springboot3+r2dbc响应式编程实践
更新时间：2022年02月11日 11:54:05 作者：麒思妙想
本文主要介绍了springboot3+r2dbc响应式编程实践，文中通过示例代码介绍的非常详细，具有一定的参考价值，感兴趣的小伙伴们可以参考一下
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>
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;
}
@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();
}
}
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 + '\'' +
'}';
}
}
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;
@Component
public 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());
}
}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;
@RestController
public 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();
}
}
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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