自制Spring-boot Starter

新建Spring boot项目

  org.springframework.boot
  spring-boot-starter-parent
  2.7.0
   

com.example
web-filter-log-boot-starter

  org.springframework.boot
  spring-boot-starter-web

定义一个web过滤器，验证Spring boot starter是否生效

// Filter
public class LogFilter implements Filter {

    private Logger logger = LoggerFactory.getLogger(LogFilter.class);

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.err.println("logFilter init...");
        logger.info("logFilter init...");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest httpServletRequest = (HttpServletRequest) servletRequest;
        logger.info("uri: {} is working.", httpServletRequest.getRequestURI());
        filterChain.doFilter(servletRequest,servletResponse);
    }

    @Override
    public void destroy() {
        logger.info("logFilter destroy...");
    }
}

// 配置Filter生效
public class LogFilterRegistrationBean extends FilterRegistrationBean {
    public LogFilterRegistrationBean() {
        super();
        this.setFilter(new LogFilter());
        this.addUrlPatterns("/*");
        this.setName("LogFilter");
        this.setOrder(1);
    }
}

定义自动配置类

// 自动配置类
@Configuration
@ConditionalOnClass({LogFilterRegistrationBean.class, LogFilter.class})
public class LogFilterAutoConfiguration {
    @Bean
    @ConditionalOnMissingBean(LogFilterRegistrationBean.class)
    public LogFilterRegistrationBean logFilterRegistrationBean() {
        return new LogFilterRegistrationBean();
    }
}

定义注解，使用注解将使该starter配置生效

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Import(EnableLogFilterImportSelector.class)
public @interface EnableLogFilter {

}

定义EnableLogFilterImportSelector用于从spring.factories加载starter自动配置类

public class EnableLogFilterImportSelector implements DeferredImportSelector, BeanClassLoaderAware, EnvironmentAware {

    private ClassLoader beanClassLoader;
    private Class annotationClass = EnableLogFilter.class;

    @Override
    public String[] selectImports(AnnotationMetadata importingClassMetadata) {

        var attributes =
                AnnotationAttributes.fromMap(importingClassMetadata
                        .getAnnotationAttributes(annotationClass.getName(), true));
        List factories = new ArrayList<>(
                new LinkedHashSet<>(SpringFactoriesLoader.loadFactoryNames(this.annotationClass, this.beanClassLoader)));
        return factories.toArray(new String[factories.size()]);
    }

    @Override
    public void setEnvironment(Environment environment) {

    }

    @Override
    public void setBeanClassLoader(ClassLoader classLoader) {
        this.beanClassLoader = classLoader;
    }
}

在resources/META-INF中添加spring.factories

com.example.annotation.EnableLogFilter=com.example.config.LogFilterAutoConfiguration

使用starter

  com.example
  web-filter-log-boot-starter

在启动类上添加EnableLogFilter注解，使starter自动配置生效

@SpringBootApplication
@EnableLogFilter
public class DemoBootApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoBootApplication.class, args);
    }

}