如何将前缀属性注入java.util.属性？

Question

Spring Boot提供了一种优雅的方法，可以使用@ConfigurationProperties（prefix="foo"）将带有特定键前缀的属性注入Configuration类。这是显示在这里和这里。问题是，如何将前缀属性注入到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

您可以定义一个用@ConfigurationProperties注释的新bean，如下所示：

@Bean
@ConfigurationProperties(prefix = "kafka")
public Properties kafkaProperties() {
    return new Properties();
}

@Bean
public Producer<String, String> producer() throws Exception {
    return new KafkaProducer<String, String>(kafkaProperties());
}

（摘自https://stackoverflow.com/a/50810923/500478)

Answer 2

这不起作用，因为此属性注入基于对象上的getter和setter，该对象应包含@ConfigurationProperties定义一个包含所需属性的类，如下所示：

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

  private int foo;

  private string bar;

  // Getters and Setter for foo and bar

}

然后像这样在配置中使用它

@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;
  }
}

使现代化

由于您评论说您不希望将每个属性表示为java代码，因此可以使用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;
  }
}

在应用程序中。属性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;
  }
}