springboot3+r2dbc響應式程式設計實踐

2022-02-11 16:01:49

Spring boot3已經M1了，最近群佬們也開始蠢蠢欲動的開始整活Reactive+Spring Boot3,跟著大家的步伐，我也來整一篇工程入門，我們將用java17+Spring Boot3+r2dbc+Reactive棧來講述，歡迎大家來討論。（關於響應式，請大家非同步到之前的文章裡，有詳細介紹。）

r2dbc

Reactor還有基於其之上的Spring WebFlux框架。包括vert.x，rxjava等等reactive技術。我們實際上在應用層已經有很多優秀的響應式處理框架。

但是有一個問題就是所有的框架都需要獲取底層的資料，而基本上關係型資料庫的底層讀寫都還是同步的。

為了解決這個問題，出現了兩個標準，一個是oracle提出的 ADBC (Asynchronous Database Access API)，另一個就是Pivotal提出的R2DBC (Reactive Relational Database Connectivity)。

R2DBC是基於Reactive Streams標準來設計的。通過使用R2DBC，你可以使用reactive API來運算元據。

同時R2DBC只是一個開放的標準，而各個具體的資料庫連線實現，需要實現這個標準。

今天我們以r2dbc-h2為例，講解一下r2dbc在Spring webFlux中的使用。

工程依賴

以下是 pom.xml清單

<?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>

組態檔

這裡我們只設定了r2dbc連結資訊

設定類

用於設定預設連結，建立初始化資料

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

建立使用者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程式碼清單如下，包含查詢列表、按id查詢，以及建立使用者等操作

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程式碼清單如下，包含了查詢列表、按id查詢，以及建立使用者等操作

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();
    }
}

啟動類清單：

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，致此我們整個 Demo 就實現完成了

參考連結：

https://zhuanlan.zhihu.com/p/299069835

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springboot3+r2dbc響應式程式設計實踐

目錄

r2dbc

工程依賴

組態檔

設定類

bean

DAO

controller

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