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    Java Util Logging (JUL) integration

    Java Util Logging integration is provided as part of the artifact:

    <dependency>
  <groupId>io.yupiik.logging</groupId>
  <artifactId>yupiik-logging-jul</artifactId>
  <version>${yupiik-logging.version}</version>
</dependency>

    Use globally

    java .... -Djava.util.logging.manager=io.yupiik.logging.jul.YupiikLogManager ...

    Configuration

    Configuration is close to default JUL one with small differences:

    1. handlers don’t need to configure themselves in their constructor or so for common properties (formatter, level, …​), the framework does it automatically

    2. InlineFormatter and JsonFormatter support aliases (reflection free instantiation) with inline and json you can use in the configuration

    Standard handler

    io.yupiik.logging.jul.handler.StandardHandler enables to log on stdout and stderr. For all level from finest/debug to info it will go on stdout and others (warnings, errors/severes) will go on stderr.

    It can be configured with the std or standard alias too.

    There is also its companion stdout or io.yupiik.logging.jul.handler.StdoutHandler which only outputs on stdout.

    File Handler

    A io.yupiik.logging.jul.handler.LocalFileHandler is also provided to be able to log in a file and rotate the log file. Indeed you can use JVM FileHandler but this one is a bit more powerful in practise if you don’t run in a container and can’t use a docker logging driver or equivalent.

    Here is its configuration - all are prefixed with io.yupiik.logging.jul.handler.LocalFileHandler. and the standard configuration (encoding, level, …​) is still supported even if not listed.

    Name Default Value Description

    filenamePattern

    ${application.base}/logs/logs.%s.%03d.log

    where log files are created, it uses String.format() and gives you the date and file number - in this order. If you replace %s by %sH you will append the hour in the filename. %sHm adds the minutes (a more precise pattern is not needed nor recommended).

    noRotation

    false

    if true, once a log file is opened, it is kept for the life of the process.

    overwrite

    false

    if true, existing files are reused.

    truncateIfExists

    false

    if true, opening a file is not in append mode (previous content is erased).

    limit

    10 Megabytes

    limit size indicating the file should be rotated - in long format

    dateCheckInterval

    5 seconds

    how often the date should be computed to rotate the file (don’t do it each time for performances reason, means you can get few records of next day in a file name with current day). In java Duration format (ex: PT5S).

    bufferSize

    -1

    if positive the in memory buffer used to store data before flushing them to the disk (in bytes)

    archiveDirectory

    ${application.base}/logs/archives/

    where compressed logs are put.

    archiveFormat

    gzip

    zip or gzip.

    archiveOlderThan

    -1

    how many days files are kept before being compressed

    purgeOlderThan

    -1

    how many days files are kept before being deleted, note: it applies on archives and not log files so 2 days of archiving and 3 days of purge makes it deleted after 5 days.

    compressionLevel

    -1

    In case of zip archiving the zip compression level (-1 for off or 0-9).

    maxArchives

    -1

    Max number of archives (zip/gzip) to keep, ignored if negative (you can review io.yupiik.logging.jul.handler.LocalFileHandlerTest.purgeMaxArchive for some sample configuration).

    Pattern formatter

    The library also provides a pattern formatter. It does not use String.format as SimpleFormatter does and can be configured either with io.yupiik.logging.jul.formatter.PatternFormatter.pattern property or passing the pattern to the formatter alias (reflection free mode): pattern(<pattern to use>). Its syntax uses % to mark elements of the log record. Here is the list:

    Name Description

    %%

    Escapes % character.

    %n

    End of line.

    %l or %level

    Log record level.

    %m or %message

    Log record message.

    %c or %logger

    Logger name.

    %C or %class

    Class name if exists or empty.

    %M or %method

    Method name if exists or empty.

    %d or %date

    The instant value. Note it can be followed by a date time formatter pattern between braces.

    %x or %exception

    The exception. It will be preceeded by a new line if existing to ensure it integrates well in log output.

    %T or %threadId

    Thread ID.

    %t or %thread or %threadName

    Thread name - only works in synchronous mode.

    %r

    Duration (in ms) since the startup of the application (creating of the pattern formatter actually).

    %uuid

    Random UUID.

    Pattern example value: %d [%l][%c][%C][%M] %m%x%n, it will output lines like 1970-01-01T00:00:00Z [INFO][the.logger][the.source][the.method] test message\n.

    JSON formatter

    JSON formatter relies on JSON-B until 1.0.2, JSON-P starting with 1.0.3 and no dependency starting with 1.0.8 so ensure to add the related dependencies. It can be done with this list for example:

    <dependency>
  <groupId>org.apache.geronimo.specs</groupId>
  <artifactId>geronimo-json_1.1_spec</artifactId>
  <version>1.5</version>
</dependency>
<dependency>
  <groupId>org.apache.johnzon</groupId>
  <artifactId>johnzon-core</artifactId>
  <version>1.2.19</version>
</dependency>
    Tip
    		 the JSON formatter can be configured passing json(useUUID=[false|true],formatMessage=[true|false],customEntriesMapper=<fqn of a Function<LogRecord, Map<String, String>>>) value instead of just json. All configuration being optional. formatMessage enables to skip the message formatting when your application does not rely on it - faster and uses less the CPU, useUUID enables to force an unique ID in the record. customEntriesMapper enables to pass a function taking the log record and converting it to a map of data to append to the json object (must be String key/values).

    Sample Configuration Files

    As with native JUL LogManager, you can configure the runtime logging with the following system property: -Djava.util.logging.config.file=<path to config file>.

    Note
    		 don’t forget -Djava.util.logging.manager=io.yupiik.logging.jul.YupiikLogManager too.

    Here is a sample configuration switching to JSON logging:

    .handlers = io.yupiik.logging.jul.handler.StandardHandler
io.yupiik.logging.jul.handler.StandardHandler.formatter = json

    The same configuration for a standard inline logging (text style) but tuning the log level:

    .handlers = io.yupiik.logging.jul.handler.StandardHandler
io.yupiik.logging.jul.handler.StandardHandler.level = FINEST
com.app.level = FINEST

    Here is a configuration using a pattern:

    .handlers = standard
standard.formatter = pattern(%d [%l][%c][%C][%M] %m%x%n)

    And finally a configuration using file output instead of standard one:

    .handlers = file
file.formatter = inline
    Tip
    		 you can set all properties as system properties and also environment variables (in uppercase and dots replaced by underscores).

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