启动加载的三回合

☞ Round 1 应用挂载监听

实现ApplicationListener接口

public class CheApplicationEnvironmentPreparedEventListener implements
    ApplicationListener<ApplicationEnvironmentPreparedEvent>{
    @Override
    public void onApplicationEvent(ApplicationEnvironmentPreparedEvent event) {
        // 核心功能写在这里哟
    }
    
}

main方法中，application.addListeners挂载

public static void main(String[] args) {
    SpringApplication application = new SpringApplication(AuthCenterApplication.class);
    application.addListeners(new CheApplicationEnvironmentPreparedEventListener());
    application.run(args);
}

分析
- 监听实现可以抽取到公共服务，但是每个微服务主函数都需要写一遍监听挂载
- 硬编码，例如：无法通过yml配置文件动态关闭开启挂载的核心功能

☞ Round 2 spring.factories挂载监听

实现ApplicationListener接口

通过event获取Environment可取得bootstap.yml配置文件内容，实现开关功能

若遇到监听重复加载2次情况，可通过event.getSpringApplication().getWebApplicationType().name())加以区分

public class CheApplicationEnvironmentPreparedEventListener implements
    ApplicationListener<ApplicationEnvironmentPreparedEvent>{
    @Override
    public void onApplicationEvent(ApplicationEnvironmentPreparedEvent event) {
        // spring.application.log 开启日志
        // 监听注入2次,name分别为NONE、SERVLET
        if("true".equals(event.getEnvironment().getProperty("che.xx")) &&
                "SERVLET".equals(event.getSpringApplication().getWebApplicationType().name())) {
            // 核心功能写在这里哟
        }
    }
    
}

src/main/resources/spring.factories文件添加监听

1	org.springframework.context.ApplicationListener=xx.yy.CheApplicationEnvironmentPreparedEventListener

分析
- spring.factories可抽取至公共服务
- 默认不启用，仅能通过bootstrap.yml自定义开启,无法通过application.yml设置

☞ Round 3 自定义@Enable 注解

EnableCheLog注解类

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import({LogImportSelector.class})
public @interface EnableCheLog {
}

LogImportSelector类

public class LogImportSelector implements ImportSelector, EnvironmentAware {
    
    private Environment environment;
    
    @Override
    public String[] selectImports(AnnotationMetadata annotationMetadata) {
        // environment获取yml配置作为开关
        if("true".equals(environment.getProperty("che.xx"))) {
            // 核心功能写在这里哟
        }
        return new String[]{};
    }
    
    @Override
    public void setEnvironment(Environment environment) {
        this.environment = environment;
    }
}

启动类

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

分析
- EnableCheLog、LogImportSelector放在公共服务
- 支持所有yml配置文件设置开关，当然也可以利用yml配置进行核心业务开发

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