Uso básico de [MyBatis-Plus] (SpringBoot)

1. ¿Qué es MyBatis-Plus?

Mybatis-Plus: Nacido para simplificar el desarrollo

        MyBatis-Plus (MP para abreviar) es una herramienta de mejora basada en MyBatis que mejora las funciones básicas de Mybatis sin realizar ningún cambio. Esto nos permite actualizar directamente los proyectos desarrollados por Mybatis a Mybatis-plus y, así como se posiciona, puede ayudarnos a simplificar aún más el proceso de desarrollo y mejorar la eficiencia del desarrollo.

        Mybatis-Plus en realidad puede verse como otra encapsulación de Mybatis. Después de la actualización, las operaciones CRUD en una sola tabla se pueden implementar fácilmente llamando a la API proporcionada por Mybatis-Plus. Además, se proporcionan varios métodos de consulta, paginación y otros comportamientos. . . Lo más importante es que los desarrolladores no tienen que escribir XML, lo que reduce en gran medida la dificultad del desarrollo.

2. Uso rápido

1. Importar dependencias

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>

        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.4.3.4</version>
        </dependency>

        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus</artifactId>
            <version>3.5.1</version>
        </dependency>

        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-annotation</artifactId>
            <version>3.5.1</version>
        </dependency>

2. Configurar los parámetros de la base de datos.

spring.datasource.password=*******
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.username=root
spring.datasource.url=jdbc:mysql://localhost:3306/library?serverTimezone=UTC
#mybatis的日志
mybatis-plus.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl
#全局设置主键生成策略
mybatis-plus.global-config.db-config.id-type=auto

3. Cree una tabla de base de datos

4. Directorio de archivos

5. clase de entidad

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Book {
    @TableId
    int bookId;
    String bookName;
    int bookCounts;
    String detail;

    @TableField(fill= FieldFill.INSERT)
    private Date createTime;

    @TableField(fill=FieldFill.INSERT_UPDATE)
    private Date updateTime;

    @Version
    @TableField(fill= FieldFill.INSERT)
    private Integer version;

}

6. Hacer mapeo de tablas

@Repository
public interface BookMapper extends BaseMapper<Book> {
}

7. Puedes empezar a probar

 3. Uso general

(1).Operaciones de búsqueda y actualización

 /**
     * 插入用户表一条数据
     */
    @Test
    public void testInsert(){
        Book b1=new Book();
        b1.setBookName("《xxxxxx》");
        b1.setBookCounts(299);
        b1.setDetail("学会使用常用的linux指令");
        int result=bookMapper.insert(b1);
        System.out.println(result);

    }
/**
     * 根据多个id查询
     */
    @Test
    public void testSelectBatchIds(){
        List<Book> books=bookMapper.selectBatchIds(Arrays.asList(1,2,3));
        books.forEach(System.out::println);
    }

    /**
     * 简单的条件查询，通过map封装查询条件
     */
    @Test
    public void testSelectMap(){
        HashMap<String,Object> map=new HashMap<>();
        map.put("book_name","《爱迪生的伟大发明》");
//        map.put("detail","睡前小故事");
        List<Book> books=bookMapper.selectByMap(map);
        books.forEach(System.out::println);
    }


    /**
     * 通过id修改用户信息
     */
    @Test
    public void testUpdateById(){
        Book b=new Book();
        b.setBookId(15);
        b.setBookName("《Linux私房菜》");
        b.setDetail("好好学习指令 这是3.0版本");
        b.setBookCounts(100);
        int res=bookMapper.updateById(b);
        System.out.println(res);
    }

(2) Uso de bloqueos optimistas

        1. Escriba una clase de configuración y agregue la función interceptora oficial. También se agrega paginación junto con esto. Recuerde escribir el campo de versión en la tabla.

    /**
     * 乐观锁插件
     * 分页插件
     */
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        //配置乐观锁
        interceptor.addInnerInterceptor(new OptimisticLockerInnerInterceptor());
        //配置分页
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
        return interceptor;
    }

    /**
     * 测试乐观锁插入
     */
    @Test
    public void testOptimisticLocker(){
        Book b1=new Book();
        b1.setBookName("《深技大入场券》");
        b1.setBookCounts(33);
        b1.setDetail("我来了，神技大");
        int result=bookMapper.insert(b1);
        System.out.println(result);

    }

    /**
     * 测试乐观锁更新
     */
    @Test
    public void testUpdateByIdOptimisticLocker(){
        //必须查询才能更新
        Book b=bookMapper.selectById(16);
        b.setBookId(16);
        b.setBookName("《深技大入场券》");
        b.setDetail("我来了，神技大 一定要上");
        b.setBookCounts(999);
        int res=bookMapper.updateById(b);
        System.out.println(res);

