【MyBatis】学习笔记05：获取参数值的两种方式

【Mybatis】学习笔记01：连接数据库，实现增删改

【Mybatis】学习笔记02：实现简单的查

【MyBatis】学习笔记03：配置文件进一步解读（非常重要）

【MyBatis】学习笔记04：配置文件模板

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目录

• 一些准备工作
• 封装SQLSessionUtils工具类
• MyBatis获取参数值的各种情况
  • 1.mapper接口方法的参数为单个的字面量类型
  • 2.mapper接口方法的参数为多个时
  • 3.mapper接口方法的参数有多个时，可以手动将这些参数放在一个map中存储
  • 4.mapper接口方法的参数是一个实体类类型的参数
  • 5.使用@Param命名参数
• 源码贴贴
  • 目录
  • cc.mllt.sky.utils.UserParameterMapper.java
  • cc.mllt.sky.jdbc.User.java
  • resources.cc.mllt.sky.utils.UserParameterMapper.xml
  • Test

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MyBatis获取参数值的两种方式：

1.字符串拼接：${}

2.占位符赋值：#{}

一些准备工作

java/cc/mllt/sky/utils

resources/cc/mllt/sky/utils

封装SQLSessionUtils工具类

package cc.mllt.sky.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 SqlSessionUtils {
    public  static SqlSession getSqlSession(){
        SqlSession sqlSession = null;
        try{
            InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
            SqlSessionFactory sqlSessionFactory  = new SqlSessionFactoryBuilder().build(is);
            sqlSession  = sqlSessionFactory.openSession(true);

        }catch (IOException e){
            e.printStackTrace();
        }

        return sqlSession;
    }
}

MyBatis获取参数值的各种情况

1.mapper接口方法的参数为单个的字面量类型

或者这样

总结

可以通过${}和#{}以任意的字符串获取参数值，但是需要注意${}的单引号问题

2.mapper接口方法的参数为多个时

总结

mapper接口方法的参数为多个时，MyBatis会将这些参数放在map集合中，以两种方式进行存储，

第一种为：arg0，arg1……为键，以参数为值

第二种为：以param1，param2……为键，以参数为值

因此只需要通过#{}和${}以键的形式访问值就可以了。

3.mapper接口方法的参数有多个时，可以手动将这些参数放在一个map中存储

4.mapper接口方法的参数是一个实体类类型的参数

实体类：属性 属性值

Map：键 值

通过#{}或${}以属性的方式访问值即可

必须是属性名字，不能乱写噢！

5.使用@Param命名参数

此时Mybatis会将这些参数放在一个Map集合中，以两种方式存储

a. 以@Param注解的值为键，以参数为值

b. 以param1，param2……为键，以参数为值

通过#{}或${}以键的方式访问值即可

源码贴贴

目录

cc.mllt.sky.utils.UserParameterMapper.java

package cc.mllt.sky.utils;

import cc.mllt.sky.jdbc.User;
import org.apache.ibatis.annotations.Param;

import java.util.Map;

public interface UserParameterMapper {
    /**
     * 登录验证
     * @param username String 用户名
     * @param password String 密码
     * @return User对象
     */
    User UserLogin(String username,String password);

    /**
     * 验证登陆
     * @return User对象
     */
    User UserLoginByMap(Map<String,Object> map);

    /**
     * 验证登陆（使用@Param注解）
     * @param username 用户名
     * @param password 用户密码
     * @return User对象
     */
    User UserLoginByParam(@Param("name") String username, @Param("password") String password);

    /**
     * 根据用户账号查询用户信息
     * @return User对象
     */
    User getUserByUserCount(String usercount);

    /**
     * 添加用户
     * @param user 用户对象
     * @return int型
     */
    int UserAdd(User user);
}

cc.mllt.sky.jdbc.User.java

package cc.mllt.sky.jdbc;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.sql.Timestamp;

public class User {
    private BigInteger userId;
    public String userName;
    private String userCount;
    private String userPassword;
    private int userGrade;
    public Timestamp userRegDate;
    private BigDecimal userBlance;

    public User( String userName,String userCount,String userPassword) {
        this.userName=userName;
        this.userCount=userCount;
        this.userPassword=userPassword;
    }

    //getter and setter

    public BigInteger getUserId() {
        return userId;
    }

    public void setUserId(BigInteger userId) {
        this.userId = userId;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserCount() {
        return userCount;
    }

    public void setUserCount(String userCount) {
        this.userCount = userCount;
    }

    public String getUserPassword() {
        return userPassword;
    }

    public void setUserPassword(String userPassword) {
        this.userPassword = userPassword;
    }

    public int getUserGrade() {
        return userGrade;
    }

    public void setUserGrade(int userGrade) {
        this.userGrade = userGrade;
    }

    public Timestamp getUserRegDate() {
        return userRegDate;
    }

    public void setUserRegDate(Timestamp userRegDate) {
        this.userRegDate = userRegDate;
    }

    public BigDecimal getUserBlance() {
        return userBlance;
    }

    public void setUserBlance(BigDecimal userBlance) {
        this.userBlance = userBlance;
    }

