Spring Boot 2.2.2.RELEASE集成Zuul依赖启动失败问题求助

问题背景 #

我们在应用中实现 Spring Cloud Zuul 代理，使用 Spring Boot Parent 2.2.2.RELEASE 时项目无法启动，此前使用 1.5.22.RELEASE 版本一切正常，现需保留高版本 Spring Boot 完成升级。

参考 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 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>1.5.22.RELEASE</version>-->
        <version>2.2.2.RELEASE</version>
        
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.wgits.crbt</groupId>
    <artifactId>zuul-proxy2</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>zuul-proxy2</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
    </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-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-zuul</artifactId>
        </dependency>
    </dependencies>
<dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-parent</artifactId>
                <version>Camden.SR1</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

启动错误信息 #

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/logging/LogFactory
    at org.springframework.boot.SpringApplication.<clinit>(SpringApplication.java:196)
    at com.wgits.crbt.ZuulProxyApplication.main(ZuulProxyApplication.java:11)
Caused by: java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory
    at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 2 more

解决方案 #

核心问题是Spring Boot 与 Spring Cloud 版本不兼容：Camden.SR1 是适配 Spring Boot 1.5.x 的旧版本，和 2.2.2.RELEASE 完全不匹配，导致依赖链断裂和冲突。

1. 升级 Spring Cloud 到兼容版本 #

Spring Boot 2.2.x 对应 Spring Cloud Hoxton 系列，修改 dependencyManagement 中的版本：

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-parent</artifactId>
            <version>Hoxton.SR8</version> <!-- 与 Spring Boot 2.2.2.RELEASE 匹配 -->
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

2. 更新 Zuul 依赖命名 #

旧版 spring-cloud-starter-zuul 在高版本 Spring Cloud 中已更名，替换为：

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-zuul</artifactId>
</dependency>

3. 移除冗余依赖 #

spring-web 已被 spring-boot-starter-web 包含，重复引入可能引发冲突，删除该依赖：

<!-- 移除冗余依赖 -->
<!-- <dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-web</artifactId>
</dependency> -->

4. 验证并补全缺失依赖 #

运行 mvn dependency:tree 检查依赖树，若仍缺失 commons-logging，显式引入：

<dependency>
    <groupId>commons-logging</groupId>
    <artifactId>commons-logging</artifactId>
    <version>1.2</version>
</dependency>

5. 长期维护建议 #

Zuul 1.x 已停止官方维护，推荐迁移至 Spring Cloud Gateway，它是 Spring 官方推出的新一代网关组件，完全适配高版本 Spring Boot，性能和扩展性更优。

内容的提问来源于stack exchange，提问作者J. Doe