spring

ApplicationContext之prepareRefresh 

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/**
 * Prepare this context for refreshing, setting its startup date and
 * active flag as well as performing any initialization of property sources.
 */
protected void prepareRefresh() {
	//开始时间
	this.startupDate = System.currentTimeMillis();
	this.closed.set(false);
	this.active.set(true);

	if (logger.isInfoEnabled()) {
		logger.info("Refreshing " + this);
	}

	// Initialize any placeholder property sources in the context environment.
	//初始化一些属性,默认里面的实现是空的，留给子类使用，扩展点之一
	initPropertySources();

	// Validate that all properties marked as required are resolvable:
	// see ConfigurablePropertyResolver#setRequiredProperties
	//得到环境信息，默认的是StandardEnvironment。然后来验证一些必要的属性是否存在，如果不存在，那么此处就会
	//抛出异常
	//StandardEnvironment用的是委托模式，validateRequiredProperties的时候委托给了自己内部的属性解析器，也就是
	//propertyResolver。
	//propertyResolver在实例化的时候，会接收属性源，解析器的父类有一个私有集合对象用于储存key；
	//validate的时候，会通过解析器的getProperty取值然后验证是否存在；
	getEnvironment().validateRequiredProperties();

	// Store pre-refresh ApplicationListeners...
	//添加一些监听器
	if (this.earlyApplicationListeners == null) {
		this.earlyApplicationListeners = new LinkedHashSet<>(this.applicationListeners);
	}
	else {
		// Reset local application listeners to pre-refresh state.
		this.applicationListeners.clear();
		this.applicationListeners.addAll(this.earlyApplicationListeners);
	}

	// Allow for the collection of early ApplicationEvents,
	// to be published once the multicaster is available...
	this.earlyApplicationEvents = new LinkedHashSet<>();
}

下面是一个使用示例：

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package com.vayne.boot;

import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.core.env.SystemEnvironmentPropertySource;

import java.util.HashMap;
import java.util.Map;

/**
 * @author Volcanno
 */
public class Boot {

    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:application.xml");
        Map<String, Object> map = new HashMap<>();
        map.put("vay", "vayne");
        map.put("alis", "alison");
        SystemEnvironmentPropertySource seps = new SystemEnvironmentPropertySource("env", map);
        context.getEnvironment().getPropertySources().addFirst(seps);
        //这里会把vay和alis添加到AbstractPropertyResolver的一个list里面。然后validate的时候，会调用子类的getProperty
        context.getEnvironment().setRequiredProperties("vay");
        context.getEnvironment().setRequiredProperties("alis");
        context.refresh();
        Object object = context.getEnvironment().getProperty("alis");
        String string = String.valueOf(object);
        System.out.println("hello, " + string);
    }
}

总结：

可以将一些需要使用的必要的属性设置到context的environment里面，然后使用的时候直接取用就可以了。