目录
1. MybatisPlus简介与特性
1.1 简介
MybatisPlus作为MyBatis的一款增强工具，就是为了简化开发，为提高效率而生。同时还提供通用的Mapper与Service，无需写SQL的情况下对表进行增删改查，可以说是十分之优秀。简而意之就是减少基础crud方法的大量重复代码编写
2. MybatisPlus的开发环境搭建
2.1 数据库创建categor表
CREATE TABLE `category` (
`id` bigint(0) NOT NULL COMMENT '主键',
`type` int(0) NULL DEFAULT NULL COMMENT '类型',
`name` varchar(64) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL COMMENT '姓名',
`sort` int(0) NOT NULL DEFAULT 0 COMMENT '顺序',
`create_time` datetime(0) NOT NULL COMMENT '创建时间',
`update_time` datetime(0) NOT NULL COMMENT '更新时间',
`create_user` bigint(0) NOT NULL COMMENT '创建人',
`update_user` bigint(0) NOT NULL COMMENT '修改人',
PRIMARY KEY (`id`) USING BTREE,
UNIQUE INDEX `idx_category_name`(`name`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_bin COMMENT = '菜品及套餐分类' ROW_FORMAT = Dynamic;
INSERT INTO `category` VALUES (1, 1, '张三', 1, '2022-05-27 09:16:58', '2022-07-15 20:25:23', 1, 1);
INSERT INTO `category` VALUES (2, 1, '李四', 2, '2022-05-27 09:17:07', '2022-06-02 14:27:22', 1, 1);
INSERT INTO `category` VALUES (3, 2, '王五', 3, '2022-05-27 09:17:28', '2022-07-09 14:37:13', 1, 1);
INSERT INTO `category` VALUES (4, 2, '赵六', 11, '2022-07-09 11:36:15', '2022-07-09 14:39:15', 1, 1);
INSERT INTO `category` VALUES (5, 3, '唐七', 5, '2022-07-09 11:40:30', '2022-07-09 14:43:45', 1, 1);
INSERT INTO `category` VALUES (6, 4, '范八', 12, '2022-07-09 14:30:07', '2022-07-09 14:39:19', 1, 1);
INSERT INTO `category` VALUES (7, 4, '杨九', 6, '2022-07-09 14:35:02', '2022-07-09 14:39:05', 1, 1);
SET FOREIGN_KEY_CHECKS = 1;
2.2 创建SpringBoot工程
请使用IDEA快速创建一个SpringBoot的工程，在pom.xml中导入以下依赖，
<!--mybatis-plus依赖-->
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.3.1</version>
</dependency>
<!-- 代码生成器所需依赖 -->
<dependency>
<groupId>org.apache.velocity</groupId>
<artifactId>velocity-engine-core</artifactId>
<version>2.2</version>
</dependency>2.3 mybatis_plus提供基础结构代码自动生成
运行以下main方法就会自动生成SpringMVC基础架构，mapper层记得加上@Mapper注解
/**
*代码自动生成类
*/
public class SggCodeGenerator {
public static void main(String[] args) {
// 1、创建代码生成器
AutoGenerator mpg = new AutoGenerator();
// 2、全局配置
GlobalConfig gc = new GlobalConfig();
String projectPath = System.getProperty("user.dir");
gc.setOutputDir(projectPath + "/src/main/java");
gc.setAuthor("玉面小白龙");
gc.setOpen(false); //生成后是否打开资源管理器
gc.setFileOverride(false); //重新生成时文件是否覆盖
gc.setServiceName("%sService"); //去掉Service接口的首字母I
gc.setIdType(null); //主键策略
gc.setDateType(DateType.ONLY_DATE);//定义生成的实体类中日期类型
gc.setSwagger2(true);//开启Swagger2模式
mpg.setGlobalConfig(gc);
// 3、数据源配置
DataSourceConfig dsc = new DataSourceConfig();
dsc.setUrl("jdbc:mysql://localhost:3306/rui?useUnicode=true&characterEncoding=utf-8&serverTimezone=UTC");
dsc.setDriverName("com.mysql.cj.jdbc.Driver");
dsc.setUsername("root");
dsc.setPassword("root");
dsc.setDbType(DbType.MYSQL);
mpg.setDataSource(dsc);
// 4、包配置
PackageConfig pc = new PackageConfig();
pc.setModuleName(null); //模块名
pc.setParent("com.example.test3");
pc.setController("controller");
pc.setEntity("entity");
pc.setService("service");
pc.setMapper("mapper");
mpg.setPackageInfo(pc);
// 5、策略配置
StrategyConfig strategy = new StrategyConfig();
strategy.setInclude("category");//对那一张表生成代码
strategy.setNaming(NamingStrategy.underline_to_camel);//数据库表映射到实体的命名策略
strategy.setTablePrefix(pc.getModuleName() + "_"); //生成实体时去掉表前缀
strategy.setColumnNaming(NamingStrategy.underline_to_camel);//数据库表字段映射到实体的命名策略
strategy.setEntityLombokModel(true); // lombok 模型 @Accessors(chain = true) setter链式操作
strategy.setRestControllerStyle(true); //restful api风格控制器
strategy.setControllerMappingHyphenStyle(true); //url中驼峰转连字符
mpg.setStrategy(strategy);
// 6、执行
mpg.execute();
}
}2.4 配置数据库来源application.yml
填写基础基础用户名和密码，以及数据库名称
server:
port: 8888
spring:
datasource:
username: xxx
password: xxx
driver-class-name: com.mysql.cj.jdbc.Driver
#连接本地数据库
url: jdbc:mysql://localhost:3306/xxx?useUnicode=true&characterEncoding=utf-8&serverTimezone=UTC
mybatis-plus:
# mapper.xml 文件扫描
mapper-locations: classpath*:/mapper/*.xml
configuration:
map-underscore-to-camel-case: true
# 日志配置
logging:
level:
com.xxx.xxx: debug
org.springframework: warn
3. 开始代码编写
3.1开始controller调用mapper层自带方法实现增删查改
1 相等判断
1.1 allEq
全部条件都相等。Map<String,Object> map = new HashMap<>();
map.put("type",1);
map.put("name","张三");
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.allEq(map);
List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
1.2 eq
指定条件相等。
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().eq(Category::getName,"李四");List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
1.3 ne
指定条件不相等。
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().ne(Category::getName,"李四");List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
2 范围判断
2.1 gt
大于指定条件。QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().gt(Category::getType,1);
List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
2.2 ge
大于等于指定条件。
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().ge(Category::getType,2);List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
