2-1-3.spring源码--ClassPathXmlApplicationContext

Spring源码–ClassPathXmlApplicationContext

概述

ClassPathXmlApplicationContext对于学习spring的小伙伴一定是不陌生的，刚才 学的时候基本都会有遇到下面这段代码：

ApplicationContext applicationContext= new ClassPathXmlApplicationContext("x.xml");
    B b=applicationContext.getBean(B.class);

官方的描述：单独xml application容器，从类文件路径上读取出容器信息，（Standalone XML application context, taking the context definition files from the class path）。

spring可以通过创建ApplicationContext容器可以实现对于bean的操作，而实现ApplicationContext接口的实现类就是ClassPathXmlApplicationContext类，这里使用多态的特性。但是具体实现是什么？需要对于源码进行解析，下面是对源码的解析。

源码

public class ClassPathXmlApplicationContext extends AbstractXmlApplicationContext {

  @Nullable
  private Resource[] configResources;
  /**
   * 重构的构造方法
   */
  public ClassPathXmlApplicationContext() {
  }
  public ClassPathXmlApplicationContext(ApplicationContext parent) {
    super(parent);
  }
  public ClassPathXmlApplicationContext(String configLocation) throws BeansException {
    this(new String[] {configLocation}, true, null);
  }
  public ClassPathXmlApplicationContext(String... configLocations) throws BeansException {
    this(configLocations, true, null);
  }
  public ClassPathXmlApplicationContext(String[] configLocations, @Nullable ApplicationContext parent)
      throws BeansException {

    this(configLocations, true, parent);
  }
  public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh) throws BeansException {
    this(configLocations, refresh, null);
  }
  //构造方法实际的实现方法
  public ClassPathXmlApplicationContext(
      String[] configLocations, boolean refresh, @Nullable ApplicationContext parent)
      throws BeansException {

    super(parent);
    setConfigLocations(configLocations);
    if (refresh) {
      //进入核心的refresh方法中
      refresh();
    }
  }
  public ClassPathXmlApplicationContext(String path, Class<?> clazz) throws BeansException  {
    this(new String[] {path}, clazz);
  }
  public ClassPathXmlApplicationContext(String[] paths, Class<?> clazz) throws BeansException {
    this(paths, clazz, null);
  }
  public ClassPathXmlApplicationContext(String[] paths, Class<?> clazz, @Nullable ApplicationContext parent)
      throws BeansException {
    super(parent);
    Assert.notNull(paths, "Path array must not be null");
    Assert.notNull(clazz, "Class argument must not be null");
    this.configResources = new Resource[paths.length];
    for (int i = 0; i < paths.length; i++) {
      this.configResources[i] = new ClassPathResource(paths[i], clazz);
    }
    refresh();
  }

  @Override
  @Nullable
  protected Resource[] getConfigResources() {
    return this.configResources;
  }
}

上述源码核心的实现方式是执行了refresh()方法。refresh()是spring代码运转的核心，这个稍后会详细解释。