MyBatis 详解(一对一,一对多,多对多)
来源:互联网 发布:js实现树状结构图 编辑:程序博客网 时间:2024/06/09 14:25
1、什么是MyBatis?
MyBatis 本是apache的一个开源项目iBatis, 2010年这个项目由apache software foundation 迁移到了google code,并且改名为MyBatis 。2013年11月迁移到Github。
iBATIS一词来源于“internet”和“abatis”的组合,是一个基于Java的持久层框架。iBATIS提供的持久层框架包括SQL Maps和Data Access Objects(DAO)。
MyBatis 是支持普通 SQL查询,存储过程和高级映射的优秀持久层框架。MyBatis 消除了几乎所有的JDBC代码和参数的手工设置以及结果集的检索。MyBatis 使用简单的 XML或注解用于配置和原始映射,将接口和 Java 的POJOs(Plain Ordinary Java Objects,普通的 Java对象)映射成数据库中的记录。
PS:本文所有代码下载链接:http://pan.baidu.com/s/1gf8CPQN 密码:t2x9
2、MyBatis 入门实例基于xml配置
①、创建MySQL数据库:mybatisDemo和表:person
create database mybatisDemo;use mybatisDemo;create table person(pid int primary key AUTO_INCREMENT, pname varchar(50), page int);
②、建立一个Java工程,并导入相应的jar包
相应的 jar 包下载链接:http://pan.baidu.com/s/1skZM09Z 密码:nkt6
③、在 MyBatisDemo 工程中添加数据库配置文件 mybatis-configuration.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><!-- 可以配置多个运行环境,但是每个 SqlSessionFactory 实例只能选择一个运行环境 一、development:开发模式 二、work:工作模式--> <environments default="development"> <!--id属性必须和上面的default一样 --> <environment > <!--事务管理器 一、JDBC:这个配置直接简单使用了 JDBC 的提交和回滚设置。它依赖于从数据源得到的连接来管理事务范围 二、MANAGED:这个配置几乎没做什么。它从来不提交或回滚一个连接。而它会让容器来管理事务的整个生命周期 比如 spring 或 JEE 应用服务器的上下文,默认情况下,它会关闭连接。然而一些容器并不希望这样, 因此如果你需要从连接中停止它,就可以将 closeConnection 属性设置为 false,比如: <transactionManager type="MANAGED"><property name="closeConnection" value="false"/></transactionManager> --> <transactionManager type="JDBC"/> <!--dataSource 元素使用标准的 JDBC 数据源接口来配置 JDBC 连接对象源 --> <dataSource type="POOLED"> <property name="driver" value="com.mysql.jdbc.Driver"/> <property name="url" value="jdbc:mysql://localhost:3306/mybatisdemo"/> <property name="username" value="root"/> <property name="password" value="root"/> </dataSource> </environment> </environments></configuration>
④、定义表所对应的实体类
package com.ys.bean;public class Person {private int pid;private String pname;private int page;public int getPid() {return pid;}public void setPid(int pid) {this.pid = pid;}public String getPname() {return pname;}public void setPname(String pname) {this.pname = pname;}public int getPage() {return page;}public void setPage(int page) {this.page = page;}@Overridepublic String toString() {return "Person [p, pname=" + pname + ", page=" + page+ "]";}}
⑤、定义操作 person 表的sql映射文件personMapper.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"><mapper namespace="com.ys.bean.personMapper"> <!-- 根据 pid 查询 person 表中的数据 id:唯一标识符,此文件中的id值不能重复 resultType:返回值类型,一条数据库记录也就对应实体类的一个对象 parameterType:参数类型,也就是查询条件的类型 --> <select resultType="com.ys.bean.Person" parameterType="int"> <!-- 这里和普通的sql 查询语句差不多,后面的 #{pid}表示占位符,里面不一定要写pid,写啥都可以,但是不要空着 --> select * from person where pid = #{pid} </select> <!-- 查询person 表所有数据 --> <select resultType="com.ys.bean.Person"> select * from person </select> <!-- 根据id更新数据 --> <update parameterType="com.ys.bean.Person"> update person set pname=#{pname},page=#{page} where pid = #{pid} </update> <!-- 向 person 表插入一条数据 --> <insert parameterType="com.ys.bean.Person"> insert into person(pid,pname,page) values(#{pid},#{pname},#{page}) </insert> <!-- 根据 pid 删除数据 --> <delete parameterType="Long"> delete from person where pid=#{pid} </delete> </mapper>
⑥、向 mybatis-configuration.xml 配置文件中注册 personMapper.xml 文件
<mappers> <!-- 注册personMapper.xml文件, personMapper.xml位于com.ys.bean这个包下,所以resource写成com/ys/bean/personMapper.xml--> <mapper resource="com/ys/bean/personMapper.xml"/> </mappers>
如下图所示:
⑦、创建测试类
