### 欢迎访问我的GitHub
> 这里分类和汇总了欣宸的全部原创(含配套源码)：[https://github.com/zq2599/blog_demos](https://github.com/zq2599/blog_demos)

- 本章是《spring4.1.8扩展实战》的第七篇，我们来尝试在容器初始化的时候对bean实例做设置；

### 控制bean的两种扩展方式
- 两种方式可以对bean做控制（例如修改某个成员变量）
1. 改变bean的定义(BeanFactoryPostProcessor接口) ，可以想象成修改了class文件，这样实例化出来的每个对象都变了；
2. 只改变实例化的对象(BeanPostProcessor接口)；

- 上述两种方式都能控制bean，第一种请参照[《spring4.1.8扩展实战之五：改变bean的定义(BeanFactoryPostProcessor接口)》](http://blog.itpub.net/70017844/viewspace-2900595/) ，今天我们来研究第二种：改变实例化的对象；

### 本章概览
- 全文由以下部分组成：
1. spring源码分析，了解BeanPostProcessor接口的实现类如何被注册到spring容器；
2. spring源码分析，了解已经注册到spring环境的BeanPostProcessor实现类如何被使用；
3. 实战，开发一个BeanPostProcessor实现类，验证是否能用来改变指定的bean；

### 源码分析：BeanPostProcessor接口的实现类如何被注册到spring容器
- 从spring容器的初始化代码看起吧，看AbstractApplicationContext类的refresh方法，如下图所示，红框中的方法负责将BeanPostProcessor接口的实现类注册到spring容器：

![image.png](https://bbs-img.huaweicloud.com/blogs/img/20220615/1655306504571766749.png)

- 展开registerBeanPostProcessors方法，发现是委托PostProcessorRegistrationDelegate类的静态方法registerBeanPostProcessors来完成注册工作的：

```java
protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
	PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);
}
```

- 展开PostProcessorRegistrationDelegate.registerBeanPostProcessors方法，里面的代码逻辑简洁整齐，意图目的一目了然：

```java
public static void registerBeanPostProcessors(
		ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
	//获取所有实现BeanPostProcessor接口的bean的名称
	String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);

//注意，此时尽管注册操作还没有开始，但是之前已经有一些特殊的bean已经注册进来了，
	//详情请看AbstractApplicationContext类的prepareBeanFactory方法，
	//因此getBeanPostProcessorCount()方法返回的数量并不为零，
	//加一是因为方法末尾会注册一个ApplicationListenerDetector接口的实现类
	int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
	//这里的BeanPostProcessorChecker也是个BeanPostProcessor的实现类，用于每个bean的初始化完成后，做一些简单的检查
	beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

//如果这些bean还实现了PriorityOrdered接口（在意执行顺序），就全部放入集合priorityOrderedPostProcessors 
	List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanPostProcessor>();
	//集合internalPostProcessors，用来存放同时实现了PriorityOrdered和MergedBeanDefinitionPostProcessor接口的bean
	List<BeanPostProcessor> internalPostProcessors = new ArrayList<BeanPostProcessor>();
	//集合orderedPostProcessorNames用来存放实现了Ordered接口的bean的名称（在意执行顺序）
	List<String> orderedPostProcessorNames = new ArrayList<String>();
	//集合nonOrderedPostProcessorNames用来存放即没实现PriorityOrdered接口，也没有实现Ordered接口的bean的名称（不关心执行顺序）
	List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
	for (String ppName : postProcessorNames) {
		if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
			BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
			//实现了PriorityOrdered接口的bean，都放入集合priorityOrderedPostProcessors
			priorityOrderedPostProcessors.add(pp);
			if (pp instanceof MergedBeanDefinitionPostProcessor) {
				//实现了MergedBeanDefinitionPostProcessor接口的bean，都放入internalPostProcessors集合
				internalPostProcessors.add(pp);
			}
		}
		else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
			//实现了Ordered接口的bean，将其名称都放入orderedPostProcessorNames集合
			orderedPostProcessorNames.add(ppName);
		}
		else {
			//既没实现PriorityOrdered接口，也没有实现Ordered接口的bean，将其名称放入nonOrderedPostProcessorNames集合
			nonOrderedPostProcessorNames.add(ppName);
		}
	}

//实现了PriorityOrdered接口的bean排序
	OrderComparator.sort(priorityOrderedPostProcessors);
	//注册到容器
	registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

List<BeanPostProcessor> orderedPostProcessors = new ArrayList<BeanPostProcessor>();
	//处理所有实现了Ordered接口的bean
	for (String ppName : orderedPostProcessorNames) {
		BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
		orderedPostProcessors.add(pp);
		//前面将所有实现了PriorityOrdered和MergedBeanDefinitionPostProcessor的bean放入internalPostProcessors，
		//此处将所有实现了Ordered和MergedBeanDefinitionPostProcessor的bean放入internalPostProcessors
		if (pp instanceof MergedBeanDefinitionPostProcessor) {
			internalPostProcessors.add(pp);
		}
	}

//实现了Ordered接口的bean排序
	OrderComparator.sort(orderedPostProcessors);
	//注册到容器
	registerBeanPostProcessors(beanFactory, orderedPostProcessors);

List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanPostProcessor>();
	for (String ppName : nonOrderedPostProcessorNames) {
		BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
		nonOrderedPostProcessors.add(pp);
		//此处将其余实现了MergedBeanDefinitionPostProcessor的bean放入internalPostProcessors
		if (pp instanceof MergedBeanDefinitionPostProcessor) {
			internalPostProcessors.add(pp);
		}
	}
	//注册到容器
	registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);

OrderComparator.sort(internalPostProcessors);
	//将所有实现了MergedBeanDefinitionPostProcessor接口的bean也注册到容器
	registerBeanPostProcessors(beanFactory, internalPostProcessors);
	//创建一个ApplicationListenerDetector对象并且注册到容器，这就是前面计算beanProcessorTargetCount的值时加一的原因
	beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}
```

