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619 lines
15 KiB
Markdown
619 lines
15 KiB
Markdown
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# MyBatis-Flex： 一个优雅的 MyBatis 增强框架
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## 特征
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#### 1、很轻量
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> MyBatis-Flex 整个框架只依赖 MyBatis，再无其他任何第三方依赖。
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#### 2、只增强
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> MyBatis-Flex 支持 CRUD、分页查询、多表查询、批量操作，但不丢失 MyBatis 原有的任何功能。
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#### 3、高性能
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> MyBatis-Flex 采用独特的技术架构、相比许多同类框架，MyBatis-Flex 的在增删改查等方面的性能均超越其 5~10 倍或以上。
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#### 4、更灵动
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> MyBatis-Flex 支持多主键、多表查询、逻辑删除、乐观锁、数据脱敏、数据加密、多数据源、分库分表、字段权限、
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> 字段加密、多租户、事务管理、SQL 审计... 等等等等。 这一切，免费且灵动。
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## QQ 群
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群号： 850176767
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## 开始
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- [快速开始](https://mybatis-flex.com/zh/intro/getting-started.html)
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- 示例 1：[Mybatis-Flex 原生（非 Spring）](./mybatis-flex-test/mybatis-flex-native-test)
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- 示例 2：[Mybatis-Flex with Spring](./mybatis-flex-test/mybatis-flex-spring-test)
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- 示例 3：[Mybatis-Flex with Spring boot](./mybatis-flex-test/mybatis-flex-spring-boot-test)
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- 示例 4：[Db + Row](./mybatis-flex-test/mybatis-flex-native-test/src/main/java/com/mybatisflex/test/DbTestStarter.java)
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## hello world（原生）
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**第 1 步：编写 Entity 实体类**
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```java
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@Table("tb_account")
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public class Account {
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@Id(keyType = KeyType.Auto)
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private Long id;
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private String userName;
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private Date birthday;
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private int sex;
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//getter setter
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}
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```
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**第 2 步：开始查询数据**
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示例 1：查询 1 条数据
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```java
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class HelloWorld {
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public static void main(String... args) {
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HikariDataSource dataSource = new HikariDataSource();
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dataSource.setJdbcUrl("jdbc:mysql://127.0.0.1:3306/mybatis-flex");
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dataSource.setUsername("username");
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dataSource.setPassword("password");
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MybatisFlexBootstrap.getInstance()
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.setDataSource(dataSource)
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.addMapper(AccountMapper.class)
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.start();
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AccountMapper mapper = MybatisFlexBootstrap.getInstance()
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.getMapper(AccountMapper.class);
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//示例1：查询 id=100 条数据
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Account account = mapper.selectOneById(100);
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}
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}
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```
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> 以上的 `AccountMapper.class` 为 Mybatis-Flex 自动通过 APT 生成，无需手动编码。也可以关闭自动生成功能，手动编写 AccountMapper，更多查看 APT 文档。
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示例2：查询列表
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```java
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//示例2：通过 QueryWrapper 构建条件查询数据列表
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QueryWrapper query = QueryWrapper.create()
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.select()
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.from(ACCOUNT) // 单表查询时表名可省略，自动使用Mapper泛型对应的表
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.where(ACCOUNT.ID.ge(100))
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.and(ACCOUNT.USER_NAME.like("张").or(ACCOUNT.USER_NAME.like("李")));
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// 执行 SQL：
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// ELECT * FROM tb_account
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// WHERE tb_account.id >= 100
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// AND (tb_account.user_name LIKE '%张%' OR tb_account.user_name LIKE '%李%' )
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List<Account> accounts = accountMapper.selectListByQuery(query);
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```
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示例3：分页查询
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```java
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// 示例3：分页查询
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// 查询第 5 页，每页 10 条数据，通过 QueryWrapper 构建条件查询
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QueryWrapper query=QueryWrapper.create()
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.select()
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.from(ACCOUNT)
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.where(ACCOUNT.ID.ge(100))
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.and(ACCOUNT.USER_NAME.like("张").or(ACCOUNT.USER_NAME.like("李")))
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.orderBy(ACCOUNT.ID.desc());
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// 执行 SQL：
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// ELECT * FROM tb_account
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// WHERE id >= 100
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// AND (user_name LIKE '%张%' OR user_name LIKE '%李%' )
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// ORDER BY `id` DESC
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// LIMIT 40,10
