动态地从父类转换为合适的子类在一个方法中。

huangapple
go评论94阅读模式
英文:

Dynamically cast to a proper subclass from parent class in a method

问题

我有一个Java interface 叫做 PlatformConfigurable。我还有两个类 PlatformProducerConfig 和 PlatformConsumerConfig。

后来，我需要为这两个类添加一个共同的配置，将一个属性设置为空字符串：

  1.     private PlatformConfigurable disableHostNameVerificationConfig(PlatformConfigurable platformConfig) {
  2.         if (platformConfig instanceof PlatformProducerConfig) {
  3.             PlatformProducerConfig oldConfig = (PlatformProducerConfig) platformConfig;
  4.             Map<String, String> additionalConfig = oldConfig.additionalProperties();
  5.             Map<String, String> newConfig = new HashMap<>(Optional.ofNullable(additionalConfig).orElseGet(ImmutableMap::of));
  6.             newConfig.put(SslConfigs.SSL_ENDPOINT_IDENTIFICATION_ALGORITHM_CONFIG, "");
  7.             return oldConfig.toBuilder().additionalProperties(newConfig).build();
  8.         }
  9.         else if (platformConfig instanceof PlatformConsumerConfig) {
  10.             PlatformConsumerConfig oldConfig = (PlatformConsumerConfig) platformConfig;
  11.             Map<String, String> additionalConfig = platformConfig.additionalProperties();
  12.             Map<String, String> newConfig = new HashMap<>(Optional.ofNullable(additionalConfig).orElseGet(ImmutableMap::of));
  13.             newConfig.put(SslConfigs.SSL_ENDPOINT_IDENTIFICATION_ALGORITHM_CONFIG, "");
  14.             return oldConfig.toBuilder().additionalProperties(newConfig).build();
  15.         }
  16.         return platformConfig;
  17.     }

我进行了对生产者或消费者配置的强制类型转换，因为 PlatformConfigurable 接口中没有声明 .toBuilder() 或 .build() 方法，而且我无法访问修改该接口，我只能实现它。

我希望摆脱重复的代码：

  1. Map<String, String> additionalConfig = platformConfig.additionalProperties();
  2. Map<String, String> newConfig = new HashMap<>(Optional.ofNullable(additionalConfig).orElseGet(ImmutableMap::of));
  3. newConfig.put(SslConfigs.SSL_ENDPOINT_IDENTIFICATION_ALGORITHM_CONFIG, "");
  4. return oldConfig.toBuilder().additionalProperties(newConfig).build();

我在考虑使用Lambda表达式，但我不确定如何做到这一点。

英文:

I have a Java interface PlatformConfigurable. I also have two classes PlatformProducerConfig and PlatformConsumerConfig.

Later on, I need to add a common config to both that sets a property to an empty string:

  1.     private PlatformConfigurable disableHostNameVerificationConfig(PlatformConfigurable platformConfig) {
  2.         if (platformConfig instanceof PlatformProducerConfig) {
  3.             PlatformProducerConfig oldConfig = (PlatformProducerConfig) platformConfig;
  4.             Map&lt;String, String&gt; additionalConfig = oldConfig.additionalProperties();
  5.             Map&lt;String, String&gt; newConfig = new HashMap&lt;&gt;(Optional.ofNullable(additionalConfig).orElseGet(ImmutableMap::of));
  6.             newConfig.put(SslConfigs.SSL_ENDPOINT_IDENTIFICATION_ALGORITHM_CONFIG, &quot;&quot;);
  7.             return oldConfig.toBuilder().additionalProperties(newConfig).build();
  8.         }
  9.         else if (platformConfig instanceof PlatformConsumerConfig) {
  10.             PlatformConsumerConfig oldConfig = (PlatformConsumerConfig) platformConfig;
  11.             Map&lt;String, String&gt; additionalConfig = platformConfig.additionalProperties();
  12.             Map&lt;String, String&gt; newConfig = new HashMap&lt;&gt;(Optional.ofNullable(additionalConfig).orElseGet(ImmutableMap::of));
  13.             newConfig.put(SslConfigs.SSL_ENDPOINT_IDENTIFICATION_ALGORITHM_CONFIG, &quot;&quot;);
  14.             return oldConfig.toBuilder().additionalProperties(newConfig).build();
  15.         }
  16.         return platformConfig;
  17.     }

I am casting to producer or consumer config because the PlatformConfigurable interface doesn't have .toBuilder() or .build() methods declared in it, and I don't have access to modify the interface, as I can only implement it.

