1.ClassPathXmlApplicationContext()

开始进入spring

ApplicationContext ac = new ClassPathXmlApplicationContext("application.xml");
application.xml文件
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">
    <context:component-scan base-package="com.mashibing"></context:component-scan>
    <bean id="person" class="com.mashibing.Person">
        <constructor-arg name="id" value="1"></constructor-arg>
        <constructor-arg name="name" value="lisi"></constructor-arg>
    </bean>
</beans>

通过new ClassPathXmlApplicationContext会调用构造方法

public class ClassPathXmlApplicationContext extends AbstractXmlApplicationContext {}
/**
 * 创建一个新的ClassPathXmlApplicationContext，从xml文件中加载给定的bean定义信息，并且刷新上下文
 */
public ClassPathXmlApplicationContext(String configLocation) throws BeansException {
    //调用下面的构造方法，此处3个参数
    this(new String[] {configLocation}, true, null);
}
//传递过来的configLocations空数组，refresh为true，parent为null
public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, 
                                      @Nullable ApplicationContext parent)
        throws BeansException {
    // 一、调用父类构造方法，进行相关的对象创建等操作，包含属性的赋值操作
    super(parent);
    // 二、
    setConfigLocations(configLocations);
    if (refresh) {
        refresh();
    }
}

一、super(parent)父类构造方法

//parent参数为null
public AbstractApplicationContext(@Nullable ApplicationContext parent) {
    //调用本类无参构造
    this();
    setParent(parent);
}

this()：AbstractApplicationContext类

AbstractApplicationContext类中一些重要信息
//创建上下文的唯一标识
private String id = ObjectUtils.identityToString(this);
//显示的名字
private String displayName = ObjectUtils.identityToString(this);
ObjectUtils工具类部分方法
//可得到(obj的全类名+'@'+obj的hashCode的十六进制字符串),如果obj为null，返回空字符串
private static final String EMPTY_STRING = "";
public static String identityToString(@Nullable Object obj) {
    // 如果对象为null
    if (obj == null) {
        // 返回空字符串
        return EMPTY_STRING;
    }
    // 拼接obj的全类名+'@'+obj的hashCode的十六进制字符串，然后返回出去
    String className = obj.getClass().getName();
    String identityHexString = getIdentityHexString(obj);
    return className + '@' + identityHexString;
}
//用来存放beanFactory的后置处理器集合
private final List<BeanFactoryPostProcessor> beanFactoryPostProcessors = new ArrayList<>();
//容器激活标志
private final AtomicBoolean active = new AtomicBoolean();
//容器关闭标志
private final AtomicBoolean closed = new AtomicBoolean();
//刷新和销毁的同步监视器
private final Object startupShutdownMonitor = new Object();
//创建一个无父类的AbstractApplicationContext对象
public AbstractApplicationContext() {
    // 创建资源模式处理器
    this.resourcePatternResolver = getResourcePatternResolver();
}
protected ResourcePatternResolver getResourcePatternResolver() {
    // 创建一个资源模式解析器(用来解析xml配置文件)
    return new PathMatchingResourcePatternResolver(this);
}
PathMatchingResourcePatternResolver类中一些重要信息
private final ResourceLoader resourceLoader;
// 创建ant方式的路径匹配器 - 目前几乎不用
private PathMatcher pathMatcher = new AntPathMatcher();
//new PathMatchingResourcePatternResolver
public PathMatchingResourcePatternResolver(ResourceLoader resourceLoader) {
    Assert.notNull(resourceLoader, "ResourceLoader must not be null");
    this.resourceLoader = resourceLoader;
}

setParent(parent)

//设置此应用程序上下文的父级。parent参数为null
@Override
public void setParent(@Nullable ApplicationContext parent) {
    this.parent = parent;
    //如果父容器不为空
    if (parent != null) {
        //获取父容器的环境对象
        Environment parentEnvironment = parent.getEnvironment();
        //如果父容器的环境对象是一个可配置的环境对象
        if (parentEnvironment instanceof ConfigurableEnvironment) {
            getEnvironment().merge((ConfigurableEnvironment) parentEnvironment);
        }
    }
}

AbstractXmlApplicationContext类

ClassPathXmlApplicationContext继承AbstractXmlApplicationContext抽象类

注意：在new子类对象时，会开辟一块内存空间，同时调用父类构造方法(并不会new一个父类对象)，再把父类中的成员变量和方法也加载到这块内存空间；至于super调用，是访问了这个空间特定部分的数据（也就是专门存储父类数据的内存部分）。

AbstractXmlApplicationContext类中一些重要信息

public abstract class AbstractXmlApplicationContext extends AbstractRefreshableConfigApplicationContext {}

// 设置xml文件的验证标志，默认是true
private boolean validating = true;

二、setConfigLocations(configLocations)

//设置应用程序上下文的配置路径，如果未设置，则实现可以根据需要使用默认值。
//此处参数locations是一个空数组
public void setConfigLocations(@Nullable String... locations) {
    if (locations != null) {
        Assert.noNullElements(locations, "Config locations must not be null");
        this.configLocations = new String[locations.length];
        for (int i = 0; i < locations.length; i++) {
            // 解析给定路径
            this.configLocations[i] = resolvePath(locations[i]).trim();
        }
    }
    else {
        this.configLocations = null;
    }
}