2.select查询用法

1.定义查询接口

UserMapper.java

package tk.mybatis.simple.mapper;

import tk.mybatis.simple.model.SysRole;

import tk.mybatis.simple.model.SysUser;

import java.util.List;

/**

 * @author weihu

 * @date 2018/8/3/003 0:01

 */

public interface UserMapper {

    /**

     * 通过id查询用户，selectById（）方法名与配置的xml文件中的id一致

     */

    SysUser selectById(Long id);

    /**

     * 查询全部用户

     */

    List<SysUser> selectAll();

    List<SysRole> selectRolesByUserId(Long userId);

}

2.配置对应的xml文件

UserMapper.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">

<!--sql语句映射文件-->

<!--因为已经配置了别名,所以resultType可以直接写类名,没有配置的话就要写类全名-->

<mapper namespace="tk.mybatis.simple.mapper.UserMapper">

    <resultMap id="userMap" type="tk.mybatis.simple.model.SysUser">

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

        <result property="userName" column="user_name"/>

        <result property="userPassword" column="user_password"/>

        <result property="userEmail" column="user_email"/>

        <result property="userInfo" column="user_info"/>

        <result property="headImg" column="head_img"/>

        <result property="createTime" column="create_time"/>

    </resultMap>

    <select id="selectById" resultMap="userMap">

       SELECT * from sys_user WHERE id=#{id}

   </select>

    <select id="selectAll" resultType="tk.mybatis.simple.model.SysUser">

               SELECT id,

                   user_name userName,

                   user_password userPassword,

                   user_email userEmail,

                   user_info userInfo,

                   head_img headImg,

                 create_time createTime

               FROM

                     sys_user

    </select>

    <select id="selectRolesByUserId" resultType="tk.mybatis.simple.model.SysRole">

        select

            r.id,

            r.role_name roleName,

            r.enabled,

            r.create_by createBy,

            r.create_time createTime,

            u.user_name as "user.userName",

            u.user_email as "user.userEmail"

        from sys_user u

        inner join sys_user_role ur on u.id=ur.user_id

        inner join sys_role r on ur.role_id=r.id

        where u.id=#{userId}

    </select>

</mapper>

<select>:映射查询语句使用的标签

id:命名空间的唯一标识符，可用来代表这条语句

resultMap：用于设置返回值的类型和映射关系

#{id}:MyBatis SQL中使用预编译参数的一种方式

property:对应实体类字段

column:对应数据库字段

3.实体类

SysUser.java

package tk.mybatis.simple.model;

import java.util.Arrays;

import java.util.Date;

/**

 * @author weihu

 * @date 2018/8/2/002 23:22

 * @desc SysUser实体类

 */

public class SysUser {

    private Long id;

    private String userName;

    private String userPassword;

    private String userEmail;

    private String userInfo;

    private byte[] headImg;

    private Date createTime;

    public Long getId() {

        return id;

    }

    public void setId(Long id) {

        this.id = id;

    }

    public String getUserName() {

        return userName;

    }

    public void setUserName(String userName) {

        this.userName = userName;

    }

    public String getUserPassword() {

        return userPassword;

    }

    public void setUserPassword(String userPassword) {

        this.userPassword = userPassword;

    }

    public String getUserEmail() {

        return userEmail;

    }

    public void setUserEmail(String userEmail) {

        this.userEmail = userEmail;

    }

    public String getUserInfo() {

        return userInfo;

    }

    public void setUserInfo(String userInfo) {

        this.userInfo = userInfo;

    }

    public byte[] getHeadImg() {

        return headImg;

    }

    public void setHeadImg(byte[] headImg) {

        this.headImg = headImg;

    }

    public Date getCreateTime() {

        return createTime;

    }

    @Override

    public String toString() {

        return "SysUser{" +

                "id=" + id +

                ", userName='" + userName + '\'' +

                ", userPassword='" + userPassword + '\'' +

                ", userEmail='" + userEmail + '\'' +

                ", userInfo='" + userInfo + '\'' +

                ", headImg=" + Arrays.toString(headImg) +

                ", createTime=" + createTime +

                '}';

    }

    public void setCreateTime(Date createTime) {

        this.createTime = createTime;

    }

}

4.BaseMapperTest.java

package tk.mybatis.simple.mapper;

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.BeforeClass;

import java.io.IOException;

import java.io.Reader;

/**

 * @author weihu

 * @date 2018/8/4/004 17:58

 * @desc 基础测试类

 */

public class BaseMapperTest {

    private static SqlSessionFactory sqlSessionFactory;

