MyBatisPlus环境搭建的步骤?
<dependency>
<groupId>com.baomidougroupId>
<artifactId>mybatis-plus-boot-starterartifactId>
<version>3.4.1version>
dependency>
<dependency>
<groupId>com.alibabagroupId>
<artifactId>druidartifactId>
<version>1.1.16version>
dependency>
注意事项1:由于mp并未被收录到idea的系统内置配置,无法直接选择加入
注意事项2:如果使用Druid数据源,需要导入对应坐标
(类名与表名对应,属性名与字段名对应)
create database if not exists mybatisplus_db character set utf8;
use mybatisplus_db;
CREATE TABLE user (
id bigint(20) primary key auto_increment,
name varchar(32) not null,
password varchar(32) not null,
age int(3) not null ,
tel varchar(32) not null
);
insert into user values(null,'tom','123456',12,'12345678910');
insert into user values(null,'jack','123456',8,'12345678910');
insert into user values(null,'jerry','123456',15,'12345678910');
insert into user values(null,'tom','123456',9,'12345678910');
insert into user values(null,'snake','123456',28,'12345678910');
insert into user values(null,'张益达','123456',22,'12345678910');
insert into user values(null,'张大炮','123456',16,'12345678910');
public class User {
private Long id;
private String name;
private String password;
private Integer age;
private String tel;
//自行添加getter、setter、toString()等方法
}
spring:
datasource:
type: com.alibaba.druid.pool.DruidDataSource
driver-class-name: com.mysql.cj.jdbc.Driver
url: jdbc:mysql://localhost:3306/mybatisplus_db?serverTimezone=UTC
username: root
password: root
package com.itheima.dao;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.itheima.domain.User;
import org.apache.ibatis.annotations.Mapper;
@Mapper
public interface UserDao extends BaseMapper<User> {
}
package com.itheima;
import com.itheima.dao.UserDao;
import com.itheima.domain.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import java.util.List;
@SpringBootTest
public class Mybatisplus01QuickstartApplicationTests {
@Autowired
private UserDao userDao;
@Test
void testGetAll() {
List<User> userList = userDao.selectList(null);
System.out.println(userList);
}
}
通过入门案例制作,MyBatisPlus的优点有哪些?
MyBatisPlus(简称MP)是基于MyBatis框架基础上开发的增强型工具,旨在简化开发、提高效率
package com.itheima;
import com.itheima.dao.UserDao;
import com.itheima.domain.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import java.util.List;
@SpringBootTest
class Mybatisplus01QuickstartApplicationTests {
@Autowired
private UserDao userDao;
@Test
void testSave() {
User user = new User();
user.setName("黑马程序员");
user.setPassword("itheima");
user.setAge(12);
user.setTel("4006184000");
userDao.insert(user);
}
@Test
void testDelete() {
userDao.deleteById(1401856123725713409L);
}
@Test
void testUpdate() {
User user = new User();
user.setId(1L);
user.setName("Tom888");
user.setPassword("tom888");
userDao.updateById(user);
}
@Test
void testGetById() {
User user = userDao.selectById(2L);
System.out.println(user);
}
@Test
void testGetAll() {
List<User> userList = userDao.selectList(null);
System.out.println(userList);
}
}
有什么简单的办法可以自动生成实体类的GET、SET方法?
<dependency>
<groupId>org.projectlombokgroupId>
<artifactId>lombokartifactId>
<version>1.18.12version>
dependency>
package com.itheima.domain;
import lombok.*;
/*
1 生成getter和setter方法:@Getter、@Setter
生成toString方法:@ToString
生成equals和hashcode方法:@EqualsAndHashCode
2 统一成以上所有:@Data
3 生成空参构造: @NoArgsConstructor
生成全参构造: @AllArgsConstructor
4 lombok还给我们提供了builder的方式创建对象,好处就是可以链式编程。 @Builder【扩展】
*/
@Data
public class User {
private Long id;
private String name;
private String password;
private Integer age;
private String tel;
}
思考一下Mybatis分页插件是如何用的?
