ConfigTransformer (kafka 2.8.1 API)

java.lang.Object
- org.apache.kafka.common.config.ConfigTransformer

```
public class ConfigTransformer
extends Object
```
This class wraps a set of ConfigProvider instances and uses them to perform transformations.
The default variable pattern is of the form ${provider:[path:]key}, where the provider corresponds to a ConfigProvider instance, as passed to ConfigTransformer(Map). The pattern will extract a set of paths (which are optional) and keys and then pass them to ConfigProvider.get(String, Set) to obtain the values with which to replace the variables.
For example, if a Map consisting of an entry with a provider name "file" and provider instance FileConfigProvider is passed to the ConfigTransformer(Map), and a Properties file with contents
```
 fileKey=someValue
 
```
resides at the path "/tmp/properties.txt", then when a configuration Map which has an entry with a key "someKey" and a value "${file:/tmp/properties.txt:fileKey}" is passed to the transform(Map) method, then the transformed Map will have an entry with key "someKey" and a value "someValue".
This class only depends on ConfigProvider.get(String, Set) and does not depend on subscription support in a ConfigProvider, such as the ConfigProvider.subscribe(String, Set, ConfigChangeCallback) and ConfigProvider.unsubscribe(String, Set, ConfigChangeCallback) methods.

Field Summary

Fields
Modifier and Type Field Description

static Pattern DEFAULT_PATTERN

Constructor Summary

Constructors
Constructor	Description
`ConfigTransformer(Map<String,ConfigProvider> configProviders)`	Creates a ConfigTransformer with the default pattern, of the form `${provider:[path:]key}`.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`ConfigTransformerResult`	`transform(Map<String,String> configs)`	Transforms the given configuration data by using the `ConfigProvider` instances to look up values to replace the variables in the pattern.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - DEFAULT_PATTERN
```
public static final Pattern DEFAULT_PATTERN
```
- Constructor Detail
  - ConfigTransformer
```
public ConfigTransformer(Map<String,ConfigProvider> configProviders)
```
    Creates a ConfigTransformer with the default pattern, of the form ${provider:[path:]key}.
    
    Parameters:
    
    configProviders - a Map of provider names and ConfigProvider instances.
- Method Detail
  - transform
```
public ConfigTransformerResult transform(Map<String,String> configs)
```
    Transforms the given configuration data by using the ConfigProvider instances to look up values to replace the variables in the pattern.
    
    Parameters:
    
    configs - the configuration values to be transformed
    
    Returns:
    
    an instance of ConfigTransformerResult