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488 lines
15 KiB
488 lines
15 KiB
# Spring PropertySources
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- Author: [HuiFer](https://github.com/huifer)
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- 源码阅读仓库: [SourceHot-spring](https://github.com/SourceHot/spring-framework-read)
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## MutablePropertySources
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- 全路径: `org.springframework.core.env.MutablePropertySources`
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- `MutablePropertySources`类内部存储了`List<PropertySource<?>>`对象,主要是针对`List<PropertySource<?>>` 进行的操作.换句话说就是对 list 操作的实现
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- 类注解如下
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```java
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public class MutablePropertySources implements PropertySources {
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private final List<PropertySource<?>> propertySourceList = new CopyOnWriteArrayList<>();
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/**
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* Create a new {@link MutablePropertySources} object.
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*
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* 构造方法
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*/
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public MutablePropertySources() {
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}
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/**
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* Create a new {@code MutablePropertySources} from the given propertySources
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* object, preserving the original order of contained {@code PropertySource} objects.
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* 构造方法, 传递一个集合, 将集合中的数据放入 {@code propertySourceList}.
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*/
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public MutablePropertySources(PropertySources propertySources) {
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this();
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// PropertySources 是一个迭代器接口的实现,通过循环取出信息放入到 propertySourceList 中
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for (PropertySource<?> propertySource : propertySources) {
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// 放入方法
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addLast(propertySource);
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}
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}
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/**
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* 获取迭代器对象
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*/
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@Override
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public Iterator<PropertySource<?>> iterator() {
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return this.propertySourceList.iterator();
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}
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/**
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* 获取 Spliterator 对象
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*/
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@Override
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public Spliterator<PropertySource<?>> spliterator() {
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return Spliterators.spliterator(this.propertySourceList, 0);
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}
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/**
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* 获取流
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*/
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@Override
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public Stream<PropertySource<?>> stream() {
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return this.propertySourceList.stream();
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}
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/**
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* 判断是否存在 name
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* @param name the {@linkplain PropertySource#getName() name of the property source} to find
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*/
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@Override
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public boolean contains(String name) {
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return this.propertySourceList.contains(PropertySource.named(name));
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}
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/**
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* 获取 PropertySource 信息
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* @param name the {@linkplain PropertySource#getName() name of the property source} to find
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* @return
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*/
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@Override
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@Nullable
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public PropertySource<?> get(String name) {
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// 获取 name 所在的索引位置
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int index = this.propertySourceList.indexOf(PropertySource.named(name));
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// get方法获取结果
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return (index != -1 ? this.propertySourceList.get(index) : null);
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}
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/**
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* Add the given property source object with highest precedence.
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*
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* 头插数据
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*/
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public void addFirst(PropertySource<?> propertySource) {
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removeIfPresent(propertySource);
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this.propertySourceList.add(0, propertySource);
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}
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/**
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* Add the given property source object with lowest precedence.
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*
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* 尾插数据
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*/
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public void addLast(PropertySource<?> propertySource) {
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removeIfPresent(propertySource);
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this.propertySourceList.add(propertySource);
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}
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/**
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* Add the given property source object with precedence immediately higher
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* than the named relative property source.
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*
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* 在relativePropertySourceName的索引位置前添加数据
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*/
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public void addBefore(String relativePropertySourceName, PropertySource<?> propertySource) {
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assertLegalRelativeAddition(relativePropertySourceName, propertySource);
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removeIfPresent(propertySource);
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int index = assertPresentAndGetIndex(relativePropertySourceName);
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addAtIndex(index, propertySource);
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}
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/**
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* Add the given property source object with precedence immediately lower
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* than the named relative property source.
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* 在relativePropertySourceName的索引位置后添加数据
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*/
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public void addAfter(String relativePropertySourceName, PropertySource<?> propertySource) {
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assertLegalRelativeAddition(relativePropertySourceName, propertySource);
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// 删除存在的数据
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removeIfPresent(propertySource);
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// 获取所有
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int index = assertPresentAndGetIndex(relativePropertySourceName);
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// 在索引+1出添加数据
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addAtIndex(index + 1, propertySource);
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}
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/**
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* Return the precedence of the given property source, {@code -1} if not found.
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* 获取索引位置
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*/
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public int precedenceOf(PropertySource<?> propertySource) {
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return this.propertySourceList.indexOf(propertySource);
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}
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/**
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* Remove and return the property source with the given name, {@code null} if not found.
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* 删除索引位置
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* @param name the name of the property source to find and remove
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*/
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@Nullable
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public PropertySource<?> remove(String name) {
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// 获取索引
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int index = this.propertySourceList.indexOf(PropertySource.named(name));
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// 删除索引上的数据
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return (index != -1 ? this.propertySourceList.remove(index) : null);
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}
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/**
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* Replace the property source with the given name with the given property source object.
