一、整合 MyBatisPlus
1. 导入依赖
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.5.1</version>
</dependency>
2. 配置文件
spring:
datasource:
driver-class-name: com.mysql.cj.jdbc.Driver
url: jdbc:mysql://127.0.0.1:3306/demo?useUnicode=true&characterEncoding=UTF-8
username: root
password: root
mybatis-plus:
# 指定 Mapper XML 文件的位置，使用 classpath 通配符指定路径
mapper-locations: classpath:/mapper/**/*.xml
# 指定实体类的包路径，用于自动扫描并注册类型别名
type-aliases-package: com.cnbai.bean
global-config:
db-config:
id-type: input
# 驼峰下划线转换（将数据库字段的下划线命名规则转换为 Java 实体类属性的驼峰命名规则）
db-column-underline: true
# 刷新 mapper
refresh-mapper: true
configuration:
# 将 Java 实体类属性的驼峰命名规则转换为数据库字段的下划线命名规则
map-underscore-to-camel-case: true
# 查询结果中包含空值的列，在映射的时候，不会映射这个字段
call-setters-on-nulls: true
# 开启 sql 日志
log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
# 关闭 sql 日志
# log-impl: org.apache.ibatis.logging.nologging.NoLoggingImpl
3. 配置类
import com.baomidou.mybatisplus.annotation.DbType;
import com.baomidou.mybatisplus.autoconfigure.MybatisPlusProperties;
import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
@Configuration
public class MybatisPlusConfig {
/**
* 加载分页插件
*/
@Bean
public MybatisPlusInterceptor mybatisPlusInterceptor() {
MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
return interceptor;
}
@Primary
@Bean
@ConfigurationProperties("mybatis-plus")
public MybatisPlusProperties mybatisPlusProperties() {
return new MybatisPlusProperties();
}
}
4. 业务类
public interface UserService extends IService<User> {}
@Service
public class UserServiceImpl extends ServiceImpl<UserDao, User> implements UserService {}
@Mapper
public interface UserDao extends BaseMapper<User> {}
5. 实体类
import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableName;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableField;
import java.io.Serializable;
@TableName(value = "t_user")
public class User implements Serializable {
@TableId(value = "id", type = IdType.INPUT)
private Integer id;
@TableField(value = "name")
private String name;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
二、查询
1. 普通查询
public List<User> queryUserList(String name) {
LambdaQueryWrapper<User> wrapper = new LambdaQueryWrapper<>();
wrapper.eq(User::getName, name);
return list(wrapper);
}
public User queryUserById(String id) {
return getBaseMapper().selectById(id);
}
2. 拼接查询
LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<>();
queryWrapper
.eq(User::getName, "张三")
.eq(User::getAge, 26);
List<User> list = list(queryWrapper);
3. 分页查询
// offset 默认从 1 开始，展示第一页
public Page<User> queryPage(Integer offset, Integer limit) {
return userDao.selectPage(PageDTO.of(offset, limit), new QueryWrapper<>());
}
4. 查询部分字段
public List<User> queryUserList() {
LambdaQueryWrapper<User> wrapper = new LambdaQueryWrapper<>();
wrapper.select(User::getName, User::getAge);
return list(wrapper);
}
三、常用条件构造器
1. 单条件
# name = 'bai'
eq("name", "bai")
