Basic use of [MyBatis-Plus] (SpringBoot)

1. What is MyBatis-Plus

Mybatis-Plus: Born to simplify development

        MyBatis-Plus (MP for short) is an enhancement tool based on MyBatis. It enhances the basic functions of Mybatis without making any changes. This allows us to directly upgrade projects developed by Mybatis to Mybatis-plus. Just as it positions itself, it can help us further simplify the development process and improve development efficiency.

        Mybatis-Plus can actually be seen as another encapsulation of Mybatis. After the upgrade, CRUD operations on a single table can be easily implemented by calling the API provided by Mybatis-Plus. In addition, various query methods, paging and other behaviors are provided. . The most important thing is that developers don’t have to write XML, which greatly reduces the difficulty of development.

2. Quick use

1. Import dependencies

        <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. Configure database parameters

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. Create a database table

4. File directory

5. Entity class

@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. Do table mapping

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

7. You can start testing

 3. General usage

(1).Find and update operations

 /**
     * 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). Use of optimistic locks

        1. Write a configuration class and add the official interceptor function. Pagination is also added together with this. Remember to write the version field in the table.

    /**
     * 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). Delete operation

    /**
     * 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) Paging query

    /**
     * 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. Complex queries

Mybatis-Plus provides two commonly used classes to handle complex query operations, QueryWrapper and 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);

    }