50 lines
1.6 KiB
Markdown
50 lines
1.6 KiB
Markdown
# Transformers
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A transfomer, as the name suggests, is a component which transforms a message.
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For example, a transformer could modify the body of a message or add or remove
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properties. Both [diverts](diverts.md) and [core bridges](core-bridges.md)
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support.
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A transformer is simply a class which implements the interface
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`org.apache.activemq.artemis.core.server.transformer.Transformer`:
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```java
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public interface Transformer {
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default void init(Map<String, String> properties) { }
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Message transform(Message message);
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}
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```
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The `init` method is called immediately after the broker instantiates the class.
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There is a default method implementation so implementing `init` is optional.
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However, if the transformer needs any configuration properties it should
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implement `init` and the broker will pass the configured key/value pairs to the
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transformer using a `java.util.Map`.
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## Configuration
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The most basic configuration requires only specifying the transformer's class
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name, e.g.:
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```xml
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<transformer-class-name>
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org.foo.MyTransformer
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</transformer-class-name>
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```
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However, if the transformer needs any configuration properties those can be
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specified using a slightly different syntax, e.g.:
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```xml
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<transformer>
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<class-name>org.foo.MyTransformerWithProperties</class-name>
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<property key="transformerKey1" value="transformerValue1"/>
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<property key="transformerKey2" value="transformerValue2"/>
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</transformer>
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```
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Any transformer implementation needs to be added to the broker's classpath. See
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the documentation on [adding runtime dependencies](using-server.md#adding-runtime-dependencies)
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to understand how to make your transformer available to the broker. |