- 以上代码已加注释，就不多解读了，有一点需要注意：对于实现了MergedBeanDefinitionPostProcessor接口的bean，在前面几次调用registerBeanPostProcessors方法的时候已经注册过了，那么在最后执行的==registerBeanPostProcessors(beanFactory, internalPostProcessors)==，岂不是将一个bean注册了多次？

- 为了弄清楚这个问题需要看registerBeanPostProcessors方法：

```java
private static void registerBeanPostProcessors(
		ConfigurableListableBeanFactory beanFactory, List<BeanPostProcessor> postProcessors) {

for (BeanPostProcessor postProcessor : postProcessors) {
		//对每个bean都调用beanFactory.addBeanPostProcessor方法来注册
		beanFactory.addBeanPostProcessor(postProcessor);
	}
}
```

- addBeanPostProcessor方法的代码在AbstractApplicationContext类中，如下所示，==先删除再添加，这样反复注册也没有问题==：

```java
@Override
public void addBeanPostProcessor(BeanPostProcessor beanPostProcessor) {
	Assert.notNull(beanPostProcessor, "BeanPostProcessor must not be null");
	//如果已经注册，就先删除掉
	this.beanPostProcessors.remove(beanPostProcessor);
	//再注册
	this.beanPostProcessors.add(beanPostProcessor);
	if (beanPostProcessor instanceof InstantiationAwareBeanPostProcessor) {
		this.hasInstantiationAwareBeanPostProcessors = true;
	}
	if (beanPostProcessor instanceof DestructionAwareBeanPostProcessor) {
		this.hasDestructionAwareBeanPostProcessors = true;
	}
}
```

- 至此，我们已经弄清楚了BeanPostProcessor实现类的bean注册到spring容器的逻辑，接下来看看spring容器如何使用这些bean；

### 源码分析，BeanPostProcessor实现类如何被使用
- 要弄清楚BeanPostProcessor接口的实现类是在哪里被用到的，还是从负责容器初始化的AbstractApplicationContext类的refresh方法看起，如下图红框中的finishBeanFactoryInitialization方法，就是负责实例化和初始化bean的：

![image.png](https://bbs-img.huaweicloud.com/blogs/img/20220615/1655306544884241859.png)

