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@ -0,0 +1,467 @@
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# BeanFactoryBeanPostProcessor 源码分析
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BeanFactoryBeanPostProcessor 是当 BeanDefinition 读取完元数据（也就是从任意资源中定义的 bean 数据）后还未实例化之前可以进行修改
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抄录并翻译官方的语句
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> `BeanFactoryPostProcessor` 操作 bean 的元数据配置. 也就是说,Spring IoC 容器允许 `BeanFactoryPostProcessor` 读取配置元数据, 并可能在容器实例化除 `BeanFactoryPostProcessor` 实例之外的任何 bean _之前_ 更改它
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tip:
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> 在 `BeanFactoryPostProcessor` (例如使用 `BeanFactory.getBean()`) 中使用这些 bean 的实例虽然在技术上是可行的,但这么来做会将 bean 过早实例化, 这违反了标准的容器生命周期. 同时也会引发一些副作用,例如绕过 bean 的后置处理。
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```java
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public interface BeanFactoryPostProcessor {
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/**
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*通过ConfigurableListableBeanFactory这个可配置的BeanFactory对我们的bean原数据进行修改
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*/
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void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException;
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}
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```
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## BeanFactoryPostProcessor 执行时期的探究
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ApplicationContext 的 refresh() 中的 invokeBeanFactoryPostProcessors 方法就开始创建我们的 BFPP(BeanFactoryPostProcessor)了
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具体执行方法 invokeBeanFactoryPostProcessors，虽然一百多行代码，其实只需要特别了解的地方就几处。
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```java
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public static void invokeBeanFactoryPostProcessors(
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ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
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Set<String> processedBeans = new HashSet<>();
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// 由于我们的beanFactory是DefaultListableBeanFactory实例是BeanDefinitionRegistry的子类所以可以进来
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if (beanFactory instanceof BeanDefinitionRegistry) {
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BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
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List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
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List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();
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for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
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if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
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BeanDefinitionRegistryPostProcessor registryProcessor =
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(BeanDefinitionRegistryPostProcessor) postProcessor;
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registryProcessor.postProcessBeanDefinitionRegistry(registry);
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registryProcessors.add(registryProcessor);
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}
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else {
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regularPostProcessors.add(postProcessor);
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}
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}
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// BeanDefinitionRegistryPostProcessor是BFPP的子类但是比BFPP提前执行
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// 顺序实现PriorityOrdered接口先被执行，然后是Ordered接口，最后是什么都没实现的BeanDefinitionRegistryPostProcessor
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/**
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*都有beanFactory.getBean方法，证明BeanDefinitionRegistryPostProcessor这个bean现在已经被创建了
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*/
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List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();
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String[] postProcessorNames =
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beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
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for (String ppName : postProcessorNames) {
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if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
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currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
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processedBeans.add(ppName);
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}
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}
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sortPostProcessors(currentRegistryProcessors, beanFactory);
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registryProcessors.addAll(currentRegistryProcessors);
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invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
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currentRegistryProcessors.clear();
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postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
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for (String ppName : postProcessorNames) {
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if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
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currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
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processedBeans.add(ppName);
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}
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}
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sortPostProcessors(currentRegistryProcessors, beanFactory);
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registryProcessors.addAll(currentRegistryProcessors);
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invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
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currentRegistryProcessors.clear();
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boolean reiterate = true;
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while (reiterate) {
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reiterate = false;
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postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
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for (String ppName : postProcessorNames) {
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if (!processedBeans.contains(ppName)) {
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currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
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processedBeans.add(ppName);
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reiterate = true;
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}
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}
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sortPostProcessors(currentRegistryProcessors, beanFactory);
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registryProcessors.addAll(currentRegistryProcessors);
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invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
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currentRegistryProcessors.clear();
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}
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invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
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invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
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}
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else {
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invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
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}
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// BFPP的执行顺序与上一样
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/**
