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Mybatis20_mybatis注解开发9

一、Mybatis的常用注解

　这几年来注解开发越来越流行，Mybatis也可以使用注解开发方式，这样我们就可以减少编写Mapper映射文件了。我们先围绕一些基本的CRUD来学习，再学习复杂映射多表操作。

　　@Insert：实现新增
　　@Update：实现更新
　　@Delete：实现删除
　　@Select：实现查询
　　@Result：实现结果集封装
　　@Results：可以与@Result 一起使用，封装多个结果集
　　@One：实现一对一结果集封装
　　@Many：实现一对多结果集封装

二、xml完成基本的crud（Mybatis的增删改查）

　　

　　User.java

复制代码
package com.itheima.domain;

import java.util.Date;

public class User {

    private int id;
    private String username;
    private String password;
    private Date birthday;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", birthday=" + birthday +
                '}';
    }
}
复制代码

　　UserMapper.java

复制代码
package com.itheima.mapper;

import com.itheima.domain.User;
import java.util.List;

public interface UserMapper {

    public void save(User user);
    public void update(User user);
    public void delete(int id);
    public User findById(int id);
    public List<User> findAll();

}
复制代码

　　UserMapper.xml

复制代码
<?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.itheima.mapper.UserMapper">

    <insert id="save" parameterType="user">
        insert into user values(#{id},#{username},#{password},#{birthday})
    </insert>

    <update id="update" parameterType="user">
        update user set username=#{username},password=#{password} where id=#{id}
    </update>

    <delete id="delete" parameterType="int">
        delete from user where id=#{id}
    </delete>

    <select id="findById" parameterType="int" resultType="user">
        select * from user where id=#{id}
    </select>

    <select id="findAll" resultType="user">
        select * from user
    </select>
</mapper>
复制代码

　　jdbc.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/test
jdbc.username=root
jdbc.password=root

　　log4j.properties

复制代码
### direct log messages to stdout ###
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.out
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n

### direct messages to file mylog.log ###
log4j.appender.file=org.apache.log4j.FileAppender
log4j.appender.file.File=c:/mylog.log
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n

### set log levels - for more verbose logging change 'info' to 'debug' ###

log4j.rootLogger=debug, stdout
复制代码

　　sqlMapConfg.xml

复制代码
<?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>
    <!--通过properties标签加载外部properties文件-->
    <properties resource="jdbc.properties"/>

    <!--定义别名-->
    <typeAliases>
        <typeAlias type="com.itheima.domain.User" alias="user"/>
    </typeAliases>

    <!--数据源环境-->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>

    <!--加载映射文件-->
    <mappers>
        <mapper resource="com/itheima/mapper/UserMapper.xml"/>
    </mappers>
</configuration>
复制代码

　　MybatisTest.java

复制代码
package com.itheima.test;

import com.itheima.domain.User;
import com.itheima.mapper.UserMapper;
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 org.junit.Before;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class MybatisTest {

    private UserMapper mapper;

    @Before
    public void before() throws IOException {
        InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        mapper = sqlSession.getMapper(UserMapper.class);
    }

    @Test
    public void testSave(){
        User user = new User();
        user.setUsername("tom");
        user.setPassword("abc");
        mapper.save(user);
    }

    @Test
    public void testUpdate(){
        User user = new User();
        user.setId(3);
        user.setUsername("lucy");
        user.setPassword("123");
        mapper.update(user);
    }

    @Test
    public void testDelete(){
        mapper.delete(3);
    }

    @Test
    public void testFindById(){
        User user = mapper.findById(2);
        System.out.println(user);
    }

    @Test
    public void testFindAll(){
        List<User> userList = mapper.findAll();
        for (User user : userList) {
            System.out.println(user);
        }
    }

}
复制代码

　执行测试各个测试方法，可以执行成功。

三、注解完成基本的crud

　修改UserMapper.java

复制代码
package com.itheima.mapper;

import com.itheima.domain.User;
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 java.util.List;

public interface UserMapper {

    @Insert("insert into user values(#{id},#{username},#{password},#{birthday})")
    public void save(User user);

    @Update("update user set username=#{username},password=#{password} where id=#{id}")
    public void update(User user);

    @Delete("delete from user where id=#{id}")
    public void delete(int id);

    @Select("select * from user where id=#{id}")
    public User findById(int id);

    @Select("select * from user")
    public List<User> findAll();

}
复制代码

　删除resources的映射文件UserMapper.xml

　修改sqlMapConfig.xml核心配置文件，我们使用了注解替代的映射文件，所以我们只需要加载使用了注解的Mapper接口即可

复制代码
<?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>
    <!--通过properties标签加载外部properties文件-->
    <properties resource="jdbc.properties"/>

    <!--定义别名-->
    <typeAliases>
        <typeAlias type="com.itheima.domain.User" alias="user"/>
    </typeAliases>

