作者：密叔
Mybatis 是什么？
Mybatis 是一个持久层框架。Java 中通过 Mybatis ，程序可以很方便的对数据库进行操作。使开发者专注于 SQL语句，避免了重复的 JDBC 代码。
- 使用 MyBatis 避免了几乎所有的 JDBC 代码和手动设置参数以及获取结果集
- 灵活且强大，支持定制化 SQL、存储过程以及高级映射
- 支持 XML 和注解两种形式编写 SQL
- 数据库中的记录可以映射为普通 Java 对象
准备
环境：
开发工具：IDEA
包管理：Maven
JDK：1.8
Mybatis ：Mybatis 3.4.6
问题场景
使用 Mybatis 完成基于简单权限设计的数据库表的相关操作、查询
涉及到的表
t_user
t_user_info
t_role
t_menu
t_user_role //关系表
t_role_menu //关系表
复制代码要做哪些操作
- t_user 表的简单增删改成
- 关联复杂查询，查询一个用户的所有权限信息
- 动态查询，包含某些菜单权限的用户
1、新建数据库表，初始化些数据
-- ----------------------------
-- Table structure for `t_menu`
-- ----------------------------
DROP TABLE IF EXISTS `t_menu`;
CREATE TABLE `t_menu` (
`id` int(10) NOT NULL AUTO_INCREMENT,
`name` varchar(50) DEFAULT NULL,
`type` int(11) DEFAULT NULL,
`url` varchar(255) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8;
-- ----------------------------
-- Table structure for `t_role`
-- ----------------------------
DROP TABLE IF EXISTS `t_role`;
CREATE TABLE `t_role` (
`id` int(10) NOT NULL AUTO_INCREMENT,
`name` varchar(100) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;
-- ----------------------------
-- Table structure for `t_role_menu`
-- ----------------------------
DROP TABLE IF EXISTS `t_role_menu`;
CREATE TABLE `t_role_menu` (
`role_id` int(10) DEFAULT NULL,
`menu_id` int(10) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
-- ----------------------------
-- Table structure for `t_user`
-- ----------------------------
DROP TABLE IF EXISTS `t_user`;
CREATE TABLE `t_user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`username` varchar(50) DEFAULT NULL,
`password` varchar(50) DEFAULT NULL,
`nickname` varchar(100) DEFAULT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `t_user_username_uindex` (`username`)
) ENGINE=InnoDB AUTO_INCREMENT=16 DEFAULT CHARSET=utf8;
-- ----------------------------
-- Table structure for `t_user_role`
-- ----------------------------
DROP TABLE IF EXISTS `t_user_role`;
CREATE TABLE `t_user_role` (
`user_id` int(10) DEFAULT NULL,
`role_id` int(10) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
SET FOREIGN_KEY_CHECKS = 1;
-- ----------------------------
-- Table structure for `t_user_info`
-- ----------------------------
DROP TABLE IF EXISTS `t_user_info`;
CREATE TABLE `t_user_info` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`user_id` int(11) DEFAULT NULL,
`name` varchar(100) COLLATE utf8_bin DEFAULT NULL,
`email` varchar(100) COLLATE utf8_bin DEFAULT NULL,
`address` varchar(255) COLLATE utf8_bin DEFAULT NULL,
`phone` varchar(20) COLLATE utf8_bin DEFAULT NULL,
`sex` varchar(2) COLLATE utf8_bin DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8 COLLATE=utf8_bin;
SET FOREIGN_KEY_CHECKS = 1;
复制代码手动初始化些数据进去，构建一些关联数据，为下面测试所用
2、构建Maven项目
组织 project 目录
└── src
├── main
│ ├── java
│ │ └── me
│ │ └── imcoding
│ │ ├── dao
│ │ ├── mapper
│ │ ├── model
│ └── resources
│ └── mapper
└── test
└── java
└── me
└── imcoding
复制代码3、引入 Mybatis 相关依赖
在 maven 环境中，需要在 pom.xml 文件中增加依赖
<dependencies>
<dependency>
<groupId>org.mybatisgroupId>
<artifactId>mybatisartifactId>
<version>3.4.6version>
dependency>
<dependency>
<groupId>mysqlgroupId>
<artifactId>mysql-connector-javaartifactId>
<version>5.1.46version>
dependency>
<dependency>
<groupId>com.alibabagroupId>
<artifactId>fastjsonartifactId>
<version>1.2.31version>
dependency>
<dependency>
<groupId>junitgroupId>
<artifactId>junitartifactId>
<version>4.11version>
<scope>testscope>
dependency>
dependencies>
复制代码4、配置 Mybatis
在 resources 目录新建 mybatis-config.xml
└── resources
├── mapper
└── mybatis-config.xml
复制代码配置以下内容
xml version="1.0" encoding="UTF-8" ?>
<configuration>
<properties resource="dbconfig.properties">properties>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="${driver}"/>
