如何将属性值注入使用注释配置的 Spring Bean? [英] How can I inject a property value into a Spring Bean which was configured using annotations?

问题描述

我有一堆 Spring bean，它们是通过注释从类路径中提取的，例如

I have a bunch of Spring beans which are picked up from the classpath via annotations, e.g.

@Repository("personDao")
public class PersonDaoImpl extends AbstractDaoImpl implements PersonDao {
    // Implementation omitted
}

在 Spring XML 文件中，有一个 PropertyPlaceholderConfigurer 定义:

In the Spring XML file, there's a PropertyPlaceholderConfigurer defined:

<bean id="propertyConfigurer" 
  class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="location" value="/WEB-INF/app.properties" />
</bean> 

我想将 app.properites 中的一个属性注入到上面显示的 bean 中.我不能简单地做类似

I want to inject one of the properties from app.properites into the bean shown above. I can't simply do something like

<bean class="com.example.PersonDaoImpl">
    <property name="maxResults" value="${results.max}"/>
</bean>

因为 PersonDaoImpl 在 Spring XML 文件中没有特征(它是通过注解从类路径中提取的).我有以下几点:

Because PersonDaoImpl does not feature in the Spring XML file (it is picked up from the classpath via annotations). I've got as far as the following:

@Repository("personDao")
public class PersonDaoImpl extends AbstractDaoImpl implements PersonDao {

    @Resource(name = "propertyConfigurer")
    protected void setProperties(PropertyPlaceholderConfigurer ppc) {
    // Now how do I access results.max? 
    }
}

但我不清楚如何从 ppc 访问我感兴趣的属性?

But it's not clear to me how I access the property I'm interested in from ppc?

推荐答案

您可以使用 EL 支持在 Spring 3 中执行此操作.示例:

You can do this in Spring 3 using EL support. Example:

@Value("#{systemProperties.databaseName}")
public void setDatabaseName(String dbName) { ... }

@Value("#{strategyBean.databaseKeyGenerator}")
public void setKeyGenerator(KeyGenerator kg) { ... }

systemProperties 是一个隐式对象，strategyBean 是一个 bean 名称.

systemProperties is an implicit object and strategyBean is a bean name.

再举一个例子，当您想从 Properties 对象中获取一个属性时，它会起作用.它还表明您可以将 @Value 应用于字段:

One more example, which works when you want to grab a property from a Properties object. It also shows that you can apply @Value to fields:

@Value("#{myProperties['github.oauth.clientId']}")
private String githubOauthClientId;

这是一个博文 我写了这篇文章以获得更多信息.

Here is a blog post I wrote about this for a little more info.

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