1 映射文件XXMapper.xml语法：
<mapper namespace="cn.kgc.mspper.UserMapper">
<select id=" findCount " …
……
</select>
</mapper>
1.1 namespace：命名空间
namespace的命名必须跟某个接口同名
1.2 id: 命名空间中唯一的标识符**
接口中的方法与映射文件中的SQL语句id一一对应
1.3 parameterType: 参数类型
（单参可以省略，多参不可以）
传入SQL语句的参数类型
1.4 resultType：返回值类型
SQL语句返回值类型的完整类名或别名
1.5 实战：
需求： 根据用户名对用户表进行模糊查询
1.6 实现：
(1)导入库 smbms_db.sql
(2)创建工程,目录
(3)pom.xml
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.20</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.1</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.21</version>
</dependency>
(4)实体类 main/java/cn.kgc.entity/User
package cn.kgc.entity;
import lombok.AllArgsConstructor;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;
@Getter
@Setter
public class User {
private Integer id;
private String userCode;
private String userName;
private String userPassword;
private Integer gender;
private String birthday;
private String phone;
private String address;
private Integer userRole;
private String creationDate;
private Integer modifyBy;
private String modifyDate;
}
(5)resources/ mybatis-config.xml、jdbc.properties
jdbc.properties
driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/smbms?characterEncoding=utf8&useSSL=false&serverTimezone=UTC&rewriteBatchedStatements=true
username=root
password=zjj
mybatis-config.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
PUBLIC "-//ibatis.apache.org//DTD Config 3.0//EN"
"http://ibatis.apache.org/dtd/ibatis-3-config.dtd">
<configuration>
<properties resource="jdbc.properties" />
<settings>
<setting name="logImpl" value="STDOUT_LOGGING"/>
</settings>
<environments default="dev">
<environment id="dev">
<transactionManager type="JDBC"></transactionManager>
<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="cn/kgc/mapper/UserMapper.xml"/>
</mappers>
</configuration>
(6) main/java/cn.kgc.mapper/UserMapper.java
package cn.kgc.mapper;
import cn.kgc.entity.User;
import org.apache.ibatis.annotations.Param;
import java.util.List;
import java.util.Map;
public interface UserMapper {
//查询记录数
Integer findCount();
}
(7) resources/ cn.kgc.mapper/UserMapper.xml
注意 : resources里创建包直接这样写 cn/kgc/mapper
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="cn.kgc.mapper.UserMapper">
<select id="findCount" resultType="java.lang.Integer" >
select count(*) from smbms_user
</select>
</mapper>
(8) main/java/cn.kgc.util/MyBatisUtil
package cn.kgc.util;
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;
public class MyBatisUtil {
private static SqlSessionFactory factory = null;
static {
try {
InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
factory = new SqlSessionFactoryBuilder().build(in);
} catch (IOException e) {
e.printStackTrace();
}
}
public static SqlSession getSqlSession(){
SqlSession sqlSession = null;
if (factory != null){
sqlSession = factory.openSession();
}
return sqlSession;
}
}
(9) test/java/cn.kgc.test/TestUserMapper.java
package cn.kgc.test;
import cn.kgc.entity.User;
import cn.kgc.mapper.UserMapper;
import cn.kgc.util.MyBatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class TestUserMapper {
@Test
public void testFindCount(){
SqlSession sqlSession = MyBatisUtil.getSqlSession();
Integer count = sqlSession.getMapper(UserMapper.class).findCount();
System.out.println("记录数："+count);
sqlSession.close();
}
}
1.7 parameterType 基础数据类型/复杂数据类型
parameterType
(1)基础数据类型:
int、String、Date等
只能传入一个，通过#{参数名}即可获取传入的值
(2)复杂数据类型:
Java实体类、Map等
通过#{属性名}或者#{map的keyName}即可获取传入值
1.8 多参实战：
需求：通过用户名模糊匹配和用户角色id 条件查询
1.9第1-3种实现：
(1)UserMapper.java
//1.通过用户名和用户角色查询列表
List<User> findByUser(User user);
//2.通过用户mine和用户角色Map容器参数查询列表
List<User> findByMap(Map<String,Object> map);
//3.通过注解方式实现多参查询