<property name="url" value="${url}"/>
<property name="username" value="${username}"/>
<property name="password" value="${password}"/>
dataSource>
environment>
environments>
<mappers>
mappers>
configuration>
复制代码外部属性配置，resources 目录下新增 dbconfig.properties 文件
└── resources
├── dbconfig.properties
├── mapper
└── mybatis-config.xml
复制代码配置内容：
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/mybatis-demo?useUnicode=true&characterEncoding=utf8
username=root
password=root
复制代码数据库连接的相关属性信息
5、获取 SqlSession
核心代码：
// 配置文件位置
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession = factory.openSession();
复制代码写个工具类 MybatisUtils：
├── java
└── me
└── imcoding
├── App.java
├── MybatisUtils.java
复制代码public class MybatisUtils {
private static SqlSessionFactory factory;
/**
* 根据 mybatis-config.xml 配置初始化 factory
*/
private static void initialFactory() {
String resource = "mybatis-config.xml";
try {
InputStream in = Resources.getResourceAsStream(resource);
factory = new SqlSessionFactoryBuilder().build(in);
} catch (IOException e) {
e.printStackTrace();
}
}
public static SqlSession getSession() {
if (factory == null) {
initialFactory();
}
// factory.openSession(true) - 开启事务自动提交
SqlSession sqlSession = factory.openSession();
return sqlSession;
}
}
复制代码基本增删改查（CURD）
1、构建 Model 类
目录：
├── model
├── Menu.java
├── Role.java
└── User.java
复制代码User
public class User {
private Integer id;
private String username;
private String password;
private String nickname;
/* setter 和 getter 省略 */
}
复制代码Role
public class Role {
private Integer id;
private String name;
// setter 和 getter 方法省略...
}
复制代码Menu
public class Menu {
private Integer id;
private String name;
private int type;
private String url;
// setter and getter ...
}
复制代码UserInfo
public class UserInfo {
private Integer id;
private String name;
private String sex;
private String address;
private String phone;
private String email;
//setter and getter....
}
复制代码2. 构建 Mapper 接口
目录：
├── mapper
└── UserMapper.java
复制代码UserMapper
public interface UserMapper {
// 新增 User
int insertUser(User user);
// 根据主键删除
int deleteUser(int id);
// 更新 User
int updateUser(User user);
// 根据主键 id 查询
User selectByKey(int id);
// 根据用户名和密码查询
User selectByUsernameAndPassword(String username, String password);
}
复制代码3、定义 Mapper xml
新建 UserMapper.xml
└── resources
├── dbconfig.properties
├── mapper
│ └── UserMapper.xml
└── mybatis-config.xml
复制代码UserMapper.xml
xml version="1.0" encoding="UTF-8" ?>
<mapper namespace="me.imcoding.mapper.UserMapper">
<insert id="insertUser" parameterType="me.imcoding.model.User">
insert into t_user(username, password, nickname)
values (#{username}, #{password}, #{nickname})
insert>
<delete id="deleteUser" >
delete from t_user where id = #{id}
delete>
<update id="updateUser" parameterType="me.imcoding.model.User">
update t_user
<set>
<if test="username != null">username = #{username}if>
<if test="password != null">password = #{password}if>
<if test="nickname != null">nickname = #{nickname}if>
set>
where id = #{id}
update>
<select id="selectUser" resultType="me.imcoding.model.User">
select
nickname,
username,
password
from t_user
where id = #{id}
select>
<select id="selectByUsernameAndPassword" resultType="me.imcoding.model.User">
select
nickname,
username,
password
from t_user
<where>
<if test="username != null">
username = #{username}
if>
<if test="password != null">
and password = #{password}
if>
where>
select>
mapper>
复制代码一定不要忘记在 mybatis-config.xml 中引入 UserMapper.xml
mybatis-config.xml
<mappers>
<mapper resource="mapper/UserMapper.xml">mapper>
mappers>
复制代码4、构建 UserDao
目录：
└── imcoding
├── App.java
├── MybatisUtils.java
├── dao
└── UserDao.java
复制代码UserDao
/**
* Author：密叔.
