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
再给大家推荐一个比较好的mybatis学习网站：www.mybatis.cn
2、MyBatis 入门实例基于xml配置
①、创建MySQL数据库：mybatisDemo和表：person
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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
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<?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 id=``"development"``>
<!--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
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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;
}
@Override
public String toString() {
return "Person [pid=" + pid + ", pname=" + pname + ", page=" + page
+ "]"``;
}
}
⑤、定义操作 person 表的sql映射文件personMapper.xml
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<?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 id=``"selectPersonById"
resultType=``"com.ys.bean.Person" parameterType=``"int"``>
<!-- 这里和普通的sql 查询语句差不多，对于只有一个查询条件后面的 #{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；如果有多个查询条件，则要写pojo类里面的属性 -->
select * from person where pid = #{pid}
</select>
<!-- 查询person 表所有数据 -->
<select id=``"getAllPerson" resultType=``"com.ys.bean.Person"``>
select * from person
</select>
<!-- 根据id更新数据 -->
<update id=``"updatePersonById" 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 id=``"addPerson" parameterType=``"com.ys.bean.Person"``>
insert into person(pid,pname,page) values(#{pid},#{pname},#{page})
</insert>
<!-- 根据 pid 删除数据 -->
<delete id=``"deletePersonById" 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
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<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
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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;
@Before
public void beforeLoadXML(){
InputStream inputStream = MyBatisTest.``class``.
getClassLoader().getResourceAsStream(``"mybatis-configuration.xml"``);
SqlSessionFactory sqlSessionFactory =
new SqlSessionFactoryBuilder().build(inputStream);
session = sqlSessionFactory.openSession();
}
@Test
public void testSelectById(){
String statement = "com.ys.bean.personMapper"``+``".selectPersonById"``;
Person p = session.selectOne(statement, 1``);
System.out.println(p);
session.close();
}
@Test
public void testGetAllPerson(){
String statement = "com.ys.bean.personMapper.getAllPerson"``;
List<Person> listPerson = session.selectList(statement);
System.out.println(listPerson);
session.close();
}
@Test
public 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();
}
@Test
public void addPerson(){
String statement = "com.ys.bean.personMapper.addPerson"``;
Person p = new Person();
p.setPname(``"add"``);
p.setPage(``11``);
session.insert(statement, p);
session.commit();
session.close();
}
@Test
public 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：
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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
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@Test
public void testAnnocation(){
PersonMapper mapper = session.getMapper(PersonMapper.``class``);
Person p = new Person();
p.setPid(``7``);
p.setPname(``"abc"``);
p.setPage(``11``);
mapper.add(p);
Person p1 = mapper.getPerson(``3``);
System.out.println(p1);
p.setPage(``100``);
mapper.updatePerson(p);
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
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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;
}
@Override
public String toString() {
return "Teacher [tid=" + tid + ", tname=" + tname + ", classes=" + classes + "]"``;
}
}
Classes.java
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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;
}
@Override
public String toString() {
return "Classes [cid=" + cid + ", 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
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<?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 id=``"getClasses" 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=``"getClassesMap"``>
<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 id=``"getTeacher" resultMap=``"getTeacherMap" parameterType=``"int"``>
select * from teacher t,classes c
where t.cid = c.cid and t.cid=#{cid}
</select>
<resultMap type=``"one.to.one.Teacher" id=``"getTeacherMap"``>
<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
property:别名(属性名) column：列名 -->
<!-- 把teacher的字段设置进去 -->
<select id=``"getClasses2" resultMap=``"getClassesMap2"``>
select * from classes c where c.cid = #{cid}
</select>
<resultMap type=``"one.to.one.Classes" id=``"getClassesMap2"``>
<id column=``"cid" property=``"cid"``/>
<result column=``"cname" property=``"cname"``/>
<collection property=``"teacher" column=``"tid" select=``"getTeacherCollection"``>
</collection>
</resultMap>
<select id=``"getTeacherCollection" 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
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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;
@Before
public void beforeLoadXML(){
InputStream inputStream = MyBatisTest.``class``.
getClassLoader().getResourceAsStream(``"mybatis-configuration.xml"``);
SqlSessionFactory sqlSessionFactory =
new SqlSessionFactoryBuilder().build(inputStream);
session = sqlSessionFactory.openSession();
}
@Test
public void testGetClasses(){
String statement = "one.to.one.classesMapper.getClasses"``;
Classes c = session.selectOne(statement, 1``);
System.out.println(c);
}
@Test
public void testGetTeacher(){
String statement = "one.to.one.classesMapper.getTeacher"``;
Teacher t = session.selectOne(statement, 1``);
System.out.println(t);
}
@Test
public 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
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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;
}
@Override
public String toString() {
return "Student [sid=" + sid + ", sname=" + sname + ", classes=" + classes + "]"``;
}
}
Classes.java
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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;
}
@Override
public String toString() {
return "Classes [cid=" + cid + ", 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
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<?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 id=``"getClasses" 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=``"getClassesMap"``>
<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
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<?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 id=``"getStudents" 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=``"getStudentMap"``>
<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
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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;
@Before
public void beforeLoadXML(){
InputStream inputStream = MyBatisTest.``class``.
getClassLoader().getResourceAsStream(``"mybatis-configuration.xml"``);
SqlSessionFactory sqlSessionFactory =
new SqlSessionFactoryBuilder().build(inputStream);
session = sqlSessionFactory.openSession();
}
@Test
public 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());
}
@Test
public 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
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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;
}
@Override
public String toString() {
return "User [uid=" + uid + ", uname=" + uname + ", groups=" + groups + "]"``;
}
}
Groups.java
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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;
}
@Override
public String toString() {
return "Group [gid=" + gid + ", gname=" + gname + ", users=" + users + "]"``;
}
}
Users_Groups.java
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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
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<?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 id=``"getUsers" 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=``"getGroupMap"``>
<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
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@Test
public 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());
}
}
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