package com.ys.test;import java.io.InputStream;import java.util.List;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;import org.junit.Before;import org.junit.Test;import com.ys.bean.Person;public class MyBatisTest {SqlSession session;@Beforepublic void beforeLoadXML(){//加载 mybatis 配置文件InputStream inputStream = MyBatisTest.class.getClassLoader().getResourceAsStream("mybatis-configuration.xml");//构建sqlSession的工厂SqlSessionFactory sqlSessionFactory =new SqlSessionFactoryBuilder().build(inputStream);//根据 sqlSessionFactory 产生 sessionsession = sqlSessionFactory.openSession();}//根据 pid 查询 person 表中的数据@Testpublic void testSelectById(){//这个字符串有 personMapper.xml 文件中 两个部分构成//<mapper namespace="com.ys.bean.personMapper"> 的 namespace 的值//<select > id 值String statement = "com.ys.bean.personMapper"+".selectPersonById";Person p = session.selectOne(statement, 1);System.out.println(p);session.close();}//查询person 表所有数据@Testpublic void testGetAllPerson(){String statement = "com.ys.bean.personMapper.getAllPerson";List<Person> listPerson = session.selectList(statement);System.out.println(listPerson);session.close();}//根据id更新数据 @Testpublic void updateById(){String statement = "com.ys.bean.personMapper.updatePersonById";Person p = new Person();p.setPid(1);p.setPname("aaa");p.setPage(11);session.update(statement, p);session.commit();session.close();}//向 person 表插入一条数据@Testpublic void addPerson(){String statement = "com.ys.bean.personMapper.addPerson";Person p = new Person();//由于我们设置了主键的自增长机制,故这里不需要手动设置 pid 的值//p.setPid(1);p.setPname("add");p.setPage(11);session.insert(statement, p);session.commit();session.close();}//根据 pid 删除person 表中的数据@Testpublic void deletePersonById(){String statement = "com.ys.bean.personMapper.deletePersonById";session.delete(statement, 1);session.commit();session.close();}}
3、MyBatis 入门实例注解配置
①、上面的前面四步都是一样的,但是第五步不一样,我们不需要创建 personMapper.xml 文件,首先在 src 目录下创建 personMapper.java 文件
内容如下:
package com.ys.annocation;import org.apache.ibatis.annotations.Delete;import org.apache.ibatis.annotations.Insert;import org.apache.ibatis.annotations.Select;import org.apache.ibatis.annotations.Update;import com.ys.bean.Person;public interface PersonMapper {@Insert("insert into person(pid,pname,page) values(#{pid},#{pname},#{page})")public int add(Person person); @Select("select * from person where pid = #{pid}")public Person getPerson(int pid);@Update("update person set pname=#{pname},page=#{page} where pid = #{pid}")public int updatePerson(Person preson);@Delete("delete from person where pid=#{pid}")public int deletePerson(int pid);}
②、向 mybatis-configuration.xml 配置文件中注册 personMapper.xml 文件
③、编写测试类
@Testpublic void testAnnocation(){PersonMapper mapper = session.getMapper(PersonMapper.class);Person p = new Person();p.setPid(7);p.setPname("abc");p.setPage(11);//调用增加方法mapper.add(p);//调用查询方法Person p1 = mapper.getPerson(3);System.out.println(p1);//调用更新方法p.setPage(100);mapper.updatePerson(p);//调用删除方法mapper.deletePerson(7);session.commit();session.close();}
4、MyBatis 入门实例 一对一 基于xml配置
这里我们以老师和班级为例,假设一般班级只能拥有有一个老师,一个老师只能带一个班级。
①、创建实体类
Teacher.java
package one.to.one;public class Teacher {private int tid;private String tname;private Classes classes;public int getTid() {return tid;}public void setTid(int tid) {this.tid = tid;}public String getTname() {return tname;}public void setTname(String tname) {this.tname = tname;}public Classes getClasses() {return classes;}public void setClasses(Classes classes) {this.classes = classes;}@Overridepublic String toString() {return "Teacher [t, tname=" + tname + ", classes=" + classes + "]";}}