    <!--数据源环境-->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>

    <!--加载映射文件-->
    <!--<mappers>-->
        <!--<mapper resource="com/itheima/mapper/UserMapper.xml"/>-->
    <!--</mappers>-->

    <!--加载映射关系 -->
    <mappers>
        <!--指定接口所在的包，扫描使用注解的类所在的包-->
        <package name="com.itheima.mapper"></package>
    </mappers>
</configuration>
复制代码

　执行MybatisTest中的测试方法，仍旧能成功。

四、Mybatis的注解实现复杂映射开发

　实现复杂关系映射之前我们可以在映射文件中通过配置<resultMap>来实现，使用注解开发后，我们可以使用@Results注解，@Result注解，@One注解，@Many注解组合完成复杂关系的配置

　 

五、一对一的注解开发

　使用上一篇（mybatis的多表操作8 ）中的场景、数据库表和实体。

　　用户表和订单表的关系为，一个用户有多个订单，一个订单只从属于一个用户

　　一对一查询的需求：查询一个订单，与此同时查询出该订单所属的用户

　Order.java同上一篇

　OrderMapper.java

复制代码
package com.itheima.mapper;

import com.itheima.domain.Order;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;
import java.util.List;

public interface OrderMapper {

    @Select("select *,o.id oid from orders o,user u where o.uid=u.id")
    @Results({
            @Result(column = "oid",property = "id"),
            @Result(column = "ordertime",property = "ordertime"),
            @Result(column = "total",property = "total"),
            @Result(column = "uid",property = "user.id"),
            @Result(column = "username",property = "user.username"),
            @Result(column = "password",property = "user.password"),
    })
    public List<Order> findAll();
}
复制代码

　　或者是(下面这种方法用的比较多)

　　　　对应的sql语句：

　　　　select * from orders;

　　　　select * from user where id=查询出订单的uid;

复制代码
package com.itheima.mapper;

import com.itheima.domain.Order;
import com.itheima.domain.User;
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 OrderMapper {

    @Select("select * from orders")
    @Results({
            @Result(column = "id", property = "id"),
            @Result(column = "ordertime", property = "ordertime"),
            @Result(column = "total",property = "total"),
            @Result(
                    property = "user",//要封装的属性名称
                    column = "uid",//根据哪个字段去查询user表的数据
                    javaType = User.class,//要封装的实体类型
                    //select属性   代表查询哪个接口的方法获得数据
                    one = @One(select = "com.itheima.mapper.UserMapper.findById")
            ),

    })
    public List<Order> findAll();
}
复制代码

　MybatisTest2.java

复制代码
package com.itheima.test;

import com.itheima.domain.Order;
import com.itheima.mapper.OrderMapper;
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 org.junit.Before;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class MybatisTest2 {

    private OrderMapper mapper;

    @Before
    public void before() throws IOException {
        InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        mapper = sqlSession.getMapper(OrderMapper.class);
    }

    @Test
    public void testFindAll(){
        List<Order> orderList = mapper.findAll();
        for (Order order : orderList) {
            System.out.println(order);
        }
    }

}
复制代码

　　执行testFindAll方法，查看控制台打印结果：

Order{id=1, ordertime=Wed Dec 12 00:00:00 CST 2018, total=3000.0, user=User{id=1, username='lucy', password='123', birthday=null}}
Order{id=2, ordertime=Wed Dec 12 00:00:00 CST 2018, total=4000.0, user=User{id=1, username='lucy', password='123', birthday=null}}
Order{id=3, ordertime=Wed Dec 12 00:00:00 CST 2018, total=5000.0, user=User{id=2, username='haohao', password='123', birthday=null}}

六、一对多的注解开发

　用户表和订单表的关系为，一个用户有多个订单，一个订单只从属于一个用户

　一对多查询的需求：查询一个用户，与此同时查询出该用户具有的订单

　对应的sql语句：

　　select * from user;
　　select * from orders where uid=查询出用户的id;

　User.java

复制代码
package com.itheima.domain;

import java.util.Date;
import java.util.List;

public class User {

    private int id;
    private String username;
    private String password;
    private Date birthday;

    //描述的是当前用户存在哪些订单
    private List<Order> orderList;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public List<Order> getOrderList() {
        return orderList;
    }

    public void setOrderList(List<Order> orderList) {
        this.orderList = orderList;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", birthday=" + birthday +
                ", orderList=" + orderList +
                '}';
    }
}
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　OrderMapper.java

复制代码
package com.itheima.mapper;

import com.itheima.domain.Order;
import com.itheima.domain.User;
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 OrderMapper {

    @Select("select * from orders where uid=#{uid}")
    public List<Order> findByUid(int uid);
}
复制代码