①:设置分页拦截器作为Spring管理的bean
package com.itheima.config;
import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class MybatisPlusConfig {
@Bean
public MybatisPlusInterceptor mybatisPlusInterceptor(){
//1 创建MybatisPlusInterceptor拦截器对象
MybatisPlusInterceptor mpInterceptor=new MybatisPlusInterceptor();
//2 添加分页拦截器
mpInterceptor.addInnerInterceptor(new PaginationInnerInterceptor());
return mpInterceptor;
}
}
②:执行分页查询
//分页查询
@Test
void testSelectPage(){
//1 创建IPage分页对象,设置分页参数
IPage<User> page=new Page<>(1,3);
//2 执行分页查询
userDao.selectPage(page,null);
//3 获取分页结果
System.out.println("当前页码值:"+page.getCurrent());
System.out.println("每页显示数:"+page.getSize());
System.out.println("总页数:"+page.getPages());
System.out.println("总条数:"+page.getTotal());
System.out.println("当前页数据:"+page.getRecords());
}
spring:
datasource:
type: com.alibaba.druid.pool.DruidDataSource
driver-class-name: com.mysql.cj.jdbc.Driver
url: jdbc:mysql://localhost:3306/mybatisplus_db?serverTimezone=UTC
username: root
password: root
# 开启mp的日志(输出到控制台)
mybatis-plus:
configuration:
log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
做法:在resources下新建一个logback.xml文件,名称固定,内容如下:
<configuration>
configuration>
关于logback参考播客:https://www.jianshu.com/p/75f9d11ae011
spring:
main:
banner-mode: off # 关闭SpringBoot启动图标(banner)
# mybatis-plus日志控制台输出
mybatis-plus:
configuration:
log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
global-config:
banner: off # 关闭mybatisplus启动图标
//方式一:按条件查询
QueryWrapper<User> qw=new QueryWrapper<>();
qw.lt("age", 18);
List<User> userList = userDao.selectList(qw);
System.out.println(userList);
//方式二:lambda格式按条件查询
QueryWrapper<User> qw = new QueryWrapper<User>();
qw.lambda().lt(User::getAge, 10);
List<User> userList = userDao.selectList(qw);
System.out.println(userList);
//方式三:lambda格式按条件查询
LambdaQueryWrapper<User> lqw = new LambdaQueryWrapper<User>();
lqw.lt(User::getAge, 10);
List<User> userList = userDao.selectList(lqw);
System.out.println(userList);
//并且关系
LambdaQueryWrapper<User> lqw = new LambdaQueryWrapper<User>();
//并且关系:10到30岁之间
lqw.lt(User::getAge, 30).gt(User::getAge, 10);
List<User> userList = userDao.selectList(lqw);
System.out.println(userList);
//或者关系
LambdaQueryWrapper<User> lqw = new LambdaQueryWrapper<User>();
//或者关系:小于10岁或者大于30岁
lqw.lt(User::getAge, 10).or().gt(User::getAge, 30);
List<User> userList = userDao.selectList(lqw);
System.out.println(userList);
如下搜索场景,在多条件查询中,有条件的值为空应该怎么解决?
Integer minAge=10; //将来有用户传递进来,此处简化成直接定义变量了
Integer maxAge=null; //将来有用户传递进来,此处简化成直接定义变量了
LambdaQueryWrapper<User> lqw = new LambdaQueryWrapper<User>();
if(minAge!=null){
lqw.gt(User::getAge, minAge);
}
if(maxAge!=null){
lqw.lt(User::getAge, maxAge);
}
List<User> userList = userDao.selectList(lqw);
userList.forEach(System.out::println);
Integer minAge=10; //将来有用户传递进来,此处简化成直接定义变量了
Integer maxAge=null; //将来有用户传递进来,此处简化成直接定义变量了
LambdaQueryWrapper<User> lqw = new LambdaQueryWrapper<User>();
//参数1:如果表达式为true,那么查询才使用该条件
lqw.gt(minAge!=null,User::getAge, minAge);
lqw.lt(maxAge!=null,User::getAge, maxAge);
List<User> userList = userDao.selectList(lqw);
userList.forEach(System.out::println);
Integer minAge=10; //将来有用户传递进来,此处简化成直接定义变量了
Integer maxAge=null; //将来有用户传递进来,此处简化成直接定义变量了
LambdaQueryWrapper<User> lqw = new LambdaQueryWrapper<User>();
//参数1:如果表达式为true,那么查询才使用该条件
lqw.gt(minAge!=null,User::getAge, minAge)
.lt(maxAge!=null,User::getAge, maxAge);
List<User> userList = userDao.selectList(lqw);
userList.forEach(System.out::println);
/*LambdaQueryWrapper lqw = new LambdaQueryWrapper();
lqw.select(User::getId, User::getName, User::getAge);*/
//或者
QueryWrapper<User> lqw = new QueryWrapper<User>();
lqw.select("id", "name", "age", "tel");
List<User> userList = userDao.selectList(lqw);
System.out.println(userList);
QueryWrapper<User> lqw = new QueryWrapper<User>();
lqw.select("count(*) as count, tel");
lqw.groupBy("tel");
List<Map<String, Object>> userList = userDao.selectMaps(lqw);
System.out.println(userList);
多条件查询有哪些组合?
