com.kdgregory.log4j.aws

Class JsonLayout

java.lang.Object

org.apache.log4j.Layout

com.kdgregory.log4j.aws.JsonLayout

All Implemented Interfaces:

org.apache.log4j.spi.OptionHandler

public class JsonLayout
extends org.apache.log4j.Layout

Formats a LogMessage as a JSON string. This is useful when directing the output of the logger into a search engine such as ElasticSearch.

The JSON object will always contain the following properties, most of which are extracted from the Log4J LoggingEvent

• timestamp: the date/time that the message was logged.
• thread: the name of the thread where the message was logged.
• logger: the name of the logger.
• level: the level of this log message.
• message: the message itself.
• processId: the PID of the invoking process, if available (this is retrieved from RuntimeMxBean and may not be available on all platforms).

The following properties will only appear if they are present in the event:

• exception: the stack trace of an associated exception. This is exposed as an array of strings, with the first element being the location where the exception was caught.
• mdc: the mapped diagnostic context. This is a child map.
• ndc: the nested diagnostic context. This is a single string that contains each of the pushed entries separated by spaces (yes, that's how Log4J does it).

The following properties are potentially expensive to compute, so will only appear if specifically enabled via configuration:

• locationInfo: the location where the logger was called. This is a child object with the following components:
  • className
  • methodName
  • fileName
  • lineNumber
• instanceId: the EC2 instance ID of the machine where the logger is running. WARNING: do not enable this elsewhere, as the operation to retrieve this value may take a long time.
• hostname: the name of the machine where the logger is running, if available (this is currently retrieved from RuntimeMxBean and may not be available on all platforms).

Lastly, you can define a set of user tags, which are written as a child object with the key tags. These are intended to provide program-level information, in the case where multiple programs send their logs to the same stream. They are set as a single comma-separate string, which may contain substitution values (example: appName=Fribble,startedAt={startupTimestamp}).

WARNING: you should not rely on the order in which elements are output. Any apparent ordering is an implementation choice and subject to change without notice.

Field Summary

Fields inherited from class org.apache.log4j.Layout

LINE_SEP, LINE_SEP_LEN

Constructor Summary

Constructors

Constructor and Description
JsonLayout()

Method Summary

Modifier and Type	Method and Description
void	activateOptions()
String	format(org.apache.log4j.spi.LoggingEvent event)
boolean	getAppendNewlines()
boolean	getEnableHostname()
boolean	getEnableInstanceId()
boolean	getEnableLocation()
String	getTags()
boolean	ignoresThrowable()
void	setAppendNewlines(boolean value)
void	setEnableHostname(boolean value)
void	setEnableInstanceId(boolean value)
void	setEnableLocation(boolean value)
void	setTags(String value)

Methods inherited from class org.apache.log4j.Layout

getContentType, getFooter, getHeader

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

JsonLayout

public JsonLayout()

Method Detail

setAppendNewlines

public void setAppendNewlines(boolean value)

getAppendNewlines

public boolean getAppendNewlines()

setEnableLocation

public void setEnableLocation(boolean value)

getEnableLocation

public boolean getEnableLocation()

setEnableInstanceId

public void setEnableInstanceId(boolean value)

getEnableInstanceId

public boolean getEnableInstanceId()

setEnableHostname

public void setEnableHostname(boolean value)

getEnableHostname

public boolean getEnableHostname()

setTags

public void setTags(String value)

getTags

public String getTags()

activateOptions

public void activateOptions()

format

public String format(org.apache.log4j.spi.LoggingEvent event)

Specified by:

format in class org.apache.log4j.Layout

ignoresThrowable

public boolean ignoresThrowable()

Specified by:

ignoresThrowable in class org.apache.log4j.Layout