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‎docs/Spring/clazz/Spring-Property.md‎

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# Spring Property
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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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- 相关类
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- `org.springframework.beans.PropertyValues`
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- `org.springframework.beans.PropertyValue`
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- `org.springframework.beans.MutablePropertyValues`
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- 类图如下
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![images](/images/spring/PropertyValues.png)
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- 在 Spring IoC 中,**非Web工程**,使用 xml 或者注解进行配置主要使用到的是 `PropertyValues` ，`PropertyValue` ，`MutablePropertyValues` 三个
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其中 `PropertyValues` 是继承迭代器，具体实现在`MutablePropertyValues` 他们处理的对象是`PropertyValues`
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关系就是这样.
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- 开始类的解析了
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## PropertyValue
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- `org.springframework.beans.PropertyValue`
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- 类图
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![](/images/spring/PropertyValue.png)
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- 这个类暂时只关注两个属性
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1. name: 属性名称
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2. value: 属性值
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对应标签`<property name="age" value="30"/>`
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属性值一一对应填入.
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## MutablePropertyValues
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- `org.springframework.beans.MutablePropertyValues`
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- 属性
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1. `propertyValueList`：属性列表, key:参数名称,value:具体数据
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2. `processedProperties`: 已经处理的属性名称
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3. `converted`: 是否转换
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```java
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public class MutablePropertyValues implements PropertyValues, Serializable {
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/**
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* 属性列表, key:参数名称,value:具体数据
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*/
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private final List<PropertyValue> propertyValueList;
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/**
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* 已经处理的属性名称
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*/
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@Nullable
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private Set<String> processedProperties;
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/**
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* 是否转换
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*/
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private volatile boolean converted = false;
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}
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```
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### 构造器
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- `MutablePropertyValues` 的一个构造器. 其他构造器的方式原理实现差不多. 核心是将构造参数转换成`PropertyValue`对象在放入`propertyValueList`中
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```java
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public MutablePropertyValues(@Nullable PropertyValues original) {
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// We can optimize this because it's all new:
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// There is no replacement of existing property values.
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if (original != null) {
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// 从列表中获取所有可能指
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PropertyValue[] pvs = original.getPropertyValues();
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this.propertyValueList = new ArrayList<>(pvs.length);
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for (PropertyValue pv : pvs) {
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// 循环插入 property values
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this.propertyValueList.add(new PropertyValue(pv));
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}
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}
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else {
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this.propertyValueList = new ArrayList<>(0);
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}
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}
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```
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### PropertyValue 的构造方法
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```JAVA
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public PropertyValue(PropertyValue original) {
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Assert.notNull(original, "Original must not be null");
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this.name = original.getName();
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this.value = original.getValue();
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this.optional = original.isOptional();
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this.converted = original.converted;
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this.convertedValue = original.convertedValue;
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this.conversionNecessary = original.conversionNecessary;
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this.resolvedTokens = original.resolvedTokens;
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setSource(original.getSource());
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copyAttributesFrom(original);
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}
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```
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- 除了最后一行是一个复杂调用. 前面几行代码都是属性赋值操作.
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- 最后一行代码会调用`AttributeAccessor`接口上的方法.
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## AttributeAccessor
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- `org.springframework.core.AttributeAccessor`
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- 完整的方法列表及作用注释
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```java
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public interface AttributeAccessor {
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/**
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* 设置属性值
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* @param name 属性值名称
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* @param value 属性值
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*/
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void setAttribute(String name, @Nullable Object value);
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/**
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* 通过属性名称获取属性值
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*
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* @param name 属性值名称
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* @return 属性值
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*/
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@Nullable
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Object getAttribute(String name);
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/**
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* 移除指定属性名称的值,返回移除的属性值
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*
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* @param name 属性值名称
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* @return 移除的属性值
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*/
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@Nullable
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Object removeAttribute(String name);
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/**
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* 是否包含属性名称
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* @param 属性名称
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*/
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boolean hasAttribute(String name);
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/**
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* 属性名称列表
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*/
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String[] attributeNames();
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}
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```
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- 回到`org.springframework.core.AttributeAccessorSupport#copyAttributesFrom`方法
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```java
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protected void copyAttributesFrom(AttributeAccessor source) {
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Assert.notNull(source, "Source must not be null");
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// 获取属性名称列表
