mybatis（输入、输出参数、ResultMap）

1、输入参数（POJO包装类）：

（1）POJO包装类：

public class QueryVo implements Serializable {
    private static final long serialVersionUID = 1L;
    private Student student;
    public Student getStudent() {
        return student;
    }

    public void setStudent(Student student) {
        this.student = student;
    }
}

需要实现序列化接口，用于实现序列化（对象转化为二进制）与反序列化（二进制转换为对象）。

（2）配置mapper.xml配置文件：

<select id="findStudentByQueryVo" parameterType="QueryVo" resultType="pers.zhb.pojo.Student">
        select * from student where sname like "%"#{student.sname}"%"
</select>

（3）创建接口：

public interface StudentMapper {
     Student findStudentById(Integer studentno);
     List<Student> findStudentByQueryVo(QueryVo vo);
}

（4）测试：

 public void findStudentByQueryVo() throws Exception {
        //加载核心配置文件
        String resource = "sqlMapConfig.xml";
        InputStream in = Resources.getResourceAsStream(resource);
        //创建SqlSessionFactory
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        //创建SqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //SqlSEssion帮我生成一个实现类  （给接口）
        StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
        QueryVo queryVo=new QueryVo();
        Student student=new Student();
        student.setSname("z");
        queryVo.setStudent(student);
        List<Student> s = studentMapper.findStudentByQueryVo(queryVo);
        for(Student ss:s){
            System.out.println(s);
        }
    }

2、输出参数

（1）接口：

public interface StudentMapper {
     Integer countStudent();
}

（2）配置文件：

    <select id="countStudent" resultType="Integer">
        select count(*) from student
    </select>

（3）测试：

 public void countStudent() throws Exception {
            //加载核心配置文件
            String resource = "sqlMapConfig.xml";
            InputStream in = Resources.getResourceAsStream(resource);
            //创建SqlSessionFactory
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
            //创建SqlSession
            SqlSession sqlSession = sqlSessionFactory.openSession();
            //SqlSEssion帮我生成一个实现类  （给接口）
            StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
            Integer countStudent = studentMapper.countStudent();
            System.out.println(countStudent);
    }

3、输出类型：ResultMap

（1）书写POJO：

public class Student implements Serializable {
    private static final long serialVersionUID = 1L;
    private String snumber;
    private String sname;
    private String sex;
    private String birthday;
    private String classno;
    private String point;
    private String phone;
    private String email;
    public String getSnumber() {
        return snumber;
    }
    public void setSnumber(String snumber) {
        this.snumber = snumber;
    }
    public String getSname() {
        return sname;
    }
    public void setSname(String sname) {
        this.sname = sname;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public String getBirthday() {
        return birthday;
    }
    public void setBirthday(String birthday) {
        this.birthday = birthday;
    }
    @Override
    public String toString() {
        return "Student [snumber=" + snumber + ", sname=" + sname + ", sex="
                + sex + ", birthday=" + birthday + ", classno=" + classno
                + ", point=" + point + ", phone=" + phone + ", email=" + email
                + "]";
    }
    public String getClassno() {
        return classno;
    }
    public void setClassno(String classno) {
        this.classno = classno;
    }
    public String getPoint() {
        return point;
    }
    public void setPoint(String point) {
        this.point = point;
    }
    public String getPhone() {
        return phone;
    }
    public void setPhone(String phone) {
        this.phone = phone;
    }
    public String getEmail() {
        return email;
    }
    public void setEmail(String email) {
        this.email = email;
    }
}

（2）接口：

public interface StudentMapper {
     List<Student> selectAllStudent();
}

（3）配置文件：

    <select id="selectAllStudent" resultType="pers.zhb.pojo.Student">
        select *  from student
    </select>

（4）书写测试类：

 public void selectAllStudent() throws Exception {
        //加载核心配置文件
        String resource = "sqlMapConfig.xml";
        InputStream in = Resources.getResourceAsStream(resource);
        //创建SqlSessionFactory
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        //创建SqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //SqlSEssion帮我生成一个实现类  （给接口）
        StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
        List<Student> students = studentMapper.selectAllStudent();
        for(Student student:students){
            System.out.println(student);
        }
    }

（5）输出结果：

DEBUG [main] - Find JAR URL: file:/D:/IdeaProjects/MybatisDemo/web/WEB-INF/classes/pers/zhb/mapper/StudentMapper.xml
DEBUG [main] - Not a JAR: file:/D:/IdeaProjects/MybatisDemo/web/WEB-INF/classes/pers/zhb/mapper/StudentMapper.xml
DEBUG [main] - Reader entry: <?xml version="1.0" encoding="UTF-8" ?>
DEBUG [main] - Checking to see if class pers.zhb.mapper.StudentMapper matches criteria [is assignable to Object]
DEBUG [main] - Opening JDBC Connection
DEBUG [main] - Created connection 517210187.
DEBUG [main] - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@1ed4004b]
DEBUG [main] - ==>  Preparing: select * from student 
DEBUG [main] - ==> Parameters: 
DEBUG [main] - <==      Total: 8
Student [snumber=null, sname=zhai, sex=男, birthday=1998-11-11, classno=tx171, point=890, phone=1234567890, email=null]
Student [snumber=null, sname=zhai2, sex=男, birthday=1998-11-11, classno=tx171, point=893, phone=19837372533, email=null]
Student [snumber=null, sname=zhai3, sex=男, birthday=1998-11-11, classno=tx171, point=892, phone=19837372534, email=null]
Student [snumber=null, sname=zhai3, sex=男, birthday=1998-11-11, classno=tx101, point=892, phone=19837372534, email=null]
Student [snumber=null, sname=qwerr, sex=男, birthday=1998-11-11, classno=tx101, point=892, phone=19837372534, email=null]
Student [snumber=null, sname=jiayou, sex=男, birthday=1998-11-11, classno=tx101, point=892, phone=19837372534, email=null]
Student [snumber=null, sname=null, sex=null, birthday=null, classno=2, point=null, phone=null, email=null]
Student [snumber=null, sname=null, sex=null, birthday=null, classno=2, point=null, phone=null, email=null]

可以看到snumber列的数据都为空，只是因为POJO中的列名与数据库中的列名不一致导致的（在sql类型处理器不能根据属性名查找数据库中的数据）。因为resultType可以指定将查询结果映射为pojo，但需要pojo的属性名和sql查询的列名一致方可映射成功。

（6）resultMap

结果集映射，映射为Student：

<id property="studentno" column="studentno"></id>

在<resultMap>标签中将数据库的字段与java类的属性进行一一映射（也可以只对不一样的字段和属性进行映射）

 <resultMap id="result" type="Student">

        <result column="studentno" property="snumber"></result>
    </resultMap>
    <select id="selectAllStudent" resultMap="result">
        select *  from student
    </select>

可以采用resultMap的方式，即使POJO中的属性与数据库的字段不一致，依旧能够查询成功。因为resultMap将字段名和属性名作一个对应关系 ，resultMap实质上还需要将查询结果映射到pojo对象中。