    @Override
    public String toString(){
        return "User{"+
                "userId='"+userId+"'"+
                ",userName='"+userName+"'"+
                "userCount='"+userCount+"'"+
                ",userPassword='"+userPassword+"'"+
                "userGrade='"+userGrade+"'"+
                ",userRegDate='"+userRegDate+"'"+
                "userBlance='"+userBlance+"'}";
    }
}

resources.cc.mllt.sky.utils.UserParameterMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="cc.mllt.sky.utils.UserParameterMapper">
<!--    User getUserByUsedCount(String usercount);-->
    <select id="getUserByUserCount" resultType="User">
   <!--select * from t_users where `userCount` = #{username}-->
        select * from t_users where `userCount` = '${username}'
    </select>
<!--    User UserLogin(String username,String password);-->
    <select id="UserLogin" resultType="User">
        <!--select * from t_users where userCount=#{arg0} and userPassword=#{arg1}-->
        <!--select * from t_users where userCount=#{param1} and userPassword=#{param2}-->
        <!--select * from t_users where userCount=#{param1} and userPassword=#{arg1}}-->
        select * from t_users where userCount='${param1}' and userPassword='${arg1}'
    </select>
<!--    User UserLoginByMap(Map<String,Object> map);-->
    <select id="UserLoginByMap" resultType="User">
        select * from t_users where userCount=#{username} and userPassword=#{password}
    </select>
<!--    int UserAdd(User user);-->
    <insert id="UserAdd">
        insert into t_users set
        `userName`=#{userName},
        `userCount`=#{userCount},
        `UserPassword`=#{userPassword},
        `userGrade`='0',
        `userBlance`='0';
    </insert>
<!--    User UserLoginByParam(@Param("name") String username, @Param("password") String password);-->
    <select id="UserLoginByParam" resultType="User">
        select * from t_users where userCount=#{name} and userPassword=#{password}
    </select>
</mapper>

Test

下面有一些测试方法是以前用到的，在本次笔记中没有用到的，可以删掉

import cc.mllt.sky.jdbc.User;
import cc.mllt.sky.jdbc.UsersMapper;
import cc.mllt.sky.utils.SqlSessionUtils;
import cc.mllt.sky.utils.UserParameterMapper;
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 org.junit.jupiter.api.Test;

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class TestUsers {

    @Test
    public void UsersAdd() throws IOException {
        InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactory sqlSessionFactory  = new SqlSessionFactoryBuilder().build(is);
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        UsersMapper mapper = sqlSession.getMapper(UsersMapper.class);
        mapper.insertUser();
    }
    @Test
    public void UsersDel() throws IOException {
        InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactory sqlSessionFactory  = new SqlSessionFactoryBuilder().build(is);
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        UsersMapper mapper = sqlSession.getMapper(UsersMapper.class);
        mapper.deleteUser();
    }
    @Test
    public void UsersUpdate() throws IOException {
        InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactory sqlSessionFactory  = new SqlSessionFactoryBuilder().build(is);
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        UsersMapper mapper = sqlSession.getMapper(UsersMapper.class);
        mapper.updateUser();
    }
    @Test
    public void UsersGetById() throws IOException {
        InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactory sqlSessionFactory  = new SqlSessionFactoryBuilder().build(is);
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        UsersMapper mapper = sqlSession.getMapper(UsersMapper.class);
        User user =  mapper.selectUserById();
        System.out.println(user);
        System.out.println(user.getUserName());
    }
    @Test
    public void UsersGetAll() throws IOException {
        InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactory sqlSessionFactory  = new SqlSessionFactoryBuilder().build(is);
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        UsersMapper mapper = sqlSession.getMapper(UsersMapper.class);
        List<User> list =  mapper.selectUser();
        list.forEach(user -> System.out.println(user));
    }

    @Test
    public void testJDBC() throws Exception{
        String username ="xrilang";
        Class.forName("");
        //创建链接对象
        Connection connection = DriverManager.getConnection("");
        //PreparedStatement ps = connection.prepareStateme                                                                                                                                                                                                                                                                                                                                                       nt("selsect * from t_users where userName = '"+username+"'");//麻烦且不安全，会造成SQL注入
        PreparedStatement ps = connection.prepareStatement("select  * from t_users where userName= ? ");
        ps.setString(1,username);

    }

    @Test
    public void GetUserByCount(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        UserParameterMapper mapper = sqlSession.getMapper(UserParameterMapper.class);
        User user = mapper.getUserByUserCount("test001");
        System.out.println(user);
    }

    @Test
    public void CheckUserLogin(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        UserParameterMapper mapper = sqlSession.getMapper(UserParameterMapper.class);
        User user = mapper.UserLogin("test001","123456改了密码");
        System.out.println(user);
    }

    @Test
    public void CheckUserLoginByMap(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        UserParameterMapper mapper = sqlSession.getMapper(UserParameterMapper.class);
        Map<String,Object> map = new HashMap<>();
        map.put("username","test001");
        map.put("password","123456改了密码");
        User user = mapper.UserLoginByMap(map);
        System.out.println(user);
    }

    @Test
    public void UserAdd(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        UserParameterMapper mapper = sqlSession.getMapper(UserParameterMapper.class);
        int result = mapper.UserAdd(new User("张三","mllt@xrilang.com","123"));
        System.out.println(result);
    }

    @Test
    public void CheckUserLoginByParam(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        UserParameterMapper mapper = sqlSession.getMapper(UserParameterMapper.class);
        Map<String,Object> map = new HashMap<>();
        User user = mapper.UserLoginByParam("test001","123456改了密码");
        System.out.println(user);
    }
}