    @BeforeClass

    public static void init(){

        try {

            Reader reader = Resources.getResourceAsReader("mybatis-config.xml");

            sqlSessionFactory=new SqlSessionFactoryBuilder().build(reader);

            reader.close();

        } catch (IOException e) {

            e.printStackTrace();

        }

    }

    //获取sqlSession

    public SqlSession getSqlSession() {

        return sqlSessionFactory.openSession();

    }

}

UserMapperTest.java

package tk.mybatis.simple.mapper;

import org.apache.ibatis.session.SqlSession;

import org.junit.Assert;

import org.junit.Test;

import tk.mybatis.simple.model.SysRole;

import tk.mybatis.simple.model.SysUser;

import java.util.List;

/**

 * @author weihu

 * @date 2018/8/5/005 9:34

 * @desc

 */

public class UserMapperTest extends BaseMapperTest {

    /**

     * 根据Id查询用户信息

     */

    @Test

    public void testSelectById(){

        SqlSession sqlSession = getSqlSession();

        try {

            //获取UserMapper接口

         UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

            SysUser sysUser = userMapper.selectById(1L);

            System.out.println(sysUser);

            System.out.println(sysUser.getUserName());

            System.out.println(sysUser.getCreateTime());

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            sqlSession.close();

        }

    }

    /**

     * 查询所有用户信息

     */

    @Test

    public void selectAllUserTest() {

        SqlSession sqlSession = getSqlSession();

        try {

            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

            List<SysUser> sysUsers = userMapper.selectAll();

            //遍历用户列表

            for (SysUser user:sysUsers){

                System.out.println(user);

            }

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            sqlSession.close();

        }

    }

    @Test

    public void testSelectRolesByUserId(){

        SqlSession sqlSession = getSqlSession();

        try {

            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

            List<SysRole> roleList = userMapper.selectRolesByUserId(1L);

            System.out.println(roleList);

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            sqlSession.close();

        }

    }

}

多表关联查询

UserMapper.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">

<!--sql语句映射文件-->

<!--因为已经配置了别名,所以resultType可以直接写类名,没有配置的话就要写类全名-->

<mapper namespace="tk.mybatis.simple.mapper.UserMapper">

    <select id="selectRolesByUserId" resultType="tk.mybatis.simple.model.SysRole">

        select

            r.id,

            r.role_name roleName,

            r.enabled,

            r.create_by createBy,

            r.create_time createTime,

            u.user_name as "user.userName",

            u.user_email as "user.userEmail"

        from sys_user u

        inner join sys_user_role ur on u.id=ur.user_id

        inner join sys_role r on ur.role_id=r.id

        where u.id=#{userId}

    </select>

</mapper>

注意:

u.user_name as "user.userName",

u.user_email as "user.userEmail"
这里设置别名的时候，使用的是"user.属性名",user是SysRole中增加的属性,userName和userEmail是SysUer对象中的属性

SysRole.java

package tk.mybatis.simple.model;

import java.util.Date;

/**

 * @author weihu

 * @date 2018/8/2/002 23:19

 * @desc

 */

public class SysRole {

    private Long id;

    private String roleName;

    private int enabled;

    private String createBy;

    private Date createTime;

    private SysUser user;

    public SysUser getUser() {

        return user;

    }

    public void setUser(SysUser user) {

        this.user = user;

    }

    public Long getId() {

        return id;

    }

    public void setId(Long id) {

        this.id = id;

    }

    public String getRoleName() {

        return roleName;

    }

    public void setRoleName(String roleName) {

        this.roleName = roleName;

    }

    public int getEnabled() {

        return enabled;

    }

    public void setEnabled(int enabled) {

        this.enabled = enabled;

    }

    public String getCreateBy() {

        return createBy;

    }

    public void setCreateBy(String createBy) {

        this.createBy = createBy;

    }

    public Date getCreateTime() {

        return createTime;

    }

    public void setCreateTime(Date createTime) {

        this.createTime = createTime;

    }

}

UserMapperTest.class

package tk.mybatis.simple.mapper;

import org.apache.ibatis.session.SqlSession;

import org.junit.Assert;

import org.junit.Test;

import tk.mybatis.simple.model.SysRole;

import tk.mybatis.simple.model.SysUser;

import java.util.List;

/**

 * @author weihu

 * @date 2018/8/5/005 9:34

 * @desc

 */

public class UserMapperTest extends BaseMapperTest {

  /**

     * 多表查询

     */

    @Test

    public void testSelectRolesByUserId(){

        SqlSession sqlSession = getSqlSession();

        try {

            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

            List<SysRole> roleList = userMapper.selectRolesByUserId(1L);

