultMap id="empResultMap" type="emp">  
    <id column="emp\_id" property="empId"></id>  
    <result column="emp\_name" property="empName"></result>  
    <result column="age" property="age"></result>  
    <result column="gender" property="gender"></result>  
    <result column="dept\_id" property="deptId"></result>  
</resultMap>

<select id="queryEmpById" resultMap="empResultMap">  
    select \* from t\_emp where emp\_id = #{id}  
</select>  

测试代码

@Test  
public void queryEmpById(){  
    SqlSession sqlSession = SqlSessionUtil.getSqlSession();  
    EmpMapper mapper = sqlSession.getMapper(EmpMapper.class);  
    Emp emp = mapper.queryEmpById(2);  
    System.out.println(emp);

    sqlSession.close();  
}