*/
public class UserDao {
// 新增
public int insertUser(User user) {
SqlSession sqlSession = MybatisUtils.getSession();
int bo;
try {
// 从 sqlSession 中获取 Mapper 实例
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
// 调用 mapper 的方法
bo = mapper.insertUser(user);
sqlSession.commit();//提交事务
return bo;
} finally {
//一定要关闭 sqlSession
sqlSession.close();
}
}
// 删除
public int deleteUser(int id) {
SqlSession sqlSession = MybatisUtils.getSession();
int bo;
try {
// 从 sqlSession 中获取 Mapper 实例
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
// 调用 mapper 的方法
bo = mapper.deleteUser(id);
sqlSession.commit();//提交事务
return bo;
} finally {
//一定要关闭 sqlSession
sqlSession.close();
}
}
// 更新
public int updateUser(User user) {
SqlSession sqlSession = MybatisUtils.getSession();
int bo;
try {
// 从 sqlSession 中获取 Mapper 实例
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
// 调用 mapper 的方法
bo = mapper.updateUser(user);
sqlSession.commit();//提交事务
return bo;
} finally {
//一定要关闭 sqlSession
sqlSession.close();
}
}
// 查询
public User selectUser(int id) {
SqlSession sqlSession = MybatisUtils.getSession();
User user;
try {
// 从 sqlSession 中获取 Mapper 实例
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
// 调用 mapper 的方法
user = mapper.selectUser(id);
sqlSession.commit();//提交事务
return user;
} finally {
//一定要关闭 sqlSession
sqlSession.close();
}
}
// 根据 username 和 password 查询
public User selectByUsernameAndPassword(String username, String password) {
SqlSession sqlSession = MybatisUtils.getSession();
User user;
try {
// 从 sqlSession 中获取 Mapper 实例
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
// 调用 mapper 的方法
user = mapper.selectByUsernameAndPassword(username, password);
sqlSession.commit();//提交事务
return user;
} finally {
//一定要关闭 sqlSession
sqlSession.close();
}
}
}
复制代码5、测试
目录：
└── test
└── java
└── me
└── imcoding
└── AppTest.java
复制代码AppTest
/**
* Author：密叔.
*/
public class UserDao {
// 新增
public int insertUser(User user) {
SqlSession sqlSession = MybatisUtils.getSession();
int bo;
try {
// 从 sqlSession 中获取 Mapper 实例
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
// 调用 mapper 的方法
bo = mapper.insertUser(user);
sqlSession.commit();//提交事务
return bo;
} finally {
//一定要关闭 sqlSession
sqlSession.close();
}
}
// 删除
public int deleteUser(int id) {
SqlSession sqlSession = MybatisUtils.getSession();
int bo;
try {
// 从 sqlSession 中获取 Mapper 实例
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
// 调用 mapper 的方法
bo = mapper.deleteUser(id);
sqlSession.commit();//提交事务
return bo;
} finally {
//一定要关闭 sqlSession
sqlSession.close();
}
}
// 更新
public int updateUser(User user) {
SqlSession sqlSession = MybatisUtils.getSession();
int bo;
try {
// 从 sqlSession 中获取 Mapper 实例
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
// 调用 mapper 的方法
bo = mapper.updateUser(user);
sqlSession.commit();//提交事务
return bo;
} finally {
//一定要关闭 sqlSession
sqlSession.close();
}
}
// 查询
public User selectUser(int id) {
SqlSession sqlSession = MybatisUtils.getSession();
User user;
try {
// 从 sqlSession 中获取 Mapper 实例
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
// 调用 mapper 的方法
user = mapper.selectUser(id);
sqlSession.commit();//提交事务
return user;
} finally {
//一定要关闭 sqlSession
sqlSession.close();
}
}
// 根据 username 和 password 查询
public User selectByUsernameAndPassword(String username, String password) {
SqlSession sqlSession = MybatisUtils.getSession();
User user;
try {
// 从 sqlSession 中获取 Mapper 实例
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
// 调用 mapper 的方法
user = mapper.selectByUsernameAndPassword(username, password);
sqlSession.commit();//提交事务
return user;
} finally {
//一定要关闭 sqlSession
sqlSession.close();
}
}
}
复制代码复杂查询
查询某个 user 的详情与菜单权限
SQL：
SELECT
u.id,
u.username,
u.password,
u.nickname,
ui.name,
ui.sex,
ui.email,
ui.address,
ui.phone,
r.id as role_id,
r.name as role_name,
m.id as menu_id,
m.name as menu_name
FROM
t_user u
LEFT outer JOIN t_user_role ur ON u.id = ur.user_id
LEFT outer JOIN t_role r ON r.id = ur.role_id
left OUTER JOIN t_role_menu rm ON rm.role_id = r.id
left outer join t_menu m on m.id = rm.menu_id
left outer join t_user_info ui on u.id = ui.user_id
WHERE u.username = '[email protected]'
复制代码1、新增接口方法
UserMapper.java
public interface UserMapper {
//....