Classes.java
package one.to.one;public class Classes {private int cid;private String cname;private Teacher teacher;public int getCid() {return cid;}public void setCid(int cid) {this.cid = cid;}public String getCname() {return cname;}public void setCname(String cname) {this.cname = cname;}public Teacher getTeacher() {return teacher;}public void setTeacher(Teacher teacher) {this.teacher = teacher;}@Overridepublic String toString() {return "Classes [c, cname=" + cname + ", teacher=" + teacher + "]";}}
②、在数据库中根据实体类创建相应的数据表
③、定义操作 Classes 表的sql映射文件classesMapper.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"><mapper namespace="one.to.one.classesMapper"><!-- 方式一:嵌套结果:使用嵌套结果映射来处理重复的联合结果的子集 封装联表查询的数据(去除重复的数据) select * from classes c, teacher t where c.tid=t.tid and c.tid=#{tid} --><select resultMap="getClassesMap" parameterType="int">select * from classes c ,teacher t where c.tid=t.tid and c.tid=#{tid}</select><resultMap type="one.to.one.Classes" ><id column="cid" property="cid"/><result column="cname" property="cname"/><association property="teacher" javaType="one.to.one.Teacher"><id column="tid" property="tid"></id><result column="tname" property="tname"/></association></resultMap><!-- 方式一:嵌套结果:使用嵌套结果映射来处理重复的联合结果的子集 封装联表查询的数据(去除重复的数据) select * from teacher t,classes c where t.cid = c.cid and t.cid=#{cid} --><select resultMap="getTeacherMap" parameterType="int">select * from teacher t,classes cwhere t.cid = c.cid and t.cid=#{cid}</select><resultMap type="one.to.one.Teacher" ><id column="tid" property="tid"/><result column="tname" property="tname"/><association property="classes" javaType="one.to.one.Classes"><id column="cid" property="cid"/><result column="cname" property="cname"/></association></resultMap><!-- 方式二:嵌套查询:通过执行另外一个SQL映射语句来返回预期的复杂类型 SELECT * FROM classes WHERE cid=1; SELECT * FROM teacher WHERE tid=1 //1 是上一个查询得到的tid的值 property:别名(属性名) column:列名 --> <!-- 把teacher的字段设置进去 --><select resultMap="getClassesMap2">select * from classes c where c.cid = #{cid}</select><resultMap type="one.to.one.Classes" ><id column="cid" property="cid"/><result column="cname" property="cname"/><collection property="teacher" column="tid" select="getTeacherCollection"></collection></resultMap><select resultType="one.to.one.Teacher">select tid tid,tname tname from teacher where tid=#{tid}</select> </mapper>
说明:我们这里一对一的关联操作,有两种方式:
1、使用嵌套结果映射来处理重复的联合结果的子集
2、通过执行另外一个SQL映射语句来返回预期的复杂类型
相关属性解释:
④、向 mybatis-configuration.xml 配置文件中注册 classesMapper.xml 文件
⑤、编写测试类
package one.to.one;import java.io.InputStream;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;import org.junit.Before;import org.junit.Test;import com.ys.test.MyBatisTest;public class OneToOneTest {SqlSession session;@Beforepublic void beforeLoadXML(){//加载 mybatis 配置文件InputStream inputStream = MyBatisTest.class.getClassLoader().getResourceAsStream("mybatis-configuration.xml");//构建sqlSession的工厂SqlSessionFactory sqlSessionFactory =new SqlSessionFactoryBuilder().build(inputStream);//根据 sqlSessionFactory 产生 sessionsession = sqlSessionFactory.openSession();}//一对一嵌套结果方式:根据教师id查询班级信息@Testpublic void testGetClasses(){String statement = "one.to.one.classesMapper.getClasses";Classes c = session.selectOne(statement, 1);System.out.println(c);}//一对一嵌套结果方式:根据班级id查询教师信息@Testpublic void testGetTeacher(){String statement = "one.to.one.classesMapper.getTeacher";Teacher t = session.selectOne(statement, 1);System.out.println(t);}//一对一嵌套查询方式:根据教师id查询班级信息@Testpublic void testGetClasses2(){String statement = "one.to.one.classesMapper.getClasses2";Classes c = session.selectOne(statement, 1);System.out.println(c);}}
