SpringBoot 常用扩展接口-工具盒子

在Spring Boot应用开发中，框架通过丰富的扩展点设计，为开发者提供了灵活的应用定制能力。这些扩展接口不仅能够无缝融入应用生命周期的各个阶段（如启动、运行、关闭），还能针对业务场景实现深度定制，显著提升代码的可维护性和可扩展性。无论是增强核心功能、统一处理全局逻辑，还是优化特定场景下的性能，Spring Boot的扩展机制都能以优雅的方式解决问题，避免对框架源码的侵入性修改。以下是一些核心扩展接口及其分类，它们将帮助开发者更好地驾驭Spring Boot的定制化能力：

一、应用启动阶段 {#%E4%B8%80%E3%80%81%E5%BA%94%E7%94%A8%E5%90%AF%E5%8A%A8%E9%98%B6%E6%AE%B5}

1. `ApplicationContextInitializer` {#1.-applicationcontextinitializer}

用途：在 ApplicationContext 初始化前执行自定义逻辑（如设置环境变量）。

示例：

public class MyInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> {
    @Override
    public void initialize(ConfigurableApplicationContext context) {
        // 自定义初始化逻辑
    }
}

注册方式 ：在 META-INF/spring.factories 中添加：

org.springframework.context.ApplicationContextInitializer=com.example.MyInitializer

2. `CommandLineRunner` {#2.-commandlinerunner}

用途：在应用启动后执行命令行参数相关的任务。

示例：

@Component
public class MyRunner implements CommandLineRunner {
    @Override
    public void run(String... args) {
        // 启动后执行的任务
    }
}

3. `ApplicationRunner` {#3.-applicationrunner}

用途：与 CommandLineRunner 类似，但参数封装为 ApplicationArguments。

示例：

@Component
public class MyAppRunner implements ApplicationRunner {
    @Override
    public void run(ApplicationArguments args) {
        // 处理参数
    }
}

二、Bean 生命周期 {#%E4%BA%8C%E3%80%81bean-%E7%94%9F%E5%91%BD%E5%91%A8%E6%9C%9F}

1. `BeanPostProcessor` {#1.-beanpostprocessor}

用途：在 Bean 初始化前后插入自定义逻辑。

示例：

@Component
public class MyBeanPostProcessor implements BeanPostProcessor {
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) {
        // Bean 初始化前的逻辑
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) {
        // Bean 初始化后的逻辑
        return bean;
    }



`}
`

2. `BeanFactoryPostProcessor` {#2.-beanfactorypostprocessor}

用途：在 Bean 定义加载后、实例化前修改 Bean 的定义。

示例：

@Component
public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
        // 修改 Bean 定义
    }
}

`SmartInitializingSingleton` {#smartinitializingsingleton}

用途：在所有单例 Bean 初始化完成后执行逻辑。

示例：

@Component
public class MySmartInitializer implements SmartInitializingSingleton {
    @Override
    public void afterSingletonsInstantiated() {
        // 单例 Bean 初始化完成后执行
    }
}

三、事件监听 {#%E4%B8%89%E3%80%81%E4%BA%8B%E4%BB%B6%E7%9B%91%E5%90%AC}

1. `ApplicationListener` {#1.-applicationlistener}

用途：监听 Spring 事件（如应用启动事件）。

示例：

@Component
public class MyEventListener implements ApplicationListener<ApplicationStartedEvent> {
    @Override
    public void onApplicationEvent(ApplicationStartedEvent event) {
        // 处理应用启动事件
    }
}

2. 自定义事件 {#2.-%E8%87%AA%E5%AE%9A%E4%B9%89%E4%BA%8B%E4%BB%B6}

发布事件：

@Autowired
private ApplicationEventPublisher eventPublisher;
`public void publishEvent() {
eventPublisher.publishEvent(new MyCustomEvent("Custom Event Data"));
}
`

监听事件

@Component
public class MyCustomEventListener implements ApplicationListener<MyCustomEvent> {
    @Override
    public void onApplicationEvent(MyCustomEvent event) {
        // 处理自定义事件
    }
}

四、Web 扩展 {#%E5%9B%9B%E3%80%81web-%E6%89%A9%E5%B1%95}

1. `WebMvcConfigurer` {#1.-webmvcconfigurer}

用途：自定义 Spring MVC 配置（如拦截器、跨域设置）。

示例：

@Configuration
public class WebConfig implements WebMvcConfigurer {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new MyInterceptor());
    }
}

2. `ServletContextInitializer` {#2.-servletcontextinitializer}

用途：在 Servlet 容器初始化时注册 Servlet、Filter 或 Listener。

示例：

@Bean
public ServletContextInitializer servletContextInitializer() {
    return servletContext -> {
        ServletRegistration.Dynamic servlet = servletContext.addServlet("myServlet", MyServlet.class);
        servlet.addMapping("/my-servlet/*");
    };
}

