java.util.Properties doesn't work properly when initializing it with another instance of java.util.Properties

huangapple
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英文:

java.util.Properties doesn't work properly when initializing it with another instance of java.util.Properties

问题

这段代码可以工作：

  1. import org.apache.kafka.clients.consumer.{ConsumerConfig, KafkaConsumer}
  2. import java.util.Properties
  4. object KafkaConsumerWithAuth extends App {
  5.     val props = new Properties()
  6.     props.setProperty(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "redacted")
  7.     props.setProperty(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer")
  8.     props.setProperty(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer")
  9.     props.setProperty("security.protocol", "SASL_SSL")
  10.     props.setProperty("sasl.mechanism", "PLAIN")
  11.     props.setProperty("sasl.jaas.config", "redacted")
  12.     props.setProperty("ssl.endpoint.identification.algorithm", "")
  13.     props.setProperty("ssl.truststore.location", "redacted.jks")
  14.     props.setProperty("ssl.truststore.password", "redacted")
  16.     lazy val consumer = new KafkaConsumer(props)
  18.     println(consumer.listTopics())
  19. }

但这段代码不行：

  1. import org.apache.kafka.clients.consumer.{ConsumerConfig, KafkaConsumer}
  2. import java.util.Properties
  4. object KafkaConsumerWithAuth extends App {
  5.     val props = new Properties({
  6.       val props = new Properties()
  7.       props.setProperty(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "redacted")
  8.       props.setProperty(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer")
  9.       props.setProperty(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer")
  10.       props.setProperty("security.protocol", "SASL_SSL")
  11.       props.setProperty("sasl.mechanism", "PLAIN")
  12.       props.setProperty("sasl.jaas.config", "redacted")
  13.       props.setProperty("ssl.endpoint.identification.algorithm", "")
  14.       props.setProperty("ssl.truststore.location", "redacted.jks")
  15.       props.setProperty("ssl.truststore.password", "redacted")
  16.       props
  17.     })
  19.     lazy val consumer = new KafkaConsumer(props)
  21.     println(consumer.listTopics())
  22. }

出现问题的原因是第二段代码中的 props 并没有正确地复制第一个 props 的配置，所以导致了错误。要使第二段代码生效，你可以使用 props.clone() 来创建一个副本，确保配置被正确复制。

至于Java版本的代码，它可以工作，因为Java中的 Properties 类的 clone 方法会创建一个副本，正确复制了配置。所以，Java版本的代码没有问题。

英文:

This code works:

  1. import org.apache.kafka.clients.consumer.{ConsumerConfig, KafkaConsumer}
  3. import java.util.Properties
  5. object KafkaConsumerWithAuth extends App {
  6.     val props = new Properties()
  7.     props.setProperty(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "redacted")
  8.     props.setProperty(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer")
  9.     props.setProperty(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer")
  10.     props.setProperty("security.protocol", "SASL_SSL")
  11.     props.setProperty("sasl.mechanism", "PLAIN")
  12.     props.setProperty("sasl.jaas.config", "redacted")
  13.     props.setProperty("ssl.endpoint.identification.algorithm", "")
  14.     props.setProperty("ssl.truststore.location", "redacted.jks")
  15.     props.setProperty("ssl.truststore.password", "redacted")
  17.   lazy val consumer = new KafkaConsumer(props)
  19.   println(consumer.listTopics())
  20. }

but this code doesn't:

  1. import org.apache.kafka.clients.consumer.{ConsumerConfig, KafkaConsumer}
  3. import java.util.Properties
  5. object KafkaConsumerWithAuth extends App {
  6.     val props = new Properties({
  7.       val props = new Properties()
  8.       props.setProperty(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "redacted")
  9.       props.setProperty(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer")
  10.       props.setProperty(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer")
  11.       props.setProperty("security.protocol", "SASL_SSL")
  12.       props.setProperty("sasl.mechanism", "PLAIN")
  13.       props.setProperty("sasl.jaas.config", "redacted")
  14.       props.setProperty("ssl.endpoint.identification.algorithm", "")
  15.       props.setProperty("ssl.truststore.location", "redacted")
  16.       props.setProperty("ssl.truststore.password", "redacted")
  17.       props
  18.     })
  21.   lazy val consumer = new KafkaConsumer(props)
  23.   println(consumer.listTopics())
  24. }

