Mybatis程序入门案例
Posted RYGAR
tags:
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思路：搭建环境--->导入Mybatis--->编写代码--->测试
1.1、搭建环境
搭建数据库
create databases if not exists `mybatis`;
use `mybatis`;
create table if not exists `user`(
`id` int(20) not null,
`name` varchar(30) default null,
`pwd` varchar(30) default null,
primary key(`id`)
)engine=innodb default charset=utf8;插入数据
insert into `user`(`id`,`name`,`pwd`) values
(1,\'孙悟空\',\'123456\'),
(2,\'猪八戒\',\'111222\'),
(3,\'唐僧\',\'789456\');新建项目
1.新建一个普通的maven项目
2.删除src目录
3.导入maven依赖
<dependencies>
<!--mysql驱动-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.46</version>
</dependency>
<!--mybatis-->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.2</version>
</dependency>
<!--junit-->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
</dependencies>
<!--在build中配置resources，来防止我们资源导出失败的问题-->
<build>
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>true</filtering>
</resource>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>true</filtering>
</resource>
</resources>
</build>
1.2、创建一个模块
编写Mybaris的核心配置文件
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> <!--configuration核心配置文件--> <configuration> <environments default="development"> <environment id="development"> <transactionManager type="JDBC"/> <dataSource type="POOLED"> <property name="driver" value="com.mysql.cj.jdbc.Driver"/> <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=utf-8&serverTimezone=Asia/Shanghai"/> <property name="username" value="root"/> <property name="password" value="root"/> </dataSource> </environment> </environments> <mappers> <mapper resource="com/jialidun/dao/UserMapper/xml"/> </mappers> </configuration>编写mybatis工具类
package com.jialidun.utils; //sqlSessionFactory--->sqlSession public class MybatisUtils{ private static SqlSessionFactory sqlSessionFactory; static{ try{ //使用mybatis第一步：获取sqlSessionFactory对象 String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); }catch(IOException e){ e.printStackTrace(); } } //既然有了 SqlSessionFactory，顾名思义，我们可以从中获得 SqlSession 的实例。 //SqlSession 提供了在数据库执行 SQL 命令所需的所有方法。 public static SqlSession getSqlSession(){ return sqlSessionFactory.openSession(); } }1.3、编写代码
实体类
package com.jialidun.pojo; @Data public class User{ private int id; private String name; private String pwd; }Dao接口
package com.jialidun.dao; public interface UserDao{ //查询全部用户 List<User> getUserList(); //根据id查询用户 User getUserById(int id); //insert 一个用户 int addUser(User user); //修改用户 int updateUser(User user); //删除用户 int deleteUser(int id); }接口实现类由原来的UserDaoImpl转变为一个Mapper配置文件
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"> <!--namespace=绑定一个对应的Dao/Mapper接口--> <mapper namespace="com.jialidun.dao.UserDao"> <!--select查询语句--> <select id="getUserList" resultType="com.jialidun.pojo.User"> select * from mybatis.user </select> <select id="getUserById" parameterType="int" resultType="com.jialidun.pojo.User"> select * from mybatis.user where id = #{id} </select> <!--对象中的属性，可以直接取出来--> <insert id="addUser" parameterType="com.jialidun.pojo.User"> insert into mybatis.user(id,name,pwd) values(#{id},#{name},#{pwd}); </insert> <update id="updateUser" parameterType="com.jialidun.pojo.User"> update mybatis.user set name=#{name},pwd=#{pwd} where id=#{id}; </update> <delete id="deleteUser" parameterType="int"> delete from mybatis.user where id=#{id}; </delete> </mapper>1.4、测试
注意点：
