springboot3+r2dbc——响应式编程实践
作者：麒思妙想
- 2022 年 2 月 17 日
本文字数：7552 字
阅读完需：约 25 分钟
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
<?xml version="1.0" encoding="UTF-8"?><project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>3.0.0-M1</version> <relativePath/> <!-- lookup parent from repository --> </parent> <groupId>wang.datahub</groupId> <artifactId>springboot3demo</artifactId> <version>0.0.1-SNAPSHOT</version> <name>springboot3demo</name> <description>Demo project for Spring Boot</description> <properties> <java.version>17</java.version> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-r2dbc</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-redis-reactive</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-rest</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-groovy-templates</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-hateoas</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-webflux</artifactId> </dependency>
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-configuration-processor</artifactId> <optional>true</optional> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-devtools</artifactId> </dependency>
<dependency> <groupId>io.r2dbc</groupId> <artifactId>r2dbc-h2</artifactId> </dependency> <dependency> <groupId>com.h2database</groupId> <artifactId>h2</artifactId> </dependency>
<dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <scope>runtime</scope> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <dependency> <groupId>io.projectreactor</groupId> <artifactId>reactor-test</artifactId> <scope>test</scope> </dependency> <dependency> <groupId>io.projectreactor</groupId> <artifactId>reactor-test</artifactId><!-- <version>3.4.14</version>--><!-- <scope>compile</scope>--> </dependency>
</dependencies>
<build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> <repositories> <repository> <id>spring-milestones</id> <name>Spring Milestones</name> <url>https://repo.spring.io/milestone</url> <snapshots> <enabled>false</enabled> </snapshots> </repository> <repository> <id>spring-snapshots</id> <name>Spring Snapshots</name> <url>https://repo.spring.io/snapshot</url> <releases> <enabled>false</enabled> </releases> </repository> </repositories> <pluginRepositories> <pluginRepository> <id>spring-milestones</id> <name>Spring Milestones</name> <url>https://repo.spring.io/milestone</url> <snapshots> <enabled>false</enabled> </snapshots> </pluginRepository> <pluginRepository> <id>spring-snapshots</id> <name>Spring Snapshots</name> <url>https://repo.spring.io/snapshot</url> <releases> <enabled>false</enabled> </releases> </pluginRepository> </pluginRepositories>
</project>
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配置文件
这里我们只配置了 r2dbc 链接信息
r2dbc: url: r2dbc:h2:mem:///test?options=DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=FALSE
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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; }
@Bean public 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()); }
@Bean public 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(); }
}
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bean
创建用户 bean
package wang.datahub.springboot3demo.bean;
import org.springframework.data.annotation.Id;
public class Users { @Id private 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; }
@Override public String toString() { return "User{" + "id=" + id + ", firstname='" + firstname + '\'' + ", lastname='" + lastname + '\'' + '}'; }}
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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<Users> 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<Users> 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<Users> 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 <T> Mono<T> close(Connection connection) { return Mono.from(connection.close()) .then(Mono.empty()); }}
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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 { @Autowired private final UsersDao usersDao;
public UsersController(UsersDao usersDao) { this.usersDao = usersDao; }
@GetMapping("/users/{id}") public Mono<ResponseEntity<Users>> 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<Users> getAllAccounts() { return usersDao.findAll(); }
@PostMapping("/createUser") public Mono<ResponseEntity<Users>> createUser(@RequestBody Users user) { return usersDao.createAccount(user) .map(acc -> new ResponseEntity<>(acc, HttpStatus.CREATED)) .log(); }}
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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); }}
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好了，致此我们整个 Demo 就实现完成了
参考链接：
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