以编程方式将 Bean 添加到 Spring Web App 上下文

Posted 2023-02-23

【中文标题】以编程方式将 Bean 添加到 Spring Web App 上下文

【英文标题】：Add Bean Programmatically to Spring Web App Context

【发布时间】：2011-05-31 06:07:24

【问题描述】：

由于是插件架构，我正在尝试以编程方式将 bean 添加到我的 web 应用程序中。我有一个通过@Component 注释创建的Spring bean，我正在实现ApplicationContextAware 接口。

我的覆盖函数如下所示：

@Override
public void setApplicationContext(ApplicationContext applicationContext)
        throws BeansException 

    // this fails
    this.applicationContext = (GenericWebApplicationContext) applicationContext;
 

基本上，我不知道如何将 bean 添加到给 setApplicationContext 的 applicationContext 对象。谁能告诉我我是怎么搞错的？

好的，这就是我最终得到的解决方案：

@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry bdr)
        throws BeansException 
    BeanDefinition definition = new RootBeanDefinition(
            <My Class>.class);

    bdr.registerBeanDefinition("<my id>", definition);

【参考方案1】：

首先初始化属性值

MutablePropertyValues mutablePropertyValues = new MutablePropertyValues();
mutablePropertyValues.add("hostName", details.getHostName());
mutablePropertyValues.add("port", details.getPort());

DefaultListableBeanFactory context = new DefaultListableBeanFactory();
GenericBeanDefinition connectionFactory = new GenericBeanDefinition();
connectionFactory.setBeanClass(Class);
connectionFactory.setPropertyValues(mutablePropertyValues);

context.registerBeanDefinition("beanName", connectionFactory);

添加到 bean 列表

ConfigurableListableBeanFactory beanFactory = ((ConfigurableApplicationContext) applicationContext).getBeanFactory();
beanFactory.registerSingleton("beanName", context.getBean("beanName"));

【参考方案2】：

为什么需要GenericWebApplicationContext 类型？ 我认为您可能可以使用任何 ApplicationContext 类型。

通常你会使用一个 init 方法（除了你的 setter 方法）：

@PostConstruct
public void init()
    AutowireCapableBeanFactory bf = this.applicationContext
        .getAutowireCapableBeanFactory();
    // wire stuff here

您可以使用任一方法连接 bean

AutowireCapableBeanFactory.autowire(Class, int mode, boolean dependencyInject)

或

AutowireCapableBeanFactory.initializeBean(Object existingbean, String beanName)

【讨论】：

当我这样做时，它不会将它们添加到 ApplicationContext

【参考方案3】：

实际上AnnotationConfigApplicationContext 派生自AbstractApplicationContext，其中有空的postProcessBeanFactory 方法可供覆盖

/**
 * Modify the application context's internal bean factory after its standard
 * initialization. All bean definitions will have been loaded, but no beans
 * will have been instantiated yet. This allows for registering special
 * BeanPostProcessors etc in certain ApplicationContext implementations.
 * @param beanFactory the bean factory used by the application context
 */
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) 

要利用这一点，请创建如下所示的 AnnotationConfigApplicationContextProvider 类（给定 Vertx 实例示例，您可以改用 MyClass）...

public class CustomAnnotationApplicationContextProvider 
private final Vertx vertx;

public CustomAnnotationApplicationContextProvider(Vertx vertx) 
    this.vertx = vertx;


/**
 * Register all beans to spring bean factory
 *
 * @param beanFactory, spring bean factory to register your instances
 */
private void configureBeans(ConfigurableListableBeanFactory beanFactory) 
    beanFactory.registerSingleton("vertx", vertx);


/**
 * Proxy method to create @link AnnotationConfigApplicationContext instance with no params
 *
 * @return @link AnnotationConfigApplicationContext instance
 */
public AnnotationConfigApplicationContext get() 
    return new AnnotationConfigApplicationContext() 

        @Override
        protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) 
            super.postProcessBeanFactory(beanFactory);
            configureBeans(beanFactory);
        
    ;


/**
 * Proxy method to call @link AnnotationConfigApplicationContext#AnnotationConfigApplicationContext(DefaultListableBeanFactory) with our logic
 *
 * @param beanFactory bean factory for spring
 * @return
 * @see AnnotationConfigApplicationContext#AnnotationConfigApplicationContext(DefaultListableBeanFactory)
 */
public AnnotationConfigApplicationContext get(DefaultListableBeanFactory beanFactory) 
    return new AnnotationConfigApplicationContext(beanFactory) 

        @Override
        protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) 
            super.postProcessBeanFactory(beanFactory);
            configureBeans(beanFactory);
        
    ;


/**
 * Proxy method to call @link AnnotationConfigApplicationContext#AnnotationConfigApplicationContext(Class[]) with our logic
 *
 * @param annotatedClasses, set of annotated classes for spring
 * @return
 * @see AnnotationConfigApplicationContext#AnnotationConfigApplicationContext(Class[])
 */
public AnnotationConfigApplicationContext get(Class<?>... annotatedClasses) 
    return new AnnotationConfigApplicationContext(annotatedClasses) 

        @Override
        protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) 
            super.postProcessBeanFactory(beanFactory);
            configureBeans(beanFactory);
        
    ;


/**
 * proxy method to call @link AnnotationConfigApplicationContext#AnnotationConfigApplicationContext(String...) with our logic
 *
 * @param basePackages set of base packages for spring
 * @return
 * @see AnnotationConfigApplicationContext#AnnotationConfigApplicationContext(String...)
 */
public AnnotationConfigApplicationContext get(String... basePackages) 
    return new AnnotationConfigApplicationContext(basePackages) 

        @Override
        protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) 
            super.postProcessBeanFactory(beanFactory);
            configureBeans(beanFactory);
        
    ;

在创建ApplicationContext 时，您可以使用

Vertx vertx = ...; // either create or for vertx, it'll be passed to main verticle
ApplicationContext context = new CustomAnnotationApplicationContextProvider(vertx).get(ApplicationSpringConfig.class);

【参考方案4】：

这是一个简单的代码：

ConfigurableListableBeanFactory beanFactory = ((ConfigurableApplicationContext) applicationContext).getBeanFactory();
beanFactory.registerSingleton(bean.getClass().getCanonicalName(), bean);

【讨论】：

你能详细说明答案吗？

【参考方案5】：

在 Spring 3.0 中，您可以使您的 bean 实现 BeanDefinitionRegistryPostProcessor 并通过 BeanDefinitionRegistry 添加新 bean。

在以前的 Spring 版本中，您可以在 BeanFactoryPostProcessor 中执行相同的操作（尽管您需要将 BeanFactory 强制转换为 BeanDefinitionRegistry，这可能会失败）。

【讨论】：

谢谢。我想最难的部分是知道要寻找什么。

请注意JavaDoc: A BeanFactoryPostProcessor may interact with and modify bean definitions, but never bean instances. Doing so may cause premature bean instantiation, violating the container and causing unintended side-effects. If bean instance interaction is required, consider implementing BeanPostProcessor instead.

BeanDefinitionRegistryPostProcessor 怎么办？假设我写了这个类。接下来是什么？如何激活它？