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Page<Account> accounts = mapper.paginate(5, 10, query);
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```
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## QueryWrapper 示例
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### select *
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```java
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QueryWrapper query = new QueryWrapper();
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query.select().from(ACCOUNT);
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// SQL:
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// SELECT * FROM tb_account
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```
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也可以通过静态方法简写成如下两种形式，效果完全相同：
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```java
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// 方式1
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QueryWrapper query = QueryWrapper.create()
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.select().from(ACCOUNT);
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// 方式2
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QueryWrapper query = select().from(ACCOUNT);
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// SQL:
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// SELECT * FROM tb_account
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```
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### select columns
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简单示例：
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```java
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QueryWrapper query = new QueryWrapper();
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query.select(ACCOUNT.ID, ACCOUNT.USER_NAME)
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.from(ACCOUNT);
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// SQL:
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// SELECT id, user_name
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// FROM tb_account
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```
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多表查询（同时展现了功能强大的 `as` 能力）：
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```java
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QueryWrapper query = new QueryWrapper()
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.select(ACCOUNT.ID
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, ACCOUNT.USER_NAME
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, ARTICLE.ID.as("articleId")
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, ARTICLE.TITLE)
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.from(ACCOUNT.as("a"), ARTICLE.as("b"))
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.where(ACCOUNT.ID.eq(ARTICLE.ACCOUNT_ID));
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// SQL:
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// SELECT a.id, a.user_name, b.id AS articleId, b.title
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// FROM tb_account AS a, tb_article AS b
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// WHERE a.id = b.account_id
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```
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### select functions
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```java
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QueryWrapper query = new QueryWrapper()
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.select(
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ACCOUNT.ID,
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ACCOUNT.USER_NAME,
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max(ACCOUNT.BIRTHDAY),
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avg(ACCOUNT.SEX).as("sex_avg")
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).from(ACCOUNT);
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// SQL:
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// SELECT id, user_name,
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// MAX(birthday),
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// AVG(sex) AS sex_avg
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// FROM tb_account
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```
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### where
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```java
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Integer num = 100;
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String userName = "michael";
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QueryWrapper queryWrapper = QueryWrapper.create()
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.select()
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.from(ACCOUNT)
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.where(ACCOUNT.ID.ge(100))
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.and(ACCOUNT.USER_NAME.like("michael"));
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// SQL:
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// SELECT * FROM tb_account
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// WHERE id >= ?
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// AND user_name LIKE ?
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```
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### where 动态条件 1
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```java
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boolean flag = false;
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QueryWrapper queryWrapper = QueryWrapper.create()
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.select().from(ACCOUNT)
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.where(flag ? ACCOUNT.ID.ge(100) : noCondition())
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.and(ACCOUNT.USER_NAME.like("michael"));
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// SQL:
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// SELECT * FROM tb_account
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// WHERE user_name LIKE ?
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```
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### where 动态条件 2
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```java
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boolean flag = false;
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QueryWrapper queryWrapper = QueryWrapper.create()
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.select().from(ACCOUNT)
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.where(ACCOUNT.ID.ge(100).when(flag))
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.and(ACCOUNT.USER_NAME.like("michael"));
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// SQL:
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// SELECT * FROM tb_account
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// WHERE user_name LIKE ?
