spring-全量自定义-PropertySources-白红宇

spring-全量自定义-PropertySources

阅读量：4144 次

发布时间：2019-05-25

本文共 5937 字，大约阅读时间需要 19 分钟。

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;	}}