SpringBoot新增监听器Listener

什么是web监听器？

　　web监听器是一种Servlet中的特殊的类，它们能帮助开发者监听web中的特定事件，比如ServletContext,HttpSession,ServletRequest的创建和销毁；变量的创建、销毁和修改等。可以在某些动作前后增加处理，实现监控。

监听器常用的用途

　　通常使用Web监听器做以下的内容：

　　统计在线人数，利用HttpSessionLisener

　　加载初始化信息：利用ServletContextListener

　　统计网站访问量

　　实现访问监控

1.编写自定义监听器BackendConfigListener继承自GenericApplicationListener

package com.shitou.deposit.listener;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.context.event.ApplicationEnvironmentPreparedEvent;
import org.springframework.boot.context.event.ApplicationPreparedEvent;
import org.springframework.boot.context.event.ApplicationReadyEvent;
import org.springframework.boot.logging.LoggingApplicationListener;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.event.GenericApplicationListener;
import org.springframework.core.ResolvableType;

import com.alibaba.fastjson.JSONObject;
import com.shitou.deposit.domain.entity.TransactionTradingChannelConfig;
import com.shitou.deposit.domain.impl.TransactionTradingChannelConfigBizFacadeImpl;

/**
 * 应用配置Spring容器监听器
 * 当容器启动时，当环境准备好时，加载远程的配置信息
 * @author zhouky
 * @since 2018年1月11日
 */
public class BackendConfigListener implements GenericApplicationListener {
    /**
     * 日志
     */
    private static Logger logger = LoggerFactory.getLogger(BackendConfigListener.class);
    
    //指定要监听的时间
    private static Class[] EVENT_TYPES = { ApplicationEnvironmentPreparedEvent.class,
            ApplicationPreparedEvent.class, ApplicationReadyEvent.class };

    private static Class[] SOURCE_TYPES = { SpringApplication.class, ApplicationContext.class };
    
    private TransactionTradingChannelConfigBizFacadeImpl transactionTradingChannelConfigBizFacadeImpl = null;

    /**
     * 程序启动时加载应用远程配置
     * 
     * @param applicationEvent
     */
    @Override
    public void onApplicationEvent(ApplicationEvent applicationEvent) {
        if (applicationEvent instanceof ApplicationReadyEvent) {
            //获取ApplicationReadyEvent中applicationContext
            ConfigurableApplicationContext applicationContext = ((ApplicationReadyEvent) applicationEvent).getApplicationContext();
            //applicationContext获取Bean
            transactionTradingChannelConfigBizFacadeImpl = (TransactionTradingChannelConfigBizFacadeImpl) applicationContext.getBean("transactionTradingChannelConfigBizFacadeImpl");
            TransactionTradingChannelConfig transactionTradingChannelConfig = transactionTradingChannelConfigBizFacadeImpl.selectByPrimaryKey(1);
            logger.info(JSONObject.toJSONString(transactionTradingChannelConfig));
            logger.info("-------------------- ApplicationReadyEvent ----------------------");
        }
    }

    @Override
    public int getOrder() {
        // 设置加载优先级，在日志之前加载
        return LoggingApplicationListener.DEFAULT_ORDER - 1;
    }

    @Override
    public boolean supportsEventType(ResolvableType resolvableType) {
        return isAssignableFrom(resolvableType.getRawClass(), EVENT_TYPES);
    }

    @Override
    public boolean supportsSourceType(Class sourceType) {
        return isAssignableFrom(sourceType, SOURCE_TYPES);
    }

    private boolean isAssignableFrom(Class type, Class... supportedTypes) {
        if (type != null) {
            for (Class supportedType : supportedTypes) {
                if (supportedType.isAssignableFrom(type)) {
                    return true;
                }
            }
        }
        return false;
    }
}

2.Application启动类添加自定义监听器

package com.shitou;


import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.embedded.ConfigurableEmbeddedServletContainer;
import org.springframework.boot.context.embedded.EmbeddedServletContainerCustomizer;
import org.springframework.boot.context.properties.ConfigurationProperties;

import com.shitou.common.utilities.ShutDownBlockHook;
import com.shitou.common.utilities.ShutDownHookLevel;
import com.shitou.config.ConfigApplicationListener;
import com.shitou.deposit.listener.BackendConfigListener;

@ConfigurationProperties("server")
@SpringBootApplication
public class Application implements EmbeddedServletContainerCustomizer {
    private static Logger logger = LoggerFactory.getLogger(Application.class);

    private int port = 8080;

    public void setPort(int port) {
        this.port = port;
    }

    public static void main(String[] args) throws InterruptedException {
        SpringApplication app = new SpringApplication(Application.class);
        // 加载remote config
        app.addListeners(new ConfigApplicationListener());
        // 加载database config
        app.addListeners(new BackendConfigListener());
        app.run(args);
        ShutDownBlockHook.registerHook(new ShutDownBlockHook.ShutDownRunning(){
            
            @Override
            public void run() {
                logger.info("Application ShutDownBlockHook .............");
            }
        }, ShutDownHookLevel.LoggingHookLevel);
    }

    @Override
    public void customize(ConfigurableEmbeddedServletContainer container) {

        container.setPort(this.port);
    }

}