spring-全量自定义-PropertySources

PropertySources:持有一个或多个PropertySoucrce对象(如果对PropertySource不熟悉,建议看一下上一篇文章)

来看一下定义:

public interface PropertySources extends Iterable>

该接口实现了Iterable接口,那么也就是该资源是可迭代,可foreach等功能;然后本身还提供了:

	default Stream> stream() {
		return StreamSupport.stream(spliterator(), false);
	}

	boolean contains(String name);

	@Nullable
	PropertySource get(String name);

通过这些接口信息我们可以看出,PropertySources主要提供对持有PropertySource提供操作扩展.

PropertySources仅有一个实现MutablePropertySources,因为这个类对理解spring环境比较重要,做一下详细说明,直接上源码:

public class MutablePropertySources implements PropertySources {

//资源hold,一个在写时copy的数组链表,可以并发访问
	private final List> propertySourceList = new CopyOnWriteArrayList<>();


	/**
	 * Create a new {@link MutablePropertySources} object.
	 */
	public MutablePropertySources() {
	}

	/**
	 * Create a new {@code MutablePropertySources} from the given propertySources
	 * object, preserving the original order of contained {@code PropertySource} objects.
	 */
	public MutablePropertySources(PropertySources propertySources) {
		this();
		for (PropertySource propertySource : propertySources) {
			addLast(propertySource);
		}
	}


	@Override
	public Iterator> iterator() {
		return this.propertySourceList.iterator();
	}

	@Override
	public Spliterator> spliterator() {
		return Spliterators.spliterator(this.propertySourceList, 0);
	}

	@Override
	public Stream> stream() {
		return this.propertySourceList.stream();
	}

	@Override
	public boolean contains(String name) {
		return this.propertySourceList.contains(PropertySource.named(name));
	}

	@Override
	@Nullable
	public PropertySource get(String name) {
		int index = this.propertySourceList.indexOf(PropertySource.named(name));
		return (index != -1 ? this.propertySourceList.get(index) : null);
	}


	/**
	 * Add the given property source object with highest precedence.
	 */
	public void addFirst(PropertySource propertySource) {
		removeIfPresent(propertySource);
		this.propertySourceList.add(0, propertySource);
	}

	/**
	 * Add the given property source object with lowest precedence.
	 */
	public void addLast(PropertySource propertySource) {
		removeIfPresent(propertySource);
		this.propertySourceList.add(propertySource);
	}

	/**
	 * Add the given property source object with precedence immediately higher
	 * than the named relative property source.
	 */
	public void addBefore(String relativePropertySourceName, PropertySource propertySource) {
		assertLegalRelativeAddition(relativePropertySourceName, propertySource);
		removeIfPresent(propertySource);
		int index = assertPresentAndGetIndex(relativePropertySourceName);
		addAtIndex(index, propertySource);
	}

	/**
	 * Add the given property source object with precedence immediately lower
	 * than the named relative property source.
	 */
	public void addAfter(String relativePropertySourceName, PropertySource propertySource) {
		assertLegalRelativeAddition(relativePropertySourceName, propertySource);
		removeIfPresent(propertySource);
		int index = assertPresentAndGetIndex(relativePropertySourceName);
		addAtIndex(index + 1, propertySource);
	}

	/**
	 * Return the precedence of the given property source, {@code -1} if not found.
	 * 优先级获取,客户端使用时,会按照index从小到大获取属性,所以如果一个属性name,在多个属性资源中含有,那么优先级高的会使用
	 */
	public int precedenceOf(PropertySource propertySource) {
		return this.propertySourceList.indexOf(propertySource);
	}

	/**
	 * Remove and return the property source with the given name, {@code null} if not found.
	 * @param name the name of the property source to find and remove
	 */
	@Nullable
	public PropertySource remove(String name) {
		int index = this.propertySourceList.indexOf(PropertySource.named(name));
		return (index != -1 ? this.propertySourceList.remove(index) : null);
	}

	/**
	 * Replace the property source with the given name with the given property source object.
	 * @param name the name of the property source to find and replace
	 * @param propertySource the replacement property source
	 * @throws IllegalArgumentException if no property source with the given name is present
	 * @see #contains
	 * 在有些情况下如ServerContext,为了保证自己的优先级,会使用StubPropertySource进行占位,实际初始化后,再使用replace进行替换
	 */
	public void replace(String name, PropertySource propertySource) {
		int index = assertPresentAndGetIndex(name);
		this.propertySourceList.set(index, propertySource);
	}

	/**
	 * Return the number of {@link PropertySource} objects contained.
	 */
	public int size() {
		return this.propertySourceList.size();
	}

	@Override
	public String toString() {
		return this.propertySourceList.toString();
	}

	/**
	 * Ensure that the given property source is not being added relative to itself.
	 */
	protected void assertLegalRelativeAddition(String relativePropertySourceName, PropertySource propertySource) {
		String newPropertySourceName = propertySource.getName();
		if (relativePropertySourceName.equals(newPropertySourceName)) {
			throw new IllegalArgumentException(
					"PropertySource named '" + newPropertySourceName + "' cannot be added relative to itself");
		}
	}

	/**
	 * Remove the given property source if it is present.
	 */
	protected void removeIfPresent(PropertySource propertySource) {
		this.propertySourceList.remove(propertySource);
	}

	/**
	 * Add the given property source at a particular index in the list.
	 */
	private void addAtIndex(int index, PropertySource propertySource) {
		removeIfPresent(propertySource);
		this.propertySourceList.add(index, propertySource);
	}

	/**
	 * Assert that the named property source is present and return its index.
	 * @param name {@linkplain PropertySource#getName() name of the property source} to find
	 * @throws IllegalArgumentException if the named property source is not present
	 */
	private int assertPresentAndGetIndex(String name) {
		int index = this.propertySourceList.indexOf(PropertySource.named(name));
		if (index == -1) {
			throw new IllegalArgumentException("PropertySource named '" + name + "' does not exist");
		}
		return index;
	}

}