4、MyBatis 入门实例 一对多,多对一 基于xml配置
这里我们以班级和学生为例,一个班级里面对应多个学生,这是一对多;反过来,多个学生对应一个班级,这是多对一
①、建立学生和班级的实体类
Student.java
package one.to.many;public class Student {private int sid;private String sname;private Classes classes;public int getSid() {return sid;}public void setSid(int sid) {this.sid = sid;}public String getSname() {return sname;}public void setSname(String sname) {this.sname = sname;}public Classes getClasses() {return classes;}public void setClasses(Classes classes) {this.classes = classes;}@Overridepublic String toString() {return "Student [s, sname=" + sname + ", classes=" + classes + "]";}}
Classes.java
package one.to.many;import java.util.Set;public class Classes {private int cid;private String cname;private Set<Student> students;public int getCid() {return cid;}public void setCid(int cid) {this.cid = cid;}public String getCname() {return cname;}public void setCname(String cname) {this.cname = cname;}public Set<Student> getStudents() {return students;}public void setStudents(Set<Student> students) {this.students = students;}@Overridepublic String toString() {return "Classes [c, cname=" + cname + ", students=" + students + "]";}}
②、在数据库中根据实体类创建相应的数据表
③、多对一:定义操作 Classes 表的sql映射文件classesMapper.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"><mapper namespace="one.to.many.classesMapper"> <select resultMap="getClassesMap"> select * from classes c,student s where s.cid=c.cid and c.cid=#{cid} </select> <resultMap type="one.to.many.Classes" > <id column="cid" property="cid"></id> <result column="cname" property="cname"/> <collection property="students" ofType="one.to.many.Student"> <id column="sid" property="sid"/> <result column="sname" property="sname"/> </collection> </resultMap> </mapper>
④、一对多:定义操作 Student 表的sql映射文件studentMapper.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"><mapper namespace="many.to.one.studentMapper"> <select resultMap="getStudentMap"> select * from classes c,student s where s.cid=c.cid and s.sid=#{sid} </select> <resultMap type="one.to.many.Student" > <id column="sid" property="sid"></id> <result column="sname" property="sname"/> <association property="classes" javaType="one.to.many.Classes"> <id column="cid" property="cid"/> <result column="cname" property="cname"/> </association> </resultMap> </mapper>
⑤、向 mybatis-configuration.xml 配置文件中注册 classesMapper.xml 、studentMapper.xml文件
⑥、编写测试类
package one.to.many;import java.io.InputStream;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;import org.junit.Before;import org.junit.Test;import com.ys.test.MyBatisTest;public class OneToManyTest {SqlSession session;@Beforepublic void beforeLoadXML(){//加载 mybatis 配置文件InputStream inputStream = MyBatisTest.class.getClassLoader().getResourceAsStream("mybatis-configuration.xml");//构建sqlSession的工厂SqlSessionFactory sqlSessionFactory =new SqlSessionFactoryBuilder().build(inputStream);//根据 sqlSessionFactory 产生 sessionsession = sqlSessionFactory.openSession();}//一对多嵌套结果方式:根据班级id查询班级所有的学生信息@Testpublic void testGetClasses(){String statement = "one.to.many.classesMapper.getClasses";Classes c = session.selectOne(statement, 1);System.out.println(c);System.out.println(c.getStudents().size());}//多对一嵌套结果方式:根据学生id查询班级信息@Testpublic void testGetStudents(){String statement = "many.to.one.studentMapper.getStudents";Student s = session.selectOne(statement, 1);System.out.println(s);System.out.println(s.getClasses());}}