- 从finishBeanFactoryInitialization方法到BeanPostProcessor的实现类被使用，中间有多层逻辑和调用，篇幅所限就不逐个展开了，直接列出堆栈信息，您可以根据此信息去查看对应源码：

```java
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean()
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean()
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean()
org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject()
org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton()
org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean()
org.springframework.beans.factory.support.AbstractBeanFactory.getBean()
org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons()
org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization()
org.springframework.context.support.AbstractApplicationContext.refresh()
org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh()
org.springframework.boot.SpringApplication.refresh()
org.springframework.boot.SpringApplication.refreshContext()
org.springframework.boot.SpringApplication.run()
org.springframework.boot.SpringApplication.run()
org.springframework.boot.SpringApplication.run()
```

- 根据上述堆栈信息，直接查看AbstractAutowireCapableBeanFactory类的initializeBean()方法：

```java
protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) {
	if (System.getSecurityManager() != null) {
		AccessController.doPrivileged(new PrivilegedAction<Object>() {
			@Override
			public Object run() {
				invokeAwareMethods(beanName, bean);
				return null;
			}
		}, getAccessControlContext());
	}
	else {
		invokeAwareMethods(beanName, bean);
	}

Object wrappedBean = bean;
	if (mbd == null || !mbd.isSynthetic()) {
		//对已经实例化的bean，在初始化前用BeanPostProcessor实现类去处理
		wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
	}

try {
		//bean的初始化
		invokeInitMethods(beanName, wrappedBean, mbd);
	}
	catch (Throwable ex) {
		throw new BeanCreationException(
				(mbd != null ? mbd.getResourceDescription() : null),
				beanName, "Invocation of init method failed", ex);
	}

if (mbd == null || !mbd.isSynthetic()) {
		//对已经实例化的bean，在初始化后用BeanPostProcessor实现类去处理
		wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
	}
	return wrappedBean;
}
```

- 如上所示，我们最关注的代码是==applyBeanPostProcessorsBeforeInitialization==和==applyBeanPostProcessorsAfterInitialization==这两个方法，它们分别在bean的初始化方法==invokeInitMethods==的前后被执行；

- 先看看applyBeanPostProcessorsBeforeInitialization方法，逻辑非常简单，就是取出所有已注册的BeanPostProcessor实现类，执行其postProcessBeforeInitialization方法，入参是当前正在做实例化和初始化的bean实例：

```java
@Override
public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
		throws BeansException {

Object result = existingBean;
	//逐一执行每个BeanPostProcessor实现类的postProcessBeforeInitialization方法
	for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
		result = beanProcessor.postProcessBeforeInitialization(result, beanName);
		if (result == null) {
			return result;
		}
	}
	return result;
}
```

- 在invokeInitMethods方法执行完毕后会执行applyBeanPostProcessorsAfterInitialization方法，代码如下，与applyBeanPostProcessorsBeforeInitialization如出一辙，仅有的不同是调用的beanProcessor的方法变成了postProcessAfterInitialization：

```java
@Override
public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
		throws BeansException {

Object result = existingBean;
	//逐一执行每个BeanPostProcessor实现类的postProcessAfterInitialization方法
	for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
		result = beanProcessor.postProcessAfterInitialization(result, beanName);
		if (result == null) {
			return result;
		}
	}
	return result;
}
```

- 以上就是spring容器初始化过程中对BeanPostProcessor实现类的使用场景，此时还剩一点疑问需要澄清：==在分析注册过程的时候，曾看到实现MergedBeanDefinitionPostProcessor接口的bean是最后注册的，那么这些MergedBeanDefinitionPostProcessor实现类在spring容器中是何处使用的呢？==

- 为了搞清这个问题，来看看AbstractAutowireCapableBeanFactory类的doCreateBean方法，前面我们分析的initializeBean方法就是在这里面被调用的：

![image.png](https://bbs-img.huaweicloud.com/blogs/img/20220615/1655306579980408462.png)

- 如上图所示，红框中就是用所有MergedBeanDefinitionPostProcessor实现类去处理当前正在实例化的bean，然后才会执行绿框中的initializeBean方法（里面是我们刚才分析的bean的初始化，BeanPostProcessor实现类被使用的逻辑）；

