MyBatis|Mybatis基本使用总括（单表/多表/动态sql） mybatis|maven|java|mysql

【MyBatis|Mybatis基本使用总括（单表/多表/动态sql）】其实就是持久层的数据控制框架

1 基本工具包（1）导入包的方式！准备：jar包，自己找，mybatis的包和mysql的驱动
maven网址：https://mvnrepository.com/artifact/org.mybatis/mybatis/3.5.6，简言之，自己准备包，根据需求选择！

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（2）maven依赖管理方式(根据需求选择合适包)！

org.mybatis mybatis 3.5.5 mysql mysql-connector-java 5.1.48 com.github.pagehelper pagehelper 5.1.4 com.github.jsqlparser jsqlparser 1.1 junit junit 4.12 log4j log4j 1.2.17 org.slf4j slf4j-log4j12 1.7.20

2基本文件（1）mybatis的主配置文件(MyBatis.xml)：

（2）数据库配置文件（jdbc.properties）

driver=com.mysql.jdbc.Driver url=jdbc:mysql:///mybatismussary username=root password=root

(3)日志配置文件（log4j.properties）

# 日志格式设置 # Global logging configuration # ERROR WARN INFO DEBUG log4j.rootLogger=DEBUG, stdout # Console output... log4j.appender.stdout=org.apache.log4j.ConsoleAppender log4j.appender.stdout.layout=org.apache.log4j.PatternLayout log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

3 配置文件的加载方式（作为参考）：

package 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; /** *2021.9.19 */ public class MybatisUtils { private static SqlSessionFactory build; static { try { InputStream resourceAsStream = Resources.getResourceAsStream("MyBatis.xml"); build = new SqlSessionFactoryBuilder().build(resourceAsStream); } catch (IOException e) { e.printStackTrace(); } }/** * @param b 传递进来的参数的值，true自动提交事务，默认的不会自动提交事务 */ public static SqlSession getSqlSession(boolean b) { return build.openSession(b); }/** * 默认的不会自动提交事务 */ public static SqlSession getSqlSession() { return build.openSession(); }}

4 使用方法：（1）基于xml的使用的用法1： xml映射文件（注意sql的写法，配置文件中已经做了说明）：

SELECT * FROM userSELECT * FROM user WHERE id = #{id}SELECT * FROM user WHERE name = #{name}INSERT INTO user VALUES (#{id},#{name},#{area},#{age}) UPDATE user SET name = #{name},age = #{age} ,area=#{area} WHERE id = #{id} DELETE FROM user where name=#{name}

（接口省略），在持久层mapper完成这一步，其他层级依次调用即可：

package Mapper; import bean.User; import org.apache.ibatis.session.SqlSession; import utils.MybatisUtils; import java.util.List; public class UserMapperImp implements UserMapper { //开启自动提交事务的方式 SqlSession sqlSession = MybatisUtils.getSqlSession(true); @Override public List selectAll() { //这块指明映射文件中的方法即可 List objects = sqlSession.selectList("mapper.selectAll"); sqlSession.close(); return objects; }@Override public User selectOneByCondition(int id) { User user = sqlSession.selectOne("mapper.selectOneById", id); sqlSession.close(); return user; }@Override public User selectOneByCondition(String name) { User user = sqlSession.selectOne("mapper.selectOneByName", name); sqlSession.close(); return user; }@Override public void insertUser(User user) { int insert = sqlSession.insert("mapper.insert", user); sqlSession.close(); System.out.println(insert); }@Override public void deleteUser(User user) { int delete = sqlSession.delete("mapper.delete", user); sqlSession.close(); System.out.println(delete); } }

（2）基于xml的用法2 xml映射文件（注意sql的写法，配置文件中已经做了说明）：

SELECT * FROM peopleSELECT * FROM people WHERE id = #{id}SELECT * FROM people WHERE name = #{name}INSERT INTO people VALUES (#{id},#{name},#{age},#{area},#{hobby},#{grade},#{number}) UPDATE people SET name = #{name},age = #{age} ,area=#{area},hobby=#{hobby},grade=#{grade},number=#{number} WHERE id = #{id} DELETE FROM people where name=#{name} select * from people #{id} select * from people id = #{id} AND name = #{name} AND age = #{age}

dao层，增删改的sql的执行结果是数字，代表改变几行数据发生改变，但是mybatis将执行的结果转化成Boolean类型了，下面的例子没有进行增删改的结果回收，其实boolean结果类型是可以回收到的，这块了解一下即可！

package mapper; import bean.People; import java.util.List; public interface PeopleMapper { List selectAll(); People selectOneById(int id); People selectOneByName(String name); void insert(People people); void delete(People people); void update(People people); //动态sql List selectByIds(List list); List selectByCondition(People people); }

业务层做如下逻辑处理，持久层只写接口，完成配置文件的映射即可

package service; import bean.People; import com.github.pagehelper.PageHelper; import mapper.PeopleMapper; import org.apache.ibatis.session.SqlSession; import utils.MybatisUtils; import java.util.List; public class ServiceImp implements PeoplerService { private SqlSession session; private PeopleMapper mapper; public ServiceImp() { session = MybatisUtils.getSqlSession(true); mapper = session.getMapper(PeopleMapper.class); }@Override public List selectAll(int index,int pageSize ) { //分页插件必须先做初始化操作 PageHelper.startPage(index,pageSize); List peoples = mapper.selectAll(); session.close(); return peoples; }/** * 动态sql.参数是集合示例： * @param list * @return */ @Override public List selectByIds(List list) { List lists = mapper.selectByIds(list); session.close(); return lists; } /** * 动态sql.参数是不定向条件： * @param people * @return */ @Override public List selectByCondition(People people) { List list = mapper.selectByCondition(people); session.close(); return list; }/************** 下面的未做实现，只作为举例*********************/ @Override public People selectOneByCondition(int id) { return null; }@Override public People selectOneByCondition(String name) { return null; }@Override public void insertUser(People people) {} @Override public void deleteUser(People people) {} }