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* 替换 name 的信息
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* @param name the name of the property source to find and replace
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* @param propertySource the replacement property source
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* @throws IllegalArgumentException if no property source with the given name is present
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* @see #contains
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*/
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public void replace(String name, PropertySource<?> propertySource) {
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// 获取索引位置
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int index = assertPresentAndGetIndex(name);
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// 设置具体所应位置的值
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this.propertySourceList.set(index, propertySource);
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}
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/**
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* Return the number of {@link PropertySource} objects contained.
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* 数量
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*/
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public int size() {
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return this.propertySourceList.size();
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}
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@Override
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public String toString() {
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return this.propertySourceList.toString();
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}
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/**
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* Ensure that the given property source is not being added relative to itself.
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* 确保两个 PropertySource 的 name不相同
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*/
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protected void assertLegalRelativeAddition(String relativePropertySourceName, PropertySource<?> propertySource) {
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// 获取 PropertySource 的名字
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String newPropertySourceName = propertySource.getName();
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// 历史名字和新的名字是否相同
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if (relativePropertySourceName.equals(newPropertySourceName)) {
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throw new IllegalArgumentException(
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"PropertySource named '" + newPropertySourceName + "' cannot be added relative to itself");
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}
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}
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/**
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* Remove the given property source if it is present.
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* 删除已存在的数据
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*/
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protected void removeIfPresent(PropertySource<?> propertySource) {
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this.propertySourceList.remove(propertySource);
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}
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/**
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* Add the given property source at a particular index in the list.
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* 指定索引位置插入数据
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*/
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private void addAtIndex(int index, PropertySource<?> propertySource) {
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removeIfPresent(propertySource);
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this.propertySourceList.add(index, propertySource);
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}
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/**
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* Assert that the named property source is present and return its index.
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* 获取 name 所在的索引位置
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* @param name {@linkplain PropertySource#getName() name of the property source} to find
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* @throws IllegalArgumentException if the named property source is not present
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*/
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private int assertPresentAndGetIndex(String name) {
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int index = this.propertySourceList.indexOf(PropertySource.named(name));
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if (index == -1) {
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throw new IllegalArgumentException("PropertySource named '" + name + "' does not exist");
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}
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return index;
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}
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}
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```
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## PropertySources
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- 类路径: `org.springframework.core.env.PropertySources`
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- 详细说明如下
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```java
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public interface PropertySources extends Iterable<PropertySource<?>> {
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/**
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* Return a sequential {@link Stream} containing the property sources.
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* 获取流
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* @since 5.1
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*/
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default Stream<PropertySource<?>> stream() {
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return StreamSupport.stream(spliterator(), false);
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}
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/**
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* Return whether a property source with the given name is contained.
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* 判断是否存在 name
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* @param name the {@linkplain PropertySource#getName() name of the property source} to find
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*/
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boolean contains(String name);
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/**
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* Return the property source with the given name, {@code null} if not found.
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* 获取 PropertySource
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* @param name the {@linkplain PropertySource#getName() name of the property source} to find
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*/
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@Nullable
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PropertySource<?> get(String name);
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}
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```
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## PropertySource
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- 类路径: `org.springframework.core.env.PropertySource`
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- 存有两个子类
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1. StubPropertySource
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2. ComparisonPropertySource 3. 调用`getSource`、`containsProperty`、`getProperty` 都会直接异常
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```java
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public abstract class PropertySource<T> {
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protected final Log logger = LogFactory.getLog(getClass());
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/**
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* 属性名称
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*/
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protected final String name;
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/**
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* 值
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*/
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protected final T source;
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/**
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* Create a new {@code PropertySource} with the given name and source object.
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*/
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public PropertySource(String name, T source) {
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Assert.hasText(name, "Property source name must contain at least one character");
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Assert.notNull(source, "Property source must not be null");
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this.name = name;
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this.source = source;
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}
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/**
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* Create a new {@code PropertySource} with the given name and with a new
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* {@code Object} instance as the underlying source.
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* <p>Often useful in testing scenarios when creating anonymous implementations
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* that never query an actual source but rather return hard-coded values.
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*/
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@SuppressWarnings("unchecked")
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public PropertySource(String name) {
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this(name, (T) new Object());
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}
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/**
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* Return a {@code PropertySource} implementation intended for collection comparison purposes only.
