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456 lines
12 KiB
Markdown
456 lines
12 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，整个框架只依赖 Mybatis 再无其他第三方依赖
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- 2、只增强，支持 Entity 的增删改查、及分页查询，但不丢失 Mybatis 原有功能
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- 3、Db + Row，可以无需实体类对数据库进行增删改查
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- 4、支持多种数据库类型，自由通过方言持续扩展
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- 5、支持联合主键，以及不同的主键内容生成策略
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- 6、极其友好的 SQL 联动查询，IDE 自动提示不再担心出错
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- 7、更多小惊喜
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## 开始
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- [Maven 依赖](./docs/zh/maven.md)
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- [示例项目](./mybatis-flex-test)
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## QQ 群
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群号： 532992631
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## hello world
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**第一步：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()
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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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**第二步，编写 Mapper 类，并继承 BaseMapper**
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```java
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public interface AccountMapper extends BaseMapper<Account> {
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//只需定义 Mapper 接口即可，可以无任何内容。
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}
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```
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**第三步：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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//示例1：查询 id=100 条数据
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Account account = MybatisFlexBootstrap.getInstance()
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.execute(AccountMapper.class, mapper ->
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mapper.selectOneById(100)
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);
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}
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}
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```
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示例2：查询列表
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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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//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)
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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 = MybatisFlexBootstrap.getInstance()
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.execute(AccountMapper.class, mapper ->
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mapper.selectListByQuery(query)
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);
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}
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}
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```
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示例3：分页查询
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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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// 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 `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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// ORDER BY `tb_account`.`id` DESC
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// LIMIT 40,10
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Page<Account> accounts = MybatisFlexBootstrap.getInstance()
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.execute(AccountMapper.class, mapper ->
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mapper.paginate(5, 10, query)
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);
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}
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}
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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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### select columns
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```java
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QueryWrapper query=new QueryWrapper();
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query.select(ACCOUNT.ID,ACCOUNT.USER_NAME).from(ACCOUNT)
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// SQL:
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// SELECT tb_account.id, tb_account.user_name
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// FROM tb_account
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```
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```java
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QueryWrapper query=new QueryWrapper();
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query.select(ACCOUNT.ALL_COLUMNS).from(ACCOUNT)
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// SQL:
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// SELECT tb_account.id, tb_account.user_name, tb_account.birthday,
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// tb_account.sex, tb_account.is_normal
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// FROM tb_account
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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 tb_account.id, tb_account.user_name,
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// MAX(tb_account.birthday),
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// AVG(tb_account.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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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 tb_account.id >= ?
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// AND tb_account.user_name LIKE ?
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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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exist(
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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 tb_account.id >= ?
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// AND EXIST (
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// SELECT 1 FROM tb_article WHERE tb_article.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).or(ACCOUNT.USER_NAME.like("michael")));
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// SQL:
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// SELECT * FROM tb_account
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// WHERE tb_account.id >= ?
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// AND (tb_account.sex = ? OR tb_account.sex = ? )
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// OR (tb_account.age IN (?,?,?) OR tb_account.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 tb_account.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 tb_account.user_name
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// HAVING tb_account.age BETWEEN ? AND ?
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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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.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
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// ON tb_account.id = tb_article.account_id
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// WHERE tb_account.age >= ?
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```
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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，
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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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## 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，
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Row 是一个 HashMap 的子类，相当于一个通用的 Entity。以下为 Db + Row 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.insertRow("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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## Entity 更新部分字段
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这部分单独拿来强调一下，是因为 MyBatis-Flex 等和其他框架的方法不太一样。在 BaseMapper 中，Mybatis-Flex 提供了如下的方法：
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```java
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update(T entity, boolean ignoreNulls)
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```
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- 第一个参数是 entity 的对象。
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- 第二个参数是是否忽略 null 值。
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但是有些场景下，我们可能希望值更新 几个 字段，甚至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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```java
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Account account = UpdateEntity.of(Account.class);
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account.setId(1);
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account.setUserName(null);
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account.setSex(1);
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accountMapper.update(account,false);
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```
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以上的示例中，会把 id 为 1 的数据中的 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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构建的对象，只会更新调用了 setter 方法的值，不调用 setter 方法的，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 set user_name = ? ,sex = ? where id = ?
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#params: null,1,1
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```
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## 多主键
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Mybatis-Flex 多主键就是在 Entity 类里有多个 `@id` 主键标识而已，比如：
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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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@Id(keyType=KeyType.Generator, value="uuid")
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private String otherId;
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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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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。
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### 自定义主键生成器
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第 1 步：编写一个类，实现 `IKeyGenerator` 接口，例如：
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```java
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public class UUIDKeyGenerator implements IKeyGenerator {
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@Override
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public Object generate(Object entity, String keyColumn) {
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return UUID.randomUUID().toString().replace("-", "");
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}
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}
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```
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第 2 步：注册 UUIDKeyGenerator
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```java
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KeyGeneratorFactory.register("myUUID",new UUIDKeyGenerator());
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```
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第 3 步：在 Entity 里使用 "myUUID" 生成器：
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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.Generator, value="myUUID")
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private String otherId;
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//getter setter
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}
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```
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### 使用数据库 Sequence 生成
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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.Sequence, value="select SEQ_USER_ID.nextval as id from dual")
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private Long id;
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}
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```
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## 更多示例
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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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