SpringBoot集成Socket服务后打包（war包）启动时如何启动Socket服务（web应用外部tomcat启动）

1、首先知道SpringBoot打包为jar和war包是不一样的（只讨论SpringBoot环境下web应用打包）
1.1、jar和war包的打开方式不一样，虽然都依赖java环境，但是jar包只需要外部提供java环境，war需要外部提供java和servlet环境
1.2、jar包和war包的启动流程不一样：
①、jar包的启动时直接由项目的主函数开始启动，此时会先初始化IOC容器，然后才会进行内置Servlet环境（一般为Tomcat）的启动。

//jar包启动入口

@SpringBootApplication

public class HelloWorldApplcation {

    public static void main(String[] args) {

        SpringApplication.run(HelloWorldApplcation.class, args);

    }

}

②、war包通常使用Tomcat进行部署启动，在tomcat启动war应用时，会先进行Servlet环境的初始化，之后才会进行到IOC容器的初始化，也就是说，在servlet初始化过程中是不能使用IOC依赖注入的。

public class ServletInitializer extends SpringBootServletInitializer {

    @Override

    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {

        return application.sources(HelloWorldApplcation.class);

    }

}

2、实现在springboot应用启动的时候启动Socket服务
2.1、jar包情况下，将Socket服务交由IOC容器进行管理，然后在IOC容器创建完成后，获取到已经初始化的Socket服务实例，然后开始Socket服务。在这样的情况下，可以在Socket服务类上进行依赖注入，也就是说可以使用@Autowired

@SpringBootApplication

public class HelloWorldApplcation {

    public static void main(String[] args) {

        ApplicationContext applicationContext = SpringApplication.run(HelloWorldApplcation.class, args);

        SocketServer socketServer =applicationContext.getBean(SocketServer.class);

        socketServer.start();

    }

}

2.2、war包情况下，由于是先进行Servlet环境的初始化，然后再进行IOC容器的创建，有了这个先后顺序，即知道，是不可能在Servlet创建时拿到WebApplicationContext对象的，下面是我的验证

package com.geniuses.sewage_zero_straight.listener;

import com.geniuses.sewage_zero_straight.net.socket.SocketServer;

import lombok.extern.slf4j.Slf4j;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.web.context.WebApplicationContext;

import org.springframework.web.context.support.WebApplicationContextUtils;

import javax.servlet.ServletContextEvent;

import javax.servlet.ServletContextListener;

import javax.servlet.annotation.WebListener;

@Slf4j

@WebListener

public class SocketListener implements ServletContextListener {

    @Autowired

    private SocketServer socketServer;

    @Override

    public void contextInitialized(ServletContextEvent sce) {

        log.info("准备启动Socket服务...");

        log.info("SocketServer:{}", socketServer);

        socketServer.start();

    }

    @Override

    public void contextDestroyed(ServletContextEvent sce) {

    }

}

package com.geniuses.sewage_zero_straight.config;

import lombok.extern.slf4j.Slf4j;

import org.springframework.web.WebApplicationInitializer;

import org.springframework.web.context.WebApplicationContext;

import org.springframework.web.context.support.WebApplicationContextUtils;

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.annotation.HandlesTypes;

@Slf4j

@HandlesTypes({WebApplicationInitializer.class})

public class SocketConfig implements WebApplicationInitializer {

    @Override

    public void onStartup(ServletContext servletContext) throws ServletException {

        WebApplicationContext webApplicationContext = WebApplicationContextUtils.getWebApplicationContext(servletContext);

        log.info("application: {}", webApplicationContext);

        //log.info("SocketServer: {}", webApplicationContext.getBean(SocketServer.class));

    }

}

关于WebApplicationInitializer理解，参见：https://blog.csdn.net/zq17865815296/article/details/79464403
以上是为测试Servlet环境中能否拿到IOC容器和能否注入Bean，发现并不能拿到对象

我就开始想啊，要怎么才能拿到IOC容器对象嘞，随后发现SpringBootServletInitializer便是创建IOC容器的起始点

//

// Source code recreated from a .class file by IntelliJ IDEA

// (powered by Fernflower decompiler)

