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