I would want to get rid of the duplicate code:

  1. Map&lt;String, String&gt; additionalConfig = platformConfig.additionalProperties();
  2.             Map&lt;String, String&gt; newConfig = new HashMap&lt;&gt;(Optional.ofNullable(additionalConfig).orElseGet(ImmutableMap::of));
  3.             newConfig.put(SslConfigs.SSL_ENDPOINT_IDENTIFICATION_ALGORITHM_CONFIG, &quot;&quot;);
  4.             return oldConfig.toBuilder().additionalProperties(newConfig).build();

I was thinking of using lambdas, but I am not 100% sure how to do it.

答案1

得分: 5

你可以像这样重构现有的代码：

  1. private PlatformConfigurable disableHostNameVerificationConfig(PlatformConfigurable platformConfig) {
  2.     if (!(platformConfig instanceof PlatformProducerConfig) && !(platformConfig instanceof PlatformConsumerConfig)) {
  3.         return platformConfig;
  4.     }
  6.     Map<String, String> additionalConfig = platformConfig.additionalProperties();
  7.     Map<String, String> newConfig = new HashMap<>(Optional.ofNullable(additionalConfig).orElseGet(Collections::emptyMap));
  8.     newConfig.put(SslConfigs.SSL_ENDPOINT_IDENTIFICATION_ALGORITHM_CONFIG, "");
  10.     if (platformConfig instanceof PlatformProducerConfig) {
  11.         return ((PlatformProducerConfig) platformConfig).toBuilder().additionalProperties(newConfig).build();
  12.     }
  13.     return ((PlatformConsumerConfig) platformConfig).toBuilder().additionalProperties(newConfig).build();
  14. }

更新

另一种方法是将与构建器相关的功能提取到单独的接口中，并在代码中使用它们：

  1. // 1. 扩展现有的 `PlatformConfigurable`
  2. public interface BuilderedPlatformConfigurable extends PlatformConfigurable {
  3.     ConfigPlatformBuilder toBuilder();
  4. }
  6. // 2. 提供具有共同实现的构建器接口
  7. public interface ConfigPlatformBuilder {
  8.     Map<String, String> additionalProperties = new HashMap<>();
  10.     BuilderedPlatformConfigurable build();
  12.     default ConfigPlatformBuilder additionalProperties(Map<String, String> properties) {
  13.         this.additionalProperties.clear();
  14.         this.additionalProperties.putAll(properties);
  15.         return this;
  16.     }
  17. }
  19. // 3. 更新 PlatformConsumerConfig 类（类似地，更新 PlatformProducerConfig）
  20. public class PlatformConsumerConfig implements BuilderedPlatformConfigurable {
  21.     private Map<String, String> additionalProperties = new HashMap<>();
  23.     @Override
  24.     public Map<String, String> additionalProperties() {
  25.         return additionalProperties;
  26.     }
  28.     public ConfigPlatformBuilder toBuilder() {
  29.         return new Builder();
  30.     }
  32.     public static class Builder implements ConfigPlatformBuilder {
  33.         public PlatformConsumerConfig build() {
  34.             PlatformConsumerConfig config = new PlatformConsumerConfig();
  35.             config.additionalProperties.putAll(this.additionalProperties);
  36.             return config;
  37.         }
  38.     }
  39. }
  41. // 4. 提供重载的方法
  42. private PlatformConfigurable disableHostNameVerificationConfig(PlatformConfigurable platformConfig) {
  43.     return platformConfig;
  44. }
  46. private PlatformConfigurable disableHostNameVerificationConfig(BuilderedPlatformConfigurable platformConfig) {
  47.     Map<String, String> additionalConfig = platformConfig.additionalProperties();
  48.     Map<String, String> newConfig = new HashMap<>(Optional.ofNullable(additionalConfig).orElseGet(Collections::emptyMap));
  49.     newConfig.put(SslConfigs.SSL_ENDPOINT_IDENTIFICATION_ALGORITHM_CONFIG, "");
  51.     return platformConfig.toBuilder().additionalProperties(newConfig).build();
  52. }