2.3 lt
小于指定条件。QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().lt(Category::getType,2);
List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
2.4 le
小于等于指定条件。
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().le(Category::getType,2);List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
2.5 between
介于指定范围之间。
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().between(Category::getType,"2","3");List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
2.6 notBetween
不介于指定范围之间。
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().notBetween(Category::getType,"2","3");List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
3 模糊匹配
3.1 like
某个字符串包含指定字符串。
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().like(Category::getCreateTime,"2022");List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
3.2 notLike
某个字符串不包含指定字符串。
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().notLike(Category::getCreateTime,"14");List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
3.3 likeLeft
某个字符串以指定字符串结尾。
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().likeLeft(Category::getCreateTime,"58");List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
3.4 likeRight
某个字符串以指定字符串开头。
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().likeRight(Category::getCreateTime,"2022");List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
4 非空判断
4.1 isNull
指定字段为null。
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().isNull(Category::getType);List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
4.2 isNotNull
指定字段不为null。
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().isNotNull(Category::getType);List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
5 in判断
5.1 in
满足指定条件之一。
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().in(Category::getType,"1","3");List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
5.2 notIn
不满足指定条件之一。
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().notIn(Category::getType,"1","3");List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
5.3 inSql
满足指定条件之一。
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().inSql (Category::getType,"1,3");List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
5.4 notInSql
不满足指定条件之一。QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().notInSql(Category::getType,"1,3");
List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
6 分组
6.1 groupBy
按字段值分组，每一组只会出现一条数据。
QueryWrapper<UserEntity> queryWrapper = new QueryWrapper();
queryWrapper.lambda().groupBy(UserEntity::getSex);
return userService.list(queryWrapper);
7 排序
7.1 orderByAsc
根据指定字段升序排序。
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().orderByAsc(Category::getCreateTime);List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
7.2 orderByDesc
根据指定字段降序排序。QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().orderByDesc(Category::getCreateTime);
List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
7.3 orderBy
根据指定字段升序/降序排序。
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().orderBy(true,false,Category::getCreateTime);List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
注：
（1）第一个参数必须为true。
（2）第二个参数为true则升序排序，为false则降序排序。
8 条件判断
8.1 having
跟sql里面的having类似。QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.select("type,count(*) as sexCount")
.groupBy("type")
.having("count(*)>1");
List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
注：（1）having()需要配合select()、groupBy()一起配合使用。
（2）having里面只能使用聚合函数。
8.2 func
主要方便在出现if...else下调用不同方法能不断链。
Boolean s = false;LambdaQueryWrapper<Category> queryWrapper = Wrappers.<Category>lambdaQuery(); queryWrapper.func(x -> {
if (s) {
x.eq(Category::getType, 2);
} else {
x.eq(Category::getType, 1); } });
List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
9 逻辑判断
9.1 and
与逻辑判断。（条件拼接）QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().eq(Category::getName,"张三")
.and(t -> t.eq(Category::getType, "1"));
List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
9.2 or
或逻辑判断。
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.lambda().eq(Category::getName,"张三").or(t -> t.eq(Category::getType, "2"));
List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
10 存在判断
10.1 exists
exists用于检查子查询是否会返回数据，该子查询实际上并不返回任何数据，有查询数据返回值为true，没有查询数据返回值为false。
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.exists("select * from category where name='张三'");List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
10.2 notExists
notExists用于检查子查询是否不会返回数据，该子查询实际上并不返回任何数据，有查询数据返回值为false，没有查询数据返回值为true。
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.notExists("select * from category where name='张三'");List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;
11 查询字段
11.1 select
QueryWrapper<Category> queryWrapper =new QueryWrapper<>(); queryWrapper.select("name,type");
List<Category> categories = categoryMapper.selectList(queryWrapper);
return "数据为"+ categories;