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```
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### where 自动忽略 null 值
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当遇到条件值为 null 时，会自动忽略该条件，不会拼接到 SQL 中
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```java
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Integer num = null;
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String userName = "michael";
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QueryWrapper queryWrapper = QueryWrapper.create()
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.select()
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.from(ACCOUNT)
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.where(ACCOUNT.ID.ge(num))
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.and(ACCOUNT.USER_NAME.like(userName));
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// SQL:
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// SELECT * FROM tb_account
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// WHERE user_name LIKE '%michael%'
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```
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### where select
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```java
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QueryWrapper queryWrapper = QueryWrapper.create()
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.select()
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.from(ACCOUNT)
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.where(ACCOUNT.ID.ge(
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select(ARTICLE.ACCOUNT_ID).from(ARTICLE).where(ARTICLE.ID.ge(100))
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));
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// SQL:
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// SELECT * FROM tb_account
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// WHERE id >=
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// (SELECT account_id FROM tb_article WHERE id >= ? )
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```
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### exists, not exists
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```java
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QueryWrapper queryWrapper=QueryWrapper.create()
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.select()
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.from(ACCOUNT)
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.where(ACCOUNT.ID.ge(100))
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.and(
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exists( // or notExists(...)
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selectOne().from(ARTICLE).where(ARTICLE.ID.ge(100))
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)
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);
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// SQL:
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// SELECT * FROM tb_account
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// WHERE id >= ?
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// AND EXIST (
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// SELECT 1 FROM tb_article WHERE id >= ?
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// )
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```
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### and (...) or (...)
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```java
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QueryWrapper queryWrapper = QueryWrapper.create()
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.select()
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.from(ACCOUNT)
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.where(ACCOUNT.ID.ge(100))
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.and(ACCOUNT.SEX.eq(1).or(ACCOUNT.SEX.eq(2)))
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.or(ACCOUNT.AGE.in(18,19,20).and(ACCOUNT.USER_NAME.like("michael")));
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// SQL:
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// SELECT * FROM tb_account
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// WHERE id >= ?
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// AND (sex = ? OR sex = ? )
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// OR (age IN (?,?,?) AND user_name LIKE ? )
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```
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### group by
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```java
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QueryWrapper queryWrapper = QueryWrapper.create()
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.select()
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.from(ACCOUNT)
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.groupBy(ACCOUNT.USER_NAME);
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// SQL:
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// SELECT * FROM tb_account
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// GROUP BY user_name
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```
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### having
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```java
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QueryWrapper queryWrapper = QueryWrapper.create()
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.select()
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.from(ACCOUNT)
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.groupBy(ACCOUNT.USER_NAME)
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.having(ACCOUNT.AGE.between(18,25));
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// SQL:
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// SELECT * FROM tb_account
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// GROUP BY user_name
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// HAVING age BETWEEN ? AND ?
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```
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### orderBy
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```java
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QueryWrapper queryWrapper = QueryWrapper.create()
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.select()
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.from(ACCOUNT)
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.orderBy(ACCOUNT.AGE.asc()
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, ACCOUNT.USER_NAME.desc().nullsLast());
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// SQL:
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// SELECT * FROM tb_account
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// ORDER BY age ASC, user_name DESC NULLS LAST
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```
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### join
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```java
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QueryWrapper queryWrapper = QueryWrapper.create()
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.select()
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.from(ACCOUNT)
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.leftJoin(ARTICLE).on(ACCOUNT.ID.eq(ARTICLE.ACCOUNT_ID))
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.innerJoin(ARTICLE).on(ACCOUNT.ID.eq(ARTICLE.ACCOUNT_ID))
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.where(ACCOUNT.AGE.ge(10));
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// SQL:
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// SELECT * FROM tb_account
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// LEFT JOIN tb_article ON tb_account.id = tb_article.account_id
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// INNER JOIN tb_article ON tb_account.id = tb_article.account_id
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// WHERE tb_account.age >= ?
