Mybatis
1、mybatis介绍
mybatis是sqlmap技术，对jdbc进行封装，将大量的sql语句外部化。
2、体验mybatis
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准备数据库和表
mysql>create table users(id int primary key auto_increment , name varchar(20) , age int) ; -
创建模块引入maven依赖
[pom.xml]
<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.oldboy</groupId> <artifactId>mybatis</artifactId> <version>1.0-SNAPSHOT</version> <dependencies> <!-- mysql驱动 --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.17</version> </dependency> <!--junit单元测试--> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.11</version> </dependency> <!-- mybatis类库 --> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.2.1</version> </dependency> </dependencies> </project> -
创建javabean
/** * User类 */ public class User { private Integer id; private String name ; private int age ; //get//set } -
创建映射文件
[resources/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"> <!-- 定义名字空间 --> <mapper namespace="users"> <!-- 定义insert语句 ,获得生成的id字段--> <insert id="insert" > insert into users(name,age) values(#{name},#{age}) </insert> </mapper> -
创建配置文件
[resources/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> <properties> <property name="driver" value="com.mysql.jdbc.Driver"/> <property name="url" value="jdbc:mysql://localhost:3306/big12"/> <property name="username" value="root"/> <property name="password" value="root"/> </properties> <environments default="development"> <environment id="development"> <transactionManager type="JDBC"/> <dataSource type="POOLED"> <property name="driver" value="${driver}"/> <property name="url" value="${url}"/> <property name="username" value="${username}"/> <property name="password" value="${password}"/> </dataSource> </environment> </environments> <mappers> <mapper resource="UserMapper.xml"/> </mappers> </configuration> -
编写测试类，实现插入
@Test
public void testInsert() throws IOException {
//加载配置文件
InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
//创建会话工厂(builder模式)
SqlSessionFactory sf = new SqlSessionFactoryBuilder().build(in);
//开启会话，相当于连接
SqlSession sess = sf.openSession();
User u = new User() ;
u.setName("tom");
u.setAge(12);
//执行插入操作
sess.insert("users.insert" , u) ;
sess.commit();
sess.close();
}
3、实现mybatis的基本操作
3.1 update
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在映射文件中增加update语句
<?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"> <!-- 定义名字空间 --> <mapper namespace="users"> <update id="update"> update users set name = #{name} , age = #{age} where id = #{id} </update> </mapper> -
调用session.update方法
... User u = new User() ; u.setName("tomas"); u.setAge(22); u.setId(1); sess.update("users.update" , u) ;
3.2 select
3.2.1 查询一个
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映射文件增加查询语句
[userMapper.xml]
... <select id="selectById" resultType="_User"> select * from users where id = #{id} </select> ... -
配置文件添加别名
[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> <typeAlias type="com.oldboy.mybatis.domain.User" alias="_User"/> </typeAliases> ... </configuration>
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API调用
User u = sess.selectOne("users.selectById" , 1) ;
3.2.2 查询多个
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添加sql语句
[userMapper.xml]
... <select id="selectAll" resultType="_User"> select * from users </select> ... -
API调用
List<User> list = sess.selectList("users.selectAll" ) ;
3.3 delete
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添加sql语句
[UserMapper.xml]
... <delete id="delete"> delete from users where id = #{id} </delete> ... -
API调用
sess.delete("users.delete" , 1) ;
4、获取数据库主键值
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数据表如果主键是自动增长的话，如果要在程序插入时得到主键值可修改映射文件，具体如下：
[UserMapper.xml]
<insert id="insert" useGeneratedKeys="true" keyProperty="id"> ... </insert>
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测试代码：
User u = new User();
sess.insert("users.insert" , u) ;
5、关联关系
5.1 多对一关联
5.1.1 保存
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创建订单表，并设置外键约束
-- 创建表 mysql>create table orders(id int primary key auto_increment, orderno varchar(20) , price float , cid int); -- 添加外键约束 mysql>alter table orders add constraint foreign key fk_cid_user_id (cid) REFERENCES users (id) ; -
创建Order类
/** * 订单类 */ public class Order { private Integer id ; private String orderNo ; private float price ; //建立多对一关联关系 private User user ; //get/set }
