SimpleLogger.md

SimpleLogger

Contents

• How SimpleLogger works
  • Differences vs. System.out
  • Differences vs. Log4J
  • Logging method calls
• HowTos
• SimpleLogger.logToNothing()

How SimpleLogger works

Unlike many logging frameworks, SimpleLogger is a combination of static methods that allows you to log based on event type rather than event level. This means you can turn on and off specific types of events that may not be interesting for test purposes, rather than setting a verbosity level. For example, you could say, "Show me all the SQL statements" or "Show me all the method entries". Also, because SimpleLogger is tagging based on the event type, it has many convenience functions to properly format and call based on that format.

Differences vs. System.out

• Single point of control
  SimpleLogger puts a single place where you can collect all log statements. From here it is trivial to log to a file or string or both. SimpleLogger also allows you to easily turn off types of logging allowing you to control the signal-to-noise ratio.
• Convenience functions for metadata
  SimpleLogger adds formatting and class names making logs consistent and robust after changing method or class names. This helps with both the writing and the reading of the logs.
• Time stamps
  SimpleLogger automatically adds timestamps plus time differences to easily detected when a problem happened and where a performance bottleneck is

Differences vs. Log4J

• Don't need to hold on to logging objects
  The common patter for Log4J is that every class has a field named LOG This tends to clutter up your files. SimpleLogger does not do this, opting instead to make all of its calls static.
• Finer control over turning off noise
  Log4J will allow you to set a level of output. In practice, this usually means everything, or just warnings. SimpleLogger, instead, allows you to toggle individual event types. For example, the following would allow you to turn on only the queries and where they came from:

SimpleLogger.get().marker = true;
SimpleLogger.get().event = false;
SimpleLogger.get().variable = false;
SimpleLogger.get().query = true;

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• Can be used concurrently with SimpleLogger
  There is nothing that prevents using both simultaneously

Logging method calls

For example, here's how you would log entry and exit from a method:

public void methodThatLogs()
{
  try (Markers markers = SimpleLogger.useMarkers())
  {
    for (int i = 0; i < 3; i++)
    {
      innerMethod(i);
    }
  }
}
private void innerMethod(int i)
{
  try (Markers markers = SimpleLogger.useMarkers())
  {
    SimpleLogger.variable("i", i);
  }
}

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Will produce the following logs:

=> Sample.methodThatLogs() - IN
   => Sample.innerMethod() - IN
      Variable: i = '0'
   <= Sample.innerMethod() - OUT
   => Sample.innerMethod() - IN
      Variable: i = '1'
   <= Sample.innerMethod() - OUT
   => Sample.innerMethod() - IN
      Variable: i = '2'
   <= Sample.innerMethod() - OUT
<= Sample.methodThatLogs() - OUT

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HowTos

• How to capture logs for testing
• How to do performance profiling

SimpleLogger.logToNothing()

SimpleLogger is used to make approvaltesting easier, but approvalTests also uses it internally. Something these bleed out in the form of messages like

=> SimpleLoggerTest.test() - IN
   => SimpleLoggerTest.test() - IN
      Event: Starting Logging
      Variable: name = 'llewellyn'
      Sql: Select * from people
      .........1.........2.........3.........4..
      Variable: Numbers.length = 5
      Numbers[0] = 1
      Numbers[1] = 2
      Numbers[2] = 3
      Numbers[3] = 4
      Numbers[4] = 5
******************************************************************************************
      
java.lang.Error -  null
******************************************************************************************
   <= SimpleLoggerTest.test() - OUT
<= SimpleLoggerTest.test() - OUT

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if you want to turn them all off just run

SimpleLogger.logToNothing();

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