如何从 applicationContext.xml 中的 bean 读取值？

Question

我需要在我的applicationContext.xml中设置一个参数值接口IP地址

我从属性文件中读取此设置并以这种方式使用它：

<bean id="hazelcastInterface" class="com.hazelcast.config.InterfacesConfig">
        <property name="interfaces">
            <list>
                <value>${interface.ip_address}</value>
            </list>
        </property>
        <property name="enabled" value="true" />
    </bean>

现在我需要从命令行参数中获取这个值。我使用 Apache Commons CLI 解析器，解析参数并从中创建我自己的 bean commandLineConf 并将其设置为 ApplicationContext。

ExternalBeanReferneceFactoryBean.setInstance("commandLineConf", conf);
beanFactory.registerBeanDefinition(
    "commandLineConf",
    BeanDefinitionBuilder.rootBeanDefinition(
        ExternalBeanReferneceFactoryBean.class)
        .getBeanDefinition());

GenericApplicationContext rootAppContext = new GenericApplicationContext(
    beanFactory);
rootAppContext.refresh();

但我不知道如何从 applicationContext.xml 中的这个 bean 获取值。我尝试了很多方法，例如但这对我不起作用。

<bean id="hazelcastInterface" class="com.hazelcast.config.InterfacesConfig">
        <property name="interfaces">
            <list>
                <value>#{commandLineConf.ipAddress}</value>
            </list>
        </property>
        <property name="enabled" value="true" />
    </bean>

我做错了什么？

Answer 1

我使用适当的类测试了您的 xml 应用程序上下文，并且我从该主服务器获得了预期的 ipAddress：

public static void main(String[] args) {

        CommandLineConf conf = new CommandLineConf();
        conf.setIpAddress("127.0.0.1");
        // create root beanFactory
        DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();

        // register bean definition for the command line
        ExternalBeanReferneceFactoryBean.setInstance("commandLineConf", conf);
        beanFactory.registerBeanDefinition(
            "commandLineConf",
            BeanDefinitionBuilder.rootBeanDefinition(
                ExternalBeanReferneceFactoryBean.class)
                .getBeanDefinition());

        GenericApplicationContext rootAppContext = new GenericApplicationContext(
            beanFactory);
        rootAppContext.refresh();

        // create the application context
        ApplicationContext appContext = new ClassPathXmlApplicationContext(new String[] { 
            "/applicationContext.xml"
        }, rootAppContext);

        InterfacesConfig hazelcastInterface = (InterfacesConfig)appContext.getBean("hazelcastInterface");
        System.out.println(hazelcastInterface.getInterfaces().get(0));

    }

所以您使用正确的语法来引用地址，即：#{commandLineConf.ipAddress}

这让我觉得问题出在 conf 变量中。您的代码没有显示它是如何填写的，我怀疑缺少 ipAddress。我不能确定，因为你没有在你的片段中包含解析的参数。 在开始构建 spring 上下文之前确保 ipAddress 存在于 conf 变量中（即通过打印它）。

我包括了你可能需要有一个工作代码的其余类：

• InterfacesConfig.java

  public class InterfacesConfig {
      private List<String>interfaces;
      private boolean enabled;
  
      public List<String> getInterfaces() {
          return interfaces;
      }
  
      public void setInterfaces(List<String> interfaces) {
          this.interfaces = interfaces;
      }
      public boolean isEnabled() {
          return enabled;
      }
  
      public void setEnabled(boolean enabled) {
          this.enabled = enabled;
      }
  
  }
  

• CommandLineConf.java

  public class CommandLineConf {
      private String ipAddress;
      public String getIpAddress() {
          return ipAddress;
      }
  
      public void setIpAddress(String ipAddress) {
          this.ipAddress = ipAddress;
      }
  }
  

• ExternalBeanReferneceFactoryBean.java

  import java.util.HashMap;
  import java.util.Map;
  
  import org.springframework.beans.factory.BeanNameAware;
  import org.springframework.beans.factory.config.AbstractFactoryBean;
  
  public class ExternalBeanReferneceFactoryBean extends AbstractFactoryBean implements BeanNameAware {
  
      private static Map<String, Object> instances = new HashMap<String, Object>();
      private String beanName;
  
      /**
       * @param instance the instance to set
       */
      public static void setInstance(String beanName, Object instance) {
          instances.put(beanName, instance);
      }
  
      @Override
      protected Object createInstance() 
          throws Exception {
          return instances.get(beanName);
      }
  
      @Override
      public Class<?> getObjectType() {
          return instances.get(beanName).getClass();
      }
  
      @Override
      public void setBeanName(String name) {
          this.beanName = name;
      }
  
  }
  

• applicationContext.xml

  <?xml version="1.0" encoding="UTF-8"?>
  <beans xmlns="http://www.springframework.org/schema/beans"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xmlns:context="http://www.springframework.org/schema/context"
      xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
      http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd">
  <bean id="hazelcastInterface" class="com.hazelcast.config.InterfacesConfig">
          <property name="interfaces">
              <list>
                  <value>#{commandLineConf.ipAddress}</value>
              </list>
          </property>
          <property name="enabled" value="true" />
      </bean>
  </beans>