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创建映射文件
[OrderMapper.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"> <!-- 定义名字空间 --> <mapper namespace="orders"> <insert id="insert"> insert into orders(orderno , price , cid) values(#{orderNo} ,#{price} , #{user.id}) </insert> </mapper> -
API
User u = new User(); u.setId(2); Order o = new Order(); o.setOrderNo("no001"); o.setPrice(2000); //设置关联关系 o.setUser(u); sess.insert("orders.insert" , o) ;
5.5.2 查询
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修改映射文件
[OrderMapper.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"> <!-- 定义名字空间 --> <mapper namespace="orders"> <insert id="insert"> insert into orders(orderno , price , cid) values(#{orderNo} ,#{price} , #{user.id}) </insert> <select id="selectOne" resultMap="rmOrder"> select o.id oid , o.orderno oorderno, o.price oprice , u.id uid , u.name uname , u.age uage from orders o left outer join users u on o.cid = u.id where o.id = #{id} </select> <!-- 定义结果映射，将字段和类属性关联在一起 --> <resultMap id="rmOrder" type="_Order"> <id column="oid" property="id"/> <result column="oorderno" property="orderNo" /> <result column="oprice" property="price" /> <association property="user" javaType="_User" column="uid"> <id column="uid" property="id"/> <result column="uname" property="name" /> <result column="uage" property="age" /> </association> </resultMap> </mapper>
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API查询
sess.selectOne("orders.selectOne" , 3) ;
5.2 一对多关联
一对多关联使用collection集合方法进行关联，表示one方有多个many实例。
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修改User类，添加orders集合属性
class User{ ... private List<Order> orders = new ArrayList<Order>() ; //get/set }
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修改UserMapper.xml文件
<?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"> <!-- 定义名字空间 --> <mapper namespace="users"> <!-- 定义insert语句 ,获得生成的id字段--> <insert id="insert" useGeneratedKeys="true" keyProperty="id"> insert into users(name,age) values(#{name},#{age}) </insert> <update id="update"> update users set name = #{name} , age = #{age} where id = #{id} </update> <delete id="delete"> delete from users where id = #{id} </delete> <select id="selectById" resultMap="rmUser"> SELECT u.id uid, u.name uname, u.age uage , o.id oid , o.orderno oorderno , o.price oprice from users u left OUTER join orders o on o.cid = u.id WHERE u.id = #{id} </select> <select id="selectAll" resultType="_User"> select * from users </select> <!-- 用户映射 --> <resultMap id="rmUser" type="_User"> <id column="uid" property="id" /> <result column="uname" property="name" /> <result column="uage" property="age"/> <collection property="orders" ofType="_Order" column="uid"> <id column="oid" property="id" /> <result column="oorderno" property="orderNo" /> <result column="oprice" property="price"/> </collection> </resultMap> </mapper>
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测试用例
sess.selectOne("users.selectById" , 2) ;
5.3 三级多对一关联
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引入OrderItem（订单项）类
class OrderItem{ private Integer id ; private String iname ; private Order order ; //get/set } -
设置Order到OrderItem之间的关联
class Order{ //toOne private User user ; //toMany private List<OrderItem> items = new ArrayList<OrderItem>() ; } class User{ ... private List<Order> orders = new ArrayList<Order>() ; }
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编写映射文件
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查询Order
[OrderMapper.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"> <!-- 定义名字空间 --> <mapper namespace="orders"> <insert id="insert" useGeneratedKeys="true" keyProperty="id"> insert into orders(orderno , price , cid) values(#{orderNo} ,#{price} , #{user.id}) </insert> <select id="selectOne" resultMap="rmOrder"> select o.id oid , o.orderno oorderno, o.price oprice, u.id uid , u.name uname , u.age uage , i.id iid , i.iname iiname from orders o left outer join users u on o.cid = u.id left outer join orderitems i on i.oid = o.id where o.id = #{id} </select> <resultMap id="rmOrder" type="_Order"> <id column="oid" property="id"/> <result column="oorderno" property="orderNo" /> <result column="oprice" property="price" /> <association property="user" javaType="_User" column="uid"> <id column="uid" property="id"/> <result column="uname" property="name" /> <result column="uage" property="age" /> </association> <collection property="items" ofType="_Item" column="oid"> <id column="iid" property="id" /> <result column="iiname" property="iname" /> </collection> </resultMap> </mapper> -