            System.out.println(roleList);

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            sqlSession.close();

        }

    }

}

2.select查询用法的更多相关文章

数据库中增加操作insert into的用法和查询select的用法
insert into的用法 1.一条insert into 可以插入多条记录 2.insert into 能判断主键是否冲突,和做出冲突处理如果主键冲突的话会报错,还能写成如果冲突就更新的形式格式 ...
Select查询命令
一开始SELECT查询的命令为 SELECT * FROM employee; SELECT 要查询的列名 FROM 表名字 WHERE 限制条件; 若要查询所有内容,就用*代 ...
MyBatis基础入门《四》接口方式.Select查询集合
MyBatis基础入门<四>接口方式.Select查询集合描述: 在<MyBatis基础入门<二>Select查询>中有说过,SQLSession有两种用法,这里 ...
mysql union 和 left join 结合查询用法
union 和 left join 结合查询用法 SELECT u.nickname,z.group_comming_type,z.id,z.user_id,z.title,z.create_time ...
mysql DML select查询
windows上的操作 1.从官网下载mysql 下载navicat,用来连接mysql的 2.打开运行启动mysql 3.在navicat上的连接打开新建连接然后输入链接名,连接名就是用户名,自己 ...
mysql子查询用法
mysql子查询用法 1 可以当值来用<pre>select id from hcyuyin_share where id=(select id from hcyuyin_share li ...
5- MySQL数据库SELECT查询操作
复习: 数据类型: 数值型:整数(int,tinyint,smallint,bigint,mediumint) 浮点型(float ,double,decimal) 字符型:char(固定长度) ,v ...
关于SubSonic3.0插件使用SqlQuery或Select查询时产生的System.NullReferenceException异常修复
早上在编写执行用例时,突然爆异常System.NullReferenceException: 未将对象引用设置到对象的实例执行代码:
为什么忘记commit也会造成select查询的性能问题
今天遇到一个很有意思的问题,一个开发人员反馈在测试服务器ORACLE数据库执行的一条简单SQL语句非常缓慢,他写的一个SQL没有返回任何数据,但是耗费了几分钟的时间.让我检查分析一下原因,分析解决过后 ...

随机推荐

Ubuntu几种常见乱码解决方法
一.网页中的flash乱码: ubuntu默认浏览器是Firefox,但是Ubuntu默认不安装像flash这种带版权的软件,所以当你浏览像youku或网页播放器时,这种带有 flash ...
10个办法让设计小白迅速get海报设计要点！
对于设计师而言,海报和宣传单的设计,几乎是每一个设计师的必修课.如今网页上的 Banner.宣传和促销的数字海报,大多脱胎于我们所熟知的海报设计. 对于推销产品.连接客户,海报始终是一种最为有趣和实用 ...
【UI测试】－－合理性
DockerDesktop简单安装和使用
一.在windows10下,安装DockerDesktop: 1.检查windows版本为企业版或专业版,并开启Hyper-v系统设置:电脑的控制面板->程序->启用或关闭Windows功 ...
VB.NET and C# 差异
VB.NET Program Structure C# Imports System Namespace Hello Class HelloWorld Overloads Share ...
linux_磁盘挂载
mount -o loop 磁盘的位置想要挂载的位置磁盘卸载 umont 挂载的磁盘的详细位置注意:磁盘卸载时你当前所在的路径不要在磁盘挂载的路径,应该其他与磁盘挂载路径不相干的路径下即可
前端之javascript的DOM对象和标签
一 DOM对象介绍什么是HTML DOM 1.1 HTML Document Object Model(文档对象模型) 1.2 HTML DOM 定义了访问和操作HTML文档的标准方法. 1.3 H ...
https网站引用http路径的js和css失效解决办法
Jazzy html 2015-03-26 在https的网站中引用http路径的js或css会导致不起作用,其形如: Html <script src="http://code. ...
Vue自定义指令报错：Failed to resolve directive: xxx
Vue自定义指令报错 Failed to resolve directive: modle 这个报错有2个原因: 1.指令单词拼错 2.Vue.directive() 这个方法没有写在 new Vue ...
修改oracle用户密码为永不过期
错误提示:ORA-28001: the password has expired (DBD ERROR: OCISessionBegin) 解决方法:修改密码为永不过期 (1)查看用户的proifle ...

2.select查询用法

2.select查询用法的更多相关文章

随机推荐

热门专题