java - 如何将前缀属性注入(inject)java.util.Properties？

Question

Spring boot 提供了一种优雅的方式，使用 @ConfigurationProperties(prefix = "foo") 将带有特定键前缀的属性注入(inject)到 Configuration 类中。显示here和 here 。问题是，如何将前缀属性注入(inject)到 java.util.Properties 实例中，如下所示？

@Configuration
@EnableConfigurationProperties
public class FactoryBeanAppConfig {

    @Bean
    @ConfigurationProperties(prefix = "kafka")
    public Producer<String, String> producer(Properties properties) throws Exception {
        Producer<String, String> producer = new KafkaProducer<String, String>(properties);
        return producer;
    }

}

Answer 1

这是行不通的，因为这个属性注入(inject)是基于应该保存@ConfigurationProperties的对象上的getter和setter 定义一个包含您想要的属性的类，如下所示:

@ConfigurationProperties(prefix = "kafka.producer")
public class MyKafkaProducerProperties {

  private int foo;

  private string bar;

  // Getters and Setter for foo and bar

}

然后在您的配置中使用它，如下所示

@Configuration
@EnableConfigurationProperties(MyKafkaProducerProperties.class)
public class FactoryBeanAppConfig {

  @Bean
  public Producer<String, String> producer(MyKafkaProducerProperties kafkaProperties) throws Exception {
    Properties properties = new Properties();
    properties.setProperty("Foo", kafkaProperties.getFoo());
    properties.setProperty("Bar", kafkaProperties.getBar());
    Producer<String, String> producer = new KafkaProducer<String, String>(properties);
    return producer;
  }
}

更新

既然您评论说您不希望将每个属性都表示为 java 代码，您可以使用 HashMap 作为 @ConfigurationProperties 中唯一的属性

@ConfigurationProperties(prefix = "kafka")
public class MyKafkaProducerProperties {

  private Map<String, String> producer= new HashMap<String, String>();

  public Map<String, String> getProducer() {
    return this.producer;
  }
}

在 application.properties 中，您可以指定如下属性:

kafka.producer.foo=hello
kafka.producer.bar=world

在您的配置中，您可以像这样使用它:

@Configuration
@EnableConfigurationProperties(MyKafkaProducerProperties.class)
public class FactoryBeanAppConfig {

  @Bean
  public Producer<String, String> producer(MyKafkaProducerProperties kafkaProperties) throws Exception {

    Properties properties = new Properties();

    for ( String key : kafkaProperties.getProducer().keySet() ) {
     properties.setProperty(key, kafkaProperties.getProducer().get(key));
    }

    Producer<String, String> producer = new KafkaProducer<String, String>(properties);
    return producer;
  }
}