The less high-tech and most popular of all debugging techniques is to use log statements to follow the evolution of an application’s state. In Mule, the state you’re interested in resides in the messages that are flowing through your configuration and, possibly, custom code.
If you’re running your Mule configuration from Eclipse, the log outputs are visible right in Eclipse console window. If you’re running Mule from the command line, the logs are visible in your OS console.
Mule’s standalone logging configuration is stored in <Mule Installation Directory>/conf/log4j2.xml: edit this file if you need to change the verbosity of the log output.
Note: If you are using Anypoint Studio, the log output appears in the
.mule directory of your Studio workspace. For example on a Mac, for an application called
Basic Tutorial, the log output is in this file:
The Logger component is a quick and easy way to log the payload of an in-flight message. Add it anywhere in a message flow you want to probe your message:
1 2 3 4 5 6 7 <flow name="FlowWithLoggers"> <http:listener config-ref="HTTP_Listener_Configuration1" path="hello" doc:name="HTTP"/> <logger level="INFO" doc:name="Logger-before"/> <base64-encoder-transformer/> <logger level="INFO" doc:name="Logger-after"/> <vm:outbound-endpoint path="next.in.line" /> </flow>
If you need more details about the message, a simple scripted logging component like the following can come handy:
1 2 3 <scripting:script name="Logger" engine="groovy"> <scripting:text>log.info(message); log.info(payload); message</scripting:text> </scripting:script>
You can reference the script component from anywhere in your flow(s) using the name you give it, in thise case "Logger":
1 2 3 4 5 6 7 <flow name="FlowWithLoggers"> <http:listener config-ref="HTTP_Listener_Configuration1" path="hello" doc:name="HTTP"/> <scripting:component script-ref="Logger" /> <base64-encoder-transformer/> <scripting:component script-ref="Logger" /> <vm:outbound-endpoint path="next.in.line" /> </flow>
You can configure what gets logged, where it gets logged, and how by editing a configuration file from your Studio project or in a folder in your standalone Mule server’s
$MULE_HOME directory. For instructions on how to modify the file, see Logging in Mule.
For more on how to use the Logger component in Studio, see Logger Component Reference