- 来看看红框中的applyMergedBeanDefinitionPostProcessors方法，主要目的是处理特殊的合成bean的定义类：

```java
protected void applyMergedBeanDefinitionPostProcessors(RootBeanDefinition mbd, Class<?> beanType, String beanName)
			throws BeansException {

try {
		//取出每个注册的BeanPostProcessor实现类
		for (BeanPostProcessor bp : getBeanPostProcessors()) {
			//只有实现了MergedBeanDefinitionPostProcessor接口才执行
			if (bp instanceof MergedBeanDefinitionPostProcessor) {
				MergedBeanDefinitionPostProcessor bdp = (MergedBeanDefinitionPostProcessor) bp;
				//执行postProcessMergedBeanDefinition
				bdp.postProcessMergedBeanDefinition(mbd, beanType, beanName);
			}
		}
	}
	catch (Exception ex) {
		throw new BeanCreationException(mbd.getResourceDescription(), beanName,
				"Post-processing failed of bean type [" + beanType + "] failed", ex);
	}
}
```

- 至此，我们对BeanPostProcessor有关的源码分析就完成了，小结一下：
1. 初始化时，spring容器有特别处理，会直接调用beanFactory.addBeanPostProcessor进行注册（例如AbstractApplicationContext类的prepareBeanFactory方法中就有）；
2. 找出所有实现了BeanPostProcessor接口的bean，注册到容器，注册顺序如下：
第一：实现了PriorityOrdered接口的，排序后；
第二：实现了Ordered接口的，排序后；
第三：既没实现PriorityOrdered接口，也没有实现Ordered接口的；
第四：实现了MergedBeanDefinitionPostProcessor接口的（这些也按照PriorityOrdered、Ordered等逻辑拍过续）；
第五：实例化一个ApplicationListenerDetector对象；
3. 实例化bean的时候，对于每个bean，先用MergedBeanDefinitionPostProcessor实现类的postProcessMergedBeanDefinition方法处理每个bean的定义类；
4. 再用BeanPostProcessor的postProcessBeforeInitialization方法处理每个bean实例；
5. bean实例初始化；
6. 用BeanPostProcessor的postProcessAfterInitialization方法处理每个bean实例；

- 源码分析结束，接下来自定义一个BeanPostProcessor实现类，验证我们之前的分析：控制bean实例；

### 实战自定义BeanPostProcessor实现类

- 本次实战的内容是创建一个springboot工程，在里面自定义一个BeanPostProcessor接口的实现类，如果您不想敲代码，也可以去github下载源码，地址和链接信息如下表所示：

| 名称      |   链接 |   备注|
| :-------- | :----| :----|
| 项目主页| https://github.com/zq2599/blog_demos | 该项目在GitHub上的主页 |
| git仓库地址(https)| https://github.com/zq2599/blog_demos.git | 该项目源码的仓库地址，https协议 |
| git仓库地址(ssh)| git@github.com:zq2599/blog_demos.git | 该项目源码的仓库地址，ssh协议 |

- 这个git项目中有多个文件夹，本章源码在文件夹customizebeanpostprocessor下，如下图红框所示：

![image.png](https://bbs-img.huaweicloud.com/blogs/img/20220615/1655306604017461655.png)

- 接下来开始实战吧：

- 基于maven创建一个springboot的web工程，名为customizebeanpostprocessor，pom.xml如下：

```xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

<groupId>com.bolingcavalry</groupId>
    <artifactId>customizebeanpostprocessor</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

<name>customizebeanpostprocessor</name>
    <description>Demo project for Spring Boot</description>

<parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.15.RELEASE</version>
        <relativePath/> 
    </parent>

<dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

<build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>
```

