springboot在prepareEnvironment函数中环境转换的问题

[GuDongYu1]

我在看springboot的源码，不太懂prepareEnvironment函数中为什么要有这个if代码块。

if的条件中是判断是否为自定义环境，如果是自定义环境那么就不会执行if代码块，如果是通过getOrCreateEnvironment创建的环境，说明不是自定义环境，那会进入if代码块执行。

进入if代码块后，会对环境进行转换，看convertEnvironmentfINecessary函数，最开始的类型判断应该一定会返回true的呀，在其他地方也没发现谁调用过convertEnvironmentIfNecessary这个函数，说明convertEnvironmentIfNecessary函数中的第二个return不会被执行。

那这么写的作用是什么，感谢各位大佬指导下。

        private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners,
			DefaultBootstrapContext bootstrapContext, ApplicationArguments applicationArguments) {
		ConfigurableEnvironment environment = getOrCreateEnvironment();
		configureEnvironment(environment, applicationArguments.getSourceArgs());
		ConfigurationPropertySources.attach(environment);
		listeners.environmentPrepared(bootstrapContext, environment);
		DefaultPropertiesPropertySource.moveToEnd(environment);
		configureAdditionalProfiles(environment);
		bindToSpringApplication(environment);
		if (!this.isCustomEnvironment) {
			environment = new EnvironmentConverter(getClassLoader()).convertEnvironmentIfNecessary(environment,
					deduceEnvironmentClass());
		}
		ConfigurationPropertySources.attach(environment);
		return environment;
	}

       StandardEnvironment convertEnvironmentIfNecessary(ConfigurableEnvironment environment,
			Class<? extends StandardEnvironment> type) {
		if (type.equals(environment.getClass())) {
			return (StandardEnvironment) environment;
		}
		return convertEnvironment(environment, type);
	}

        private ConfigurableEnvironment getOrCreateEnvironment() {
		if (this.environment != null) {
			return this.environment;
		}
		switch (this.webApplicationType) {
		case SERVLET:
			return new StandardServletEnvironment();
		case REACTIVE:
			return new StandardReactiveWebEnvironment();
		default:
			return new StandardEnvironment();
		}
	}

     private Class<? extends StandardEnvironment> deduceEnvironmentClass() {
		switch (this.webApplicationType) {
		case SERVLET:
			return StandardServletEnvironment.class;
		case REACTIVE:
			return StandardReactiveWebEnvironment.class;
		default:
			return StandardEnvironment.class;
		}
	}

[KeepSayingNo]

做环境预处理是因为springboot支持不同的启动方式，它必须要清楚当前是什么环境才能决定以哪种方式启动，不想spring mvc，你的web server是外部的