實現mybatis的簡易增刪改查的基本步驟記錄

0.專案結構

1.第一步：確保mybatis的jar包都有

　　從此https://github.com/mybatis/mybatis-3/releases地址可以獲取所需的jar包

基本一個簡易的mybatis需要這個jar包，其中mysql-connector-java-5.137.jar是連線mysql所需

2.構建資料庫表的POJO物件，最終mybatis的查詢都會對映到它上面，活著將其存入資料庫中(資料庫表別忘了建）

package com.mybatis.pojo;

public class Role {
    
 
private Integer id;
    private String roleName;
    private String note;
    
        /**setter and gettet

    @Override
    public String toString() {
        return "Role [id=" + id + ", roleName=" + roleName + ", note=" + note + "]";
    }
    
    
}

3..構建對映器，採用XML方式構建，包含一個介面和一個XML檔案，把他們都放入到com.mybatis.mapper包裡

介面RoleMapper.java

package com.mybatis.mapper;

import com.mybatis.pojo.Role;

public interface RoleMapper {
    public Role getRole(Integer id);
}

對應的XML檔案：RoleMapper.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對應於mapper介面的位置 -->	
<mapper namespace="com.mybatis.mapper.RoleMapper">

<!-- 對應於增刪改查語句，以select/update/delete/insert開頭
     id值對應於介面內的方法名，parameterType值對應於方法的引數型別
     resultType對應於方法的返回值型別 -->
<select id="getRole" parameterType="Integer" resultType="role">
	select * from t_role where id=#{id}
</select>

</mapper>

4.設定用於連線資料庫的XML檔案mybatis-config.xml

<?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>

<typeAliases><!-- 別名  -->
		<typeAlias alias="role" type="com.mybatis.pojo.Role"/>
</typeAliases>
	
	<!-- 資料庫環境 -->
	<environments default="development">
		<environment id="development">
			<transactionManager type="JDBC" />
			<!-- type="POOLED"指mybatis內部提供的連線池方式 -->
			<dataSource type="POOLED">
				<property name="driver" value="com.mysql.jdbc.Driver"/>
				<property name="url" value="jdbc:mysql://localhost:3306/ssm"/>
				<property name="username" value="root"/>
				<property name="password" value="root"/>
			</dataSource>
		</environment>
	</environments>
	
	<!-- 對映檔案 -->
	<mappers>
		<mapper resource="com/mybatis/mapper/RoleMapper.xml" />
	</mappers>

</configuration>

5.建立獲取SqlSeesionFactory和SqlSession的工具類，當然也可以直接放到主函式內

package com.mybatis.utils;

import java.io.IOException;
import java.io.InputStream;

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 com.mybatis.utils.SqlSessionFactoryUtils;

public class SqlSessionFactoryUtils {
	
	//使用單例模式
	private final static Class<SqlSessionFactoryUtils> LOCK=SqlSessionFactoryUtils.class;
	
	private static SqlSessionFactory sqlSessionFactory=null;
	
	private SqlSessionFactoryUtils(){}
	
	//獲取SqlSeesionFactory
	public static SqlSessionFactory getSqlSessionFactory(){
		synchronized(LOCK){
			if(sqlSessionFactory !=null){
				return sqlSessionFactory;
			}
			String resource="mybatis-config.xml";
			InputStream inputStream;
			try{
				inputStream=Resources.getResourceAsStream(resource);
				sqlSessionFactory=new SqlSessionFactoryBuilder().build(inputStream);
			}catch(IOException e){
				e.printStackTrace();
				return null;
			}
			return sqlSessionFactory;
		}
	}
	
	//獲取SqlSession
	public static SqlSession openSqlSession(){
		if(sqlSessionFactory==null){
			getSqlSessionFactory();
		}
		return sqlSessionFactory.openSession();
	}
}

6.測試類

package com.mybatis.main;

import org.apache.ibatis.session.SqlSession;
import org.apache.log4j.Logger;

import com.mybatis.mapper.RoleMapper;
import com.mybatis.pojo.Role;
import com.mybatis.utils.SqlSessionFactoryUtils;

public class Main {
	public static void main(String[] args) {
		Logger log=Logger.getLogger(Main.class);
		SqlSession sqlSession=null;
		try{
			sqlSession=SqlSessionFactoryUtils.openSqlSession();
			RoleMapper roleMapper=sqlSession.getMapper(RoleMapper.class);
			Role role=roleMapper.getRole(1);
			log.info(role.getRoleName());
			System.out.println(role);
		}catch(Exception e){
			e.printStackTrace();
		}finally{
			if(sqlSession != null){
				sqlSession.close();
			}
		}
	}
}

至此一個簡單的mybatis例項已經執行成功了