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```
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### limit... offset
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```java
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QueryWrapper queryWrapper = QueryWrapper.create()
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.select()
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.from(ACCOUNT)
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.orderBy(ACCOUNT.ID.desc())
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.limit(10)
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.offset(20);
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// MySql:
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// SELECT * FROM `tb_account` ORDER BY `id` DESC LIMIT 20, 10
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// PostgreSQL:
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// SELECT * FROM "tb_account" ORDER BY "id" DESC LIMIT 20 OFFSET 10
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// Informix:
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// SELECT SKIP 20 FIRST 10 * FROM "tb_account" ORDER BY "id" DESC
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// Oracle:
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// SELECT * FROM (SELECT TEMP_DATAS.*,
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// ROWNUM RN FROM (
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// SELECT * FROM "tb_account" ORDER BY "id" DESC)
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// TEMP_DATAS WHERE ROWNUM <=30)
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// WHERE RN >20
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// Db2:
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// SELECT * FROM "tb_account" ORDER BY "id" DESC
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// OFFSET 20 ROWS FETCH NEXT 10 ROWS ONLY
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// Sybase:
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// SELECT TOP 10 START AT 21 * FROM "tb_account" ORDER BY "id" DESC
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// Firebird:
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// SELECT * FROM "tb_account" ORDER BY "id" DESC ROWS 20 TO 30
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```
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> 在以上的 "limit... offset" 示例中，Mybatis-Flex 能够自动识别当前数据库，并生成不同的 SQL，用户也可以很轻易的通过
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> `DialectFactory` 注册（新增或改写）自己的实现方言。
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### 存在疑问？
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**疑问 1：QueryWrapper 是否可以在分布式项目中通过 RPC 传输？**
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答：可以。
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**疑问 2：如何通过实体类 Account.java 生成 QueryWrapper 所需要的 "ACCOUNT" 类 ?**
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答：Mybatis-Flex 使用了 APT（Annotation Processing Tool）技术，在项目编译的时候，会自动根据 Entity 类定义的字段帮你生成 "ACCOUNT" 类以及 Entity 对应的 Mapper 类，
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通过开发工具构建项目（如下图），或者执行 maven 编译命令: `mvn clean package` 都可以自动生成。这个原理和 lombok 一致。
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> 更多关于 Mybatis-Flex APT 的配置，请点击 [这里](./docs/zh/others/apt.md)。
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## Db + Row 工具类
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Db + Row 工具类，提供了在 Entity 实体类之外的数据库操作能力。使用 Db + Row 时，无需对数据库表进行映射， Row 是一个 HashMap 的子类，相当于一个通用的 Entity。以下为 Db + Row
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的一些示例：
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```java
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//使用原生 SQL 插入数据
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String sql="insert into tb_account(id,name) value (?, ?)";
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Db.insertBySql(sql, 1, "michael");
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//使用 Row 插入数据
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Row account = new Row();
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account.set("id", 100);
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account.set("name", "Michael");
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Db.insert("tb_account", account);
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//根据主键查询数据
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Row row = Db.selectOneById("tb_account", "id", 1);
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//Row 可以直接转换为 Entity 实体类，且性能极高
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Account account = row.toEntity(Account.class);
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//查询所有大于 18 岁的用户
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String listsql = "select * from tb_account where age > ?"
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List<Row> rows = Db.selectListBySql(sql, 18);
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//分页查询：每页 10 条数据，查询第 3 页的年龄大于 18 的用户
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QueryWrapper query = QueryWrapper.create()
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.where(ACCOUNT.AGE.ge(18));
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Page<Row> rowPage = Db.paginate("tb_account", 3, 10, query);
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```
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> Db 工具类还提供了更多 增、删、改、查和分页查询等方法。
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>
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> 具体参考： [Db.java](./mybatis-flex-core/src/main/java/com/mybatisflex/core/row/Db.java) 。
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>
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> 更多关于 Row 插入时的**主键生成机制**、以及Db 的**事务管理**等，请点击 [这里](./docs/zh/core/db-row.md) 。
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## Entity 部分字段更新
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相比市面上的其他框架，这部分的功能应该也算是 MyBatis-Flex 的亮点之一。在 BaseMapper 中，Mybatis-Flex 提供了如下的方法：
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|
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```java
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update(T entity)
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```
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有些场景下，我们可能希望只更新 几个 字段，而其中个别字段需要更新为 null。此时需要用到 `UpdateEntity` 工具类，以下是示例代码：
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|
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```java
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Account account = UpdateEntity.of(Account.class);
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account.setId(100);
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account.setUserName(null);
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account.setSex(1);
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accountMapper.update(account);
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```
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以上的示例中，会把 id 为 100 这条数据中的 user_name 字段更新为 null，sex 字段更新为 1，其他字段不会被更新。也就是说，通过 `UpdateEntity`
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创建的对象，只会更新调用了 setter 方法的字段，若不调用 setter 方法，不管这个对象里的属性的值是什么，都不会更新到数据库。
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||
|
||
其生成的 sql 内容如下：
|
||
|
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```sql
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update tb_account
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set user_name = ?, sex = ? where id = ?
