Spring-以编程方式生成一组bean

Spring-以编程方式生成一组bean

你需要即时声明新bean并将它们注入Spring的应用程序上下文中，就像它们只是普通bean一样，这意味着它们必须经受代理，后处理等 *** 作，即它们必须经受Spring bean生命周期的约束。 。

请参阅

BeanDefinitionRegistryPostProcessor.postProcessBeanDefinitionRegistry()

方法 javadocs。这正是你所需要的，因为它使你可以在装入常规bean定义之后 但 实例化任何单个bean之前修改Spring的应用程序上下文。

@Configurationpublic class ConfigLoader implements BeanDefinitionRegistryPostProcessor {    private final List<String> configurations;    public ConfigLoader() {        this.configurations = new linkedList<>();        // TODO Get names of different configurations, just the names!        // i.e. You could manually read from some config file        // or scan classpath by yourself to find classes         // that implement MyConfiguration interface.        // (You can even hardpre config names to start seeing how this works)        // important: you can't autowire anything yet,         // because Spring has not instantiated any bean so far!        for (String readConfigurationName : readConfigurationNames) { this.configurations.add(readConfigurationName);        }    }    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {        // iterate over your configurations and create the beans definitions it needs        for (String configName : this.configurations) { this.quartzConfiguration(configName, registry); this.quartzModule(configName, registry); this.healthCheck(configName, registry); // etc.        }    }    private void quartzConfiguration(String configName, BeanDefinitionRegistry registry) throws BeansException {        String beanName = configName + "_QuartzConfiguration";        BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(QuartzConfiguration.class).setLazyInit(true);         // TODO Add what the bean needs to be properly initialized        // i.e. constructor arguments, properties, shutdown methods, etc        // BeanDefinitionBuilder let's you add whatever you need        // Now add the bean definition with given bean name        registry.registerBeanDefinition(beanName, builder.getBeanDefinition());    }    private void quartzModule(String configName, BeanDefinitionRegistry registry) throws BeansException {        String beanName = configName + "_QuartzModule";        BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(QuartzModule.class).setLazyInit(true);         builder.addConstructorArgReference(configName + "_QuartzConfiguration"); // quartz configuration bean as constructor argument        // Now add the bean definition with given bean name        registry.registerBeanDefinition(beanName, builder.getBeanDefinition());    }    private void healthCheck(String configName, BeanDefinitionRegistry registry) throws BeansException {        String beanName = configName + "_HealthCheck";        BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(HealthCheck.class).setLazyInit(true);         // TODO Add what the bean needs to be properly initialized        // i.e. constructor arguments, properties, shutdown methods, etc        // BeanDefinitionBuilder let's you add whatever you need        // Now add the bean definition with given bean name        registry.registerBeanDefinition(beanName, builder.getBeanDefinition());    }    // And so on for other beans...}

这有效地声明了你需要的bean，并将它们注入Spring的应用程序上下文中，每种配置都有一组bean。你必须依靠某种命名模式，然后在需要的地方通过名称自动连接bean：

@Servicepublic class MyService {    @Resource(name="config1_QuartzConfiguration")    private QuartzConfiguration config1_QuartzConfiguration;    @Resource(name="config1_QuartzModule")    private QuartzModule config1_QuartzModule;    @Resource(name="config1_HealthCheck")    private HealthCheck config1_HealthCheck;    ...}

笔记：

1. 如果你要从文件中手动读取配置名称，请使用Spring的ClassPathResource.getInputStream()。

2. 如果你自己扫描类路径，强烈建议你使用令人惊叹的Reflections库。

3. 你必须为每个bean定义手动设置所有属性和依赖项。每个bean定义都独立于其他bean定义，即，你不能重用它们，也不能在另一个内部设置它们，等等。想想它们就像你在以旧的XML方式声明bean一样。

4. 检查BeanDefinitionBuilder javadocs和GenericBeanDefinition javadocs以获得更多详细信息。