org.apache.ibatis.binding.BindingException:Type interface com.jialidun.dao.UserDao is not know to the MapperRegistry.package com.jialidun.dao; public class UserDaoTest{ @Test public void test(){ //第一步：获得SqlSession对象 SqlSession sqlSession = MybatisUtils.getSqlSession(); try{ UserDao userDao= sqlSession.getMapper(UserDao.class); List<User> userList = userDao.getUserList(); //方式二： //List<User> userList = sqlSession.selectList("com.jialidun.dao.UserDao.getUserList"); for(User user:userList){ System.out.println(user); } }catch(Exception e){ e.printStackTrace(); }finally{ //关闭SqlSession sqlSession.close(); } } @Test public void getUserById(){ SqlSession sqlSession = MybatisUtils.getSqlSession(); UserMapper mapper = sqlSession.getMapper(UserDao.class); User user = mapper.getUserById(1); System.out,println(user); sqlSession.close(); } @Test public void addUser(){ SqlSession sqlSession = MybatisUtils.getSqlSession(); UserMapper mapper = sqlSession.getMapper(UserDao.class); int num = mapper.addUser(4,"沙和尚","444555"); if(num>0){ System.out.println("添加用户成功！"); } //提交事务 sqlSession.commit(); sqlSession.close(); } @Test public void updateUser(){ SqlSession sqlSession = MybatisUtils.getSqlSession(); UserMapper mapper = sqlSession.getMapper(UserDao.class); mapper.updateUser(new User(4,"悟净","666666")); //提交事务 sqlSession.commit(); sqlSession.close(); } @Test public void deleteUser(){ SqlSession sqlSession = MybatisUtils.getSqlSession(); UserMapper mapper = sqlSession.getMapper(UserDao.class); mapper.deleteUser(4); //提交事务 sqlSession.commit(); sqlSession.close(); } }可能遇到的问题：
1.配置文件没有注册
2.绑定接口错误
3.方法名不对
4.返回类型不对
5.Maven导出资源问题2、Mtbatis的CRUD操作
2.1、namespace
namespace中的包名要和Dao/mapper接口的包名一致！
2.2、select
选择，查询语句
- id：就是对应的namespace中的方法名；
- resultType：sql语句执行的返回值！
parameterType：参数类型
1.编写接口/根据id查询用户 User getUserById(int id);2.编写对应的mapper中的sql语句
<select id="getUserById" parameterType="int" resultType="com.jialidun.pojo.User"> select * from mybatis.user where id = #{id} </select>3.测试
@Test public void getUserById(){ SqlSession sqlSession = MybatisUtils.getSqlSession(); UserMapper mapper = sqlSession.getMapper(UserDao.class); User user = mapper.getUserById(1); System.out,println(user); sqlSession.close(); }2.3、Insert
1.编写接口
//insert 一个用户 int addUser(User user);2.编写对应的mapper值得sql
<!--对象中的属性，可以直接取出来--> <insert id="addUser" parameterType="com.jialidun.pojo.User"> insert into mybatis.user(id,name,pwd) values(#{id},#{name},#{pwd}); </insert>3.测试
@Test public void addUser(){ SqlSession sqlSession = MybatisUtils.getSqlSession(); UserMapper mapper = sqlSession.getMapper(UserDao.class); int num = mapper.addUser(4,"沙和尚","444555"); if(num>0){ System.out.println("添加用户成功！"); } //提交事务 sqlSession.commit(); sqlSession.close(); }2.4、update
1.编写接口
//修改用户 int updateUser(User user);2.编写对应的mapper值得sql
<update id="updateUser" parameterType="com.jialidun.pojo.User"> update mybatis.user set name=#{name},pwd=#{pwd} where id=#{id}; </update>3.测试
@Test public void updateUser(){ SqlSession sqlSession = MybatisUtils.getSqlSession(); UserMapper mapper = sqlSession.getMapper(UserDao.class); mapper.updateUser(new User(4,"悟净","666666")); //提交事务 sqlSession.commit(); sqlSession.close(); }2.5、delete
1.编写接口
//删除用户 int deleteUser(int id);2.编写对应的mapper值得sql
<delete id="deleteUser" parameterType="int"> delete from mybatis.user where id=#{id}; </delete>3.测试
@Test public void deleteUser(){ SqlSession sqlSession = MybatisUtils.getSqlSession(); UserMapper mapper = sqlSession.getMapper(UserDao.class); mapper.deleteUser(4); //提交事务 sqlSession.commit(); sqlSession.close(); }
注意点：
- 增删改需要提交事务！
3、分析错误
- 标签不要匹配错
- resource绑定mapper，需要使用路径！
- 程序配置文件必须符合规范！
- NullPointException，没有注册到资源！
- maveb资源没有导出问题！
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