LambdaQueryWrapper<User> lqw = new LambdaQueryWrapper<User>();
//等同于=
lqw.eq(User::getName, "Jerry").eq(User::getPassword, "jerry");
User loginUser = userDao.selectOne(lqw);
System.out.println(loginUser);
LambdaQueryWrapper<User> lqw = new LambdaQueryWrapper<User>();
//范围查询 lt le gt ge eq between
lqw.between(User::getAge, 10, 30);
List<User> userList = userDao.selectList(lqw);
System.out.println(userList);
LambdaQueryWrapper<User> lqw = new LambdaQueryWrapper<User>();
//模糊匹配 like
lqw.likeLeft(User::getName, "J");
List<User> userList = userDao.selectList(lqw);
System.out.println(userList);
QueryWrapper<User> qw = new QueryWrapper<User>();
qw.select("gender","count(*) as nums");
qw.groupBy("gender");
List<Map<String, Object>> maps = userDao.selectMaps(qw);
System.out.println(maps);
题目:基于MyBatisPlus_Ex1模块,完成Top5功能的开发。
说明:
①:Top5指根据销售量排序(提示:对销售量进行降序排序)
②:Top5是仅获取前5条数据(提示:使用分页功能控制数据显示数量)
思考表的字段和实体类的属性不对应,查询会怎么样?
@Data
@TableName("tbl_user")
public class User {
/*
id为Long类型,因为数据库中id为bigint类型,
并且mybatis有自己的一套id生成方案,生成出来的id必须是Long类型
*/
private Long id;
private String name;
@TableField(value = "pwd",select = false)
private String password;
private Integer age;
private String tel;
@TableField(exist = false) //表示online字段不参与CRUD操作
private Boolean online;
}
主键生成的策略有哪几种方式?
不同的表应用不同的id生成策略
名称:@TableId
类型:属性注解
位置:模型类中用于表示主键的属性定义上方
作用:设置当前类中主键属性的生成策略
相关属性
type:设置主键属性的生成策略,值参照IdType枚举值
mybatis-plus:
global-config:
db-config:
id-type: assign_id
table-prefix: tbl_
MyBatisPlus是否支持批量操作?
//删除指定多条数据
List<Long> list = new ArrayList<>();
list.add(1402551342481838081L);
list.add(1402553134049501186L);
list.add(1402553619611430913L);
userDao.deleteBatchIds(list);
//查询指定多条数据
List<Long> list = new ArrayList<>();
list.add(1L);
list.add(3L);
list.add(4L);
userDao.selectBatchIds(list);
在实际环境中,如果想删除一条数据,是否会真的从数据库中删除该条数据?
删除操作业务问题:业务数据从数据库中丢弃
逻辑删除:为数据设置是否可用状态字段,删除时设置状态字段为不可用状态,数据保留在数据库中
package com.itheima.domain;
import com.baomidou.mybatisplus.annotation.*;
import lombok.Data;
@Data
public class User {
private Long id;
//逻辑删除字段,标记当前记录是否被删除
@TableLogic
private Integer deleted;
}
mybatis-plus:
global-config:
db-config:
table-prefix: tbl_
# 逻辑删除字段名
logic-delete-field: deleted
# 逻辑删除字面值:未删除为0
logic-not-delete-value: 0
# 逻辑删除字面值:删除为1
logic-delete-value: 1
逻辑删除本质:逻辑删除的本质其实是修改操作。如果加了逻辑删除字段,查询数据时也会自动带上逻辑删除字段。
乐观锁主张的思想是什么?
