Spring Boot迁移至Ubuntu后ApplicationContextProvider抛出NullPointerException

问题 #

Spring Boot 3.2.4应用在Windows 10/Server 2019上运行正常，但迁移至Ubuntu 24.04后，调用ApplicationContextProvider.getApplicationContext()抛出NullPointerException，所有环境均使用openjdk-18.0.1。

相关代码 #

ApplicationContextProvider（实现ApplicationContextAware）

@Component
public class ApplicationContextProvider implements ApplicationContextAware {
    private static ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(@NotNull ApplicationContext applicationContext) throws BeansException {
        ApplicationContextProvider.applicationContext = applicationContext;
    }

    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }
}

报错触发类MainBuilderUtil

@Component
public class MainBuilderUtil {
    MainChannelCredentialsUtil mainChannelCredentialsUtil;

    public final OAuth2Credential credentialMain = new OAuth2Credential("provider",
            ApplicationContextProvider.getApplicationContext().getBean(MainChannelCredentialsUtil.class).getMainToken());

    @Autowired
    private MainBuilderUtil(MainChannelCredentialsUtil mainChannelCredentialsUtil) {
        this.mainChannelCredentialsUtil = mainChannelCredentialsUtil;
    }

    public final Client ClientMain =
            ClientBuilder.builder()
                    .withEnableChat(true)
                    .withChatAccount(credentialMain)
                    .build();

    //getters
}

报错堆栈信息 #

Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.bot.springbootbot.connections.channels.builder_utils.MainBuilderUtil]: Constructor threw exception
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:221) ~[spring-beans-6.1.5.jar!/:6.1.5]
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:111) ~[spring-beans-6.1.5.jar!/:6.1.5]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:315) ~[spring-beans-6.1.5.jar!/:6.1.5]
    ... 24 common frames omitted
Caused by: java.lang.NullPointerException: Cannot invoke "org.springframework.context.ApplicationContext.getBean(java.lang.Class)" because the return value of "com.bot.springbootbot.ApplicationContextProvider.getApplicationContext()" is null
    at com.bot.springbootbot.connections.channels.builder_utils.MainBuilderUtil.<init>(MainBuilderUtil.java:18) ~[!/:0.0.1-SNAPSHOT]
    at java.base/jdk.internal.reflect.DirectConstructorHandleAccessor.newInstance(DirectConstructorHandleAccessor.java:62) ~[na:na]
    at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:502) ~[na:na]
    at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:486) ~[na:na]
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:208) ~[spring-beans-6.1.5.jar!/:6.1.5]
    ... 26 common frames omitted

启动警告信息 #

WARN 6417 --- [SpringBootBot] [           main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'mainBuilderUtil' defined in URL [jar:nested:/usr/SpringBootBot/target/SpringBootBot-0.0.1-SNAPSHOT.jar/!BOOT-INF/classes/!/com/bot/springbootbot/connections/channels/builder_utils/MainBuilderUtil.class]: Failed to instantiate [com.bot.springbootbot.connections.channels.builder_utils.MainBuilderUtil]: Constructor threw exception

已知该类无需作为Spring Bean，但此前Windows环境可行，更换JDK无效，需明确跨系统报错原因及解决办法。

原因分析与解决办法 #

核心原因 #

Windows与Linux环境下Spring Bean的初始化顺序存在差异。Windows环境中ApplicationContextProvider恰好先于MainBuilderUtil完成初始化，静态变量被赋值；但Ubuntu环境中，MainBuilderUtil的实例化（包含成员变量credentialMain的初始化）早于ApplicationContextProvider的setApplicationContext方法执行，导致静态applicationContext为null，触发空指针异常。

这种依赖初始化顺序的实现本身不具备稳定性，Windows环境能运行只是巧合，并非正确写法。

解决办法 #

方案1：移除Spring Bean管理，手动初始化（推荐，符合你提到的该类无需作为Bean的需求）

1. 删除MainBuilderUtil上的@Component注解，不再让Spring接管该类的实例化。
2. 修改代码，通过构造函数传入依赖，彻底避免依赖静态上下文：

public class MainBuilderUtil {
    private final MainChannelCredentialsUtil mainChannelCredentialsUtil;
    public final OAuth2Credential credentialMain;
    public final Client ClientMain;

    public MainBuilderUtil(MainChannelCredentialsUtil mainChannelCredentialsUtil) {
        this.mainChannelCredentialsUtil = mainChannelCredentialsUtil;
        this.credentialMain = new OAuth2Credential("provider", mainChannelCredentialsUtil.getMainToken());
        this.ClientMain = ClientBuilder.builder()
                .withEnableChat(true)
                .withChatAccount(credentialMain)
                .build();
    }

    // getters
}

3. 在需要使用MainBuilderUtil的Spring Bean中，通过注入的MainChannelCredentialsUtil手动创建实例：

@Autowired
private MainChannelCredentialsUtil credentialsUtil;

public void businessMethod() {
    MainBuilderUtil builderUtil = new MainBuilderUtil(credentialsUtil);
    // 使用builderUtil完成业务逻辑
}

方案2：保留Spring Bean，修正初始化时机

如果必须让Spring管理MainBuilderUtil，则需要避免在成员变量初始化阶段依赖静态上下文，改用@PostConstruct注解在Bean完全初始化后执行逻辑：

@Component
public class MainBuilderUtil {
    @Autowired
    private MainChannelCredentialsUtil mainChannelCredentialsUtil;

    public OAuth2Credential credentialMain;
    public Client ClientMain;

    @PostConstruct
    public void init() {
        this.credentialMain = new OAuth2Credential("provider", mainChannelCredentialsUtil.getMainToken());
        this.ClientMain = ClientBuilder.builder()
                .withEnableChat(true)
                .withChatAccount(credentialMain)
                .build();
    }

    // getters
}

此方式下，credentialMain和ClientMain会在Spring完成mainChannelCredentialsUtil注入，且整个Bean初始化完成后再初始化，彻底摆脱对不稳定初始化顺序的依赖。

内容的提问来源于stack exchange，提问作者maximuz666