動態Spring bean創建

Question

我正在使用一個API，以XXXLocalServiceUtil類的形式公開服務，它們是單例對象的靜態包裝。相反，使用靜態XXXLocalServiceUtil方法我想注入XXXLocalService對象本身，直接在我的代碼使用它們，例如：

@Named 
public class MyMailingService {   
    @Inject UserLocalService userService; 

    public String mailUser(String email) { 
     User user = userService.getUser(email); 
     emailUser(user); 
    } 
} 

而且配置我applicationContext.xml像這樣：

<beans ...> 
    <bean class="x.y.z.UserLocalServiceUtil" factory-method="getService"/> 
    <bean class="x.y.z.CompanyLocalServiceUtil" factory-method="getService"/> 
    ... 
</beans> 

這完美的作品。現在，我所說的這個API有大約100個這樣的XXXLocalServiceUtil類，每個類都有自己的靜態getService方法，它返回實際的服務。我不希望在我的applicationContext.xml中列出所有這些服務，而是希望讓Spring爲我注入的每個XXXLocalService找到正確的XXXLocalServiceUtil類。所以我需要的是某種動態bean工廠，當然會在懶惰加載的基礎上爲我完成工作。

有人知道如何輕鬆實現這一點嗎？

Answer 1

您可以使用GenericApplicationContext將bean動態加載到applicationContext以及在xml中聲明的其他spring bean。下面是使用Reflections library ...

private static final Pattern SERVICE_UTIL_PATTERN = Pattern.compile(".*LocalServiceUtil.*"); 

public static void main(String[] args) { 
    ConfigurationBuilder builder = new ConfigurationBuilder().addUrls(
      ClasspathHelper.forPackage("x.y.z")) 
      .setScanners(new SubTypesScanner(false)); 
    Reflections reflections = new Reflections(builder); 
    GenericApplicationContext applicationContext = new GenericApplicationContext(); 
    Set<Class<? extends Object>> classes = reflections.getSubTypesOf(Object.class); 

    for (Class<? extends Object> serviceUtilClass : classes) { 
     String className = serviceUtilClass.getName(); 

     if (SERVICE_UTIL_PATTERN.matcher(className).matches()) { 
      GenericBeanDefinition beanDefinition = new GenericBeanDefinition(); 
      beanDefinition.setBeanClassName(className); 
      beanDefinition.setFactoryMethodName("getService"); 
      beanDefinition.setLazyInit(true); 

      String beanName = StringUtils.uncapitalize(serviceClass.getSimpleName().replace("Util", "")); 
      applicationContext.registerBeanDefinition(beanName, beanDefinition); 
     } 
    } 

    XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(applicationContext); 
    reader.loadBeanDefinitions("classpath:/applicationContext.xml"); 
    applicationContext.refresh(); 
} 

更新的例子來實現：要在Web應用程序中使用這個，你可以簡單地擴展Spring的XmlWebApplicationContext並重寫initBeanDefinitionReader方法如下...

private static final Pattern SERVICE_UTIL_PATTERN = Pattern.compile(".*LocalServiceUtil.*"); 

@Override 
protected void initBeanDefinitionReader(
     XmlBeanDefinitionReader beanDefinitionReader) { 
    ConfigurationBuilder builder = new ConfigurationBuilder().addUrls(
      ClasspathHelper.forPackage("x.y.z")) 
      .setScanners(new SubTypesScanner(false)); 
    Reflections reflections = new Reflections(builder); 
    Set<Class<? extends Object>> classes = reflections.getSubTypesOf(Object.class); 
    BeanDefinitionRegistry registry = beanDefinitionReader.getRegistry(); 

    for (Class<? extends Object> serviceClass : classes) { 
     String className = serviceClass.getName(); 

     if (SERVICE_UTIL_PATTERN.matcher(className).matches()) { 
      GenericBeanDefinition beanDefinition = new GenericBeanDefinition(); 
      beanDefinition.setBeanClassName(className); 
      beanDefinition.setFactoryMethodName("getService"); 
      beanDefinition.setLazyInit(true); 
      String beanName = StringUtils.uncapitalize(serviceClass 
        .getSimpleName().replace("Util", "")); 
      registry.registerBeanDefinition(beanName, beanDefinition); 
     } 
    } 
} 

}

，並添加以下context-param您的web.xml ...

<context-param> 
    <param-name>contextClass</param-name> 
    <param-value>x.y.z.MyXmlWebApplicationContext</param-value> 
</context-param> 

Answer 2

有一兩件事你可以嘗試是改變@Inject到@Autowired並在applicationContext.xml中定義的類型自動裝配，像這樣：

<beans ... default-autowire="byType"> 
    ... 
</beans> 

@Inject和@Autowired相當，但春天的@Autowired註解有優勢要求要求屬性被強制注入。

另一種解決方案：

而不是使用的工廠，你可以用豆範圍原型。

您的XXXLocalService必須實現ApplicationContextAware接口，並通過它獲取原型bean，即：

@Named 
public class MyMailingService implements ApplicationContextAware {   
    @Inject UserLocalService userService; 

    private ApplicationContext appContext; 

    @Override 
    public void setApplicationContext(ApplicationContext applicationContext) { 
     this.appContext = applicationContext; 
    } 

    public String mailUser(String email) { 
     User user = (User) appContext.getBean("user"); 
     emailUser(user); 
    } 
} 

和你的applicationContext.xml的樣子：

<beans ...> 
    <bean id="user" class="x.y.z.User" scope="prototype"/> 
    ... 
</beans> 

隨着getBean()每次調用你會得到該類型的新對象，與注射在豆一切的好處。