SpringBoot 整合MybatisPlus

1、加载依赖: MybatisPlus的依赖 （将mybatis、mybatis-spring的依赖去除）

<!-- mybatisPlus的相关依赖,   不需要加载 mybatis-spring-boot-starter -->
<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.3.2</version>
</dependency>

2、修改Mapper接口

@Mapper
public interface EmployeeMapper extends BaseMapper<Employee>{
    //根据id查询
    public Employee  queryById(int empno) throws Exception;
    //查询指定页数据
    public List<Employee>  queryByPage(@Param("start")int start, @Param("pageSize") int pageSize) throws Exception;
    // 添加员工
    public void add(Employee emp) throws Exception;
}

3、修改springBoot对mybatis的配置

#Mybatisplus的配置
mybatis-plus:
  type-aliases-package: com.zl.app.entity //给类定义别名
  mapper-locations: classpath*:mapper/*Mapper.xml //mapper扫描器

4、编写一个MybatisPlus的配置类, 配置一个分页插件

@Configuration
//@EnableTransactionManagement
public class MybatisPlusConfig {
    
    //配置一个分页插件
    @Bean
    public PaginationInterceptor paginationInterceptor() {
        PaginationInterceptor paginationInterceptor = new PaginationInterceptor();
        // 开启 count 的 join 优化,只针对部分 left join
        paginationInterceptor.setCountSqlParser(new JsqlParserCountOptimize(true));
        return paginationInterceptor;
    }
}

5、 如果数据库的表名与类名不一样,需要使用@TableName注解

@Data
@TableName("emp") //如果数据库表名与类名不一致
public class Employee {
    @TableId //如果数据库id与属性不一样
    private Integer empno;
    @TableFieId //如果数据库其他字段与属性不一样
    private String ename;
    private String job;
    private Integer mgr;
    private Date hiredate;
    private Double comm;
    private Double sal;
    private Integer deptno;
}

测试分页：

@Override
public Page<Employee> queryByPage2(int pageIndex, int pageSize) throws Exception {
    //创建Page对象
    Page<Employee> page = new Page<>(pageIndex,pageSize);
    empMapper.selectPage(page, null);
    return page;
}

@Test
public void test7()  throws Exception{
    Page<Employee> page = empService.queryByPage2(1, 3);
    System.out.println(page.getRecords());
    System.out.println("总页数:"+page.getPages());
    System.out.println("总记录数:"+page.getTotal());
    System.out.println("当前页:"+page.getCurrent());
    System.out.println("页容量:"+page.getSize());
}