我使用Axon + Spring Boot创建一个简单的应用程序,只是为了确保在实际项目中使用Axon框架之前,先了解Axon框架中的基本组件。
类TaskAggregate中有一个用@CommandHandler注释的方法,当我通过CommandGateway发送命令时应该调用该方法,但运行该应用程序后却出现异常:
Exception in thread "main" org.axonframework.commandhandling.NoHandlerForCommandException: No handler was subscribed to command [com.xxx.axontest.task.CreateTaskCommand]
根据文档,@ CommandHandler批注应足以将命令处理程序订阅到命令总线。我想我一定很想念东西。您能否看一下下面的代码,并指出正确的方向?
pom.xml
<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>
<groupId>com.xxx</groupId>
<artifactId>axon-test</artifactId>
<version>0.0.1-SNAPSHOT</version>
<properties>
<axon.version>3.0.6</axon.version>
</properties>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.7.RELEASE</version>
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.axonframework</groupId>
<artifactId>axon-spring-boot-starter</artifactId>
<version>${axon.version}</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
App.java
package com.xxx.axontest;
import org.axonframework.commandhandling.gateway.CommandGateway;
import org.axonframework.eventsourcing.eventstore.EventStorageEngine;
import org.axonframework.eventsourcing.eventstore.inmemory.InMemoryEventStorageEngine;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.Bean;
import com.xxx.axontest.task.CreateTaskCommand;
@SpringBootApplication
public class App {
public static void main(String[] args) {
ConfigurableApplicationContext configurableApplicationContext = SpringApplication.run(App.class, args);
CommandGateway commandGateway = configurableApplicationContext.getBean(CommandGateway.class);
commandGateway.send(new CreateTaskCommand(123, "asd"));
}
@Bean
public EventStorageEngine eventStorageEngine() {
return new InMemoryEventStorageEngine();
}
@Bean
public AnnotationCommandHandlerBeanPostProcessor
annotationCommandHandlerBeanPostProcessor() {
return new AnnotationCommandHandlerBeanPostProcessor();
}
}
CreateTaskCommand.java
package com.xxx.axontest.task;
import org.axonframework.commandhandling.TargetAggregateIdentifier;
public class CreateTaskCommand {
@TargetAggregateIdentifier
private int taskId;
private String name;
public CreateTaskCommand(int taskId, String name) {
this.taskId = taskId;
this.name = name;
}
public int getTaskId() {
return taskId;
}
public String getName() {
return name;
}
}
TaskCreatedEvent.java
package com.xxx.axontest.task;
import org.axonframework.commandhandling.TargetAggregateIdentifier;
public class TaskCreatedEvent {
@TargetAggregateIdentifier
private int taskId;
private String name;
public int getTaskId() {
return taskId;
}
public String getName() {
return name;
}
}
TaskAggregate.java
package com.xxx.axontest.task;
import org.apache.log4j.LogManager;
import org.apache.log4j.Logger;
import org.axonframework.commandhandling.CommandHandler;
import org.axonframework.commandhandling.model.AggregateIdentifier;
import org.axonframework.commandhandling.model.AggregateLifecycle;
import org.axonframework.eventsourcing.EventSourcingHandler;
import org.axonframework.spring.stereotype.Aggregate;
@AggregateRoot
public class TaskAggregate {
private Logger logger = LogManager.getLogger(TaskCreatedEvent.class);
@AggregateIdentifier
private int taskId;
private String name;
@CommandHandler
public void handleCommand(CreateTaskCommand createTaskCommand) {
logger.info("Command received");
AggregateLifecycle.apply(new TaskCreatedEvent());
}
@EventSourcingHandler
public void onTaskCreatedEvent(TaskCreatedEvent taskCreatedEvent) {
logger.info("Event received");
}
public int getTaskId() {
return taskId;
}
public void setTaskId(int taskId) {
this.taskId = taskId;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
提前致谢。
最佳答案
我认为您需要使用@Aggregate而不是@AggregateRoot
来注释聚合。@Aggregate
作为注释既是注释,但Spring Boot Axon Starter模块也使用它来表示该类必须创建聚集工厂和@AggregateRoot
。
此外,这意味着还将在聚合上找到Repository
带注释的函数,并将其注册到@CommandHandler
,可能会解决您捕获的异常。
否则,Allard在YouTube上的webinars在版本3中启动Axon应用程序可能会给您一些启示。
但是,简而言之,请尝试将CommandBus
注释切换为@AggregateRoot
:-)
但是,此外,您应该将@Aggregate
的@CommandHandler
带注释的函数调整为CreateTaskCommand
的构造函数。
最后,Axon要求您为聚合使用一个no-arg构造函数,因此还要在其中添加TaskAggregate
构造函数。