在Spring Boot自动配置中使用子类扩展java数据源

Question

我正在尝试编写一个自动配置库，它向任何DataSource添加功能。我已经编写了一个子类，我将在这里调用CustomDataSource，它覆盖了DataSource的一些方法

@Configuration
@ConditionalOnBean(DataSource.class)
@AutoConfigureAfter(DataSourceAutoConfiguration.class)
public class CustomDataSourceAutoConfiguration {

    private final DataSource dataSource;

    public CustomDataSourceAutoConfiguration(DataSource dataSource) {
        this.dataSource = dataSource;
    }

    @Primary
    @Bean
    public CustomDataSource customDataSource() {
        return new CustomDataSource(dataSource);
    }
}

但我找不到一种方法让我做我想做的事。它将始终导致循环引用和例外情况：

BeanCurrentlyInCreationException: Error creating bean with name 'customDataSource': Requested bean is currently in creation: Is there an unresolvable circular reference?

有办法解决这个问题吗

Answer 1

我通过实现BeanPostProcessor找到了解决这个问题的方法：

public class DataSourcePostProcessor implements BeanPostProcessor {

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) {
        if (bean instanceof DataSource && !(bean instanceof CustomDataSource)) {
            return new CustomDataSource((DataSource) bean);
        } else {
            return bean;
        }
    }

}

postProcessAfterInitialization方法可以显式地用于在代理中包装bean，引用^{} documentation：

[...] post-processors that wrap beans with proxies will normally implement postProcessAfterInitialization(java.lang.Object, java.lang.String).