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*都有beanFactory.getBean方法，证明BFPP这个bean现在已经被创建了
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*/
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String[] postProcessorNames =
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beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
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List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
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List<String> orderedPostProcessorNames = new ArrayList<>();
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List<String> nonOrderedPostProcessorNames = new ArrayList<>();
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for (String ppName : postProcessorNames) {
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if (processedBeans.contains(ppName)) {
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}
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else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
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priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
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}
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else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
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orderedPostProcessorNames.add(ppName);
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}
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else {
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nonOrderedPostProcessorNames.add(ppName);
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}
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}
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sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
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invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
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List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
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for (String postProcessorName : orderedPostProcessorNames) {
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orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
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}
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sortPostProcessors(orderedPostProcessors, beanFactory);
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invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
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List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
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for (String postProcessorName : nonOrderedPostProcessorNames) {
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nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
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}
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invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
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beanFactory.clearMetadataCache();
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}
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```
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我们可以具体分析一下 BeanFactoryPostProcessor 的子类 CustomEditorConfigurer 自定义属性编辑器来巩固一下执行流程
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所谓属性编辑器是当你要自定义更改配置文件中的属性属性时，如 String 类型转为 Date 或者其他，下面的一个小例子展示如何 String 类型的属性怎么转化为 Address 属性
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## 简单工程（Spring-version-5.3.18)
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Person 类
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```java
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package cn.demo1;
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import lombok.Getter;
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import lombok.Setter;
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@Setter
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@Getter
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@ToString
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public class Person {
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private String name;
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private Address address;
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}
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```
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Address 类
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```java
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package cn.demo1;
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@Setter
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@Getter
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@ToString
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public class Address {
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private String city;
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private String town;
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}
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```
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AddressParse 类
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```java
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package cn.demo1;
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import java.beans.PropertyEditorSupport;
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public class AddressParse extends PropertyEditorSupport {
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@Override
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public void setAsText(String text) throws IllegalArgumentException {
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final String[] vals = text.split(",");
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Address addr = new Address();
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addr.setProvince(vals[0]);
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addr.setCity(vals[1]);
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setValue(addr);
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}
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}
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```
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MyCustomEditor 类
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```java
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package cn.demo1;
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import org.springframework.beans.PropertyEditorRegistrar;
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import org.springframework.beans.PropertyEditorRegistry;
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public class MyCustomEditor implements PropertyEditorRegistrar {
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@Override
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public void registerCustomEditors(PropertyEditorRegistry registry) {
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registry.registerCustomEditor(Address.class, new AddressParse());
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}
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}
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```
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配置文件 test1.xml
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```java
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<?xml version="1.0" encoding="UTF-8"?>
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<beans xmlns="http://www.springframework.org/schema/beans"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/aop https://www.springframework.org/schema/aop/spring-aop.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">
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<!-- 待属性编辑的bean，value代表的就是string类型-->
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<bean class="cn.demo1.Person" id="person">
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<property name="name" value="李华"/>
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<property name="address" value="四川,成都"/>
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</bean>
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<!-- 注册属性编辑器-->
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<bean class="org.springframework.beans.factory.config.CustomEditorConfigurer" id="configurer">
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<property name="propertyEditorRegistrars">