    }

(3) Eliminar operación

    /**
     * 根据id删除
     */
    @Test
    public void testDeleteById(){
        int id=bookMapper.deleteById(17);
        System.out.println(id);
    }

    /**
     * 批量删除数据
     */
    @Test
    public void testDeleteBatchByIds(){
        int result=bookMapper.deleteBatchIds(Arrays.asList(18,19));
        System.out.println(result);
    }
    /**
     * 条件删除
     */
    @Test
    public void testDeleteByMap(){
        //DELETE FROM book WHERE book_counts = ?
        HashMap<String,Object> map=new HashMap<>();
        map.put("book_counts",299);
        int result=bookMapper.deleteByMap(map);
    }

(4) consulta de paginación

    /**
     * 分页查询
     */
    @Test
    public void testSelectPage(){
        //current 目前的
        Page<Book> page=new Page<>(1,5);
        bookMapper.selectPage(page, Wrappers.<Book>lambdaQuery().ge(Book::getBookId,2));
        List<Book> record=page.getRecords();
        record.forEach(System.out::println);

        //常用方法
//        boolean hasNext=page.hasNext();
//        boolean hasPrevious=page.hasPrevious();
//        System.out.println(hasNext+" "+hasPrevious);
    }

4. Consultas complejas

Mybatis-Plus proporciona dos clases de uso común para manejar operaciones de consulta complejas, QueryWrapper y UpdateWrapper.

 /**
     * 复杂查询的
     * ge gt le lt isNull isNotNull的用法
     */
    @Test
    public void testQueryWrapper1(){
        QueryWrapper<Book> query=new QueryWrapper<>();
        //SELECT COUNT(*) AS total FROM book WHERE (book_counts >= ? AND book_name IS NOT NULL)
        query.ge("book_counts",60).isNotNull("book_name");
        //SELECT book_id,book_name,book_counts,detail,create_time,update_time,version FROM book
        // WHERE (book_counts >= ? AND book_name IS NOT NULL) LIMIT ?
        Page<Book> page=new Page<>(1,5);
        bookMapper.selectPage(page,query);
        page.getRecords().forEach(System.out::println);
    }


    /**
     *
     * 复杂查询的
     *   eq ne的用法
     */
    @Test
    public void testQueryWrapper2(){
        QueryWrapper<Book> queryWrapper=new QueryWrapper<>();
        queryWrapper.eq("book_id",13);
        Book book=bookMapper.selectOne(queryWrapper);
        System.out.println(book);
    }

    /**
     *
     * 复杂查询的
     *   between notBetween的用法
     */
    @Test
    public void testQueryWrapper3(){
        //SELECT book_id,book_name,book_counts,detail,create_time,update_time,version FROM book
        // WHERE (book_counts BETWEEN ? AND ?)
        QueryWrapper<Book> queryWrapper=new QueryWrapper<>();
        queryWrapper.between("book_counts",20,60);
        List<Book> book=bookMapper.selectList(queryWrapper);
        book.forEach(System.out::println);
    }

    /**
     *
     * 复杂查询的
     *   allEq的用法
     */
    @Test
    public void testQueryWrapper4(){
        HashMap<String,Object> map=new HashMap();
        map.put("book_name","《1003夜》");
        map.put("detail","睡前小故事");
        QueryWrapper<Book> queryWrapper=new QueryWrapper<>();
        //SELECT book_id,book_name,book_counts,detail,create_time,update_time,version FROM book
        // WHERE (detail = ? AND book_name = ?)
        queryWrapper.allEq(map);
        List<Book> l=bookMapper.selectList(queryWrapper);
        l.forEach(System.out::println);
    }

    /**
     *
     * 复杂查询的
     *   like notLike likeLeft likeRight
     */
    @Test
    public void testQueryWrapper5(){
        QueryWrapper<Book> queryWrapper=new QueryWrapper<>();
        queryWrapper.like("book_name","ql")
                .notLike("book_name","no");
        //SELECT book_id,book_name,book_counts,detail,create_time,update_time,version FROM book
        // WHERE (book_name LIKE ? AND book_name NOT LIKE ?)
        List<Map<String,Object>> list=bookMapper.selectMaps(queryWrapper);
        System.out.println(list);