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String[] attributeNames = source.attributeNames();
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// 循环属性名称列表
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for (String attributeName : attributeNames) {
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// 设置属性
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// name: 属性名称,value: 从入参中获取属性名称对应的属性值
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setAttribute(attributeName, source.getAttribute(attributeName));
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}
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}
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```
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### setAttribute
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- 一个map操作
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```java
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@Override
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public void setAttribute(String name, @Nullable Object value) {
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Assert.notNull(name, "Name must not be null");
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if (value != null) {
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this.attributes.put(name, value);
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}
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else {
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removeAttribute(name);
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}
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}
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```
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## addPropertyValue
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- `org.springframework.beans.MutablePropertyValues#addPropertyValue(org.springframework.beans.PropertyValue)`
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```java
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public MutablePropertyValues addPropertyValue(PropertyValue pv) {
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// 循环获取 属性对象
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for (int i = 0; i < this.propertyValueList.size(); i++) {
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// 正在处理的 属性对象
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PropertyValue currentPv = this.propertyValueList.get(i);
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// 正在处理的属性对象名称和添加的属性对象名称比较
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// 如果相同会做一个合并操作
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if (currentPv.getName().equals(pv.getName())) {
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// 合并属性
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pv = mergeIfRequired(pv, currentPv);
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// 重新设置
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setPropertyValueAt(pv, i);
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return this;
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}
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}
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// 放入 list 集合
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this.propertyValueList.add(pv);
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return this;
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}
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```
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## mergeIfRequired
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- `org.springframework.beans.MutablePropertyValues#mergeIfRequired`
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- 这段代码会取舍新老数据.
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1. 如果是`Mergeable`类型会做合并操作
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2. 直接返回新数据
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```java
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private PropertyValue mergeIfRequired(PropertyValue newPv, PropertyValue currentPv) {
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Object value = newPv.getValue();
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if (value instanceof Mergeable) {
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Mergeable mergeable = (Mergeable) value;
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if (mergeable.isMergeEnabled()) {
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// 获取合并的结果,放入对象
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Object merged = mergeable.merge(currentPv.getValue());
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// 创建新的 属性对象
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return new PropertyValue(newPv.getName(), merged);
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}
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}
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return newPv;
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}
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```
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- 配合测试代码，跟容易看懂.
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```java
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@Test
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public void testAddOrOverride() {
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MutablePropertyValues pvs = new MutablePropertyValues();
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pvs.addPropertyValue(new PropertyValue("forname", "Tony"));
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pvs.addPropertyValue(new PropertyValue("surname", "Blair"));
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pvs.addPropertyValue(new PropertyValue("age", "50"));
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doTestTony(pvs);
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PropertyValue addedPv = new PropertyValue("rod", "Rod");
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pvs.addPropertyValue(addedPv);
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assertThat(pvs.getPropertyValue("rod").equals(addedPv)).isTrue();
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PropertyValue changedPv = new PropertyValue("forname", "Greg");
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pvs.addPropertyValue(changedPv);
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assertThat(pvs.getPropertyValue("forname").equals(changedPv)).isTrue();
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}
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```
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## Mergeable
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新的接口`Mergeable`
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- `org.springframework.beans.Mergeable`
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```java
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public interface Mergeable {
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/**
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* 是否需要合并
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*/
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boolean isMergeEnabled();
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/**
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* 合并方法
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*/
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Object merge(@Nullable Object parent);
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}
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```
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![](/images/spring/Mergeable.png)
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- 看一下 List 怎么实现`merge`
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```java
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@Override
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@SuppressWarnings("unchecked")
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public List<E> merge(@Nullable Object parent) {
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if (!this.mergeEnabled) {
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throw new IllegalStateException("Not allowed to merge when the 'mergeEnabled' property is set to 'false'");
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}
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if (parent == null) {
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return this;
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}
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if (!(parent instanceof List)) {
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throw new IllegalArgumentException("Cannot merge with object of type [" + parent.getClass() + "]");
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}
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List<E> merged = new ManagedList<>();
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merged.addAll((List<E>) parent);
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merged.addAll(this);
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return merged;
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}
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```
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- 在 list 视线中就是讲两个结果合并. 事实上其他的几个都是这个操作. 这里就不贴所有的代码了

‎images/spring/Mergeable.png‎

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‎images/spring/MutablePropertyValues-构造.png‎

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‎images/spring/PropertyValue.png‎

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‎images/spring/PropertyValues.png‎

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