Log - 6.3

Talend ESB Mediation Developer Guide

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6.3
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Design and Development
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Talend ESB

How can I log processing a Message ?

Camel provides many ways to log processing a message. Here is just some examples:

The log DSL allows you to use Simple language to construct a dynamic message which gets logged. For example you can do

from("direct:start").log("Processing ${id}").
   to("bean:foo");

Which will construct a String message at runtime using the Simple language. The log message will by logged at INFO level using the route id as the log name. By default a route is named route-1, route-2 etc. But you can use the routeId("myCoolRoute") to set a route name of choice.

Important

What is the difference between log in the DSL and Log component? The log DSL is much lighter and meant for logging human logs such as Starting to do ... and so on. It can only log a message based on the Simple language. On the other hand Camel Component: Log component is a full fledged component which involves using endpoints and etc. The Camel Component: Log component is meant for logging the Message itself and you have many URI options to control what you would like to be logged.

Important

As of Camel 2.12.4/2.13.1, if no logger name or logger instance is passed to log DSL, there's a Registry lookup performed to find single instance of org.slf4j.Logger. If such instance is found, it is used instead of creating a new logger instance. If more instances are found, the behavior defaults to creating a new instance of logger.

Important

If the message body is stream based, then logging the message body, may cause the message body to be empty afterwards. See this FAQ. For streamed messages you can use Stream caching to allow logging the message body and be able to read the message body afterwards again.

The log DSL have overloaded methods to set the logging level and/or name as well.

from("direct:start").log(LoggingLevel.DEBUG, "Processing ${id}").
    to("bean:foo");

and to set a logger name

from("direct:start").log(LoggingLevel.DEBUG, "com.mycompany.MyCoolRoute", 
"Processing ${id}").to("bean:foo");

Since Camel 2.12.4/2.13.1 the logger instance may be used as well:

from("direct:start").log(LoggingLeven.DEBUG, 
org.slf4j.LoggerFactory.getLogger("com.mycompany.mylogger"), "Processing 
${id}").to("bean:foo");

For example you can use this to log the file name being processed if you consume files.

from("file://target/files").log(LoggingLevel.DEBUG, 
   "Processing file ${file:name}").to("bean:foo");

Using log DSL from Spring

In Spring DSL it is also easy to use log DSL as shown below:

<route id="foo">
   <from uri="direct:foo"/>
   <log message="Got ${body}"/>
   <to uri="mock:foo"/>
</route>

The log tag has attributes to set the message, loggingLevel and logName. For example:

<route id="baz">
   <from uri="direct:baz"/>
   <log message="Me Got ${body}" loggingLevel="FATAL" 
   logName="com.mycompany.MyCoolRoute"/>
   <to uri="mock:baz"/>
</route>

Since Camel 2.12.4/2.13.1 it is possible to reference logger instance. For example:

<bean id="myLogger" class="org.slf4j.LoggerFactory" 
factory-method="getLogger" xmlns="http://www.springframework.org/schema/beans">
    <constructor-arg value="com.mycompany.mylogger" />
</bean>
 
<route id="moo" xmlns="http://camel.apache.org/schema/spring">
    <from uri="direct:moo"/>
    <log message="Me Got ${body}" loggingLevel="INFO" loggerRef="myLogger"/>
    <to uri="mock:baz"/>
</route>

Using slf4j Marker

You can specify a marker name in the DSL:

<route id="baz">
   <from uri="direct:baz"/>
   <log message="Received ${body}" loggingLevel="FATAL" 
   logName="com.mycompany.MyCoolRoute" 
       marker="myMarker"/>
   <to uri="mock:baz"/>
</route>

Using log DSL in OSGi

Improvement as of Camel 2.12.4/2.13.1

When using log DSL inside OSGi (e.g., in Karaf), the underlying logging mechanisms are provided by PAX logging. It searches for a bundle which invokes org.slf4j.LoggerFactory.getLogger() method and associates the bundle with the logger instance. Passing only logger name to log DSL results in associating camel-core bundle with the logger instance created.

In some scenarios it is required that the bundle associated with logger should be the bundle which contains route definition. This is possible using provided logger instance both for Java DSL and Spring DSL (see the examples above).