3. `WebFluxConfigurer` {#3.-webfluxconfigurer}

用途：在响应式 Web 应用（WebFlux）中自定义配置，如路由、编解码器、CORS 等。

示例：


@Configuration
public class WebFluxConfig implements WebFluxConfigurer {

    @Override
    public void addCorsMappings(CorsRegistry registry) {
        // 配置CORS（跨域资源共享）
        registry.addMapping("/api/**") // 对API路径应用CORS配置
                .allowedOrigins("https://example.com") // 允许的来源
                .allowedMethods("GET", "POST", "PUT", "DELETE") // 允许的HTTP方法
                .allowCredentials(true) // 允许发送身份凭证
                .maxAge(3600); // 预检请求结果缓存时间（秒）

        log.info("响应式应用CORS配置已应用");
    }

    @Override
    public void configureViewResolvers(ViewResolverRegistry registry) {
        // 配置视图解析器
        registry.freeMarker();
    }

    @Override
    public void addFormatters(FormatterRegistry registry) {
        // 添加自定义格式转换器
        registry.addConverter(new MonoConverter());
    }



`}`

4. `HandlerMethodArgumentResolver` {#4.-handlermethodargumentresolver}

用途：自定义控制器方法参数的解析逻辑（如从请求头、Cookie 中提取参数）。

示例：

@Component
public class CurrentUserArgumentResolver implements HandlerMethodArgumentResolver {

    @Autowired
    private UserService userService;

    @Override
    public boolean supportsParameter(MethodParameter parameter) {
        // 判断方法参数是否支持此解析器
        // 这里检查参数是否有@CurrentUser注解且类型为User
        return parameter.hasParameterAnnotation(CurrentUser.class) 
               &amp;&amp; parameter.getParameterType().equals(User.class);
    }

    @Override
    public Object resolveArgument(
            MethodParameter parameter, 
            ModelAndViewContainer mavContainer,
            NativeWebRequest webRequest, 
            WebDataBinderFactory binderFactory) throws Exception {

        // 从请求中解析出参数值
        // 例如，从HTTP请求头或会话中获取用户ID，然后加载用户对象
        String authHeader = webRequest.getHeader("Authorization");
        if (authHeader != null &amp;&amp; authHeader.startsWith("Bearer ")) {
            // 从Authorization头提取token
            String token = authHeader.substring(7);
            // 使用token查找用户
            return userService.findUserByToken(token);
        }

        // 如果找不到用户，可以返回null或抛出异常
        return null;
    }



`}
`

注册方式 ：在WebMvcConfigurer或WebFluxConfigurer中添加：

// 注册参数解析器
@Configuration
public class WebMvcConfig implements WebMvcConfigurer {

    @Autowired
    private CurrentUserArgumentResolver currentUserArgumentResolver;

    @Override
    public void addArgumentResolvers(List&lt;HandlerMethodArgumentResolver&gt; resolvers) {
        resolvers.add(currentUserArgumentResolver);
    }



`}`

五、条件化配置 {#%E4%BA%94%E3%80%81%E6%9D%A1%E4%BB%B6%E5%8C%96%E9%85%8D%E7%BD%AE}

1. `Condition` {#1.-condition}

用途：根据条件决定是否加载 Bean 或配置类。

示例：

public class MyCondition implements Condition {
    @Override
    public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
        return context.getEnvironment().containsProperty("enable.feature");
    }
}
`@Configuration
@Conditional(MyCondition.class)
public class MyFeatureConfig {
// 条件满足时加载的配置
}
`

2. `@ConditionalOnProperty` {#2.-%40conditionalonproperty}

用途：根据配置文件属性决定是否生效。

示例：

@Bean
@ConditionalOnProperty(name = "cache.enabled", havingValue = "true")
public CacheManager cacheManager() {
    return new EhCacheManager();
}

六、健康检查与监控 {#%E5%85%AD%E3%80%81%E5%81%A5%E5%BA%B7%E6%A3%80%E6%9F%A5%E4%B8%8E%E7%9B%91%E6%8E%A7}

1. `HealthIndicator` {#1.-healthindicator}

用途：自定义健康检查端点。

示例：

@Component
public class MyHealthIndicator implements HealthIndicator {
    @Override
    public Health health() {
        // 检查自定义组件的健康状态
        return Health.up().withDetail("detail", "OK").build();
    }
}

2. `Endpoint` {#2.-endpoint}

用途：自定义 Actuator 端点。

示例：

@Component
@Endpoint(id = "my-endpoint")
public class MyCustomEndpoint {
    @ReadOperation
    public String getInfo() {
        return "Custom Endpoint Data";
    }
}