注意：这只是您提供的代码的翻译部分，没有其他附加内容。

英文:

You could just refactor existing code like this:

  1. private PlatfromConfigurable disableHostNameVerificationConfig(Platfromonfigurable platfromConfig) {
  2. if (!(platformConfig instanceof PlatformProducerConfig) &amp;&amp; !(platformConfig instanceof PlatformConsumerConfig)) {
  3. return platformConfig;
  4. }
  5. Map&lt;String, String&gt; additionalConfig = platformConfig.additionalProperties();
  6. Map&lt;String, String&gt; newConfig = new HashMap&lt;&gt;(Optional.ofNullable(additionalConfig).orElseGet(ImmutableMap::of));
  7. newConfig.put(SslConfigs.SSL_ENDPOINT_IDENTIFICATION_ALGORITHM_CONFIG, &quot;&quot;);
  8. if (platformConfig instanceof PlatformProducerConfig) {
  9. return ((PlatformProducerConfig)platformConfig).toBuilder().additionalProperties(newConfig).build();
  10. }
  11. return ((PlatformConsumerConfig)platformConfig).toBuilder().additionalProperties(newConfig).build();
  12. }

Update

Another approach could be to extract functionality related to the builder to separate interfaces and use them in this way:

  1. // 1. extend existing `PlatformConfigurable`
  2. public interface BuilderedPlatformConfigurable extends PlatformConfigurable {
  3. ConfigPlatformBuilder toBuilder();
  4. }
  5. // 2. provide builder interface with common implementation
  6. public interface ConfigPlatformBuilder {
  7. Map&lt;String, String&gt; additionalProperties = new HashMap&lt;&gt;();
  8. BuilderedPlatformConfigurable build();
  9. default ConfigPlatformBuilder additionalProperties(Map&lt;String, String&gt; properties) {
  10. this.additionalProperties.clear();
  11. this.additionalProperties.putAll(properties);
  12. return this;
  13. }
  14. }
  15. // 3. update PlatformConsumerConfig class (similarly, PlatformProducerConfig)
  16. public class PlatformConsumerConfig implements BuilderedPlatformConfigurable {
  17. private Map&lt;String, String&gt; additionalProperties = new HashMap&lt;&gt;();
  18. @Override
  19. public Map&lt;String, String&gt; additionalProperties() {
  20. return additionalProperties;
  21. }
  22. public ConfigPlatformBuilder toBuilder() {
  23. return new Builder();
  24. }
  25. public static class Builder implements ConfigPlatformBuilder {
  26. public PlatformConsumerConfig build() {
  27. PlatformConsumerConfig config = new PlatformConsumerConfig();
  28. config.additionalPropertie.putAll(this.additionalProperties);
  29. return config;
  30. }
  31. }
  32. }
  33. // 4. provide overloaded method
  34. private PlatformConfigurable disableHostNameVerificationConfig(PlatformConfigurable platformConfig) {
  35. return platformConfig;
  36. }
  37. private PlatformConfigurable disableHostNameVerificationConfig(BuilderedPlatformConfigurable platformConfig) {
  38. Map&lt;String, String&gt; additionalConfig = platformConfig.additionalProperties();
  39. Map&lt;String, String&gt; newConfig = new HashMap&lt;&gt;(Optional.ofNullable(additionalConfig).orElseGet(Map::of));
  40. newConfig.put(SslConfigs.SSL_ENDPOINT_IDENTIFICATION_ALGORITHM_CONFIG, &quot;&quot;);
  41. return platformConfig.toBuilder().additionalProperties(newConfig).build();
  42. }

答案2

得分: 4

使用泛型，对 Alex Rudenko 的答案 进行进一步扩展：

  1. private <P extends PlatformConfigurable> P disableHostNameVerificationConfig(P platformConfig, BiFunction<P, Map<String, String>, P> appender) {
  2.     Map<String, String> additionalConfig = platformConfig.additionalProperties();
  3.     Map<String, String> newConfig = new HashMap<>(Optional.ofNullable(additionalConfig).orElseGet(ImmutableMap::of));
  4.     newConfig.put(SslConfigs.SSL_ENDPOINT_IDENTIFICATION_ALGORITHM_CONFIG, "");
  6.     return appender.apply(platformConfig, newConfig);
  7. }