2. 拼接 AND
# name = ? AND age = ?
.eq("name", "张三").eq("age", 26);
3. 拼接 OR
# id = 1 or name = 'bai'
.eq("id",1).or().eq("name","bai")
4. 嵌套
# or ( name = '李白' and status <> '活着' )
.or ( x -> x.eq("name", "李白").ne("status", "活着") )
# and ( name = '李白' or ( name = '张三' and age = 12 ) )
.and( x -> x.eq("name", "李白").or( y -> y.eq("name", "张三").eq("age", 12) ) )
四、注解查询
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.ResultType;
import org.apache.ibatis.annotations.Select;
import java.util.List;
@Mapper
public interface UserDao extends BaseMapper<User> {
@Select("select * from t_user where name = #{name}")
@ResultType(User.class)
List<User> getUserListByName(@Param("name") String name);
@Select("select * from t_user where id = #{id}")
@ResultType(User.class)
User getUserById(@Param("id") String id);
@Select("select name from t_user where id = #{id}")
String getUserNameById(@Param("id") String id);
}
五、xml 查询
1. 直接返回查询结果
List<Map<String,Object>> queryUser();
<?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.bai.dao.UserDao">
<select id="queryUser" resultType="java.util.Map">
select * from user
</select>
</mapper>
2. 返回对象集合
List<User> queryUser();
<?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.bai.dao.UserDao">
<select id="queryUser" resultType="User">
select * from user
</select>
</mapper>
3. 返回单个对象
User queryUserById();
<?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.bai.dao.UserDao">
<select id="queryUserById" resultType="User">
select * from user where id = '1'
</select>
</mapper>
4. 返回整型
int queryUserCount();
<?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.bai.dao.UserDao">
<select id="queryUserCount" resultType="java.lang.Integer">
select count(*) from user
</select>
</mapper>
5. 返回字符串集合
List<String> queryUserName();
<?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.bai.dao.UserDao">
<resultMap id="userNameMap" type="java.lang.String">
<result column="name" typeHandler="org.apache.ibatis.type.StringTypeHandler" />
</resultMap>
<select id="queryUserName" resultMap="userNameMap">
select name from user
</select>
</mapper>
六、处理 Json 数据
1. 存储
实体类中某个字段属性是 List，Map 之类的可以转为 Json 格式，其在 MySQL 中存储字段类型可以设置为 Json 类型，添加注解将此类型映射为 Json 存入数据库中
注：插入时可以不定义
autoResultMap = true，查询时必须定义
@TableName(value = "t_user")
public class User {
@TableId
private int id;
@TableField(value = "user_info", typeHandler = JacksonTypeHandler.class)
private JSONArray userInfo;
@TableField(value = "info", typeHandler = JacksonTypeHandler.class)
private JSONObject info;
}
2. 取出
当没有使用到 xml 时
@TableName(value = "t_user", autoResultMap = true)
public class User {
@TableId
private int id;
@TableField(value = "user_info", typeHandler = JacksonTypeHandler.class)
private JSONArray userInfo;
@TableField(value = "info", typeHandler = JacksonTypeHandler.class)
private JSONObject info;
}
当使用了 xml 时
<result property="userInfo" column="user_info" typeHandler="com.baomidou.mybatisplus.extension.handlers.JacksonTypeHandler"/>
<result property="info" column="info" typeHandler="com.baomidou.mybatisplus.extension.handlers.JacksonTypeHandler"/>
七、循环遍历集合
/**
* List : User(id=1, name=zhangsan, age=21)
* List : User(id=2, name=lisi, age=22)
*
* Map : User(id=2, name=lisi, age=22)
* Map : User(id=3, name=wangwu, age=23)
*/
public void queryTest() {
userService.queryByList();
userService.queryByMap();
userService.updateByMap();
userService.updateByList();
}
1. UserService
public class UserService {
@Resource
UserDao userDao;
public void queryByList() {
List<Integer> list = new ArrayList<>();
list.add(1);
list.add(2);
userDao.queryByList(list);
}
public void queryByMap() {
Map<String, Object> map = new HashMap<>();
map.put("name", username);
userDao.queryByMap(map);
}
public void updateByMap() {
Map<Integer, Integer> map = new HashMap<>();
map.put(2, 21);
map.put(3, 31);
userDao.updateByMap(map);
}
public void updateByList() {
List<User> list = new ArrayList<>();
list.add(user1);
list.add(user2);
userDao.updateByList(list);
}
}
2. UserDao
public interface UserDao extends BaseMapper<User> {
// UserMapper.xml 中 collection 的值对应 @Param 里的值
