MyBatis-parameterType参数的理解1

当方法参数较多时，使用对象，对象只要有属性，每个属性有set，get方法

属性名必须和表的列名相同，否则返回的对象的属性为空

    select id,name ,email,age from student where
    name =#{name,javaType=java.lang.String,jdbcType=VARCHAR}
    or
    age=#{age,javaType=java.lang.Integer,jdbcType=INTEGER}

这个方式不推荐使用，

：可读性不好，arg0和arg1不清晰是什么值

：List selectByPosition(String name,Integer age);

方添加了一个参数，结果错误

：select id,name ,email,age from student where name =#{arg0} or age=#{arg1}

当arg1和arg0换位置，会影响结果

不推荐使用，Map集合，

：List selectStudentByMap(Map map);

并不清楚Map的参数有几个，也不知道参数的类型

：select id,name ,email,age from student where name =#{myname} or age=#{myage}

通过key获取值，key值不具有统一性

StudentDao接口：

package com.bjpowernode.dao;

import com.bjpowernode.domain.Student;
import com.bjpowernode.vo.QueryParama;
import org.apache.ibatis.annotations.Param;

import java.util.List;
import java.util.Map;

public interface StudentDao {
    //查询学生
    Student selectById(Integer id);

    //dao接口的方法是一个简单类型的  java基本数据类型 和字符串
    Student selectByEmail(String email);

    
    List selectByNameOrAge(@Param(value="myname") String name,
                                    @Param("myage") Integer age);

    
    List selectByObject(Student student);

    //对象不局限于实体类，他可以是任意的一个实体类，有属性，有Sett Gett方法就能使用
    List selectByQueryParama(QueryParama parama);

    //使用位置获取参数
    List selectByPosition(String name,Integer age);

    
    List selectStudentByMap(Map map);

    //更新
    int updateStudent(Student student);


    //${}占位符的使用查询 ,使用@Param命名
    List queryStudent(@Param("studentName") String name);


    //按id排序
    List queryStudentOrderById();

    //按照name排序
    List queryStudentOrderName();

    //传入利用占位符特定参数查询
    List queryStudentOrderByColName(@Param("myname") String name,@Param("colName") String colName,@Param("colName") String tableName);
}

StudentDao.xml：




    
    
    
    
        select id,name ,email,age from student where id=#{studentid}
    


    
        select id,name ,email,age from student where name =#{myname} or age=#{myage}
    


    
        select id,name ,email,age from student where name =#{p1} or age=#{p2}
    


    
        select id,name ,email,age from student where name =#{myname} or age=#{myage}
    


    
        update student set name=#{name},email=#{email} where id=#{id}
    



    
        select * from student order by id
    


    
    
        select * from ${tableName} where name=#{myname} order by ${colName} desc

Student类：

package com.bjpowernode.domain;

public class Student {
    //属性名和列明保持一致
    private Integer id;
    private  String name;
    private String email;
    private Integer age;

    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 String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public Integer getAge() {
        return age;
    }

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

    @Override
    public String toString() {
        return "学生实体信息{" +
                "id=" + id +
                ", name='" + name + ''' +
                ", email='" + email + ''' +
                ", age=" + age +
                '}';
    }
}

MyBatistUtil工具类：

package com.bjpowernode.utils;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.InputStream;


public class MybatisUtil {
    private static SqlSessionFactory factory=null;

    // 通过静态代码块，当MybatisUtil类被虚拟机加载的时候，就执行以下代码，把SqlSessionFactory factory创建一次
    //读取主配置文件
    static{
        try{
            String config="mybatis.xml";
            InputStream inputStream = Resources.getResourceAsStream(config);
            factory=new SqlSessionFactoryBuilder().build(inputStream);
        }catch(IOException e){
            e.printStackTrace();
        }
    }

    //创建方法，获取SqlSession对象
    public static SqlSession getSqlSession(){
        SqlSession session=null;
        if (factory!=null){
            session=factory.openSession();//openSession(true)
        }
        return session;
    }
}

