Spring CompositePropertySource

/**
 * set 集合
 */
private final Set<PropertySource<?>> propertySources = new LinkedHashSet<>();


/**
 * Create a new {@code CompositePropertySource}.
 * @param name the name of the property source
 */
public CompositePropertySource(String name) {
	super(name);
}


@Override
@Nullable
public Object getProperty(String name) {
	// 循环
	for (PropertySource<?> propertySource : this.propertySources) {
		// 获取存储内容
		Object candidate = propertySource.getProperty(name);
		if (candidate != null) {
			return candidate;
		}
	}
	return null;
}

@Override
public boolean containsProperty(String name) {
	for (PropertySource<?> propertySource : this.propertySources) {
		// 是否存在name
		if (propertySource.containsProperty(name)) {
			return true;
		}
	}
	return false;
}

@Override
public String[] getPropertyNames() {
	Set<String> names = new LinkedHashSet<>();
	for (PropertySource<?> propertySource : this.propertySources) {
		// 类型不同抛出异常
		if (!(propertySource instanceof EnumerablePropertySource)) {
			throw new IllegalStateException(
					"Failed to enumerate property names due to non-enumerable property source: " + propertySource);
		}
		// 批量添加
		names.addAll(Arrays.asList(((EnumerablePropertySource<?>) propertySource).getPropertyNames()));
	}
	// 转换成 array
	return StringUtils.toStringArray(names);
}


/**
 * Add the given {@link PropertySource} to the end of the chain.
 * @param propertySource the PropertySource to add
 */
public void addPropertySource(PropertySource<?> propertySource) {
	this.propertySources.add(propertySource);
}

/**
 * Add the given {@link PropertySource} to the start of the chain.
 * @param propertySource the PropertySource to add
 * @since 4.1
 */
public void addFirstPropertySource(PropertySource<?> propertySource) {
	// 头插
	List<PropertySource<?>> existing = new ArrayList<>(this.propertySources);
	this.propertySources.clear();
	this.propertySources.add(propertySource);
	this.propertySources.addAll(existing);
}

/**
 * Return all property sources that this composite source holds.
 * @since 4.1.1
 */
public Collection<PropertySource<?>> getPropertySources() {
	return this.propertySources;
}


@Override
public String toString() {
	return getClass().getSimpleName() + " {name='" + this.name + "', propertySources=" + this.propertySources + "}";
}

</details>