    }

    /**
     *
     * 复杂查询的
     *   in notIn inSql notInSql exist notExists
     */
    @Test
    public void testQueryWrapper6(){
        QueryWrapper<Book> queryWrapper=new QueryWrapper<>();
        queryWrapper.inSql("book_id","select book_id from Book where book_id<10");
        //SELECT book_id,book_name,book_counts,detail,create_time,update_time,version FROM book
        //      WHERE (book_id IN (select book_id from Book where book_id<10))
        List<Object> bookIds=bookMapper.selectObjs(queryWrapper);
        System.out.println(bookIds);
    }

    /**
     *
     * 复杂查询的
     *   or and
     */
    @Test
    public void testQueryWrapper7(){
        UpdateWrapper<Book> updateWrapper=new UpdateWrapper<>();
        Book book=new Book();
        book.setBookId(15);
        book.setBookName("《Linux私房菜》");
        book.setBookCounts(81);

//        UPDATE book SET book_name=?, book_counts=?, update_time=?
//              WHERE (book_name LIKE ? OR book_counts LIKE ?)
        updateWrapper.like("book_name","《Linux私房菜》").or().like("book_counts",15);
        int result=bookMapper.update(book,updateWrapper);
        System.out.println(result);

    }

    /**
     *
     * 复杂查询的
     *   嵌套or  嵌套and
     */
    @Test
    public void testQueryWrapper8(){
        UpdateWrapper<Book> updateWrapper=new UpdateWrapper<>();
        Book book=new Book();
        book.setBookId(13);
        book.setBookName("《Mysql高级进阶》");
        book.setBookCounts(88);
        //UPDATE book SET book_name=?, book_counts=?, update_time=?
        //          WHERE (book_name LIKE ? OR (detail = ? AND book_counts <> ?))
        //使用了lambda表达式，or中的表达式后面的条件会加上括号
        updateWrapper.like("book_name","xxx")
                .or(i->i.eq("detail","xxxxxx").ne("book_counts",999));

//        UPDATE book SET book_name=?, book_counts=?, update_time=?
//                  WHERE (book_name LIKE ? OR detail = ? AND book_counts <> ?)
//        updateWrapper.like("book_name","xxx")
//                .or().eq("detail","xxxxxx").ne("book_counts",999);
        int result=bookMapper.update(book,updateWrapper);
        System.out.println(result);
    }


    /**
     *
     * 复杂查询的
     *   9.orderBy orderByDesc orderByAsc
     */
    @Test
    public void testQueryWrapper9(){
        //SELECT book_id,book_name,book_counts,detail,create_time,update_time,version FROM book
        //              ORDER BY book_id ASC

//        orderBy(执行条件,'是否正序',排序的列)
        QueryWrapper<Book> queryWrapper=new QueryWrapper<>();
        queryWrapper.orderBy(true,true,"book_id");
        List<Book> books=bookMapper.selectList(queryWrapper);
        System.out.println(books);
    }

    /**
     *
     * 复杂查询的
     *   10.last
     *   只能调用一次，多次调用以最后一次为准 有sql注入的风险
     */
    @Test
    public void testQueryWrapper10(){
        QueryWrapper<Book> queryWrapper=new QueryWrapper<>();
        //SELECT book_id,book_name,book_counts,detail,create_time,update_time,version FROM book
        //          limit 1
        queryWrapper.last("limit 1");
        Book book=bookMapper.selectOne(queryWrapper);
        System.out.println(book);
    }

    /**
     *
     * 复杂查询的
     *   11. 指点呀查询的列
     */
    @Test
    public void testQueryWrapper11(){
        QueryWrapper<Book> queryWrapper=new QueryWrapper<>();
        //SELECT book_id,book_name FROM book
        queryWrapper.select("book_id","book_name");
        List<Book> list=bookMapper.selectList(queryWrapper);
        list.forEach(System.out::println);

    }

    /**
     *
     * 复杂查询的
     *   12. set setSql
     */
    @Test
    public void testQueryWrapper12(){
        UpdateWrapper<Book> updateWrapper=new UpdateWrapper<>();
        Book book=new Book();
        book.setDetail("xxxx");
        //UPDATE book SET book_counts=?, detail=?, update_time=?, book_name=?,book_counts=?
        //          WHERE (book_name LIKE ? OR book_id BETWEEN ? AND ?)
        updateWrapper.like("book_name","《xxxxxxxxx》")
                .or()
                .between("book_id",1,20)
                .set("book_name","《Redis入门学习》")
//                .setSql("detail='学好努力做缓存'")
                .set("book_counts",50);
        int result=bookMapper.update(book,updateWrapper);
        System.out.println(result);
        System.out.println(book);

    }