a snapshot of the content of the Exchange at any given node it passed in the route
When used Camel will by default log the snapshot at INFO level. This example demonstrates how to persist trace snapshots using JPA into a database. This allows you to store this information and query them from a SQL prompt, giving you full power to analyze the data.
This requires Camel 2.0, the camel-jpa component and configuration of the target database.
Camel uses the org.apache.camel.processor.interceptor.JpaTraceEventMessage JPA @Entity as data model.
This class has been enhanced with JPA annotations.
The class has the following properties in the JPA model:
Primary key that is generated by the database
Timestamp when the snapshot was generated. Is the system time of the JMV in which Camel is running
the URI of the starting consumer the Exchange was created (usually a from in the route).
id of the previous step in the route. Is null if there wasn't a previous node such as the start.
In this example we use Hibernate JPA and a HSQLDB as database.
Running the example
The README.txt states how to run the example from either ANT or Maven.
Here we show running with Maven:
When the application starts it start:
in the console
a GUI for browsing the SQL database
Select the console where the application should prompt you to enter some words. Try entering: Camel
The application should respond with a text quote.
You can also enter multiple quotes separate with space, and the response should be the best quote based on the list of words given.
See the file src/main/resources/META-INF/spring/camel-context.xml to give you an idea how it works.
You can enter: Camel Beer and it should be smart enough to find a quote for the beer
Seeing the trace events
When the program was started a GUI application was started as well. Its a SQL prompt for the database. So try entering:
select * from camel_messagetraced
And it should return the list of trace events in the SQL.
We enter this sql: select id, shortExchangeId, previousNode, toNode, body from camel_messagetraced and get the output as the picture below:
The diagram below illustrates the route diagram generated using Visualisation.
We receive an Exchange from the in stream, then its split using the splitWords method. Then the quote method is invoked before its aggregated and finally sent to the stream out to be printed in the console.
If we look at the 6 rows from the traced SQL and with the route diagram in mind we can get a better understand how the Exchange was routed.
1. The Exchange does not have a previousNode so its the first step where its consumed from the input stream and that its going to the splitter.
2. The exchange id has changed and this is the output of the splitter as it creates a new Exchange. We can also see this one has one word in the body. This Exchange is being routed to the quote bean next.
3. This is the 2nd output from the splitter containing the 2nd word. This Exchange is being routed to the quote bean next.
4. This is the Beer Exchange where we can see the output from the quote server and that its being routed to the aggregator.
5. This is the Camel Exchange where we can see the output from the quote server and that its being routed to the aggregator.
6. This is the result of the aggregator where the Exchange ending with id 0-2 "was the winner" and is being routed as the aggregated result to the stream out.