七、其他扩展点 {#%E4%B8%83%E3%80%81%E5%85%B6%E4%BB%96%E6%89%A9%E5%B1%95%E7%82%B9}

1. `EnvironmentPostProcessor` {#1.-environmentpostprocessor}

用途：在环境变量加载后修改配置。

示例：

public class MyEnvPostProcessor implements EnvironmentPostProcessor {
    @Override
    public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {
        // 修改环境变量
    }
}

2. `FailureAnalyzer` {#2.-failureanalyzer}

用途：自定义应用启动失败时的错误分析。

示例：

public class MyFailureAnalyzer extends AbstractFailureAnalyzer<MyException> {
    @Override
    protected FailureAnalysis analyze(Throwable rootFailure, MyException cause) {
        return new FailureAnalysis("Description", "Action", cause);
    }
}

3. `ErrorAttributes` {#3.-errorattributes}

用途：定制全局错误响应信息（如 HTTP 错误码、错误消息格式）。

示例：

@Component
public class CustomErrorAttributes extends DefaultErrorAttributes {

    @Override
    public Map&lt;String, Object&gt; getErrorAttributes(WebRequest webRequest, ErrorAttributeOptions options) {
        // 获取默认的错误属性
        Map&lt;String, Object&gt; errorAttributes = super.getErrorAttributes(webRequest, options);

        // 添加自定义错误属性
        errorAttributes.put("appName", "MyAwesomeApp");
        errorAttributes.put("timestamp", LocalDateTime.now().toString());

        // 移除不想暴露的错误信息
        errorAttributes.remove("trace");

        // 获取原始异常以便添加更多上下文
        Throwable error = getError(webRequest);
        if (error instanceof BusinessException) {
            BusinessException businessEx = (BusinessException) error;
            errorAttributes.put("errorCode", businessEx.getErrorCode());
            errorAttributes.put("domain", businessEx.getDomain());
        }

        return errorAttributes;
    }



`}
`

八、执行顺序与优先级 {#%E5%85%AB%E3%80%81%E6%89%A7%E8%A1%8C%E9%A1%BA%E5%BA%8F%E4%B8%8E%E4%BC%98%E5%85%88%E7%BA%A7}

@Order注解：指定 Bean 的加载顺序（值越小优先级越高）。

@Component
@Order(1)
public class HighPriorityBean implements CommandLineRunner {
    // 优先执行
}

通过合理使用这些扩展接口，可以灵活定制 Spring Boot 应用的行为，满足复杂业务场景的需求。

51工具盒子

SpringBoot 常用扩展接口

一、应用启动阶段 {#%E4%B8%80%E3%80%81%E5%BA%94%E7%94%A8%E5%90%AF%E5%8A%A8%E9%98%B6%E6%AE%B5}

1. `ApplicationContextInitializer` {#1.-applicationcontextinitializer}

2. `CommandLineRunner` {#2.-commandlinerunner}

3. `ApplicationRunner` {#3.-applicationrunner}

二、Bean 生命周期 {#%E4%BA%8C%E3%80%81bean-%E7%94%9F%E5%91%BD%E5%91%A8%E6%9C%9F}

1. `BeanPostProcessor` {#1.-beanpostprocessor}

2. `BeanFactoryPostProcessor` {#2.-beanfactorypostprocessor}

`SmartInitializingSingleton` {#smartinitializingsingleton}

三、事件监听 {#%E4%B8%89%E3%80%81%E4%BA%8B%E4%BB%B6%E7%9B%91%E5%90%AC}

1. `ApplicationListener` {#1.-applicationlistener}

2. 自定义事件 {#2.-%E8%87%AA%E5%AE%9A%E4%B9%89%E4%BA%8B%E4%BB%B6}

四、Web 扩展 {#%E5%9B%9B%E3%80%81web-%E6%89%A9%E5%B1%95}

1. `WebMvcConfigurer` {#1.-webmvcconfigurer}

2. `ServletContextInitializer` {#2.-servletcontextinitializer}

3. `WebFluxConfigurer` {#3.-webfluxconfigurer}

4. `HandlerMethodArgumentResolver` {#4.-handlermethodargumentresolver}

五、条件化配置 {#%E4%BA%94%E3%80%81%E6%9D%A1%E4%BB%B6%E5%8C%96%E9%85%8D%E7%BD%AE}

1. `Condition` {#1.-condition}

2. `@ConditionalOnProperty` {#2.-%40conditionalonproperty}

六、健康检查与监控 {#%E5%85%AD%E3%80%81%E5%81%A5%E5%BA%B7%E6%A3%80%E6%9F%A5%E4%B8%8E%E7%9B%91%E6%8E%A7}