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<list>
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<bean class="cn.demo1.MyCustomEditor"/>
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</list>
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</property>
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</bean>
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</beans>
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```
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测试类 EdT
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```java
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package cn.test1;
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import cn.demo1.Person;
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import org.junit.Test;
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import org.springframework.context.ApplicationContext;
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import org.springframework.context.support.ClassPathXmlApplicationContext;
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public class EdT {
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@Test
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public void test1() {
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ApplicationContext context = new ClassPathXmlApplicationContext("test1.xml");
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final Person bean = context.getBean(Person.class);
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System.out.println(bean);
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}
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}
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=====================测试结果
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Person(name=李华, address=Address(province=四川, city=成都))
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```
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可以看见我们成功的将 String 类型转化为 Address 类型，让我们来看看实现流程，
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- 首先实现 PropertyEditorSupport 来自定义属性编辑规则
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- 其次将你的编辑规则给到 PropertyEditorRegistrar 子类里进行注册
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- 最后在 Spring 中配置 CustomEditorConfigurer 类然后注入你的 PropertyEditorRegistrar 注册器
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让我们 debug 走一遍
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如果你已经耐心看完上面的`BeanFactoryPostProcessor执行时期的探究`那么你应该可以知道接下来我们的步骤应该是进入 invokeBeanFactoryPostProcessors 这个方法里了
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```java
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private static void invokeBeanFactoryPostProcessors(
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Collection<? extends BeanFactoryPostProcessor> postProcessors, ConfigurableListableBeanFactory beanFactory) {
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for (BeanFactoryPostProcessor postProcessor : postProcessors) {
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StartupStep postProcessBeanFactory = beanFactory.getApplicationStartup().start("spring.context.bean-factory.post-process")
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.tag("postProcessor", postProcessor::toString);
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postProcessor.postProcessBeanFactory(beanFactory);
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postProcessBeanFactory.end();
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}
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}
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```
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很明显它执行 postProcessBeanFactory 这个方法
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我们探究的 BFPP 正是 CustomEditorConfigurer，所以这个是 CustomEditorConfigurer 对 BFPP 的 postProcessBeanFactory 实现
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```java
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// 必然有个set方法让我们进行注入
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public void setPropertyEditorRegistrars(PropertyEditorRegistrar[] propertyEditorRegistrars) {
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this.propertyEditorRegistrars = propertyEditorRegistrars;
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}
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@Override
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public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
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if (this.propertyEditorRegistrars != null) {
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for (PropertyEditorRegistrar propertyEditorRegistrar : this.propertyEditorRegistrars) {
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// 把它加入Bean工厂里后面可以进行调用
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private final Set<PropertyEditorRegistrar> propertyEditorRegistrars = new LinkedHashSet<>(4);
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beanFactory.addPropertyEditorRegistrar(propertyEditorRegistrar);
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}
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}
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if (this.customEditors != null) {
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this.customEditors.forEach(beanFactory::registerCustomEditor);
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}
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}
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```
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关于这个注册器使用要到后面填充属性的时候才会用到，
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> 我其实觉得这个有点瑕疵，因为 BFPP 作用影响应该是当 Spring 还未创建 bean 的时候，可以用 BFPP 进行修改操作，可是这个属性编辑却影响了 bean 创建过后的修改操作，那么它就替代了 BPP（BeanPostProcessor)的作用发挥了。（以上仅仅代表个人的观点，有可能是我想错了）
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当我们 debug 到 AbstractAutowireCapableBeanFactory 的 populateBean 这个方法填充 bean 的属性的时候，
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让我们看看它的方法，其中我省略了大部分无关代码
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```java
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protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
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// 这个是如果你配置的bean中有属性值的话
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// 也就是如下的配置，那么pvs不会为空的
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/**
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<bean class="cn.demo1.Person" id="person">
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<property name="name" value="李华"/>
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<property name="address" value="四川,成都"/>
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</bean>
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*/
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PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null);
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if (pvs != null) {
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// 属性操作
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applyPropertyValues(beanName, mbd, bw, pvs);
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}
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}
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```
|
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让我们继续看看 applyPropertyValues 这个方法，无关的代码我也给省略了
|
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|
```java
|
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|
|
protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {
|
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// PropertyValues接口的默认实现。允许对属性进行简单操作，并提供构造函数以支持从 Map 进行深度复制和构造。
|
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|
|
MutablePropertyValues mpvs = null;
|
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|
|
|
List<PropertyValue> original;
|
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|
|
|
// 可以进去
|
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|
|
|
if (pvs instanceof MutablePropertyValues) {
|
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|
|
mpvs = (MutablePropertyValues) pvs;
|
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|
|
|
// 默认为false，即我们需要类型转换
|
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|
|
|
if (mpvs.isConverted()) {
|
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|
|
|
// Shortcut: use the pre-converted values as-is.