- 创建Utils.java，里面有一些静态的工具方法，例如打印当前堆栈：

```java
package com.bolingcavalry.customizebeanpostprocessor.util;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class Utils {

private static final Logger logger = LoggerFactory.getLogger(Utils.class);

/**
     * 打印当前线程堆栈信息
     * @param prefix
     */
    public static void printTrack(String prefix){
        StackTraceElement[] st = Thread.currentThread().getStackTrace();

if(null==st){
            logger.info("invalid stack");
            return;
        }

StringBuffer sbf =new StringBuffer();

for(StackTraceElement e:st){
            if(sbf.length()>0){
                sbf.append(" <- ");
                sbf.append(System.getProperty("line.separator"));
            }

sbf.append(java.text.MessageFormat.format("{0}.{1}() {2}"
                    ,e.getClassName()
                    ,e.getMethodName()
                    ,e.getLineNumber()));
        }

logger.info(prefix
                + "\n************************************************************\n"
                + sbf.toString()
                + "\n************************************************************");
    }
}
```

- 创建接口CalculateService，定义了几个方法：

```java
package com.bolingcavalry.customizebeanpostprocessor.service;

public interface CalculateService {
    /**
     * 整数加法
     * @param a
     * @param b
     * @return
     */
    int add(int a, int b);

/**
     * 返回当前实现类的描述信息
     * @return
     */
    String getServiceDesc();

/**
     * 设置当前实现类的描述信息
     * @return
     */
    void setServiceDesc(String serviceDesc);
}
```

- 创建CalculateService的实现类CalculateServiceImpl，并且用@Service注解将定义为spring的bean：

```java
package com.bolingcavalry.customizebeanpostprocessor.service.impl;

import com.bolingcavalry.customizebeanpostprocessor.service.CalculateService;
import org.springframework.stereotype.Service;

@Service("calculateService")
public class CalculateServiceImpl implements CalculateService {

private String serviceDesc = "desc from class";

@Override
    public int add(int a, int b) {
        return a + b;
    }

@Override
    public String getServiceDesc() {
        return serviceDesc;
    }

@Override
    public void setServiceDesc(String serviceDesc) {
        this.serviceDesc = serviceDesc;
    }
}
```

- ==注意该类的成员变量serviceDesc，值已经固定为"desc from class"；==

- 创建Controller类HelloController，在响应web请求的时候，会用到calculateService提供的服务：

```java
package com.bolingcavalry.customizebeanpostprocessor.controller;

import com.bolingcavalry.customizebeanpostprocessor.service.CalculateService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloController {

@Autowired(required = false)
    CalculateService calculateService;

@GetMapping("/add/{a}/{b}")
    public String add(@PathVariable("a") int a, @PathVariable("b") int b){
        return "add result : " + calculateService.add(a, b) + ", from [" + calculateService.getServiceDesc() + "]";
    }
}
```

- 如上所示，正常情况下，web响应为"add result : x， from [desc from class]"，这个==desc from class==，就是CalculateServiceImpl的成员变量serviceDesc的值；

- 创建BeanPostProcessor的实现类CustomizeBeanPostProcessor，这里面会修改calculateService实例的成员变量serviceDesc的值，记得用注解@Component将其设置为bean：

```java
package com.bolingcavalry.customizebeanpostprocessor.processor;

import com.bolingcavalry.customizebeanpostprocessor.service.CalculateService;
import com.bolingcavalry.customizebeanpostprocessor.util.Utils;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.stereotype.Component;

@Component
public class CustomizeBeanPostProcessor implements BeanPostProcessor {
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        if("calculateService".equals(beanName)) {
	    //打印当前堆栈
            Utils.printTrack("do postProcess before initialization");
            CalculateService calculateService = (CalculateService)bean;
            //修改calculateService实例的成员变量serviceDesc的值
            calculateService.setServiceDesc("desc from " + this.getClass().getSimpleName());
        }
        return bean;
    }

@Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        if("calculateService".equals(beanName)) {
            //打印当前堆栈
            Utils.printTrack("do postProcess after initialization");
        }
        return bean;
    }
}
```