1. `HealthIndicator` {#1.-healthindicator}

2. `Endpoint` {#2.-endpoint}

七、其他扩展点 {#%E4%B8%83%E3%80%81%E5%85%B6%E4%BB%96%E6%89%A9%E5%B1%95%E7%82%B9}

1. `EnvironmentPostProcessor` {#1.-environmentpostprocessor}

2. `FailureAnalyzer` {#2.-failureanalyzer}

3. `ErrorAttributes` {#3.-errorattributes}

八、执行顺序与优先级 {#%E5%85%AB%E3%80%81%E6%89%A7%E8%A1%8C%E9%A1%BA%E5%BA%8F%E4%B8%8E%E4%BC%98%E5%85%88%E7%BA%A7}

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快捷分类

一、应用启动阶段 {#%E4%B8%80%E3%80%81%E5%BA%94%E7%94%A8%E5%90%AF%E5%8A%A8%E9%98%B6%E6%AE%B5}

1. ApplicationContextInitializer {#1.-applicationcontextinitializer}

2. CommandLineRunner {#2.-commandlinerunner}

3. ApplicationRunner {#3.-applicationrunner}

二、Bean 生命周期 {#%E4%BA%8C%E3%80%81bean-%E7%94%9F%E5%91%BD%E5%91%A8%E6%9C%9F}

1. BeanPostProcessor {#1.-beanpostprocessor}

2. BeanFactoryPostProcessor {#2.-beanfactorypostprocessor}

SmartInitializingSingleton {#smartinitializingsingleton}

三、事件监听 {#%E4%B8%89%E3%80%81%E4%BA%8B%E4%BB%B6%E7%9B%91%E5%90%AC}

1. ApplicationListener {#1.-applicationlistener}

2. 自定义事件 {#2.-%E8%87%AA%E5%AE%9A%E4%B9%89%E4%BA%8B%E4%BB%B6}

四、Web 扩展 {#%E5%9B%9B%E3%80%81web-%E6%89%A9%E5%B1%95}

1. WebMvcConfigurer {#1.-webmvcconfigurer}

2. ServletContextInitializer {#2.-servletcontextinitializer}

3. WebFluxConfigurer {#3.-webfluxconfigurer}

4. HandlerMethodArgumentResolver {#4.-handlermethodargumentresolver}

五、条件化配置 {#%E4%BA%94%E3%80%81%E6%9D%A1%E4%BB%B6%E5%8C%96%E9%85%8D%E7%BD%AE}

1. Condition {#1.-condition}

2. @ConditionalOnProperty {#2.-%40conditionalonproperty}

六、健康检查与监控 {#%E5%85%AD%E3%80%81%E5%81%A5%E5%BA%B7%E6%A3%80%E6%9F%A5%E4%B8%8E%E7%9B%91%E6%8E%A7}

1. HealthIndicator {#1.-healthindicator}

2. Endpoint {#2.-endpoint}

七、其他扩展点 {#%E4%B8%83%E3%80%81%E5%85%B6%E4%BB%96%E6%89%A9%E5%B1%95%E7%82%B9}

1. EnvironmentPostProcessor {#1.-environmentpostprocessor}

2. FailureAnalyzer {#2.-failureanalyzer}

3. ErrorAttributes {#3.-errorattributes}

八、执行顺序与优先级 {#%E5%85%AB%E3%80%81%E6%89%A7%E8%A1%8C%E9%A1%BA%E5%BA%8F%E4%B8%8E%E4%BC%98%E5%85%88%E7%BA%A7}

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快捷分类

1. `ApplicationContextInitializer` {#1.-applicationcontextinitializer}

2. `CommandLineRunner` {#2.-commandlinerunner}

3. `ApplicationRunner` {#3.-applicationrunner}

1. `BeanPostProcessor` {#1.-beanpostprocessor}

2. `BeanFactoryPostProcessor` {#2.-beanfactorypostprocessor}

`SmartInitializingSingleton` {#smartinitializingsingleton}

1. `ApplicationListener` {#1.-applicationlistener}

1. `WebMvcConfigurer` {#1.-webmvcconfigurer}

2. `ServletContextInitializer` {#2.-servletcontextinitializer}

3. `WebFluxConfigurer` {#3.-webfluxconfigurer}

4. `HandlerMethodArgumentResolver` {#4.-handlermethodargumentresolver}

1. `Condition` {#1.-condition}

2. `@ConditionalOnProperty` {#2.-%40conditionalonproperty}

1. `HealthIndicator` {#1.-healthindicator}

2. `Endpoint` {#2.-endpoint}

1. `EnvironmentPostProcessor` {#1.-environmentpostprocessor}

2. `FailureAnalyzer` {#2.-failureanalyzer}

3. `ErrorAttributes` {#3.-errorattributes}