补充：
注意：以上xml映射文件是使用的单表的形式，下面举例一对多，一对一，多对多关系，作为写法参考，sql基础还是需要有的：

select s.id id,s.name name,s.age age,s.grade grade,s.mainteacher mainteacher,s.sex sex,c.id cid,c.name cname from student s,card c where s.id=c.sid select s.id id,s.name name,s.age age,s.grade grade,s.mainteacher mainteacher,s.sex sex,t.id tid,t.name tname,t.coures coures from student s,teacher t where t.name = s.mainteacher select s.id id,s.name name,s.age age,s.grade grade,s.mainteacher mainteacher,s.sex sex,c.cid cid,c.cname cname from student s,mid m,course c where m.sid=s.id and m.cid=c.cid

mapper文件

package mapper; import bean.Student; import bean.Teacher; import java.util.List; public interface Mapper { //one to one List selectAllStudent(); //one to many List selectAllTeacher(); List selectAllStudentClasses(); }

（3）纯注解的使用方式：作为参考样例：唯一变只是在映射文件是否使用xml文件主配置文件：

单表使用示例（主要还是在mapper映射接口上做操作）：
说明：通过注解@select@dealte@insertt@update进行标注方法写sql的形式

package mapper; import bean.Student; import org.apache.ibatis.annotations.Select; import java.util.List; public interface Mappers { /** * 简单的单表查询示例示例 * @return */ @Select("select * from student") List selectAll(); /** * 多表查询，用到看资料就行，太烦！ * @return */ @Select("") List selectAllCard(); }

多表示例（很少用到，用到来查）：
一对一：

import org.apache.ibatis.annotations.One; import org.apache.ibatis.annotations.Result; import org.apache.ibatis.annotations.Results; import org.apache.ibatis.annotations.Select; import java.util.List; public interface CardMapper { //查询全部 @Select("SELECT * FROM card") @Results({ @Result(column = "id",property = "id"), @Result(column = "number",property = "number"), @Result( property = "p",// 被包含对象的变量名 javaType = Person.class,// 被包含对象的实际数据类型 column = "pid",// 根据查询出的card表中的pid字段来查询person表 /* one、@One 一对一固定写法 select属性：指定调用哪个接口中的哪个方法 */ one = @One(select = "com.itheima.one_to_one.PersonMapper.selectById") ) }) public abstract List selectAll(); }

public interface PersonMapper { //根据id查询 @Select("SELECT * FROM person WHERE id=#{id}") public abstract Person selectById(Integer id); }

一对多：

import org.apache.ibatis.annotations.Many; import org.apache.ibatis.annotations.Result; import org.apache.ibatis.annotations.Results; import org.apache.ibatis.annotations.Select; import java.util.List; public interface ClassesMapper { //查询全部 @Select("SELECT * FROM classes") @Results({ @Result(column = "id",property = "id"), @Result(column = "name",property = "name"), @Result( property = "students",// 被包含对象的变量名 javaType = List.class,// 被包含对象的实际数据类型 column = "id",// 根据查询出的classes表的id字段来查询student表 /* many、@Many 一对多查询的固定写法 select属性：指定调用哪个接口中的哪个查询方法 */many = @Many(select = "com.itheima.one_to_many.StudentMapper.selectByCid") ) }) public abstract List selectAll(); }

import org.apache.ibatis.annotations.Select; import java.util.List; public interface StudentMapper { //根据cid查询student表 @Select("SELECT * FROM student WHERE cid=#{cid}") public abstract List selectByCid(Integer cid); }

多对多：

import org.apache.ibatis.annotations.Many; import org.apache.ibatis.annotations.Result; import org.apache.ibatis.annotations.Results; import org.apache.ibatis.annotations.Select; import java.util.List; public interface StudentMapper { //查询全部 @Select("SELECT DISTINCT s.id,s.name,s.age" + " FROM " + "student s,stu_cr sc " + "WHERE " + "sc.sid=s.id")@Results({ @Result(column = "id",property = "id"), @Result(column = "name",property = "name"), @Result(column = "age",property = "age"), @Result( property = "courses",// 被包含对象的变量名 javaType = List.class,// 被包含对象的实际数据类型 column = "id",// 根据查询出student表的id来作为关联条件，去查询中间表和课程表 /* many、@Many 一对多查询的固定写法 select属性：指定调用哪个接口中的哪个查询方法 */ many = @Many(select = "com.itheima.many_to_many.CourseMapper.selectBySid") ) }) public abstract List selectAll(); }

import org.apache.ibatis.annotations.Select; import java.util.List; public interface CourseMapper { //根据学生id查询所选课程 @Select("SELECT c.id,c.name " + "FROM stu_cr sc,course c " + "+WHERE sc.cid=c.id AND sc.sid=#{id}") public abstract List selectBySid(Integer id); }

最后最后一种纯注解用法，用到再说，很烦的那种：在我的资料中有样例，用到再参考

参数获取方式补充：