虽然 spring5 也推出了 WebFlux 这一套异步技术栈，这种极大提升吞吐的玩法在 node 里玩的风生水起，但 java 世界里异步依旧不是主流，Vertx 倒是做了不少对异步的支持，但是其对于数据访问层的封装依旧还是挺精简的，传统的 javaer 还是受不了这种没有对象映射的工具库，于是我尝试将 Mybatis 移植到了异步驱动上，让数据访问层的工作变得更简单一些。给个例子：@Sql(User.class)public interface CommonMapper { @Select(columns = “id,age,username”) @OrderBy(“id desc”) @Page @ModelConditions({ @ModelCondition(field = “username”, criterion = Criterions.EQUAL), @ModelCondition(field = “maxAge”, column = “age”, criterion = Criterions.LESS), @ModelCondition(field = “minAge”, column = “age”, criterion = Criterions.GREATER) }) void query(UserSearch userSearch, DataHandler<List<User>> handler);}上面是 mapper 接口定义，方法的最后一个参数因为异步的原因所以变成了一个回调，不同的是有很多注解来表达 sql，看到这些注解应该不难猜出 sql 语句吧。如果不喜欢你当然可以继续使用 mapper.xml 的方式来写 sql。更多内容移步代码库吧~AsyncDaoasyncDao是一款异步非阻塞模型下的数据访问层工具。MySQL only. 基于MySQL的异步驱动借鉴了Mybatis的mapping 和 dynamicSQL的内容，Mybatiser可以无缝切换注解表达SQL的能力事务支持SpringBoot支持Mybatis like使用上与Mybatis几乎一致，由于异步非阻塞的关系，数据的返回都会通过回调DataHandler来完成，所以方法定义参数的最后一个一定是DataHandler类型。由于需要提取方法的参数名，于是需要加上编译参数-parameters，请将它在IDE和maven里配置上。public interface CommonDao { void query(User user, DataHandler<List<User>> handler); void querySingle(User user, DataHandler<User> handler); void querySingleMap(User user, DataHandler<Map> handler); void insert(User user,DataHandler<Long> handler); void update(User user,DataHandler<Long> handler); void delete(User user,DataHandler<Long> handler);}mapper.xml与Mybatis几乎一致的写法(覆盖常见标签，一些不常用标签可能不支持，动态SQL建议使用注解SQL功能)<?xml version=“1.0” encoding=“UTF-8”?><mapper namespace=“com.tg.async.mapper.CommonDao”> <resultMap id=“BaseResultMap” type=“com.tg.async.mapper.User”> <id column=“id” property=“id”/> <result column=“old_address” property=“oldAddress”/> <result column=“created_at” property=“createdAt”/> <result column=“password” property=“password”/> <result column=“now_address” property=“nowAddress”/> <result column=“state” property=“state”/> <result column=“age” property=“age”/> <result column=“username” property=“username”/> <result column=“updated_at” property=“updatedAt”/> </resultMap> <select id=“query” resultMap=“BaseResultMap”>select * from T_User <where> <if test=“user.username!=null and user.username!=’’">AND username = #{user.username}</if> <if test=“user.age != null”>OR age > #{user.age}</if> </where> order by id desc </select> <insert id=“insert” useGeneratedKeys=“true” keyProperty=“id”>insert into T_User <trim prefix=”(" suffix=")" suffixOverrides=","> <if test=“user.oldAddress != null”>old_address,</if> <if test=“user.createdAt != null”>created_at,</if> <if test=“user.password != null”>password,</if> <if test=“user.nowAddress != null”>now_address,</if> <if test=“user.state != null”>state,</if> <if test=“user.age != null”>age,</if> <if test=“user.username != null”>username,</if> <if test=“user.updatedAt != null”>updated_at,</if> </trim> <trim prefix=“values (” suffix=")" suffixOverrides=","> <if test=“user.oldAddress != null”>#{user.oldAddress},</if> <if test=“user.createdAt != null”>#{user.createdAt},</if> <if test=“user.password != null”>#{user.password},</if> <if test=“user.nowAddress != null”>#{user.nowAddress},</if> <if test=“user.state != null”>#{user.state},</if> <if test=“user.age != null”>#{user.age},</if> <if test=“user.username != null”>#{user.username},</if> <if test=“user.updatedAt != null”>#{user.updatedAt},</if> </trim> </insert> <update id=“update”> update T_User <set> <if test=“user.password != null”>password=#{user.password},</if> <if test=“user.age != null”>age=#{user.age},</if> </set> where id = #{user.id} </update></mapper>注解SQL在XML里写SQL对于一些常见SQL实在是重复劳动，so这里允许你利用注解来表达SQL，该怎么做呢？