springboot3+r2dbc响应式编程实践 springboot3+r2dbc响应式编程实践

r2dbc
工程依赖
配置文件

配置类
bean
DAO
controller

Spring boot3已经M1了，最近群佬们也开始蠢蠢欲动的开始整活Reactive+Spring Boot3,跟着大家的步伐，我也来整一篇工程入门，我们将用java17+Spring Boot3+r2dbc+Reactive栈来讲述，欢迎大家来讨论。（关于响应式，请大家异步到之前的文章里，有详细介绍。）

r2dbc Reactor还有基于其之上的Spring WebFlux框架。包括vert.x，rxjava等等reactive技术。我们实际上在应用层已经有很多优秀的响应式处理框架。
但是有一个问题就是所有的框架都需要获取底层的数据，而基本上关系型数据库的底层读写都还是同步的。
为了解决这个问题，出现了两个标准，一个是oracle提出的 ADBC (Asynchronous Database Access API)，另一个就是Pivotal提出的R2DBC (Reactive Relational Database Connectivity)。
R2DBC是基于Reactive Streams标准来设计的。通过使用R2DBC，你可以使用reactive API来操作数据。
同时R2DBC只是一个开放的标准，而各个具体的数据库连接实现，需要实现这个标准。
今天我们以r2dbc-h2为例，讲解一下r2dbc在Spring webFlux中的使用。

工程依赖以下是 pom.xml清单

4.0.0org.springframework.bootspring-boot-starter-parent3.0.0-M1 wang.datahubspringboot3demo0.0.1-SNAPSHOTspringboot3demoDemo project for Spring Boot17org.springframework.bootspring-boot-starter-data-r2dbcorg.springframework.bootspring-boot-starter-data-redis-reactiveorg.springframework.bootspring-boot-starter-data-restorg.springframework.bootspring-boot-starter-groovy-templatesorg.springframework.bootspring-boot-starter-hateoasorg.springframework.bootspring-boot-starter-weborg.springframework.bootspring-boot-starter-webfluxorg.springframework.bootspring-boot-configuration-processortrueorg.springframework.bootspring-boot-devtoolsio.r2dbcr2dbc-h2com.h2databaseh2mysqlmysql-connector-javaruntimeorg.springframework.bootspring-boot-starter-testtestio.projectreactorreactor-testtestio.projectreactorreactor-testorg.springframework.bootspring-boot-maven-pluginspring-milestonesSpring Milestoneshttps://repo.spring.io/milestonefalsespring-snapshotsSpring Snapshotshttps://repo.spring.io/snapshotfalsespring-milestonesSpring Milestoneshttps://repo.spring.io/milestonefalsespring-snapshotsSpring Snapshotshttps://repo.spring.io/snapshotfalse

配置文件这里我们只配置了r2dbc链接信息

配置类
用于配置默认链接，创建初始化数据

package wang.datahub.springboot3demo.config; import io.netty.util.internal.StringUtil; import io.r2dbc.spi.ConnectionFactories; import io.r2dbc.spi.ConnectionFactory; import io.r2dbc.spi.ConnectionFactoryOptions; import org.springframework.beans.factory.annotation.Value; import org.springframework.boot.CommandLineRunner; import org.springframework.boot.context.properties.ConfigurationProperties; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import reactor.core.publisher.Flux; import static io.r2dbc.spi.ConnectionFactoryOptions.*; @Configuration@ConfigurationProperties(prefix = "r2dbc")public class DBConfig {private String url; private String user; private String password; public String getUrl() {return url; }public void setUrl(String url) {this.url = url; }public String getUser() {return user; }public void setUser(String user) {this.user = user; }public String getPassword() {return password; }public void setPassword(String password) {this.password = password; }@Beanpublic ConnectionFactory connectionFactory() {System.out.println("url ==> "+url); ConnectionFactoryOptions baseOptions = ConnectionFactoryOptions.parse(url); ConnectionFactoryOptions.Builder ob = ConnectionFactoryOptions.builder().from(baseOptions); if (!StringUtil.isNullOrEmpty(user)) {ob = ob.option(USER, user); }if (!StringUtil.isNullOrEmpty(password)) {ob = ob.option(PASSWORD, password); }return ConnectionFactories.get(ob.build()); }@Beanpublic CommandLineRunner initDatabase(ConnectionFactory cf) {return (args) ->Flux.from(cf.create()).flatMap(c ->Flux.from(c.createBatch().add("drop table if exists Users").add("create table Users(" +"id IDENTITY(1,1)," +"firstname varchar(80) not null," +"lastname varchar(80) not null)").add("insert into Users(firstname,lastname)" +"values('Jacky','Li')").add("insert into Users(firstname,lastname)" +"values('Doudou','Li')").add("insert into Users(firstname,lastname)" +"values('Maimai','Li')").execute()).doFinally((st) -> c.close())).log().blockLast(); }}

bean
创建用户bean

package wang.datahub.springboot3demo.bean; import org.springframework.data.annotation.Id; public class Users {@Idprivate Long id; private String firstname; private String lastname; public Users(){}public Users(Long id, String firstname, String lastname) {this.id = id; this.firstname = firstname; this.lastname = lastname; }public Long getId() {return id; }public void setId(Long id) {this.id = id; }public String getFirstname() {return firstname; }public void setFirstname(String firstname) {this.firstname = firstname; }public String getLastname() {return lastname; }public void setLastname(String lastname) {this.lastname = lastname; }@Overridepublic String toString() {return "User{" +"id=" + id +", firstname='" + firstname + '\'' +", lastname='" + lastname + '\'' +'}'; }}