假设对于任何 PlatformConfigurable 的子类型（包括 PlatformConfigurable 本身），这样做是安全的。

然后可以这样调用：

  1. disableHostNameVerificationConfig(
  2.     platformProducerConfig,
  3.     (p, config) -> p.toBuilder().setAdditionalConfig(config).build());
  5. disableHostNameVerificationConfig(
  6.     platformConsumerConfig,
  7.     (p, config) -> p.toBuilder().setAdditionalConfig(config).build());

如果愿意，可以创建辅助方法来隐藏 BiFunction：

  1. private PlatformProducerConfig disableHostNameVerificationConfig(PlatformProducerConfig config) {
  2.   return disableHostNameVerificationConfig(
  3.       platformConfigurable,
  4.       (p, config) -> p.toBuilder().setAdditionalConfig(config).build());
  5. }
  7. private PlatformConsumerConfig disableHostNameVerificationConfig(PlatformConsumerConfig config) {
  8.   return disableHostNameVerificationConfig(
  9.       platformConfigurable,
  10.       (p, config) -> p.toBuilder().setAdditionalConfig(config).build());
  11. }

实际上，我认为更好的方法是不使用泛型或 lambda 表达式：编写一个方法来创建更新后的映射：

  1. private static Map<String, String> newConfig(PlatformConfigurable platformConfig) {
  2.   Map<String, String> additionalConfig = platformConfig.additionalProperties();
  3.   Map<String, String> newConfig = additionalConfig != null ? new HashMap<>(additionalConfig) : new HashMap<>();
  5.   newConfig.put(SslConfigs.SSL_ENDPOINT_IDENTIFICATION_ALGORITHM_CONFIG, "");
  6.   return newConfig;
  7. }

然后只需编写两个重载方法：

  1. private PlatformProducerConfig disableHostNameVerificationConfig(PlatformProducerConfig config) {
  2.   return config.toBuilder().setAdditionalConfig(newConfig(config)).build();
  3. } 
  5. private PlatformConsumerConfig disableHostNameVerificationConfig(PlatformConsumerConfig config) {
  6.   return config.toBuilder().setAdditionalConfig(newConfig(config)).build();
  7. }
英文:

Taking Alex Rudenko's answer a bit further, using generics:

  1. private &lt;P extends PlatformConfigurable&gt; P disableHostNameVerificationConfig(P platformConfig, BiFunction&lt;P, Map&lt;String, String&gt;, P&gt; appender) {
  2. Map&lt;String, String&gt; additionalConfig = platformConfig.additionalProperties();
  3. Map&lt;String, String&gt; newConfig = new HashMap&lt;&gt;(Optional.ofNullable(additionalConfig).orElseGet(ImmutableMap::of));
  4. newConfig.put(SslConfigs.SSL_ENDPOINT_IDENTIFICATION_ALGORITHM_CONFIG, &quot;&quot;);
  5. return appender.apply(platformConfig, newConfig);
  6. }

This assumes that it is safe to do this for any subtype of PlatformConfigurable (and PlatformConfigurable itself).

Then invoke like:

  1. disableHostNameVerificationConfig(
  2. platformProducerConfig,
  3. (p, config) -&gt; p.toBuilder().setAdditionalConfig(config).build());
  4. disableHostNameVerificationConfig(
  5. platformConsumerConfig,
  6. (p, config) -&gt; p.toBuilder().setAdditionalConfig(config).build());

If you like, create helper methods to hide the BiFunctions:

  1. private PlatformProducerConfig disableHostNameVerificationConfig(PlatformProducerConfig config) {
  2. return disableHostNameVerificationConfig(
  3. platformConfigurable,
  4. (p, config) -&gt; p.toBuilder().setAdditionalConfig(config).build());
  5. }
  6. private PlatformConsumerConfig disableHostNameVerificationConfig(PlatformConsumerConfig config) {
  7. return disableHostNameVerificationConfig(
  8. platformConfigurable,
  9. (p, config) -&gt; p.toBuilder().setAdditionalConfig(config).build());
  10. }

Actually, I think a better way to do it would be without generics or lambdas: write a method which creates an updated map:

  1. private static Map&lt;String, String&gt; newConfig(PlatformConfigurable platformConfig) {
  2. Map&lt;String, String&gt; additionalConfig = platformConfig.additionalProperties();
  3. Map&lt;String, String&gt; newConfig = additionalConfig != null ? new HashMap&lt;&gt;(additionalConfig) : new HashMap&lt;&gt;();
  4. newConfig.put(SslConfigs.SSL_ENDPOINT_IDENTIFICATION_ALGORITHM_CONFIG, &quot;&quot;);
  5. return newConfig;
  6. }

and then just have two overloads:

  1. private PlatformProducerConfig disableHostNameVerificationConfig(PlatformProducerConfig config) {
  2. return config.toBuilder().setAdditionalConfig(newConfig(config)).build();
  3. } 
  4. private PlatformConsumerConfig disableHostNameVerificationConfig(PlatformConsumerConfig config) {
  5. return config.toBuilder().setAdditionalConfig(newConfig(config)).build();
  6. }

答案3

得分: 1

  1. // 添加在Alex Rudenko的回答中的一点，并创建不同函数以添加不同接口的实现。
  3. private PlatformConfigurable disableHostNameVerificationConfig(PlatformConfigurable platformConfig) {
  4.     if ((platformConfig == null)) {
  5.         return platformConfig;
  6.     }
  8.     Map<String, String> additionalConfig = platformConfig.additionalProperties();
  9.     Map<String, String> newConfig = new HashMap<>(Optional.ofNullable(additionalConfig).orElseGet(ImmutableMap::of));
  10.     newConfig.put(SslConfigs.SSL_ENDPOINT_IDENTIFICATION_ALGORITHM_CONFIG, "");
  11.     return PlatformConfigurableObject(platformConfig, newConfig);
  12. }
  14. // 因此，您可以在不同的方法中处理所有实例，以后只需更改此方法即可添加后续的PlatformXCofing类。单一责任原则。
  16. private PlatformConfigurable PlatformConfigurableObject(PlatformConfigurable platformConfig, Map<String, String> newConfig) {
  17.     if (platformConfig instanceof PlatformProducerConfig) {
  18.         return ((PlatformProducerConfig) platformConfig).toBuilder().additionalProperties(newConfig).build();
  19.     } else if (platformConfig instanceof PlatformConsumerConfig) {
  20.         return ((PlatformConsumerConfig) platformConfig).toBuilder().additionalProperties(newConfig).build();
  21.     } else {
  22.         return platformConfig;
  23.     }
  24. }
英文:

Adding one thing in Alex Rudenko's answer, and making different function to add different implementations of interfaces.

  1. private PlatformConfigurable disableHostNameVerificationConfig(PlatformConfigurable platformConfig) {
  2.     if ((platformConfig == null)) {
  3.         return platformConfig;
  4.     }
  6.     Map&lt;String, String&gt; additionalConfig = platformConfig.additionalProperties();
  7.     Map&lt;String, String&gt; newConfig = new HashMap&lt;&gt;(Optional.ofNullable(additionalConfig).orElseGet(ImmutableMap::of));
  8.     newConfig.put(SslConfigs.SSL_ENDPOINT_IDENTIFICATION_ALGORITHM_CONFIG, &quot;&quot;);
  9.     return PlatformConfigurableObject(platformConfig, newConfig);
  10. }

So you can handle all instances in a different method, and whenever PlatfromXCofing classes are added later you only have to change this method. Single Responsibility Principle.

  1. private PlatformConfigurable PlatformConfigurableObject(PlatformConfigurable platformConfig, Map&lt;String, String&gt; newConfig){
  2.     if (platformConfig instanceof PlatformProducerConfig) {
  3.         return ((PlatformProducerConfig)platformConfig).toBuilder().additionalProperties(newConfig).build();
  4.     } else if (platformConfig instanceof PlatformConsumerConfig){
  5.         return ((PlatformConsumerConfig)platformConfig).toBuilder().additionalProperties(newConfig).build();
  6.     } else{
  7.     return platformConfig;
  8.     }
  9. }

huangapple
  • 本文由 发表于 2020年5月29日 23:57:21
  • 转载请务必保留本文链接：https://go.coder-hub.com/62089984.html
  • generics
  • java
  • java-8
  • lambda
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