MybatisPlus 学习笔记
学习了MybatisPlus 之后，可以让我们告别繁琐又没有技术含量的增删改查，其实我们工作中大部分接口几乎都是此类工作，所以用它就完了，效率杠杠的。
SpringBoot 集成
- MAVEN
<!--mybatis-plus依赖-->
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.4.2</version>
</dependency>
<!-- 数据库连接池 -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.47</version>
</dependency>
<!-- 测试类-->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
</dependency>
<!-- lombok -->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.22</version>
<scope>provided</scope>
</dependency>
- application.yml
# mysql连接信息
spring:
datasource:
driver-class-name: com.mysql.jdbc.Driver
url: jdbc:mysql://localhost:3306/testMyBatisPlus?characterEncoding=utf8&useSSL=false&serverTimezone=Asia/Shanghai&rewriteBatchedStatements=true
username: root
password: root
thymeleaf:
cache: false #设置为false，否则会有缓存，导致页面没法及时看到更新后的效果。
#修改端口号默认是8080
server:
port: 8888
#mybatis-plus相关配置
mybatis-plus:
mapper-locations: classpath:mapper/*.xml #扫描mapper下的所有xml文件
type-aliases-package: com.zwl.entity #扫描实体类包/配置别名
- 创建实体类
//数据库表自己建
@Data
public class Student {
private Integer id;
private String name;
private Integer age;
private String desc;
}
- mapper继承
// 集成BaseMapper接口 类型为实体类类型
public interface StudentMapper extends BaseMapper<Student> {
}
Mybatis plus 基本用法
- service封装一层mapper ，使用起来更加便捷
//iservice接口
public interface IStudentService extends IService<Student> {
}
//实现类
@Service
public class StudentServiceImpl extends ServiceImpl<StudentMapper, Student> implements IStudentService {
}
@RestController
public class StudentController {
//使用 直接注入即可
@Autowired
private IStudentService studentService;
}
- 此时的service 已经继承了mybatis plus 所有封装函数。如图，顺带可以看下目录结构
内置函数操作示例
GET
// 查询内置函数有点多 不一一说了 会用几个关键的就行
default T getOne(Wrapper<T> queryWrapper)
default int count() // 总条数
default int count(Wrapper<T> queryWrapper) //条件筛选后的总条数
default List<T> list() // 全部数据
default List<T> list(Wrapper<T> queryWrapper) //条件筛选后的全部数据
default <E extends IPage<T>> E page(E page) // 分页查询
default <E extends IPage<T>> E page(E page, Wrapper<T> queryWrapper) // 分页条件查询
count
@GetMapping("getCount")
public void getCount(){
int count = studentService.count();
System.out.println(count);
}
countByTerm
@GetMapping("getCountByTerm")
public void getCountByTerm(){
// 查询 年龄大于8岁 and 姓名为小明的总数
QueryWrapper qw = new QueryWrapper();
qw.gt("age","8");
qw.eq("name","小明");
int count = studentService.count(qw);
System.out.println(count);
}
//注： wrapper内置函数说明:eq相等 ne不相等 gt大于 lt小于 ge大于等于 le 小于等于
getOne
@GetMapping("getOne")
public void getOne(){
QueryWrapper qw = new QueryWrapper();
qw.eq("name","小八");
// getOne 只返回一个 多条报错 TooManyResultsException
Student student = studentService.getOne(qw);
System.out.println(student);
}
list
@GetMapping("get")
public void get(){
List<Student> list = studentService.list();
for (Student student : list) {
System.out.println(student.toString());
}
}
listByWrapper
@GetMapping("listByWrapper")
public void listByWrapper(){
QueryWrapper<Student> qw = new QueryWrapper();
qw.eq("age","10");
List<Student> list = studentService.list(qw);
for (Student student : list) {
System.out.println(student);
}
}
page
//配置类加上
@Configuration
public class MybatisConfig {
@Bean
public MybatisPlusInterceptor mybatisPlusInterceptor() {
MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
return interceptor;
}
}
@GetMapping("get")
public void get(){
// 页数 1 每页10
Page<Student> page = new Page<>(1,10);
Page<Student> page1 = studentService.page(page);
List<Student> records = page1.getRecords();
for (Student record : records) {
System.out.println(record);
}
}
//page条件查询一样 new个QueryWrapper对象 直接用
INSERT
//直接save函数即可 service类已经指定了实体类类型
@GetMapping("insert")
public void insert(){
Student student = new Student();
student.setAge(10);
student.setName("小王");
student.setDesc("小王是一名学生");
studentService.save(student);
}
UPDATE
updateById
//通过Id 修改数据
@GetMapping("updateById")
public void updateById(){
Student student = new Student();
student.setId(1);
student.setDesc("小明是一个坏学生");
studentService.updateById(student);
}
updateByTerm
// 通过指定条件更改
//例如将全部name为小明的数据age修改为10
@GetMapping("updateByTerm")
public void updateByTerm(){
// wrapper函数 说明:eq相等 ne不相等 gt大于 lt小于 ge大于等于 le 小于等于
UpdateWrapper<Student> uw = new UpdateWrapper();
uw.eq("name","小明");
Student student = new Student();
student.setAge(10);
studentService.update(student,uw);
}
updateBatch
// 批量修改
@GetMapping("updateBatch")
public void updateBatch(){
List<Student> studentList = new ArrayList<>();
Student student = new Student();
student.setDesc("小王是一名好学生");
student.setId(2);
studentList.add(student);
Student student1= new Student();
student1.setDesc("小明是体育老师");
student1.setId(1);
studentList.add(student1);
studentService.updateBatchById(studentList);
}
DELETE
// mybatis plus 提供四个 remove 函数
default boolean removeById(Serializable id)
default boolean removeByMap(Map<String, Object> columnMap)
default boolean remove(Wrapper<T> queryWrapper)
default boolean removeByIds(Collection<? extends Serializable> idList)
removeById
@GetMapping("removeById")
public void removeById(){
studentService.removeById(1);
}
removeByIds
@GetMapping("removeByIds")
public void removeByIds(){
List<Integer> tarList = new ArrayList<>();
tarList.add(1);
tarList.add(2);
tarList.add(3);
studentService.removeByIds(tarList);
}
removeByMap
@GetMapping("removeByMap")
public void removeByMap(){
// 属性与值的映射
Map<String,Object> tarMap = new HashMap<>();
tarMap.put("name","小明");
studentService.removeByMap(tarMap);
}
remove
// 指定条件进行删除
// 示例 删除姓名叫小明 且年龄大于10岁的数据。
@GetMapping("removeByWrapper")
public void removeByWrapper(){
QueryWrapper wrapper = new QueryWrapper();
wrapper.eq("name","小明");
wrapper.gt("age","10");
studentService.remove(wrapper);
}
项目源码
链接：https://pan.baidu.com/s/1IG8ouS4QF53pvZNsW0OuYw
提取码：6kwa