查询OrderItem
[OrderItem.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"> <!-- 定义名字空间 --> <mapper namespace="orderitems"> <insert id="insert" useGeneratedKeys="true" keyProperty="id"> insert into orderitems(iname, oid) values(#{iname} ,#{order.id}) </insert> <select id="selectOne" resultMap="rmItem"> select o.id oid , o.orderno oorderno, o.price oprice, u.id uid , u.name uname , u.age uage , i.id iid , i.iname iiname from orderitems i left outer join orders o on i.oid = o.id left outer join users u on o.cid = u.id where i.id = #{id} ; </select> <resultMap id="rmItem" type="_Item"> <id column="iid" property="id" /> <result column="iiname" property="iname"/> <association property="order" column="oid" javaType="_Order"> <id column="oid" property="id"/> <result column="oorderno" property="orderNo"/> <result column="oprice" property="price"/> <association property="user" column="uid" javaType="_User"> <id column="uid" property="id" /> <result column="uname" property="name"/> <result column="uage" property="age" /> </association> </association> </resultMap> </mapper> -
查询User
[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"> <!-- 定义名字空间 --> <mapper namespace="users"> <!-- 定义insert语句 ,获得生成的id字段--> <insert id="insert" useGeneratedKeys="true" keyProperty="id"> insert into users(name,age) values(#{name},#{age}) </insert> <update id="update"> update users set name = #{name} , age = #{age} where id = #{id} </update> <delete id="delete"> delete from users where id = #{id} </delete> <select id="selectById" resultMap="rmUser"> select o.id oid , o.orderno oorderno, o.price oprice, u.id uid , u.name uname , u.age uage , i.id iid , i.iname iiname from users u left outer join orders o on o.cid = u.id left outer join orderitems i on i.oid = o.id where u.id = #{id} </select> <select id="selectAll" resultType="_User"> select * from users </select> <!-- 用户映射 --> <resultMap id="rmUser" type="_User"> <id column="uid" property="id" /> <result column="uname" property="name" /> <result column="uage" property="age"/> <collection property="orders" ofType="_Order" column="uid"> <id column="oid" property="id" /> <result column="oorderno" property="orderNo" /> <result column="oprice" property="price"/> <collection property="items" ofType="_Item" column="oid"> <id column="iid" property="id"/> <result column="iiname" property="iname" /> </collection> </collection> </resultMap> </mapper>
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5.4 多对一自关联
区域信息时典型的自关联信息，自己和自己进行关联。
5.4.1 表结构
| id | areaname | parentid |
|---|---|---|
| 1 | 全国 | NULL |
| 2 | 河北 | 1 |
| 3 | 河南 | 1 |
| 4 | 保定 | 2 |
5.4.2 类设计
public class Area {
private Integer id ;
private String areaName ;
private Area parentArea ;
private List<Area> children = new ArrayList<Area>();
//get/set
}
5.4.3 映射方式
<?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">
<!-- 定义名字空间 -->
<mapper namespace="areas">
<insert id="insert" useGeneratedKeys="true" keyProperty="id">
insert into areas(areaname, pid) values(#{areaName} , #{parentArea.id})
</insert>
<select id="selectOne" resultMap="rmArea">
select
a.id aid ,
a.areaname aareaname ,
b.id bid ,
b.areaname bareaname ,
c.id cid ,
c.areaname careaname
from
areas a
left OUTER join areas b on b.pid = a.id
left OUTER join areas c on c.pid = b.id
WHERE
a.id = #{id}
</select>
<resultMap id="rmArea" type="_Area">
<id column="aid" property="id"/>
<result column="aareaname" property="areaName" />
<collection property="children" ofType="_Area" column="aid">
<id column="bid" property="id" />
<result column="bareaname" property="areaName"/>
<collection property="children" ofType="_Area" column="bid">
<id column="cid" property="id" />
<result column="careaname" property="areaName" />
</collection>
</collection>
</resultMap>
</mapper>
5.5 一对一关联
5.5.1 主键关联
主键关联是一张表的主键和另一张表保持一致，因从属表的主键也是外键。
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表结构
[husbands_pk]
id(主键) name ... 1 tom . 2 tomas . 3 tomasLee . [wifes_pk]