5、MyBatis 入门实例 多对多 基于xml配置
这里我们以 users 表和 groups 表为例,一个 users 可能加入多个 groups,而一个 groups 可能包含多个 users,故构成 多对多 的关联
①、在数据库中建立相应的表
users 表
groups 表
两者之间的关联表users_groups表
②、建立对应的实体类
Users.java
package many.to.many;import java.util.Set;public class Users {private int uid;private String uname;private Set<Groups> groups;public int getUid() {return uid;}public void setUid(int uid) {this.uid = uid;}public String getUname() {return uname;}public void setUname(String uname) {this.uname = uname;}public Set<Groups> getGroups() {return groups;}public void setGroups(Set<Groups> groups) {this.groups = groups;}@Overridepublic String toString() {return "User [u, uname=" + uname + ", groups=" + groups + "]";}}
Groups.java
package many.to.many;import java.util.Set;public class Groups {private int gid;private String gname;private Set<Users> users;public int getGid() {return gid;}public void setGid(int gid) {this.gid = gid;}public String getGname() {return gname;}public void setGname(String gname) {this.gname = gname;}public Set<Users> getUsers() {return users;}public void setUsers(Set<Users> users) {this.users = users;}@Overridepublic String toString() {return "Group [g, gname=" + gname + ", users=" + users + "]";}}
Users_Groups.java
package many.to.many;public class Users_Groups {private Users user;private Groups group;public Users getUser() {return user;}public void setUser(Users user) {this.user = user;}public Groups getGroup() {return group;}public void setGroup(Groups group) {this.group = group;}}
③、多对多:定义操作 sql映射文件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"><mapper namespace="many.to.many.userMapper"><!-- 给一个用户 id,查看该用户下的所有用户组信息 --> <select resultMap="getGroupMap"> select g.gid,g.gname from users_groups ug,groups g where ug.group_id=g.gid and ug.user_id=#{uid} </select> <resultMap type="many.to.many.Groups" > <id column="gid" property="gid"/> <result column="gname" property="gname"/> <collection property="users" ofType="many.to.many.Users"> <id column="uid" property="uid"/> <result column="uname" property="uname"/> </collection> </resultMap> </mapper>
⑤、向 mybatis-configuration.xml 配置文件中注册 userMapper.xml文件
⑥、编写测试类
//多对多:根据根据用户 id 查询所有的用户组信息@Testpublic void testGetGroups(){String statement = "many.to.many.userMapper.getUsers";List<Groups> listGroup = session.selectList(statement,1);for(Groups g : listGroup){System.out.println(g.toString());}}
- MyBatis 详解(一对一,一对多,多对多)
- MyBatis 详解(一对一,一对多,多对多)
- MyBatis 一对一、一对多
- mybatis 一对一,一对多
- mybatis 一对一 一对多 多对一 多对多
- MyBatis入门(二)-一对一,一对多
- MyBatis 一对一、一对多的
- Mybatis一对一和一对多
- mybatis一对一,一对多查询
- mybatis教程---MyBatis一对一、MyBatis一对多
- mybatis映射 一对一、一对多、多对多高级映射
- mybatis中的高级映射一对一、一对多、多对多
- mybatis一对一,一对多,多对多的关联查询
- mybatis一对一,一对多,多对多查询
- Mybatis(2、关系映射一对一、一对多、多对多)
- mybatis 一对一、一对多、多对多的设计
- mybatis高级映射(一对一,一对多,多对多)
- 【Mybatis】一对一,一对多,多对多映射
- java插入hbase数据时报错:java.lang.IllegalArgumentException:No columns to insert
- Spring(15)——基于注解的支持
- Fiddler(一)
- 使用clang命令行查看.cpp文件
- 01串 【nyoj-252】【动态规划】
- MyBatis 详解(一对一,一对多,多对多)
- Android动画之属性动画
- tomcat/jedis参数
- jQuery获取select中所有option值
- Linux find常见用法示例
- Python Matplotlib实现三维数据的散点图绘制
- XGBoost 与 Boosted Tree
- java通过反射获取泛型参数
- 多线程的应用场景