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* <p>Primarily for internal use, but given a collection of {@code PropertySource} objects, may be
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* used as follows:
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* <pre class="code">
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* {@code List<PropertySource<?>> sources = new ArrayList<PropertySource<?>>();
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* sources.add(new MapPropertySource("sourceA", mapA));
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* sources.add(new MapPropertySource("sourceB", mapB));
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* assert sources.contains(PropertySource.named("sourceA"));
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* assert sources.contains(PropertySource.named("sourceB"));
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* assert !sources.contains(PropertySource.named("sourceC"));
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* }</pre>
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* The returned {@code PropertySource} will throw {@code UnsupportedOperationException}
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* if any methods other than {@code equals(Object)}, {@code hashCode()}, and {@code toString()}
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* are called.
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* @param name the name of the comparison {@code PropertySource} to be created and returned.
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*/
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public static PropertySource<?> named(String name) {
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return new ComparisonPropertySource(name);
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}
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/**
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* Return the name of this {@code PropertySource}.
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*/
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public String getName() {
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return this.name;
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}
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/**
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* Return the underlying source object for this {@code PropertySource}.
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*/
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public T getSource() {
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return this.source;
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}
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/**
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* Return whether this {@code PropertySource} contains the given name.
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* <p>This implementation simply checks for a {@code null} return value
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* from {@link #getProperty(String)}. Subclasses may wish to implement
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* a more efficient algorithm if possible.
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* @param name the property name to find
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*/
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public boolean containsProperty(String name) {
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// getProperty 抽象方法子类实现
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return (getProperty(name) != null);
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}
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/**
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* Return the value associated with the given name,
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* or {@code null} if not found.
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* // getProperty 抽象方法子类实现
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* @param name the property to find
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* @see PropertyResolver#getRequiredProperty(String)
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*/
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@Nullable
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public abstract Object getProperty(String name);
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/**
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* This {@code PropertySource} object is equal to the given object if:
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* <ul>
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* <li>they are the same instance
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* <li>the {@code name} properties for both objects are equal
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* </ul>
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* <p>No properties other than {@code name} are evaluated.
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*/
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@Override
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public boolean equals(@Nullable Object other) {
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return (this == other || (other instanceof PropertySource &&
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ObjectUtils.nullSafeEquals(this.name, ((PropertySource<?>) other).name)));
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}
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/**
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* Return a hash code derived from the {@code name} property
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* of this {@code PropertySource} object.
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*/
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@Override
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public int hashCode() {
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return ObjectUtils.nullSafeHashCode(this.name);
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}
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/**
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* Produce concise output (type and name) if the current log level does not include
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* debug. If debug is enabled, produce verbose output including the hash code of the
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* PropertySource instance and every name/value property pair.
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* <p>This variable verbosity is useful as a property source such as system properties
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* or environment variables may contain an arbitrary number of property pairs,
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* potentially leading to difficult to read exception and log messages.
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* @see Log#isDebugEnabled()
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*/
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@Override
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public String toString() {
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if (logger.isDebugEnabled()) {
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return getClass().getSimpleName() + "@" + System.identityHashCode(this) +
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" {name='" + this.name + "', properties=" + this.source + "}";
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}
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else {
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return getClass().getSimpleName() + " {name='" + this.name + "'}";
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}
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}
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/**
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* {@code PropertySource} to be used as a placeholder in cases where an actual
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* property source cannot be eagerly initialized at application context
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* creation time. For example, a {@code ServletContext}-based property source
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* must wait until the {@code ServletContext} object is available to its enclosing
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* {@code ApplicationContext}. In such cases, a stub should be used to hold the
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* intended default position/order of the property source, then be replaced
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* during context refresh.
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* @see org.springframework.context.support.AbstractApplicationContext#initPropertySources()
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* @see org.springframework.web.context.support.StandardServletEnvironment
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* @see org.springframework.web.context.support.ServletContextPropertySource
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*/
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public static class StubPropertySource extends PropertySource<Object> {
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public StubPropertySource(String name) {
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super(name, new Object());
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}
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/**
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* Always returns {@code null}.
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*/
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@Override
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@Nullable
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public String getProperty(String name) {
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return null;
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}
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}
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/**
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* A {@code PropertySource} implementation intended for collection comparison
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* purposes.
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*
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* @see PropertySource#named(String)
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*/
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static class ComparisonPropertySource extends StubPropertySource {
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// 异常信息
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private static final String USAGE_ERROR =
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"ComparisonPropertySource instances are for use with collection comparison only";
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public ComparisonPropertySource(String name) {
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super(name);
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}
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@Override
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public Object getSource() {
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// 抛异常
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throw new UnsupportedOperationException(USAGE_ERROR);
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}
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@Override
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public boolean containsProperty(String name) {
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// 抛异常
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throw new UnsupportedOperationException(USAGE_ERROR);
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}
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@Override
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@Nullable
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public String getProperty(String name) {
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// 抛异常
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throw new UnsupportedOperationException(USAGE_ERROR);
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}
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}
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}
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```
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类图
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