id(主键，外键) name ... 1 jerry . 2 jerry2 . 3 jerry3 . -
类设计
public class Husband { private Integer id ; private String hname ; private Wife wife ; } public class Wife { private Husband husband ; private String wname ; }
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映射方式
[HusbandPKMapper.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"> <!-- 定义名字空间 --> <mapper namespace="husbands"> <insert id="insert" useGeneratedKeys="true" keyProperty="id"> insert into husbands(hname) values(#{hname}) </insert> <select id="selectOne" resultMap="rmHusband"> select h.id hid , h.hname hhname , w.wname wwname from husbands h left OUTER join wifes w on w.hid = h.id WHERE h.id = #{id} </select> <resultMap id="rmHusband" type="_Husband"> <id column="hid" property="id" /> <result column="hhname" property="hname"/> <association property="wife" javaType="_Wife" column="hid"> <result column="wwname" property="wname" /> <association property="husband" column="hid" javaType="_Husband"> <id column="hid" property="id" /> <result column="hhname" property="hname"/> </association> </association> </resultMap> </mapper>
[WifePKMapper.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"> <!-- 定义名字空间 --> <mapper namespace="wifes"> <insert id="insert"> insert into wifes(hid, wname) values(#{husband.id} , #{wname}) </insert> </mapper>
5.5.2 外键关联
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表结构
[husbands_fk]
id(主键) name .. 1 tom . 2 3 [wifes_fk]
id(主键) name hid(外键，唯一约束) 1 1 2 2 3 3
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类设计
public class HusbandFK { private Integer id ; private String hname ; private WifeFK wife ; } public class WifeFK { private Integer id ; private String wname ; private HusbandFK husband ; }
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映射关系
[HusbandFKMapper.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"> <!-- 定义名字空间 --> <mapper namespace="husbands_fk"> <insert id="insert" useGeneratedKeys="true" keyProperty="id"> insert into husbands_fk(hname) values(#{hname}) </insert> </mapper>
[WifeFKMapper.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"> <!-- 定义名字空间 --> <mapper namespace="wifes_fk"> <insert id="insert" useGeneratedKeys="true" keyProperty="id"> insert into wifes_fk(wname, hid) values(#{wname} , #{husband.id}) </insert> </mapper>
5.6 多对多关系
多对多关系需要引入中间表，使用联合主键分别和两端的表进行关联，典型是师生表。
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准备表结构
-- 教师表 create table teas(id int primary key auto_increment, tname varchar(20)) ; -- 学生表 create table stus(id int primary key auto_increment, sname varchar(20)) ; -- 关联表,联合主键，双外键引用 create table links(tid int , sid int , primary key (tid,sid) , foreign key (tid) references teas (id) , foreign key (sid) references stus (id)) ; -
类设计
public class Teacher { private Integer id ; private String tname ; private List<Student> stus = new ArrayList<Student>() ; } public class Student { private Integer id ; private String sname ; private List<Teacher> teas = new ArrayList<Teacher>() ; }
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映射方式
插入数据需要包含循环操作，且要设置运行执行多条语句。
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TeacherMapper.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"> <!-- 定义名字空间 --> <mapper namespace="teas"> <insert id="insert" useGeneratedKeys="true" keyProperty="id"> insert into teas(tname) values(#{tname}) </insert> <!-- 循环插入关系表 --> <insert id="insertLink"> <foreach collection="stus" item="s"> insert into links(tid,sid) values(#{id} , #{s.id}) ; </foreach> </insert> <select id="selectOne" resultMap="rmTeacher"> select t.id tid , t.tname ttname , s.id sid , s.sname ssname from teas t left outer join links l on l.tid = t.id left outer join stus s on l.sid = s.id WHERE t.id = #{id} </select> <resultMap id="rmTeacher" type="_Teacher"> <id column="tid" property="id"/> <result column="ttname" property="tname"/> <collection property="stus" ofType="_Student" column="tid"> <id column="sid" property="id" /> <result column="ssname" property="sname"/> </collection> </resultMap> </mapper>
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配置执行多条语句
[mybatis-config.xml]
... <property name="url" value="jdbc:mysql://localhost:3306/big12?allowMultiQueries=true"/> ...
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