List<User> findByConditions(@Param("name") String userName,@Param("role") Integer userRole);
(2)UserMapper.xml
<select id="findByUser" resultType="cn.kgc.entity.User" parameterType="cn.kgc.entity.User">
select * from smbms_user where userName like concat('%',#{userName},'%')
and userRole = #{userRole}
</select>
<select id="findByMap" resultType="cn.kgc.entity.User" parameterType="java.util.Map">
-- MyBatis的Aliase配置 可以省略 cn.kgc.entity
select * from smbms_user where userName like concat('%',#{userName},'%')
and userRole = #{userRole}
</select>
<select id="findByConditions" resultType="cn.kgc.entity.User" >
select * from smbms_user where userName like concat('%',#{name},'%')
and userRole = #{role}
</select>
(3)TestUserMapper
@Test
public void testFindByUser(){
SqlSession sqlSession = MyBatisUtil.getSqlSession();
User user = new User();
user.setUserName("王");
user.setUserRole(3);
List<User> list = sqlSession.getMapper(UserMapper.class).findByUser(user);
for (User u: list) {
System.out.println("userName：" + u.getUserName() + " userPassword：" + u.getUserPassword());
}
//数据库里时间有个0000000 可能会报错 脏数据，记得改掉
sqlSession.close();
}
@Test
public void testFindByMap(){
SqlSession sqlSession = MyBatisUtil.getSqlSession();
Map<String, Object> map = new HashMap<>();
map.put("userName","孙");
map.put("userRole",3);
List<User> list = sqlSession.getMapper(UserMapper.class).findByMap(map);
for (User u: list) {
System.out.println("userName：" + u.getUserName() + " userPassword：" + u.getUserPassword());
}
sqlSession.close();
}
@Test
public void findByConditions(){
SqlSession sqlSession = MyBatisUtil.getSqlSession();
List<User> list = sqlSession.getMapper(UserMapper.class).findByConditions("孙",3);
for (User u: list) {
System.out.println("userName：" + u.getUserName() + " userPassword：" + u.getUserPassword());
}
sqlSession.close();
}
1.10 resultMap 描述如何将结果集映射到Java对象
(面试题)
**resultType ：**直接表示返回类型
基本数据类型
复杂数据类型
**resultMap ：**对外部resultMap的引用
应用场景：
数据库字段信息与对象属性不一致
复杂的联合查询，*控制映射结果
二者不能同时存在，本质上都是Map数据结构
1.11 通过用户名和角色编码查询用户列表
(1)User.java
private String userRoleName;
(2)UserMapper.java
//ResultMap实战
List<User> FindByResultMap(User user);
(3)UserMapper.xml
<select id="FindByResultMap" parameterType="cn.kgc.entity.User" resultMap="userList">
select a.id,a.userCode,b.roleName from smbms_user a,smbms_role b where a.userRole = b.id
and userName like concat('%',#{userName},'%')
and userRole = #{userRole}
-- select a.id,a.userCode,b.roleName from smbms_user a left join smbms_role b on a.userRole = b.id
-- and userName like concat('%',#{userName},'%')
-- and userRole = #{userRole}
</select>
<resultMap id="userList" type="cn.kgc.entity.User">
<result property="id" column="id"></result>
<result property="userCode" column="userCode"></result>
<result property="userRoleName" column="roleName"></result>
</resultMap>
<!-- 不用上述方法，就用别名as 上述方法针对杠精 id因为两个一样-->
(4)TestUserMapper.java
@Test
public void findByConditions2(){
SqlSession sqlSession = MyBatisUtil.getSqlSession();
User user = new User();
user.setUserName("王");
user.setUserRole(3);
List<User> list = sqlSession.getMapper(UserMapper.class).FindByResultMap(user);
for (User u: list) {
System.out.println("用户id:" + u.getId() + " 用户编码：" + u.getUserCode() + " 角色名称：" + u.getUserRoleName());
}
sqlSession.close();
}
2.增删改（Mybatis (一) 有讲过）
核心注意点：
insert、update、delete元素均没有resultType属性
但是都要有sqlSession.commit();
(1)实现用户表的增加操作（省略）
(2)实现用户表的修改操作（省略）
(3)实现修改当前用户密码的功能-@Param（省略）
核心思想：超过三个参数建议封装成对象，两个参数建议使用@Param
用注解就不用写参数
(4)根据用户id删除用户信息（省略）
3.resultMap
核心思想
id
一般对应数据库中该行的主键id，设置此项可提高MyBatis性能
result
映射到JavaBean的某个“简单类型”属性
association
映射到JavaBean的某个“复杂类型”属性，比如JavaBean类
collection
映射到JavaBean的某个“复杂类型”属性，比如集合