|
|
|
|
|
try {
|
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|
|
|
bw.setPropertyValues(mpvs);
|
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|
|
return;
|
|
|
|
|
}
|
|
|
|
|
catch (BeansException ex) {
|
|
|
|
|
throw new BeanCreationException(
|
|
|
|
|
mbd.getResourceDescription(), beanName, "Error setting property values", ex);
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
// 把bean的属性以列表的形式展示出来
|
|
|
|
|
original = mpvs.getPropertyValueList();
|
|
|
|
|
}
|
|
|
|
|
else {
|
|
|
|
|
original = Arrays.asList(pvs.getPropertyValues());
|
|
|
|
|
}
|
|
|
|
|
// 默认为空
|
|
|
|
|
TypeConverter converter = getCustomTypeConverter();
|
|
|
|
|
if (converter == null) {
|
|
|
|
|
converter = bw;
|
|
|
|
|
}
|
|
|
|
|
// 就一个组合类，帮助更好的bean的属性的解析
|
|
|
|
|
BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, converter);
|
|
|
|
|
|
|
|
|
|
// 深拷贝
|
|
|
|
|
List<PropertyValue> deepCopy = new ArrayList<>(original.size());
|
|
|
|
|
boolean resolveNecessary = false;
|
|
|
|
|
for (PropertyValue pv : original) {
|
|
|
|
|
if (pv.isConverted()) {
|
|
|
|
|
deepCopy.add(pv);
|
|
|
|
|
}
|
|
|
|
|
else {
|
|
|
|
|
// 获取bean的属性名字
|
|
|
|
|
String propertyName = pv.getName();
|
|
|
|
|
//获取bean属性值的包装对象
|
|
|
|
|
Object originalValue = pv.getValue();
|
|
|
|
|
// 自动装配的事情
|
|
|
|
|
if (originalValue == AutowiredPropertyMarker.INSTANCE) {
|
|
|
|
|
Method writeMethod = bw.getPropertyDescriptor(propertyName).getWriteMethod();
|
|
|
|
|
if (writeMethod == null) {
|
|
|
|
|
throw new IllegalArgumentException("Autowire marker for property without write method: " + pv);
|
|
|
|
|
}
|
|
|
|
|
originalValue = new DependencyDescriptor(new MethodParameter(writeMethod, 0), true);
|
|
|
|
|
}
|
|
|
|
|
// 把bean的属性值从包装类中分离出来
|
|
|
|
|
Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);
|
|
|
|
|
Object convertedValue = resolvedValue;
|
|
|
|
|
// 一般为true
|
|
|
|
|
boolean convertible = bw.isWritableProperty(propertyName) &&
|
|
|
|
|
!PropertyAccessorUtils.isNestedOrIndexedProperty(propertyName);
|
|
|
|
|
if (convertible) {
|
|
|
|
|
// 这个就是重点，对应我们的属性转化
|
|
|
|
|
convertedValue = convertForProperty(resolvedValue, propertyName, bw, converter);
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
继续追踪
|
|
|
|
|
|
|
|
|
|
```java
|
|
|
|
|
@Nullable
|
|
|
|
|
private Object convertForProperty(
|
|
|
|
|
@Nullable Object value, String propertyName, BeanWrapper bw, TypeConverter converter) {
|
|
|
|
|
// BeanWrapperImpl是继承TypeConverter的
|
|
|
|
|
if (converter instanceof BeanWrapperImpl) {
|
|
|
|
|
// 所以执行下面的方法
|
|
|
|
|
return ((BeanWrapperImpl) converter).convertForProperty(value, propertyName);
|
|
|
|
|
}
|
|
|
|
|
else {
|
|
|
|
|
PropertyDescriptor pd = bw.getPropertyDescriptor(propertyName);
|
|
|
|
|
MethodParameter methodParam = BeanUtils.getWriteMethodParameter(pd);
|
|
|
|
|
return converter.convertIfNecessary(value, pd.getPropertyType(), methodParam);
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
```java
|
|
|
|
|
@Nullable
|
|
|
|
|
public Object convertForProperty(@Nullable Object value, String propertyName) throws TypeMismatchException {
|
|
|
|
|
CachedIntrospectionResults cachedIntrospectionResults = getCachedIntrospectionResults();
|
|
|
|
|
PropertyDescriptor pd = cachedIntrospectionResults.getPropertyDescriptor(propertyName);
|
|
|
|
|
if (pd == null) {
|
|
|
|
|
throw new InvalidPropertyException(getRootClass(), getNestedPath() + propertyName,
|
|
|
|
|
"No property '" + propertyName + "' found");
|
|
|
|
|
}
|
|
|
|
|
TypeDescriptor td = cachedIntrospectionResults.getTypeDescriptor(pd);
|
|
|
|
|
if (td == null) {
|
|
|
|
|
td = cachedIntrospectionResults.addTypeDescriptor(pd, new TypeDescriptor(property(pd)));
|
|
|
|
|
}
|
|
|
|
|
// 上面的工作不用管，全是一些前戏工作，这个才是主题，至此我们的流程就到这里结束吧
|
|
|
|
|
// 后面的流程太多了，大部分都是处理细节，你只需要知道大概的脉络就行，就是最终它肯定会
|
|
|
|
|
// 走到AddressParse这个核心处理
|
|
|
|
|
return convertForProperty(propertyName, null, value, td);
|
|
|
|
|
}
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
你可以自己可以尝试 debug 一下，看别人实践真的不如自己动手实践一下，Spring 的包装类实属太多，但是可以抓住核心流程进行 debug。
|
cocolimo
4 years ago
committed by
GitHub