//

package org.springframework.boot.web.servlet.support;

import java.util.Collections;

import javax.servlet.ServletConfig;

import javax.servlet.ServletContext;

import javax.servlet.ServletContextEvent;

import javax.servlet.ServletException;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.builder.ParentContextApplicationContextInitializer;

import org.springframework.boot.builder.SpringApplicationBuilder;

import org.springframework.boot.context.event.ApplicationEnvironmentPreparedEvent;

import org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext;

import org.springframework.context.ApplicationContext;

import org.springframework.context.ApplicationContextInitializer;

import org.springframework.context.ApplicationListener;

import org.springframework.context.annotation.Configuration;

import org.springframework.core.Ordered;

import org.springframework.core.annotation.AnnotationUtils;

import org.springframework.core.env.ConfigurableEnvironment;

import org.springframework.util.Assert;

import org.springframework.web.WebApplicationInitializer;

import org.springframework.web.context.ConfigurableWebEnvironment;

import org.springframework.web.context.ContextLoaderListener;

import org.springframework.web.context.WebApplicationContext;

public abstract class SpringBootServletInitializer implements WebApplicationInitializer {

    protected Log logger;

    private boolean registerErrorPageFilter = true;

    public SpringBootServletInitializer() {

    }

    protected final void setRegisterErrorPageFilter(boolean registerErrorPageFilter) {

        this.registerErrorPageFilter = registerErrorPageFilter;

    }

    public void onStartup(ServletContext servletContext) throws ServletException {

        this.logger = LogFactory.getLog(this.getClass());

        //这里开始创建IOC容器

        WebApplicationContext rootAppContext = this.createRootApplicationContext(servletContext);

        if (rootAppContext != null) {

            servletContext.addListener(new ContextLoaderListener(rootAppContext) {

                public void contextInitialized(ServletContextEvent event) {

                }

            });

        } else {

            this.logger.debug("No ContextLoaderListener registered, as createRootApplicationContext() did not return an application context");

        }

    }

    //IOC容器创建方法

    protected WebApplicationContext createRootApplicationContext(ServletContext servletContext) {

        SpringApplicationBuilder builder = this.createSpringApplicationBuilder();

        builder.main(this.getClass());

        ApplicationContext parent = this.getExistingRootWebApplicationContext(servletContext);

        if (parent != null) {

            this.logger.info("Root context already created (using as parent).");

            servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, (Object)null);

            builder.initializers(new ApplicationContextInitializer[]{new ParentContextApplicationContextInitializer(parent)});

        }

        builder.initializers(new ApplicationContextInitializer[]{new ServletContextApplicationContextInitializer(servletContext)});

        builder.contextClass(AnnotationConfigServletWebServerApplicationContext.class);

        builder = this.configure(builder);

        builder.listeners(new ApplicationListener[]{new SpringBootServletInitializer.WebEnvironmentPropertySourceInitializer(servletContext)});

        SpringApplication application = builder.build();

        if (application.getAllSources().isEmpty() && AnnotationUtils.findAnnotation(this.getClass(), Configuration.class) != null) {

            application.addPrimarySources(Collections.singleton(this.getClass()));

        }

        Assert.state(!application.getAllSources().isEmpty(), "No SpringApplication sources have been defined. Either override the configure method or add an @Configuration annotation");

        if (this.registerErrorPageFilter) {

            application.addPrimarySources(Collections.singleton(ErrorPageFilterConfiguration.class));

        }

        return this.run(application);

    }

    protected WebApplicationContext run(SpringApplication application) {

        return (WebApplicationContext)application.run(new String[0]);

    }

    }

}

这个时候我想到，如果不将SocketServer交由IOC进行管理，那么可以在实现的WebApplicationInitializer自定义类中启动SocketServer

package com.geniuses.sewage_zero_straight.config;

import lombok.extern.slf4j.Slf4j;

import org.springframework.web.WebApplicationInitializer;

import org.springframework.web.context.WebApplicationContext;

import org.springframework.web.context.support.WebApplicationContextUtils;

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.annotation.HandlesTypes;

/**

 *

 */

@Slf4j

@HandlesTypes({WebApplicationInitializer.class})

public class SocketConfig implements WebApplicationInitializer {

    @Override

    public void onStartup(ServletContext servletContext) throws ServletException {

       new Thread(new SocketRunnable(new SocketServer())).start();

    }

}

这里为什么要用一个新的线程来启动Socket服务，因为SocketServer服务端的实现中，使用while循环进行等待客户端socket进行连接，启动时便开始等待（阻塞），如果不使用一个新的线程启动，那么整个war应用服务启动线程便会在此处阻塞。这样虽然可以解决Socket服务随着应用启动而启动，但是又出现了一个新的问题，那就是SocketServer无法使用@Autowired了，因为SocketServer没有被IOC进行管理，无法进行依赖的注入。如果你不需要依赖，那么此法可行。

然后我又开始思考了，如果我需要进行依赖注入，由IOC进行SocketServer的管理，那么我要怎么样才能获取到WebApplicationContext对象，然后再通过该对象拿到SocketServer实例，然后再启动Socket服务。如果我继承了SpringBootServletInitializer，并重写onStartup方法，再重写的onStartup方法中进行Socket服务的启动会怎么样，最后发现Socket服务启动了，但是进行了两次onStartup方法的调用，第一次是自定义的SpringBootServletInitializer的实现类，第二次便是SpringBootServletInitializer类。即便只会启动一次，这样的代码也具有着极强的侵入性，便放弃了。