package com.itheima.domain;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableLogic;
import com.baomidou.mybatisplus.annotation.Version;
import lombok.Data;
@Data
public class User {
private Long id;
@Version
private Integer version;
}
package com.itheima.config;
import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.OptimisticLockerInnerInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class MpConfig {
@Bean
public MybatisPlusInterceptor mpInterceptor() {
//1.定义Mp拦截器
MybatisPlusInterceptor mpInterceptor = new MybatisPlusInterceptor();
//2.添加乐观锁拦截器
mpInterceptor.addInnerInterceptor(new OptimisticLockerInnerInterceptor());
return mpInterceptor;
}
}
@Test
public void testUpdate() {
/*User user = new User();
user.setId(3L);
user.setName("Jock666");
user.setVersion(1);
userDao.updateById(user);*/
//1.先通过要修改的数据id将当前数据查询出来
//User user = userDao.selectById(3L);
//2.将要修改的属性逐一设置进去
//user.setName("Jock888");
//userDao.updateById(user);
//1.先通过要修改的数据id将当前数据查询出来
User user = userDao.selectById(3L); //version=3
User user2 = userDao.selectById(3L); //version=3
user2.setName("Jock aaa");
userDao.updateById(user2); //version=>4
user.setName("Jock bbb");
userDao.updateById(user); //verion=3?条件还成立吗?
}
如果只给一张表的字段信息,能够推演出Domain、Dao层的代码?
<dependency>
<groupId>com.baomidougroupId>
<artifactId>mybatis-plus-generatorartifactId>
<version>3.4.1version>
dependency>
<dependency>
<groupId>org.apache.velocitygroupId>
<artifactId>velocity-engine-coreartifactId>
<version>2.3version>
dependency>
package com.itheima;
import com.baomidou.mybatisplus.generator.AutoGenerator;
import com.baomidou.mybatisplus.generator.config.DataSourceConfig;
public class Generator {
public static void main(String[] args) {
//1. 创建代码生成器对象,执行生成代码操作
AutoGenerator autoGenerator = new AutoGenerator();
//2. 数据源相关配置:读取数据库中的信息,根据数据库表结构生成代码
DataSourceConfig dataSource = new DataSourceConfig();
dataSource.setDriverName("com.mysql.cj.jdbc.Driver");
dataSource.setUrl("jdbc:mysql://localhost:3306/mybatisplus_db?serverTimezone=UTC");
dataSource.setUsername("root");
dataSource.setPassword("root");
autoGenerator.setDataSource(dataSource);
//3. 执行生成操作
autoGenerator.execute();
}
}
//设置全局配置
GlobalConfig globalConfig = new GlobalConfig();
globalConfig.setOutputDir(System.getProperty("user.dir")+"/mybatisplus_04_generator/src/main/java"); //设置代码生成位置
globalConfig.setOpen(false); //设置生成完毕后是否打开生成代码所在的目录
globalConfig.setAuthor("黑马程序员"); //设置作者
globalConfig.setFileOverride(true); //设置是否覆盖原始生成的文件
globalConfig.setMapperName("%sDao"); //设置数据层接口名,%s为占位符,指代模块名称
globalConfig.setIdType(IdType.ASSIGN_ID); //设置Id生成策略
autoGenerator.setGlobalConfig(globalConfig);
//设置包名相关配置
PackageConfig packageInfo = new PackageConfig();
packageInfo.setParent("com.aaa"); //设置生成的包名,与代码所在位置不冲突,二者叠加组成完整路径
packageInfo.setEntity("domain"); //设置实体类包名
packageInfo.setMapper("dao"); //设置数据层包名
autoGenerator.setPackageInfo(packageInfo);
//策略设置
StrategyConfig strategyConfig = new StrategyConfig();
strategyConfig.setInclude("tbl_user"); //设置当前参与生成的表名,参数为可变参数
strategyConfig.setTablePrefix("tbl_"); //设置数据库表的前缀名称,模块名 = 数据库表名 - 前缀名 例如: User = tbl_user - tbl_
strategyConfig.setRestControllerStyle(true); //设置是否启用Rest风格
strategyConfig.setVersionFieldName("version"); //设置乐观锁字段名
strategyConfig.setLogicDeleteFieldName("deleted"); //设置逻辑删除字段名
strategyConfig.setEntityLombokModel(true); //设置是否启用lombok
autoGenerator.setStrategy(strategyConfig);
说明:在资料中也提供了CodeGenerator代码生成器类,根据实际情况修改后可以直接使用。