Java Logger, Spring Logging, LogStash

•  Package
• java.util.logging.*
• Instance
• private final static Logger logger = Logger.getLogger(Demo.class.getName())
• Print to concole
  
• logger.log(Level.WARNING, "too close to 0");
• Print to File
• FileHandler logFile = new FileHandler("c:\test.txt");
  logFile.setFormatter(new SimpleFormatter());
  Logger.addHandler(logFile);
  

Log Handlers

• ConsoleHandler: Writing to console
  
• StreamHandler: Writing to Stream
  
• FileHandler: Writing to Files
  
• SocketHandler: Writing to TCP port
  
• MemoryHandler: Writing to Memory buffers

 Formatters

• SimpleFormatter
• XMLFormatter - default one
• This shows date, millis, sequence, logger, level, class, method, thread, message

Log Settings

• logging.properties  in ..\jdk\jre\lib
• handlers property
• .level
• formatter
• 
  

 Spring

• Debugging vs Troubleshooting 
• Spring boot starter web has the logging packages. Hence, no specific maven entry required.
  
• Levels of logging
• Error, Warn, Info, Debug, Trace
• Default logging level Info
• Usage in code
  
• Logger logger = LoggerFactory.getLogger("MyClass.class");
• Logger logger = LoggerFactory.getLogger(getClass());
• logger.error("");
• logger.warn("");
• logger.info("");
• logger.debug("");
• logger.trace("");
• Message printed as
• Date Time LogLevel ClassName Message
• Default log level is Info
• Change the default log level
• logging.level.root = debug
• logging.level.<package name>=trace
• logging.level.<fully qualified Class>=trace
• Log to file
• logging.file.name =app.log
• logging.file.max-size=10M

https://www.youtube.com/watch?v=vZQMoY_2_AA

https://www.javainuse.com/spring/springboot-microservice-elk

https://www.youtube.com/watch?v=5s9pR9UUtAU

Logstash

• bin/logstash -e "input { stdin { } } output { stdout { } }"
• bin/logstash -f config/pipelines/pipeline.conf --config.reload.automatic
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