@Override

public void onStartup(ServletContext servletContext) throws ServletException {

        this.logger = LogFactory.getLog(this.getClass());

        //这里开始创建IOC容器

        WebApplicationContext rootAppContext = this.createRootApplicationContext(servletContext);

    //在这里进行启动Socket服务

    new Thread(new SocketRunnable(rootAppContext.getBean(SocketServer.class))).start();

        if (rootAppContext != null) {

            servletContext.addListener(new ContextLoaderListener(rootAppContext) {

                public void contextInitialized(ServletContextEvent event) {

                }

            });

        } else {

            this.logger.debug("No ContextLoaderListener registered, as createRootApplicationContext() did not return an application context");

        }

    }

然后我又开始思考，既然有ServletContextListener 监听ServletContext对象的创建以及销毁，那么是不是有监听IOC容器的创建和销毁嘞，随后开始进行了百度
.................................................
是的，没错，这个真的有，详情参见：https://blog.csdn.net/qq_40693828/article/details/81448934
感谢大佬
其实在这里想到了Javaweb整合spring的时候，好像有一个初始化IOC容器的监听器来着，忘了，活该自己技术差......
在这里将SocketServer注入到SocketThread中，这里还有一个疑问，在这里使用@Autowired注入SocketThread不是很稳定，猜测可能与IOC的初始化时间前后有关系，不知道是为何

package com.geniuses.sewage_zero_straight.listener;

import com.geniuses.sewage_zero_straight.net.socket.SocketServer;

import com.geniuses.sewage_zero_straight.net.socket.SocketThread;

import lombok.extern.slf4j.Slf4j;

import org.springframework.stereotype.Component;

import org.springframework.web.context.ContextLoaderListener;

import org.springframework.web.context.WebApplicationContext;

import org.springframework.web.context.support.WebApplicationContextUtils;

import javax.servlet.ServletContext;

import javax.servlet.ServletContextEvent;

import javax.servlet.annotation.WebListener;

@Slf4j

@WebListener

public class MyContextLoaderListener extends ContextLoaderListener {

    @Override

    public void contextInitialized(ServletContextEvent event) {

        ServletContext servletContext = event.getServletContext();

        WebApplicationContext webApplicationContext = WebApplicationContextUtils.getWebApplicationContext(servletContext);

        log.info("webApplicationContext:{}",webApplicationContext);

        SocketThread socketThread = webApplicationContext.getBean(SocketThread.class);

        servletContext.setAttribute("SocketThread", socketThread);//在这里放进去之后......，好像也没有必要放，可以从WebApplicationContext中获取...

        log.info("socketThread:{}", socketThread);

        socketThread.start();

    }

}

在百度的过程中，突然看见一博客，https://www.jianshu.com/p/90063de8cf9b，感谢这位大神

在这里由SocketThread实现InitializingBean，实现afterPropertiesSet，这样，在该类的依赖注入完毕之后，会自动调用afterPropertiesSet方法，这样便可以在这里启动socket服务。关于InitializingBean的介绍，参见上面的这个链接。

package com.geniuses.sewage_zero_straight.net.socket;

import lombok.extern.slf4j.Slf4j;

import org.springframework.beans.factory.InitializingBean;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Component;

@Slf4j

@Component

public class SocketThread extends Thread implements InitializingBean {

    @Autowired

    private SocketServer socketServer;

    @Override

    public void run() {

        log.info("当前线程名：{}", Thread.currentThread().getName());

        log.info("由当前线程开始启动Socket服务...");

        socketServer.start();

    }

    @Override

    public void afterPropertiesSet() throws Exception {

        start();

    }

}

至此，我是不想再想了。
在这里感谢下面的几篇博客：
监听器介绍：https://blog.csdn.net/m0_38075425/article/details/81164501
自启动监听类（InitializingBean）介绍：https://www.jianshu.com/p/90063de8cf9b
springboot中启动流程说明：https://www.jb51.net/article/142981.htm
SpringBoot中WebApplicationInitializer的理解：https://blog.csdn.net/zq17865815296/article/details/79464403
Spring中ContextLoaderListener作用：https://blog.csdn.net/qq_40693828/article/details/81448934

最后说一下我的开发环境：win7_64旗舰版、jdk1.8、idea、tomcat8.5

SpringBoot集成Socket服务后打包（war包）启动时如何启动Socket服务（web应用外部tomcat启动）

SpringBoot集成Socket服务后打包（war包）启动时如何启动Socket服务（web应用外部tomcat启动）的相关教程结束。

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