准备阶段

前几块代码都是为了后面的实例化做准备。

主体流程

注册 ConversionService ↓
注册 EmbeddedValueResolver ↓
实例化 Initialize LoadTimeWeaverAware beans ↓
取消临时的类加载器 ↓
冻结 bean 定义元数据

代码块-注册 ConversionService

可以通过转换服务进行数据类型的转换，如：String 转换为 Date 。

// 注册 ConversionService
if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) &&
        beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) {
    beanFactory.setConversionService(
            beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));
}

代码演示
首先准备一个转换器，用于将 String 转换成 LocalDateTime。

@Component
public class OrgConverter implements Converter<String, LocalDateTime> {
    @Override
    public LocalDateTime convert(String source) {
        DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        return LocalDateTime.parse(source, dateTimeFormatter);
    }
}

注册转换器

@Configuration
public class ConverterServiceConfig {
    @Bean
    public ConversionServiceFactoryBean conversionService() {
        ConversionServiceFactoryBean conversionServiceFactoryBean = new ConversionServiceFactoryBean();
        HashSet<Object> set = new HashSet<>();
        set.add(new OrgConverter());
        conversionServiceFactoryBean.setConverters(set);
        return conversionServiceFactoryBean;
    }
}

测试

public class OrgConverterApp {
    public static void main(String[] args) {
        // 根据注解加载bean
        AnnotationConfigApplicationContext context
                = new AnnotationConfigApplicationContext("cn.lichenghao.converter");
        ConversionService conversionService = context.getBeanFactory().getConversionService();
        LocalDateTime convert = conversionService.convert("2023-01-21 13:36:28", LocalDateTime.class);
        System.out.println(convert);
    }
}

代码块-注册值解析器

// 如果没有值解析器，就添加一个
if (!beanFactory.hasEmbeddedValueResolver()) {
    beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
}

代码块-Initialize LoadTimeWeaverAware beans

String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
for (String weaverAwareName : weaverAwareNames) {
    getBean(weaverAwareName);
}

代码块-取消临时的类加载器

// 取消临时的类加载器
beanFactory.setTempClassLoader(null);

代码块-冻结元数据

beanFactory.freezeConfiguration();
public void freezeConfiguration() {
    this.configurationFrozen = true;
    this.frozenBeanDefinitionNames = StringUtils.toStringArray(this.beanDefinitionNames);
}