List<User> queryByList(@Param("list") List<Integer> userList);
// 此处不能使用 @Param , 或者不用 Map 直接传参 -> queryByMap(@Param("name") String username);
List<Map<String, Object>> queryByMap(Map<String, Object> map);
void updateByMap(@Param("map") Map<Integer, Integer> map);
void updateByList(@Param("list") List<User> userList);
}
3. UserMapper
<?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.bai.dao.UserDao">
<resultMap id="userMap" type="User">
<id column="id" jdbcType="INTEGER" property="id" />
<result column="name" jdbcType="VARCHAR" property="name" />
<result column="age" jdbcType="INTEGER" property="age" />
</resultMap>
<select id="queryByList" parameterType="java.util.List" resultMap="userMap">
select * from user where
<choose>
<when test="list != null and list.size() > 0">
id in
<foreach collection="list" item="id" open="(" separator="," close=")">
#{id}
</foreach>
</when>
<otherwise>
1 = 2
</otherwise>
</choose>
</select>
<select id="queryByMap" parameterType="java.util.Map" resultType="java.util.Map">
select id, name as username, age from user where
<if test="name != null and name != ''">
name = #{name}
</if>
</select>
<update id="updateByMap" parameterType="java.util.Map">
<foreach collection="map" index="id" item="age" separator=";">
update user set age = #{age} where id = #{id}
</foreach>
</update>
<update id="updateByList" parameterType="java.util.List">
<foreach collection="list" index="index" item="user">
update user set age = #{user.age} where id = #{user.id}
</foreach>
</update>
</mapper>
4. 增加配置参数
Mybatis 批量更新时需要在 url 后加上 &allowMultiQueries=true
application.yml文章来源：https://www.toymoban.com/news/detail-767879.html
spring:
datasource:
username: root
password: root
url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true
driver-class-name: com.mysql.jdbc.Driver
否则会报错文章来源地址https://www.toymoban.com/news/detail-767879.html
org.springframework.jdbc.BadSqlGrammarException:
### Error updating database. Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'update user set age = 1 where id = 3' at line 3
### The error may involve com.bai.faker.mapper.UserMapper.updateByMapThree-Inline
### The error occurred while setting parameters
### SQL: update user set age = ? where id = ? ; update user set age = ? where id = ?
### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'update user set age = 1 where id = 3' at line 3
; bad SQL grammar []; nested exception is com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'update user set age = 1 where id = 3' at line 3
... ...
八、执行 Sql 文件
1. UserService
import com.baomidou.mybatisplus.extension.service.IService;
import javax.sql.DataSource;
import java.io.File;
public interface UserService extends IService<User> {
void executeSqlFile(DataSource dataSource, File sqlFile);
}
2. UserServiceImpl
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import org.springframework.stereotype.Service;
import javax.sql.DataSource;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;
@Service
public class UserServiceImpl extends ServiceImpl<UserDao, User> implements UserService {
@Override
public void executeSqlFile(DataSource dataSource, File sqlFile) {
Connection connection = null;
FileReader reader = null;
Statement statement = null;
try {
connection = dataSource.getConnection();
connection.setAutoCommit(false);
statement = connection.createStatement();
reader = new FileReader(sqlFile);
String line;
int size = 0;
BufferedReader bufferedReader = new BufferedReader(reader);
while ((line = bufferedReader.readLine()) != null) {
if (size % 1000 == 0) {
statement.executeBatch();
connection.commit();
}
statement.addBatch(line);
size++;
}
statement.executeBatch();
connection.commit();
bufferedReader.close();
} catch (Exception e) {
if (connection != null) {
try {
connection.rollback();
} catch (SQLException e1) {
e1.printStackTrace();
}
}
} finally {
try {
if (statement != null) {
statement.close();
}
if (connection != null) {
connection.close();
}
if (reader != null) {
reader.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
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