@EventListener spring boot 编译失败答案

【问题标题】：@EventListener spring boot fails to compile@EventListener spring boot 编译失败
【发布时间】：2021-04-19 12:03:12
【问题描述】：

编写了我的第一个计算刷新次数的 Spring Boot 应用程序。我打印到端口 8080 "Hello World" + Counter。

计数器应在每次用户刷新时增加，并在“Hello World”字符串后实时显示刷新次数。

为此，我使用@RestController 和@EventListener 接口。

在构建我的应用时，@EventListener 导入和接口调用失败：

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.3.2:compile (default-compile) on project backend: Compilation failure: Compilation failure: 
[ERROR] /home/project/backend/src/main/java/com/iz/backend/myController.java:[9,58] error: cannot find symbol
[ERROR]  package org.springframework.cloud.context.config.annotation
[ERROR] /home/project/backend/src/main/java/com/iz/backend/myController.java:[57,5] error: incompatible types: EventListener cannot be converted to Annotation

类：

package com.iz.backend;

import org.springframework.stereotype.Controller;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.cloud.context.config.annotation.RefreshScope;
import org.springframework.cloud.context.config.annotation.EventListener;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import java.io.IOException;
import java.nio.file.Files; 
import java.nio.file.Paths;
import java.nio.file.Path;

@RefreshScope
@RestController //interface
public class myController {

    static int counter = -1;

    @RequestMapping("/")
    public String helloWorld() {

        try
        {
            return "Hello World " + counter;
        } 
        catch (IOException e) 
        {
            e.printStackTrace();
        }

        return "Failed to execute";
    }
    
    @EventListener
    public void handleContextRefreshEvent(ContextRefreshedEvent event) {
        counter += 1;
    }
}

pom.xml 文件：

<?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>2.4.1</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.iz</groupId>
<artifactId>backend</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>backend</name>
<description>Demo project for Spring Boot</description>

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

<dependencies>
    <dependency>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-source-plugin</artifactId>
        <version>2.4</version>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-aop</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-devtools</artifactId>
        <optional>true</optional>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>compile</scope>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-actuator</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter</artifactId>
        <version>3.0.0</version>
    </dependency>

</dependencies>

<build>
    <plugins>

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>2.3.2</version>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
            </configuration>
        </plugin>

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

MAVEN 3.6.3，JAVA 11

【问题讨论】：

EventListener 有两个导入。删除一个（可能是java.util.EventListener）。
我不小心把这一行加到了这里。现已编辑。在我的实际代码中 java.util.EventListener 不存在。

标签： java spring-boot maven pom.xml

【解决方案1】：

我建议您执行以下操作：

删除try catch块（在相应的try块中永远不会抛出异常'java.io.IOException'）
优化导入（您有重复/不明确的导入）
使用像 AtomicInteger 这样的东西作为计数器

【讨论】：