简述

配置BeanFactory的标准特性，为后续的Bean创建做准备。

这是refresh()方法的第3步，在BeanFactory创建完成（obtainFreshBeanFactory）之后执行。

主要工作包括：
- 设置类加载器和表达式解析器
- 添加基础的BeanPostProcessor
- 忽略特定的依赖接口（Aware接口）
- 注册可解析的依赖（BeanFactory、ApplicationContext等）
- 注册环境相关的单例Bean

核心流程

  1. 设置BeanFactory的ClassLoader和SpEL表达式解析器
  2. 添加ApplicationContextAwareProcessor（处理Aware接口回调）
  3. 忽略Aware接口的自动装配
  4. 注册可解析依赖（BeanFactory、ResourceLoader等）
  5. 注册环境Bean（environment、systemProperties等）

源码分析

public abstract class AbstractApplicationContext extends DefaultResourceLoader
        implements ConfigurableApplicationContext {
    protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
        // Tell the internal bean factory to use the context's class loader etc.
        beanFactory.setBeanClassLoader(getClassLoader());
        beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
        beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

        // Configure the bean factory with context callbacks.
        beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
        beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
        beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
        beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
        beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
        beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
        beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);

        // BeanFactory interface not registered as resolvable type in a plain factory.
        // MessageSource registered (and found for autowiring) as a bean.
        beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
        beanFactory.registerResolvableDependency(ResourceLoader.class, this);
        beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
        beanFactory.registerResolvableDependency(ApplicationContext.class, this);

        // Register early post-processor for detecting inner beans as ApplicationListeners.
        beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));

        // Detect a LoadTimeWeaver and prepare for weaving, if found.
        if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
            beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
            // Set a temporary ClassLoader for type matching.
            beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
        }

        // Register default environment beans.
        if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
            beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
        }
        if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
            beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
        }
        if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
            beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
        }
    }
}

各项配置的作用详解

1. 设置ClassLoader

beanFactory.setBeanClassLoader(getClassLoader());

作用：
- BeanFactory使用此ClassLoader加载Bean的Class
- 默认使用Thread.currentThread().getContextClassLoader()
- 确保Bean类可以被正确加载

2. 设置SpEL表达式解析器

beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));

作用：
- 用于解析Bean定义中的SpEL表达式
- 支持#{}语法，例如：@Value("#{systemProperties['user.home']}")
- 可以在XML配置中使用：<property name="age" value="#{userBean.age + 10}"/>

3. 添加属性编辑器注册器

beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

作用：
- 注册一系列属性编辑器（PropertyEditor）
- 用于类型转换，例如String→File、String→URL等
- 支持Resource类型的自动转换

常见的PropertyEditor：
- FileEditor: String → File
- URLEditor: String → URL
- ClassEditor: String → Class
- ResourceEditor: String → Resource

4. 添加ApplicationContextAwareProcessor

beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));

作用：
- 处理各种Aware接口的回调
- 在Bean初始化前注入容器相关对象

ApplicationContextAwareProcessor处理的Aware接口：
- EnvironmentAware: 注入Environment
- EmbeddedValueResolverAware: 注入值解析器
- ResourceLoaderAware: 注入ResourceLoader
- ApplicationEventPublisherAware: 注入事件发布器
- MessageSourceAware: 注入MessageSource
- ApplicationContextAware: 注入ApplicationContext

示例：

@Component
public class MyBean implements ApplicationContextAware {

    private ApplicationContext context;

    @Override
    public void setApplicationContext(ApplicationContext context) {
        this.context = context;
        // 可以在这里使用ApplicationContext
    }
}

5. 忽略Aware接口的自动装配

beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);

作用：
- 防止这些接口通过@Autowired等方式被自动装配
- 这些接口的setter方法由ApplicationContextAwareProcessor专门处理
- 避免冲突和重复注入

6. 注册可解析依赖

beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
beanFactory.registerResolvableDependency(ResourceLoader.class, this);
beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
beanFactory.registerResolvableDependency(ApplicationContext.class, this);

作用：
- 允许直接注入这些类型，即使它们不是Bean
- 注入时会使用这里注册的实例

示例：

@Component
public class MyService {

    // 可以直接注入，不需要定义Bean
    @Autowired
    private ApplicationContext context;

    @Autowired
    private BeanFactory beanFactory;

    @Autowired
    private ResourceLoader resourceLoader;
}

7. 添加ApplicationListenerDetector

beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));

作用：
- 检测实现了ApplicationListener接口的Bean
- 自动将它们注册为事件监听器
- 在Bean销毁时自动移除

8. 处理LoadTimeWeaver

if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
    beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
    beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}

作用：
- 支持AspectJ的加载时织入（Load-Time Weaving）
- 用于在类加载时进行字节码增强
- 需要JVM启动参数：-javaagent:spring-instrument.jar

9. 注册环境Bean

if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
    beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
}
if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
    beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
}
if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
    beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
}

作用：
- 注册环境相关的单例Bean
- 可以直接注入使用

注册的Bean：
- environment: StandardEnvironment实例
- systemProperties: System.getProperties()
- systemEnvironment: System.getenv()

示例：

@Component
public class MyConfig {

    @Autowired
    @Qualifier("systemProperties")
    private Map<String, Object> systemProperties;

    @Autowired
    @Qualifier("systemEnvironment")
    private Map<String, Object> systemEnvironment;

    public void printInfo() {
        System.out.println("Java Home: " + systemProperties.get("java.home"));
        System.out.println("PATH: " + systemEnvironment.get("PATH"));
    }
}

BeanPostProcessor的作用

此阶段添加的BeanPostProcessor会在Bean实例化过程中起作用：

BeanPostProcessor 作用时机 主要功能
ApplicationContextAwareProcessor 初始化前 处理Aware接口回调
ApplicationListenerDetector 初始化后 注册ApplicationListener
LoadTimeWeaverAwareProcessor 初始化前 处理LoadTimeWeaverAware

执行时机

在prepareBeanFactory执行时：
- ✅ BeanFactory已创建
- ✅ 可以配置BeanFactory
- ❌ BeanDefinition还未注册（在invokeBeanFactoryPostProcessors中注册）
- ❌ Bean还未实例化

参考调用栈

prepareBeanFactory:665, AbstractApplicationContext (org.springframework.context.support)
refresh:525, AbstractApplicationContext (org.springframework.context.support)
refresh:143, ServletWebServerApplicationContext (org.springframework.boot.web.servlet.context)
refresh:755, SpringApplication (org.springframework.boot)
refreshContext:402, SpringApplication (org.springframework.boot)
run:312, SpringApplication (org.springframework.boot)

相关链接