// 查询 user 详细信息，以map方式返回结果
User selectUserInfo(int id);
//....
}
复制代码2、UserMapper.xml 新增查询
UserMapper.xml
<mapper>
.....
<select id="selectUserInfo" resultMap="UserResultMap">
SELECT
u.id,
u.username,
u.password,
u.nickname,
ui.id as ui_id,
ui.name as ui_name,
ui.sex as ui_sex,
ui.email as ui_email,
ui.address as ui_address,
ui.phone as ui_phone,
r.id as role_id,
r.name as role_name,
m.id as menu_id,
m.name as menu_name
FROM
t_user u
LEFT outer JOIN t_user_role ur ON u.id = ur.user_id
LEFT outer JOIN t_role r ON r.id = ur.role_id
left OUTER JOIN t_role_menu rm ON rm.role_id = r.id
left outer join t_menu m on m.id = rm.menu_id
left outer join t_user_info ui on u.id = ui.user_id
WHERE u.id = #{id}
select>
<resultMap id="UserResultMap" type="me.imcoding.model.User">
<constructor>
<idArg column="id" javaType="int" >idArg>
constructor>
<result column="username" property="username">result>
<result column="password" property="password">result>
<result column="nickname" property="nickname">result>
<association property="userInfo" javaType="me.imcoding.model.UserInfo" >
<id column="ui_id" property="id">id>
<result column="ui_name" property="name">result>
<result column="ui_sex" property="sex">result>
<result column="ui_email" property="email">result>
<result column="ui_address" property="address">result>
<result column="ui_phone" property="phone">result>
association>
<collection property="roles" ofType="me.imcoding.model.Role">
<id column="role_id" property="id">id>
<result column="role_name" property="name">result>
collection>
<collection property="menus" ofType="me.imcoding.model.Menu">
<id column="menu_id" property="id">id>
<result column="menu_name" property="name">result>
collection>
resultMap>
....
mapper>
复制代码3、User 类新增属性和构造
User
public class User {
// ....
// 无参构造
public User() {}
// id 参数构造,@Param("id") 与mapper xml 中的 name属性一致
public User(Integer id) {
this.id = id;
}
private UserInfo userInfo;
private List roles;
private List 4、UserDao 新增查询
UserDao
public class UserDao {
//....
// 查询用户的所有详细信息
public User selectUserInfo(int id) {
SqlSession sqlSession = MybatisUtils.getSession();
User user;
try {
// 从 sqlSession 中获取 Mapper 实例
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
// 调用 mapper 的方法
user = mapper.selectUserInfo(id);
return user;
} finally {
//一定要关闭 sqlSession
sqlSession.close();
}
}
// ....
}
复制代码5、测试
AppTest
public class AppTest {
//......
@Test
public void selectUserInfo() {
UserDao dao = new UserDao();
User user = dao.selectUserInfo(1);
System.out.println(JSON.toJSONString(user,true));
}
//......
}
复制代码结果：
{
"id":1,
"menus":[
{
"id":1,
"name":"站点信息",
"type":0
},
{
"id":2,
"name":"车辆查询",
"type":0
},
{
"id":3,
"name":"人员管理",
"type":0
},
{
"id":4,
"name":"用户管理",
"type":0
},
{
"id":5,
"name":"角色管理",
"type":0
},
{
"id":6,
"name":"菜单管理",
"type":0
},
{
"id":7,
"name":"站点维护",
"type":0
}
],
"nickname":"方方",
"password":"111111",
"roles":[
{
"id":1,
"name":"管理员"
}
],
"userInfo":{
"address":"上海闵行区58",
"email":"[email protected]",
"id":1,
"name":"方达",
"phone":"18276546543",
"sex":"男"
},
"username":"[email protected]"
}
复制代码源码
mybatis-practice
Mybatis 知识边界
- Mybatis 引入
- Mybatis 的必要配置
- Mybatis Mapper XML （映射文件）
- Mybatis 动态 SQL
- Mybatis SqlSession
- Mybatis 代码生成
- Mybatis 缓存
- Mybatis 事务
学习资源：www.mybatis.org/mybatis-3/z…
Mybatis 核心知识
-
Mapper XML 映射文件的使用规则
学习：www.mybatis.org/mybatis-3/z…
-
动态 SQL 的处理规则
学习：www.mybatis.org/mybatis-3/z…