How come? I wanted to program it this way, because I wanted props to also be lazy, setProperty triggers execution if you do it like this:

  1. lazy val props = new Property()
  2. props.setProperty(..., ...) // this triggers execution, so I can't go with this approach

When I run the code that doesn't work, I get this error:

  1. Exception in thread "main" org.apache.kafka.common.config.ConfigException: Invalid value null for configuration key.deserializer: must be non-null.
  2. 	at org.apache.kafka.clients.consumer.ConsumerConfig.appendDeserializerToConfig(ConsumerConfig.java:630)
  3. 	at org.apache.kafka.clients.consumer.KafkaConsumer.<init>(KafkaConsumer.java:671)
  4. 	at org.apache.kafka.clients.consumer.KafkaConsumer.<init>(KafkaConsumer.java:652)
  5. 	at org.apache.kafka.clients.consumer.KafkaConsumer.<init>(KafkaConsumer.java:632)
  6. 	at main.KafkaConsumerWithAuth$.consumer$lzycompute(KafkaConsumerWithAuth.scala:23)
  7. 	at main.KafkaConsumerWithAuth$.consumer(KafkaConsumerWithAuth.scala:23)
  8. 	at main.KafkaConsumerWithAuth$.delayedEndpoint$main$KafkaConsumerWithAuth$1(KafkaConsumerWithAuth.scala:25)
  9. 	at main.KafkaConsumerWithAuth$delayedInit$body.apply(KafkaConsumerWithAuth.scala:7)
  10. 	at scala.Function0$class.apply$mcV$sp(Function0.scala:40)
  11. 	at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)
  12. 	at scala.App$$anonfun$main$1.apply(App.scala:76)
  13. 	at scala.App$$anonfun$main$1.apply(App.scala:76)
  14. 	at scala.collection.immutable.List.foreach(List.scala:381)
  15. 	at scala.collection.generic.TraversableForwarder$class.foreach(TraversableForwarder.scala:35)
  16. 	at scala.App$class.main(App.scala:76)
  17. 	at main.KafkaConsumerWithAuth$.main(KafkaConsumerWithAuth.scala:7)
  18. 	at main.KafkaConsumerWithAuth.main(KafkaConsumerWithAuth.scala)

So, it looks like the inner java.util.Properties object wasn't copied properly.

I tried the same approach with java, when you have 1 java.util.Properties instance and you create another one with it, it also doesn't work:

  1. import org.apache.kafka.clients.consumer.ConsumerConfig;
  2. import org.apache.kafka.clients.consumer.KafkaConsumer;
  4. import java.util.Properties;
  6. public class KafkaConsumerJava {
  7.     public static void main(String[] args) {
  8.         Properties props = new Properties();
  9.         props.setProperty(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "redacted");
  10.         props.setProperty(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
  11.         props.setProperty(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
  12.         props.setProperty("security.protocol", "SASL_SSL");
  13.         props.setProperty("sasl.mechanism", "PLAIN");
  14.         props.setProperty("sasl.jaas.config", "redacted");
  15.         props.setProperty("ssl.endpoint.identification.algorithm", "");
  16.         props.setProperty("ssl.truststore.location", "redacted");
  17.         props.setProperty("ssl.truststore.password", "redacted");
  18.         Properties props2 = new Properties(props);
  20.         KafkaConsumer<String, String> consumer = new KafkaConsumer<String, String>(props2);
  21.         System.out.println(consumer.listTopics());
  22.     }
  23. }

答案1

得分: 1

根据文档，构造函数 Properties(Properties) 用于设置一组默认属性值，而不是用于设置属性值。

英文:

Per the documentation, the constructor Properties(Properties) is used to set a list of default property values, not to set the property values.

答案2

得分: 1

你应该使用props1.putAll(props2)来合并这两者。

英文:

You should use props1.putAll(props2) if you want to merge the two.

huangapple
  • 本文由 发表于 2023年6月29日 05:02:01
  • 转载请务必保留本文链接：https://go.coder-hub.com/76576682.html
  • apache-kafka
  • java
  • scala
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