　UserMapper.java

复制代码
package com.itheima.mapper;

import com.itheima.domain.User;
import org.apache.ibatis.annotations.*;

import java.util.List;

public interface UserMapper {

    @Select("select * from user")
    @Results({
            @Result(id = true,column = "id",property = "id"),
            @Result(column = "username",property = "username"),
            @Result(column = "password",property = "password"),
            @Result(
                    column = "id",
                    property = "orderList",
                    javaType = List.class,
                    many = @Many(select = "com.itheima.mapper.OrderMapper.findByUid")
            )
    })
    public List<User> findUserAndOrderAll();

}
复制代码

　MyBatisTest.java新增测试方法

    @Test
    public void testFindUserAndOrderAll(){
        List<User> userAndOrderAll = mapper.findUserAndOrderAll();
        for (User user : userAndOrderAll) {
            System.out.println(user);
        }
    }

　执行此测试方法，查看控制台打印结果：

User{id=1, username='lucy', password='123', birthday=Wed Dec 12 00:00:00 CST 2018, orderList=[Order{id=1, ordertime=Wed Dec 12 00:00:00 CST 2018, total=3000.0, user=null}, Order{id=2, ordertime=Wed Dec 12 00:00:00 CST 2018, total=4000.0, user=null}]}
User{id=2, username='haohao', password='123', birthday=Thu Dec 12 00:00:00 CST 2019, orderList=[Order{id=3, ordertime=Wed Dec 12 00:00:00 CST 2018, total=5000.0, user=null}]}

七、多对多的注解开发

　用户表和角色表的关系为，一个用户有多个角色，一个角色被多个用户使用

　多对多查询的需求：查询用户同时查询出该用户的所有角色

　对应的sql语句：

　　　select * from user;
　　　select * from sys_role r,sys_user_role ur where r.id=ur.roleid and ur.userid=用户的id

　User.java

复制代码
package com.itheima.domain;

import java.util.Date;
import java.util.List;

public class User {

    private int id;
    private String username;
    private String password;
    private Date birthday;

    //描述的是当前用户具备哪些角色
    private List<Role> roleList;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public List<Role> getRoleList() {
        return roleList;
    }

    public void setRoleList(List<Role> roleList) {
        this.roleList = roleList;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", birthday=" + birthday +
                ", roleList=" + roleList +
                '}';
    }
}
复制代码

　Role.java

复制代码
package com.itheima.domain;

public class Role {

    private int id;
    private String roleName;
    private String roleDesc;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getRoleName() {
        return roleName;
    }

    public void setRolename(String roleName) {
        this.roleName = roleName;
    }

    public String getRoleDesc() {
        return roleDesc;
    }

    public void setRoleDesc(String roleDesc) {
        this.roleDesc = roleDesc;
    }

    @Override
    public String toString() {
        return "Role{" +
                "id=" + id +
                ", rolename='" + roleName + '\'' +
                ", roleDesc='" + roleDesc + '\'' +
                '}';
    }

}
复制代码

　RoleMapper.java

复制代码
package com.itheima.mapper;

import com.itheima.domain.Role;
import org.apache.ibatis.annotations.Select;
import java.util.List;

public interface RoleMapper {

    @Select("select * from sys_role r,sys_user_role ur where r.id=ur.roleid and ur.userid=#{uid}")
    public List<Role> findByUid(int uid);

}
复制代码

　UserMapper.java

复制代码
package com.itheima.mapper;

import com.itheima.domain.User;
import org.apache.ibatis.annotations.*;

import java.util.List;

public interface UserMapper {

    @Select("select * from user")
    @Results({
            @Result(id = true,column = "id",property = "id"),
            @Result(id=true,column = "username",property = "username"),
            @Result(id=true,column = "password",property = "password"),
            @Result(
                    column = "id",//user表查询出的id
                    property = "roleList",
                    javaType = List.class,
                    many = @Many(select = "com.itheima.mapper.RoleMapper.findByUid")
            )
    })
    public List<User> findUserAndRoleAll();

}
复制代码

　MybatisTest.java中新增测试方法

    @Test
    public void testFindUserAndRoleAll(){
        List<User> userAndRoleAll = mapper.findUserAndRoleAll();
        for (User user : userAndRoleAll) {
            System.out.println(user);
        }
    }

　　执行测试方法，查看控制台打印结果：

User{id=1, username='lucy', password='123', birthday=Wed Dec 12 00:00:00 CST 2018, roleList=[Role{id=1, rolename='CTO', roleDesc='CTO'}, Role{id=2, rolename='COO', roleDesc='COO'}]}
User{id=2, username='haohao', password='123', birthday=Thu Dec 12 00:00:00 CST 2019, roleList=[Role{id=1, rolename='CTO', roleDesc='CTO'}, Role{id=2, rolename='COO', roleDesc='COO'}]}

 

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