新建一个mybatis项目需要首先配置好maven环境
具体的mavne问题在我的其他博客中有提到
思路：搭建环境–>导入Mybatis–>编写代码–>测试
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
<!--导入依赖-->
<dependencies>
<!--导入mysql依赖-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.45</version>
</dependency>
<!--导入mybatis依赖-->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.2</version>
</dependency>
<!--导入junit-->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
</dependencies>
1.创建一个模块
- 编写mybatis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">
<!--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.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/essy?useSSL=false&useUnicode=true&characterEncoding=UTF-8;"/>
<property name="username" value="1234"/>
<property name="password" value="1234"/>
</dataSource>
</environment>
</environments>
</configuration>`
- 编写mybatis的工具类
package com.superman.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;
//sqlSessionFactory工厂模式 sqlSession
public class MybatisUtil {
private static SqlSessionFactory sqlSessionFactory;
static {
try {
//使用mybatis的第一步：获取sqlSessionFactory对象，mybatis官网
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
}
//有了sqlSessionFactory，我们就可以从中获得sessionSql的实例
//sqlSession包含了面向数据库执行SQL命令所需的所有方法
public static SqlSession getSqlSession() {
SqlSession sqlSession=sqlSessionFactory.openSession();
return sqlSession;
}
}
2.编写代码
- 实体类
package com.superman.pojo;
//实体类
public class User {
private int id;
private String username;
private String birthday;
private String sex;
private String address;
public User() {
}
public User(int id, String username, String birthday, String sex, String address) {
this.id = id;
this.username = username;
this.birthday = birthday;
this.sex = sex;
this.address = address;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getBirthday() {
return birthday;
}
public void setBirthday(String birthday) {
this.birthday = birthday;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", birthday='" + birthday + '\'' +
", sex='" + sex + '\'' +
", address='" + address + '\'' +
'}';
}
}
- dao接口
package com.superman.dao;
import com.superman.pojo.User;
import java.util.List;
public interface UserDao {
List<User> getUserList();
}
- 同时配置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.superman.dao.UserDao">
<select id="getUserList" resultType="com.superman.pojo.User">
select * from eesy.user
</select>
</mapper>
3.测试代码
注意点：
org.apache.ibatis.binding.BindingException: Type interface com.superman.dao.UserDao is not known to the MapperRegistry.
MapperRegistry是什么？
核心配置文件中注册mappers
package com.superman.dao;
import com.superman.pojo.User;
import com.superman.utils.MybatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import java.util.List;
public class UserDaoTest {
@Test
public void test() {
//第一步：获得sqlsession对象
SqlSession sqlSession = MybatisUtil.getSqlSession();
//方式一：执行SQL
UserDao mapper=sqlSession.getMapper(UserDao.class);
List<User> userList=mapper.getUserList();
for (User user : userList) {
System.out.println(user);
}
//关闭SqlSession
sqlSession.close();
}
}
可能遇到的问题有java不支持发行版本5，在我的另一篇博客中有提到。
同时还涉及到一个过滤的问题：
需要在所有的pom.xml文件中增加下面的代码
<!--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/resources</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>true</filtering>
</resource>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>true</filtering>
</resource>
</resources>
</build>
总结：
1.mybatis的工具类
2.因为工具类需要resources配置文件，所以在resources中写一个配置文件
3.环境准备完成以后写实体类
4.写完实体类以后写接口
5.为接口写一个mapper.xml
6.写一个test进行测试