DAO
dao代码清单如下，包含查询列表、按id查询，以及创建用户等操作

package wang.datahub.springboot3demo.dao; import io.r2dbc.spi.Connection; import io.r2dbc.spi.ConnectionFactory; import org.springframework.data.r2dbc.core.R2dbcEntityTemplate; import org.springframework.data.relational.core.query.Query; import org.springframework.stereotype.Component; import reactor.core.publisher.Flux; import reactor.core.publisher.Mono; import wang.datahub.springboot3demo.bean.Users; import static org.springframework.data.r2dbc.query.Criteria.where; import static org.springframework.data.relational.core.query.Query.query; @Componentpublic class UsersDao {private ConnectionFactory connectionFactory; private R2dbcEntityTemplate template; public UsersDao(ConnectionFactory connectionFactory) {this.connectionFactory = connectionFactory; this.template = new R2dbcEntityTemplate(connectionFactory); }public Mono findById(long id) {return this.template.selectOne(query(where("id").is(id)),Users.class); //return Mono.from(connectionFactory.create())//.flatMap(c -> Mono.from(c.createStatement("select id,firstname,lastname from Users where id = $1")//.bind("$1", id)//.execute())//.doFinally((st) -> close(c)))//.map(result -> result.map((row, meta) ->//new Users(row.get("id", Long.class),//row.get("firstname", String.class),//row.get("lastname", String.class))))//.flatMap( p -> Mono.from(p)); }public Flux findAll() {return this.template.select(Users.class).all(); //return Mono.from(connectionFactory.create())//.flatMap((c) -> Mono.from(c.createStatement("select id,firstname,lastname from users")//.execute())//.doFinally((st) -> close(c)))//.flatMapMany(result -> Flux.from(result.map((row, meta) -> {//Users acc = new Users(); //acc.setId(row.get("id", Long.class)); //acc.setFirstname(row.get("firstname", String.class)); //acc.setLastname(row.get("lastname", String.class)); //return acc; //}))); }public Mono createAccount(Users account) {return Mono.from(connectionFactory.create()).flatMap(c -> Mono.from(c.beginTransaction()).then(Mono.from(c.createStatement("insert into Users(firstname,lastname) values($1,$2)").bind("$1", account.getFirstname()).bind("$2", account.getLastname()).returnGeneratedValues("id").execute())).map(result -> result.map((row, meta) ->new Users(row.get("id", Long.class),account.getFirstname(),account.getLastname()))).flatMap(pub -> Mono.from(pub)).delayUntil(r -> c.commitTransaction()).doFinally((st) -> c.close())); }private Mono close(Connection connection) {return Mono.from(connection.close()).then(Mono.empty()); }}

controller
controller代码清单如下，包含了查询列表、按id查询，以及创建用户等操作

package wang.datahub.springboot3demo.controller; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.http.HttpStatus; import org.springframework.http.ResponseEntity; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.*; import reactor.core.publisher.Flux; import reactor.core.publisher.Mono; import wang.datahub.springboot3demo.bean.Users; import wang.datahub.springboot3demo.dao.UsersDao; @RestControllerpublic class UsersController {@Autowiredprivate final UsersDao usersDao; public UsersController(UsersDao usersDao) {this.usersDao = usersDao; }@GetMapping("/users/{id}")public Mono> getUsers(@PathVariable("id") Long id) {return usersDao.findById(id).map(acc -> new ResponseEntity<>(acc, HttpStatus.OK)).switchIfEmpty(Mono.just(new ResponseEntity<>(null, HttpStatus.NOT_FOUND))); }@GetMapping("/users")public Flux getAllAccounts() {return usersDao.findAll(); }@PostMapping("/createUser")public Mono> createUser(@RequestBody Users user) {return usersDao.createAccount(user).map(acc -> new ResponseEntity<>(acc, HttpStatus.CREATED)).log(); }}

启动类清单：

package wang.datahub.springboot3demo; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.boot.context.properties.EnableConfigurationProperties; import wang.datahub.springboot3demo.config.DBConfig; @SpringBootApplication@EnableConfigurationProperties(DBConfig.class)public class WebFluxR2dbcApp {public static void main(String[] args) {SpringApplication.run(WebFluxR2dbcApp.class, args); }}

好了，致此我们整个 Demo 就实现完成了
参考链接：
https://zhuanlan.zhihu.com/p/299069835
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