Table与Model关联@Table(name = “T_User”)public class User { @Id(“id”) private Long id; //建议全部用包装类型，并注意mysql中字段类型与java类型的对应关系，mysql的int不会自动装换到这里的long private String username; private Integer age; @Column(“now_address”) private String nowAddress; @Column(“created_at”) private LocalDateTime createdAt; //asyncDao 里sql的时间类型都用joda，注意不是JDK8提供的那个，而是第三方包org.joda.time @Ignore private String remrk;@Table记录数据表的名字 @Id记录主键信息 @Column映射了表字段和属性的关系，如果表字段和类属性同名，那么可以省略这个注解 @Ingore忽略这个类属性，没有哪个表字段与它关联。定义接口@Sql(User.class)public interface CommonDao { @Select(columns = “id,age,username”) @OrderBy(“id desc”) @Page @ModelConditions({ @ModelCondition(field = “username”, criterion = Criterions.EQUAL), @ModelCondition(field = “maxAge”, column = “age”, criterion = Criterions.LESS), @ModelCondition(field = “minAge”, column = “age”, criterion = Criterions.GREATER) }) void query(UserSearch userSearch, DataHandler<List<User>> handler); @Select(columns = “age,username”) @OrderBy(“id desc”) void queryParam(@Condition String username, @Condition(criterion = Criterions.GREATER) Integer age, @OffSet int offset, @Limit int limit, DataHandler<List<User>> handler); @Select(columns = “username,age”, sqlMode = SqlMode.COMMON) void queryList(@Condition(criterion = Criterions.IN, column = “id”) int[] ids, DataHandler<List<User>> handler); @Insert(useGeneratedKeys = true, keyProperty = “id”) void insert(User user, DataHandler<Long> handler); @Update @ModelConditions(@ModelCondition(field = “id”)) void update(User user, DataHandler<Long> handler); @Delete @ModelConditions(@ModelCondition(field = “id”)) void delete(User user, DataHandler<Long> handler);}看到这些注解你应该能猜出来SQL长什么样，接下来解释一下这些注解查询@Select(columns = “id,age,username”)@OrderBy(“id desc”)@Page@ModelConditions({ @ModelCondition(field = “username”, criterion = Criterions.EQUAL), @ModelCondition(field = “maxAge”, column = “age”, criterion = Criterions.LESS), @ModelCondition(field = “minAge”, column = “age”, criterion = Criterions.GREATER)})void query(UserSearch userSearch, DataHandler<List<User>> handler);@Selectcolumns:默认 select *可以配置columns(“username,age”)选择部分字段；SqlMode:有两个选择，SqlMode.SELECTIVE 和 SqlMode.COMMON，区别是selective会检查查询条件的字段是否为null来实现动态的查询，即值为null时不会成为查询条件。并且@Select，@Count，@Update，@Delete都有selective这个属性。@Conditioncriterion：查询条件，=,<,>,in等，具体见Criterionscolumn：与表字段的对应，若与字段名相同可不配置attach：连接 and,or， 默认是andtest：SqlMode为selective下的判断表达式，类似Mybatis<if test=“username != null”>里的test属性，动态化查询条件@Limit，@OffSet为分页字段。方法的参数不加任何注解一样会被当做查询条件，如下面两个函数效果是一样的：@Select()void queryUser(Integer age,DataHandler<List<User>> handler);@Select()void queryUser(@Condition(criterion = Criterions.EQUAL, column = “age”) Integer age,DataHandler<List<User>> handler);查询Model上面的例子在查询条件比较多时方法参数会比较多，我们可以把查询条件封装到一个类里，使用@ModelConditions来注解查询条件，注意被@ModelConditions注解的方法只能有两个参数，一个是查询model，一个是DataHandler。@Select@Page@ModelConditions({ @ModelCondition(field = “username”, criterion = Criterions.EQUAL), @ModelCondition(field = “minAge”, column = “age”, criterion = Criterions.GREATER), @ModelCondition(field = “maxAge”, column = “age”, criterion = Criterions.LESS), @ModelCondition(field = “ids”, column = “id”, criterion = Criterions.IN)})void queryUser5(UserSearch userSearch,DataHandler<List<User>> handler);@ModelConditionfield:必填，查询条件中类对应的属性column：对应的表字段test：动态SQL的判断表达式@Page只能用在ModelConditions下的查询，并且方法参数的那个类应该有offset，limit这两个属性，或者 使用@Page(offsetField = “offset”,limitField = “limit”)指定具体字段统计@Countvoid count(DataHandler<Integer> handler);//返回Long类型插入@Insert(useGeneratedKeys = true, keyProperty = “id”)//返回自增idvoid insert(User user, DataHandler<Long> handler);更新@Update(columns = “username,age”)//选择更新某几个列void update(User user, DataHandler<Long> handler);//返回affectedRows删除@Deleteint delete(@Condition(criterion = Criterions.GREATER, column = “age”) int min, @Condition(criterion = Criterions.LESS, column = “age”) int max, DataHandler<Long> handler);@Delete@ModelConditions(@ModelCondition(field = “id”))void delete(User user, DataHandler<Long> handler);使用简单的编程使用AsyncConfig asyncConfig = new AsyncConfig();PoolConfiguration configuration = new PoolConfiguration(“username”, “localhost”, 3306, “password”, “database-name”);asyncConfig.setPoolConfiguration(configuration);asyncConfig.setMapperPackages(“com.tg.async.mapper”);//mapper接口asyncConfig.setXmlLocations(“mapper/”);//xml目录,classpath的相对路径,不支持绝对路径AsyncDaoFactory asyncDaoFactory = AsyncDaoFactory.build(asyncConfig);CommonDao commonDao = asyncDaoFactory.getMapper(CommonDao.class); UserSearch userSearch = new UserSearch();userSearch.setUsername(“ha”);userSearch.setMaxAge(28);userSearch.setMinAge(8);userSearch.setLimit(5);CountDownLatch latch = new CountDownLatch(1);commonDao.query(user, users -> { System.out.println(users); latch.countDown();});latch.await(); 事务Mybatis和Spring体系里有一个非常好用的@Translactional注解，我们知道事务本质就是依赖connection的rollback等操作，那么一个事务下多个SQL就要共用这一个connection，如何共享呢？传统的阻塞体系下ThreadLocal就成了实现这一点的完美解决方案。那么在异步世界里，要实现mybatis-spring一样的上层Api来完成事务操作是一件非常困难的事，难点就在于Api太上层，以至于无法实现connection共享。于是这里自能退而求其次，使用编程式的方式来使用事务，抽象出一个Translaction，具体的mapper通过translaction.getMapper()来获取，这样通过同一个Translaction得到的Mapper都将共用一个connection。CountDownLatch latch = new CountDownLatch(1);AsyncConfig asyncConfig = new AsyncConfig();PoolConfiguration configuration = new PoolConfiguration(“username”, “localhost”, 3306, “password”, “database-name”);asyncConfig.setPoolConfiguration(configuration);asyncConfig.setMapperPackages(“com.tg.async.mapper”);asyncConfig.setXmlLocations(“mapper/”);asyncDaoFactory = AsyncDaoFactory.build(asyncConfig);asyncDaoFactory.startTranslation(res -> { Translaction translaction = res.result(); System.out.println(translaction); CommonDao commonDao = translaction.getMapper(CommonDao.class); User user = new User(); user.setUsername(“insert”); user.setPassword(“1234”); user.setAge(28); commonDao.insert(user, id -> { System.out.println(id); translaction.rollback(Void -> { latch.countDown(); }); });});latch.await();SpringBoot虽然Spring5推出了WebFlux，但异步体系在Spring里依旧不是主流。在异步化改造的过程中，大部分人也往往会保留Spring的IOC，而将其他交给Vertx，所以asyncDao对于Spring的支持就是将Mapper注入IOC容器。quick startYAML配置文件：async: dao: mapperLocations: /mapper #xml目录,classpath的相对路径,不支持绝对路径 basePackages: com.tg.mapper #mapper所在包 username: username host: localhost port: 3306 password: pass database: database-name maxTotal: 12 maxIdle: 12 minIdle: 1 maxWaitMillis: 10000添加@Mapper来实现注入@Mapper@Sql(User.class)public interface CommonDao { @Select(columns = “id,age,username”) @OrderBy(“id desc”) @Page(offsetField = “offset”, limitField = “limit”) @ModelConditions({ @ModelCondition(field = “username”, criterion = Criterions.EQUAL), @ModelCondition(field = “maxAge”, column = “age”, criterion = Criterions.LESS), @ModelCondition(field = “minAge”, column = “age”, criterion = Criterions.GREATER) }) void query(UserSearch userSearch, DataHandler<List<User>> handler);}通过@EnableAsyncDao来开启支持，简单示例：@SpringBootApplication@EnableAsyncDaopublic class DemoApplication { public static void main(String[] args){ ApplicationContext applicationContext = SpringApplication.run(DemoApplication.class); CommonDao commonDao = applicationContext.getBean(CommonDao.class); UserSearch userSearch = new UserSearch(); userSearch.setUsername(“ha”); userSearch.setMaxAge(28); userSearch.setMinAge(8); userSearch.setLimit(5); commonDao.query(userSearch, users -> { System.out.println(“result: " + users); }); }}
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