|
||
#params: null,1,100
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```
|
||
|
||
|
||
## 自定义 TypeHandler
|
||
|
||
使用 @Column 注解：
|
||
|
||
```java
|
||
@Table("tb_account")
|
||
public class Account {
|
||
|
||
@Id(keyType = KeyType.Auto)
|
||
private Long id;
|
||
|
||
private String userName;
|
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|
||
@Column(typeHandler = Fastjson2TypeHandler.class)
|
||
private Map<String, Object> options;
|
||
|
||
//getter setter
|
||
|
||
public void addOption(String key, Object value) {
|
||
if (options == null) {
|
||
options = new HashMap<>();
|
||
}
|
||
options.put(key, value);
|
||
}
|
||
}
|
||
```
|
||
|
||
插入数据：
|
||
|
||
```java
|
||
Account account = new Account();
|
||
account.setUserName("test");
|
||
account.addOption("c1", 11);
|
||
account.addOption("c2", "zhang");
|
||
account.addOption("c3", new Date());
|
||
```
|
||
mybatis 日志：
|
||
```
|
||
==> Preparing: INSERT INTO tb_account (user_name, options) VALUES (?, ?)
|
||
==> Parameters: test(String), {"c3":"2023-03-17 09:10:16.546","c1":11,"c2":"zhang"}(String)
|
||
```
|
||
|
||
## 多主键
|
||
|
||
Mybatis-Flex 多主键就是在 Entity 类里有多个 `@Id` 注解标识而已，比如：
|
||
|
||
```java
|
||
|
||
@Table("tb_account")
|
||
public class Account {
|
||
|
||
@Id(keyType = KeyType.Auto)
|
||
private Long id;
|
||
|
||
@Id(keyType = KeyType.Generator, value = "uuid")
|
||
private String otherId;
|
||
|
||
//getter setter
|
||
}
|
||
```
|
||
|
||
当我们保存数据的时候，Account 的 id 主键为自增，而 otherId 主键则通过 uuid 生成。
|
||
|
||
### 自定义主键生成器
|
||
|
||
第 1 步：编写一个类，实现 `IKeyGenerator` 接口，例如：
|
||
|
||
```java
|
||
public class UUIDKeyGenerator implements IKeyGenerator {
|
||
|
||
@Override
|
||
public Object generate(Object entity, String keyColumn) {
|
||
return UUID.randomUUID().toString().replace("-", "");
|
||
}
|
||
}
|
||
```
|
||
|
||
第 2 步：注册 UUIDKeyGenerator
|
||
|
||
```java
|
||
KeyGeneratorFactory.register("myUUID", new UUIDKeyGenerator());
|
||
```
|
||
|
||
第 3 步：在 Entity 里使用 "myUUID" 生成器：
|
||
|
||
```java
|
||
|
||
@Table("tb_account")
|
||
public class Account {
|
||
|
||
@Id(keyType = KeyType.Generator, value = "myUUID")
|
||
private String otherId;
|
||
|
||
//getter setter
|
||
}
|
||
```
|
||
|
||
### 使用数据库 Sequence 生成
|
||
|
||
```java
|
||
|
||
@Table("tb_account")
|
||
public class Account {
|
||
|
||
@Id(keyType = KeyType.Sequence, value = "select SEQ_USER_ID.nextval as id from dual")
|
||
private Long id;
|
||
|
||
}
|
||
```
|
||
|
||
> 更多关于主键的配置，请点击 [这里](./docs/zh/core/id.md)
|
||
|
||
## 更多文档
|
||
|
||
- [https://mybatis-flex.com](https://mybatis-flex.com)
|
||
|
||
## 还有问题？
|
||
|
||
加入 QQ 交流群： 850176767
|
||
|
||
|
||
|