QueryParama类：

package com.bjpowernode.vo;

public class QueryParama {
    private Object p1;
    private Object p2;

    public Object getP1() {
        return p1;
    }

    public void setP1(Object p1) {
        this.p1 = p1;
    }

    public Object getP2() {
        return p2;
    }

    public void setP2(Object p2) {
        this.p2 = p2;
    }
}

主配置文件MyBatis.xml：

测试类MyTest：

package com.bjpowernode;

import com.bjpowernode.dao.StudentDao;
import com.bjpowernode.domain.Student;
import com.bjpowernode.utils.MybatisUtil;
import com.bjpowernode.vo.QueryParama;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.HashMap;
import java.util.List;
import java.util.Map;


public class MyTest {
    //查询测试
    @Test
    public void testSelectById(){
        //获取SqlSession
        SqlSession session= MybatisUtil.getSqlSession();
       //获取dao代理
        StudentDao dao=session.getMapper(StudentDao.class);
        //调用方法
        Student student=dao.selectById(1005);
        System.out.println("student="+student);
        //4.关闭SqlSession对象
        session.close();
    }
    //方法一个参数，查询测试
    @Test
    public void testOneParameterSelectEmail(){
        //获取SqlSession
        SqlSession session= MybatisUtil.getSqlSession();
        //获取dao代理
        StudentDao dao=session.getMapper(StudentDao.class);
        //调用方法
        Student student=dao.selectByEmail("lifeng@qq.com");
        System.out.println("email=="+student);
        //4.关闭SqlSession对象
        session.close();
    }
    //方法多个参数，查询测试
    @Test
    public void testSelectByNameOrAge(){
        //获取SqlSession
        SqlSession session= MybatisUtil.getSqlSession();
        //获取dao代理
        StudentDao dao=session.getMapper(StudentDao.class);
        //调用方法
        List students=dao.selectByNameOrAge("李四",26);

        students.forEach(stu-> System.out.println("stu"+stu));
        //4.关闭SqlSession对象
        session.close();
    }
    //方法参数传递一个对象Student，查询测试
    @Test
    public void testSelectByObject(){
        //获取SqlSession
        SqlSession session= MybatisUtil.getSqlSession();
        //获取dao代理
        StudentDao dao=session.getMapper(StudentDao.class);

        Student student=new Student();
        student.setName("李思思");
        student.setAge(22);

        //调用方法
        List students=dao.selectByObject(student);

        students.forEach(stu-> System.out.println("stu"+stu));
        //4.关闭SqlSession对象
        session.close();
    }

    //QueryParama类作为对象，查询测试
    @Test
    public void testSelectByObject2(){
        //获取SqlSession
        SqlSession session= MybatisUtil.getSqlSession();
        //获取dao代理
        StudentDao dao=session.getMapper(StudentDao.class);

        QueryParama parama=new QueryParama();
        parama.setP1("东皇");
        parama.setP2(20);

        //调用方法
        List students=dao.selectByQueryParama(parama);

        students.forEach(stu-> System.out.println("stu"+stu));
        //4.关闭SqlSession对象
        session.close();
    }
    //按位置进行传递参数查询，测试
    @Test
    public void testSelectByPosition(){
        //获取SqlSession
        SqlSession session= MybatisUtil.getSqlSession();
        //获取dao代理
        StudentDao dao=session.getMapper(StudentDao.class);

        //调用方法
        List students=dao.selectByPosition("李四",20);
        students.forEach(stu-> System.out.println("stu"+stu));
        //4.关闭SqlSession对象
        session.close();
    }
    //使用Map传递参数查询，测试
    @Test
    public void testSelectByMap(){
        //获取SqlSession
        SqlSession session= MybatisUtil.getSqlSession();
        //获取dao代理
        StudentDao dao=session.getMapper(StudentDao.class);

        //使用Map传递参数
        Map data=new HashMap<>();
        data.put("myname","李思思");
        data.put("myage",20);

        //调用方法
        List students=dao.selectStudentByMap(data);
        students.forEach(stu-> System.out.println("stu"+stu));
        //4.关闭SqlSession对象
        session.close();
    }

    //更新，测试
    @Test
    public void testUpdateStudent(){
        //获取SqlSession
        SqlSession session= MybatisUtil.getSqlSession();
        //获取dao代理
        StudentDao dao=session.getMapper(StudentDao.class);

        Student student=new Student();
        student.setId(1003);
        student.setName("张峰");
        student.setEmail("zhangfeng@qq.com");
        student.setAge(20);

        //调用方法
        int rows=dao.updateStudent(student);
        //提交
        session.commit();

        System.out.println("更新学生的rows="+rows);
        //4.关闭SqlSession对象
        session.close();
    }



}

第一个测试结果：

2：

MyBatis-parameterType参数的理解1

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