(1)根据用户角色id获取用户列表-association
A.核心思想：
association
复杂的类型关联，一对一
内部嵌套
映射一个嵌套JavaBean属性
属性
property：映射数据库列的实体对象的属性
javaType：完整Java类名或者别名
resultMap：引用外部resultMap
子元素
id
result
property：映射数据库列的实体对象的属性
column：数据库列名或者别名
B.实战：
利用User-Role实现查询用户列表
根据smbms_user 里的userRole
去对应的smbms_role对应的id
然后查出对应的roleName
Role:
package cn.kgc.entity;
import lombok.Getter;
import lombok.Setter;
import java.util.Date;
@Getter
@Setter
public class Role {
private Integer id;
private String roleCode;
private String roleName;
private Integer createdBy;
private Date creationDate;
private Integer modifyBy;
private Date modifyDate;
}
User
private Role role;
UserMapper
//利用User-Role实现查询用户列表
List<User> findUserRole(Integer userRole);
UserMapper.xml
<select id="findUserRole" parameterType="java.lang.Integer" resultMap="userRoleResult">
SELECT a.id,a.userCode,b.roleName FROM smbms_user a,smbms_role b
WHERE a.userRole = b.id AND a.userRole = #{userRole}
</select>
<!-- resultMap 将查询到的复杂数据（比如查询到几个表中数据）映射到一个结果集当中。-->
<!-- 映射User类的结果集-->
<!-- resultMap最终还是要将结果映射到User上，type就是指定映射到哪一个User -->
<!-- property：主键在pojo中的属性名 -->
<!-- column：主键在数据库中的列名 -->
<resultMap id="userRoleResult" type="cn.kgc.entity.User">
<id property="id" column="id"></id>
<result property="userCode" column="userCode"></result>
<!-- association映射关联对象Role的结果集-->
<association property="role" javaType="cn.kgc.entity.Role">
<result property="roleName" column="roleName"></result>
</association>
</resultMap>
TestUserMapper
@Test
public void findUserRole() {
SqlSession sqlSession = MyBatisUtil.getSqlSession();
List<User> userRole = sqlSession.getMapper(UserMapper.class).findUserRole(1);
for (User u: userRole) {
System.out.println(
"Id：" + u.getId() + " Code：" + u.getUserCode() + " RoleName:" + u.getRole().getRoleName());
}
sqlSession.close();
}
结果：
(2)获取指定用户的相关信息及其地址列表-collection
A核心思想：
collection
复杂类型集合，一对多
内部嵌套
映射一个嵌套结果集到一个列表
属性
property：映射数据库列的实体对象的属性
ofType：完整Java类名或者别名(集合所包括的类型)
resultMap：引用外部resultMap
子元素
id
result
property：映射数据库列的实体对象的属性
column：数据库列名或者别名
B实战:
collection实现查询用户地址集合列表
根据smbms_user的id
去对应smbms_address里的userId
其中用户地址可能不止一个
Address.java
package cn.kgc.entity;
import lombok.Getter;
import lombok.Setter;
import java.util.Date;
@Getter
@Setter
public class Address {
private Integer id;
private String contact;
private String addressDesc;
private String postCode;
private String tel;
private Integer createdBy;
private Date creationDate;
private Integer modifyBy;
private Date modifyDate;
private Integer userId;
}
User.java
private List<Address> addressList;
UserMapper.java
//collection实现查询用户地址集合列表
List<User> findUserAddressListById(@Param("id") Integer id);
UserMapper.xml
<select id="findUserAddressListById" resultMap="UserAddressResult">
select a.id,a.userCode,b.addressDesc from smbms_user a ,smbms_address b
where a.id = b.userid
and a.id = #{id}
</select>
<resultMap id="UserAddressResult" type="cn.kgc.entity.User">
<id property="id" column="id"></id>
<result property="userCode" column="userCode"></result>
<collection property="addressList" ofType="cn.kgc.entity.Address">
<result property="addressDesc" column="addressDesc" />
</collection>
</resultMap>
TestUserMapper
@Test
public void findUserAddressListById() {
SqlSession sqlSession = MyBatisUtil.getSqlSession();
List<User> userRole = sqlSession.getMapper(UserMapper.class).findUserAddressListById(1);
for (User u: userRole) {
System.out.println("userId：" + u.getId() + " userCode：" + u.getUserCode());
List<Address> addressList = u.getAddressList();
for (Address a :addressList){
System.out.println(" addressDesc:" + a.getAddressDesc());
}
}
sqlSession.close();
}
题外话：
shift + alt + \ 能显示时间
----2021.11.30&12.01