- 启动应用，在启动日志中可以看到CustomizeBeanPostProcessor实例的两个方法被调用时打印的堆栈日志，和之前我们分析的源码是一致的：

```shell
2018-09-02 18:35:53.618  INFO 22520 --- [           main] c.b.c.util.Utils                         : do postProcess before initialization
************************************************************
java.lang.Thread.getStackTrace() 1,559 <- 
com.bolingcavalry.customizebeanpostprocessor.util.Utils.printTrack() 15 <- 
com.bolingcavalry.customizebeanpostprocessor.processor.CustomizeBeanPostProcessor.postProcessBeforeInitialization() 14 <- 
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInitialization() 409 <- 
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean() 1,626 <- 
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean() 555 <- 
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean() 483 <- 
org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject() 312 <- 
org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton() 230 <- 
org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean() 308 <- 
org.springframework.beans.factory.support.AbstractBeanFactory.getBean() 202 <- 
org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate() 208 <- 
org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency() 1,138 <- 
org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency() 1,066 <- 
org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject() 585 <- 
org.springframework.beans.factory.annotation.InjectionMetadata.inject() 88 <- 
org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues() 366 <- 
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean() 1,272 <- 
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean() 553 <- 
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean() 483 <- 
org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject() 312 <- 
org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton() 230 <- 
org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean() 308 <- 
org.springframework.beans.factory.support.AbstractBeanFactory.getBean() 197 <- 
org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons() 761 <- 
org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization() 867 <- 
org.springframework.context.support.AbstractApplicationContext.refresh() 543 <- 
org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh() 122 <- 
org.springframework.boot.SpringApplication.refresh() 693 <- 
org.springframework.boot.SpringApplication.refreshContext() 360 <- 
org.springframework.boot.SpringApplication.run() 303 <- 
org.springframework.boot.SpringApplication.run() 1,118 <- 
org.springframework.boot.SpringApplication.run() 1,107 <- 
com.bolingcavalry.customizebeanpostprocessor.CustomizebeanpostprocessorApplication.main() 10
************************************************************
2018-09-02 18:35:53.619  INFO 22520 --- [           main] c.b.c.util.Utils                         : do postProcess after initialization
************************************************************
java.lang.Thread.getStackTrace() 1,559 <- 
com.bolingcavalry.customizebeanpostprocessor.util.Utils.printTrack() 15 <- 
com.bolingcavalry.customizebeanpostprocessor.processor.CustomizeBeanPostProcessor.postProcessAfterInitialization() 24 <- 
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsAfterInitialization() 423 <- 
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean() 1,638 <- 
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean() 555 <- 
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean() 483 <- 
org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject() 312 <- 
org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton() 230 <- 
org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean() 308 <- 
org.springframework.beans.factory.support.AbstractBeanFactory.getBean() 202 <- 
org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate() 208 <- 
org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency() 1,138 <- 
org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency() 1,066 <- 
org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject() 585 <- 
org.springframework.beans.factory.annotation.InjectionMetadata.inject() 88 <- 
org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues() 366 <- 
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean() 1,272 <- 
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean() 553 <- 
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean() 483 <- 
org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject() 312 <- 
org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton() 230 <- 
org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean() 308 <- 
org.springframework.beans.factory.support.AbstractBeanFactory.getBean() 197 <- 
org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons() 761 <- 
org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization() 867 <- 
org.springframework.context.support.AbstractApplicationContext.refresh() 543 <- 
org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh() 122 <- 
org.springframework.boot.SpringApplication.refresh() 693 <- 
org.springframework.boot.SpringApplication.refreshContext() 360 <- 
org.springframework.boot.SpringApplication.run() 303 <- 
org.springframework.boot.SpringApplication.run() 1,118 <- 
org.springframework.boot.SpringApplication.run() 1,107 <- 
com.bolingcavalry.customizebeanpostprocessor.CustomizebeanpostprocessorApplication.main() 10
************************************************************
```

- 在浏览器访问地址：http://localhost:8080/add/1/2，可以看到响应如下图所示，calculateService的成员变量serviceDesc的值已经被CustomizeBeanPostProcessor改为==desc from CustomizeBeanPostProcessor==：

![image.png](https://bbs-img.huaweicloud.com/blogs/img/20220615/1655306636943519055.png)

- 至此，本次实战就完成了，从spring源码分析再到动手实战，我们对BeanPostProcessor的扩展有了更深入的认识，也希望这种扩展能帮助您更好的控制bean实例为业务需求服务；

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