使用反应式数据库客户端扩展 Spring WebFlux 应用程序时出现问题：冲突的 Maven 依赖项？

Question

我有一个基于此代码制作的小型 Spring WebFlux 应用程序：

https://github.com/chang-chao/spring-webflux-reactive-jdbc-sample

据我所知，这是纯反应式编程和通常的阻塞关系数据库之间的某种混合。

现在我的任务是将反应式数据库客户端添加到我的应用程序。我盯着这个指南：

https://spring.io/guides/gs/accessing-data-r2dbc/

但是一旦我将以下依赖项添加到我的 pom.xml:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-r2dbc</artifactId>
    <version>2.3.4.RELEASE</version>
</dependency>

<dependency>
    <groupId>io.r2dbc</groupId>
    <artifactId>r2dbc-h2</artifactId>
    <version>0.8.4.RELEASE</version>
    <scope>runtime</scope>
</dependency>

我的 WORKING 应用程序启动失败，提示找不到自动装配的存储库 bean。一旦我删除了上面的两个依赖项，这个错误就消失了。

工作应用的 pom.xml 初始完整：

<?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>2.3.4.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.freelance</groupId>
    <artifactId>studentlist</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>student-list</name>
    <description>Spring WebFlux application for managing students</description>

    <properties>
        <java.version>11</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-webflux</artifactId>
            <version>2.3.4.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
            <version>2.3.4.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <version>2.3.4.RELEASE</version>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>io.projectreactor</groupId>
            <artifactId>reactor-test</artifactId>
            <version>3.3.10.RELEASE</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <version>1.4.200</version>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

我想有些依赖项相互冲突。有没有办法将这些依赖项与我的所有其他依赖项一起实际使用，以便我能够遵循该指南？

不知道这个问题是否需要app的Java代码，如果需要，需要哪几段。现在我只添加 application.properties:

spring.h2.console.enabled=true
spring.h2.console.path=/h2_console

spring.datasource.url=jdbc:h2:~/studentlist
spring.datasource.platform=h2
spring.datasource.initialization-mode=always
spring.datasource.username=sa
spring.datasource.password=
spring.datasource.driverClassName=org.h2.Driver

spring.jpa.generate-ddl=true
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect
spring.jpa.hibernate.ddl-auto = update
spring.jpa.show-sql=true

logging.level.org.springframework=warn
logging.level.org.hibernate.type.descriptor.sql.BasicBinder=trace
logging.level.org.hibernate.SQL=warn
logging.level.io.netty=warn

spring.datasource.maximum-pool-size=100

添加其中之一这两个依赖项，spring-boot-starter-data-r2dbc或r2dbc-h2，没有第二个就足以导致这个错误：

2020-10-20 15:31:26.008  WARN 11580 --- [           main] onfigReactiveWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'studentController': Unsatisfied dependency expressed through field 'studentService'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'studentService': Unsatisfied dependency expressed through field 'studentRepository'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.freelance.studentlist.repository.StudentRepository' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
2020-10-20 15:31:26.123 ERROR 11580 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : 

***************************
APPLICATION FAILED TO START
***************************

Description:

Field studentRepository in com.freelance.studentlist.service.StudentServiceImpl required a bean of type 'com.freelance.studentlist.repository.StudentRepository' that could not be found.

The injection point has the following annotations:
    - @org.springframework.beans.factory.annotation.Autowired(required=true)


Action:

Consider defining a bean of type 'com.freelance.studentlist.repository.StudentRepository' in your configuration.


Process finished with exit code 1

我删除了 JPA 依赖项，目前我正在尝试只使用 r2dbc。

我想我的 application.properties 将不再有效。你能帮我改一下吗？我使用指南中的代码片段：

public class R2DBCConfiguration extends AbstractR2dbcConfiguration {
    @Bean
    public H2ConnectionFactory connectionFactory() {
        return new H2ConnectionFactory(
                H2ConnectionConfiguration.builder()
                        .url("jdbc:h2:~/studentlist;DB_CLOSE_DELAY=-1;TRACE_LEVEL_FILE=4")
                        .username("sa")
                        .build());
    }
}

我强烈怀疑这样的url对r2dbc无效。在 r2dbc H2（不是内存中，只是本地数据库）的情况下，jdbc:h2:~/studentlist URL 的有效替代是什么？

我应该如何更改 application.properties 中的这段代码？ URL 特别是！

**spring.datasource.url=jdbc:h2:~/studentlist**
spring.datasource.platform=h2
spring.datasource.initialization-mode=always
spring.datasource.username=sa
spring.datasource.password=
spring.datasource.driverClassName=org.h2.Driver

知道的请帮忙！现在不能google一个合适的例子...

Answer 1

spring.datasource 用于传统的 Jdbc 数据源，要配置 R2dbc 连接，请在 Spring 引导 application.properties 中使用 spring.r2dbc 前缀。

检查 my Spring R2dbc example，如果您是 Spring Data R2dbc 的新手，Readme.md.

中的文档

使用反应式数据库客户端扩展 Spring WebFlux 应用程序时出现问题：冲突的 Maven 依赖项？

Problem extending Spring WebFlux application with reactive DB client: conflicting Maven dependencies?

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spring-webflux

spring-data-r2dbc