找不到 KafkaTemplate bean，即使我已经定义了一个

Question

我的环境上下文如下所示：

- Spring Boot v2.5.12
- Maven Multi Module project (this is a module, it imports its Spring Boot dependencies from the parent pom)
- JDK 11

我收到的错误如下所示：

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

Description:

Parameter 1 of constructor in com.example.group.service.SomeServiceImpl required a bean of type 'org.springframework.kafka.core.KafkaTemplate' that could not be found.


Action:

Consider defining a bean of type 'org.springframework.kafka.core.KafkaTemplate' in your configuration.

相关文件：

<!-- ${base.dir}/pom.xml -->
<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <parent>
        <groupId>com.example</groupId>
        <artifactId>master-config</artifactId>
        <version>1.1.2</version>
    </parent>

    <groupId>com.example.group</groupId>
    <artifactId>parent-pom</artifactId>
    <version>1.0.0-SNAPSHOT</version>
    <packaging>pom</packaging>

    <modules>
        <module>app1</module>
        <module>app2</module>
    </modules>

    <properties>
        <java.version>11</java.version>
        <maven.compiler.release>${java.version}</maven.compiler.release>
        <spring.boot.version>2.5.12</spring.boot.version>
    </properties>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>${spring.boot.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <!-- Omitted -->
        </dependencies>
    </dependencyManagement>
</project>

<!-- ${base.dir}/app2/pom.xml -->
<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>com.example.group</groupId>
        <artifactId>parent-pom</artifactId>
        <version>1.0.0-SNAPSHOT</version>
    </parent>

    <artifactId>app2</artifactId>

    <properties>
        <maven.compiler.source>11</maven.compiler.source>
        <maven.compiler.target>11</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</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-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.kafka</groupId>
            <artifactId>spring-kafka</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.kafka</groupId>
            <artifactId>spring-kafka-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
</project>

// ${base.dir}/app2/src/main/java/com/example/group/SomeApplication.java

package com.example.group;

/* Imports omitted */

@SpringBootApplication
public class SomeApplication {
    public static void main(String[] args) {
        SpringApplication.run(SomeApplication.class, args);
    }
}

// ${base.dir}/app2/src/main/java/com/example/group/configuration/AppConfig.java
package com.example.group.configuration;

/* Imports omitted */

@Configuration
public class AppConfig {

    @Bean
    public KafkaTemplate<Bytes, Object> kafkaTemplate(ProducerFactory<Bytes, Object> kafkaProducerFactory) {
        return new KafkaTemplate<>(kafkaProducerFactory);
    }

    @Bean
    public ProducerFactory<Bytes, Object> kafkaProducerFactory() {
        Map<String, Object> producerProperties = /* Config omitted */;
        return new DefaultKafkaProducerFactory<>(producerProperties);
    }
}

// ${base.dir}/app2/src/main/java/com/example/group/service/SomeService.java
package com.example.group.service;

/* Imports omitted */

@Service
public final class SomeServiceImpl implements SomeService {
    private static final Logger LOGGER = LoggerFactory.getLogger(SomeServiceImpl.class);

    private final KafkaTemplate<Bytes, Object> kafkaTemplate;
    private final String topic;

    @Autowired
    public SomeServiceImpl(
        KafkaTemplate<Bytes, Object> kafkaTemplate,
        @Value("${topic}") String topic) {
        this.kafkaTemplate = kafkaTemplate;
        this.topic = topic;
    }

    /* omitted */
}

这很奇怪，我不明白为什么 Spring 一直告诉我找不到 KafkaTemplate bean。甚至 IntelliJ 也告诉我它找不到 KafkaTemplate.

的自动装配候选者

我尝试过的事情

正在删除我的自定义 @Beans，并依赖 KafkaAutoConfiguration（它失败了，说找不到 ProducerFactory）
为 KafkaTemplate bean 命名，并在 SomeService

@Qualifier

移动 @Bean 定义。

None 这些都奏效了，所以我束手无策。任何见解都会有所帮助。

Answer 1

原来这是PEBKAC的情况（键盘和椅子之间存在问题）。

我的配置对象中的 Bytes 类型引用 com.google.common.primitives.Bytes，我的服务 class 中的 Bytes 引用 org.apache.kafka.common.utils.Bytes。

自学：

检查你的类型。

找不到 KafkaTemplate bean，即使我已经定义了一个

Can't find KafkaTemplate bean, even though I've defined one

java

autowired

apache-kafka

spring-boot

spring-kafka

我尝试过的事情