CrowdforGeeks | Build Skills with Online Courses from Top Institutions

Top 100+ Log4j Interview Questions And Answers

Question 1. What Is Log4j?

Answer :

log4j is a reliable, rapid and flexible logging framework (APIs) written in Java, which is distributed below the Apache Software License.

Log4j has been ported to the C, C++, C#, Perl, Python, Ruby, and Eiffel languages.

Log4j is exceptionally configurable via external configuration documents at runtime. It views the logging technique in terms of degrees of priorities and gives mechanisms to direct logging statistics to a terrific kind of locations, such as a database, file, console, UNIX Syslog, and so forth.

Question 2. What Are The Components Of Log4j?

Answer :

log4j has 3 most important additives −

loggers: Responsible for shooting logging records.
Appenders: Responsible for publishing logging records to various desired locations.
Layouts: Responsible for formatting logging statistics in specific styles.
HTML Interview Questions
Question three. What Are The Features Of Log4j?

Answer :

Following are capabilities of log4j −

It is thread-safe.
It is optimized for speed.
It is based totally on a named logger hierarchy.
It supports multiple output appenders in step with logger.
It supports internationalization.
It isn't always restricted to a predefined set of centers.
Logging behavior may be set at runtime the use of a configuration document.
It is designed to address Java Exceptions from the begin.
It uses multiple levels, particularly ALL, TRACE, DEBUG, INFO, WARN, ERROR and FATAL.
The layout of the log output may be without difficulty changed by way of extending the Layout class.
The target of the log output as well as the writing method may be altered by using implementations of the Appender interface.
It is fail-prevent. However, even though it virtually strives to make certain delivery, log4j does no longer assure that every log statement could be brought to its vacation spot.
Question four. What Are Pros And Cons Of Logging?

Answer :

Following are the Pros and Cons of Logging −

Logging is an vital factor of the software improvement. A nicely-written logging code offers quick debugging, smooth maintenance, and based garage of an utility's runtime facts.
Logging does have its drawbacks also. It can sluggish down an application. If too verbose, it could cause scrolling blindness. To alleviate those issues, log4j is designed to be reliable, fast and extensible.
Since logging is hardly ever the principle cognizance of an application, the log4j API strives to be simple to understand and to use.
HTML Tutorial
Question five. What Is The Purpose Of Logger Object?

Answer :

Logger Object − The top-degree layer of log4j architecture is the Logger which gives the Logger object. The Logger item is chargeable for capturing logging data and they're saved in a namespace hierarchy.

HTML five Interview Questions
Question 6. What Is The Purpose Of Layout Object?

Answer :

Layout Object − The layout layer of log4j architecture presents objects that are used to format logging statistics in distinct styles. It gives guide to appender items before publishing logging data.

Layout objects play an important role in publishing logging statistics in a way that is human-readable and reusable.

Question 7. What Is The Purpose Of Appender Object?

Answer :

Appender Object − This is a lower-stage layer of log4j architecture which provides Appender objects. The Appender object is answerable for publishing logging data to numerous favored destinations which include a database, record, console, UNIX Syslog, and so on.

HTML five Tutorial AJAX Interview Questions
Question 8. What Is The Purpose Of Level Object?

Answer :

Level Object - The Level object defines the granularity and priority of any logging information. There are seven ranges of logging defined inside the API: OFF, DEBUG, INFO, ERROR, WARN, FATAL, and ALL.

Question nine. What Is The Purpose Of Filter Object?

Answer :

Filter Object − The Filter object is used to investigate logging data and make in addition decisions on whether that facts ought to be logged or not. An Appender objects will have several Filter gadgets related to them. If logging records is handed to a specific Appender object, all of the Filter gadgets associated with that Appender want to approve the logging statistics earlier than it can be published to the connected vacation spot.

JSP Interview Questions
Question 10. What Is The Purpose Of Objectrenderer Object?

Answer :

ObjectRenderer − The ObjectRenderer item is specialised in providing a String representation of various objects passed to the logging framework. This item is used by Layout items to prepare the very last logging records.

AJAX Tutorial
Question eleven. What Is The Purpose Of Logmanager Object?

Answer :

LogManager − The LogManager object manages the logging framework. It is accountable for studying the initial configuration parameters from a gadget-extensive configuration document or a configuration magnificence.

Quark Xpress Interview Questions
Question 12. What Is The Use Of Log4j.Residences?

Answer :

The log4j.Houses file is a log4j configuration file which continues properties in key-fee pairs. By default, the LogManager appears for a report named log4j.Properties inside the CLASSPATH.

HTML Interview Questions
Question thirteen. What Is The Purpose Of Layout Object In Appender?

Answer :

layout − Appender uses the Layout objects and the conversion sample related to them to layout the logging facts.

JSP Tutorial
Question 14. What Is The Purpose Of Target In Appender?

Answer :

goal − The goal may be a console, a record, or every other object depending on the appender.

Question 15. What Is The Purpose Of Level In Appender?

Answer :

level − The degree is needed to control the filtration of the log messages.

JavaMail API Interview Questions
Question 16. What Is The Purpose Of Threshold In Appender?

Answer :

threshold − Appender will have a threshold stage associated with it unbiased of the logger level. The Appender ignores any logging messages that have a level decrease than the brink degree.

JavaMail API Tutorial
Question 17. What Is The Purpose Of Filter In Appender?

Answer :

filter out − The Filter objects can analyze logging information past stage matching and determine whether logging requests ought to be dealt with through a specific Appender or overlooked.

JUnit Interview Questions
Question 18. How Will You Define A Root Logger With Appender File Using Log4j.Properties?

Answer :

Following syntax defines the basis logger with appender report:

# Define the root logger with appender report
log = /usr/domestic/log4j
log4j.RootLogger = DEBUG, FILE

HTML five Interview Questions
Question 19. How Will You Define A File Appender Using Log4j.Residences?

Answer :

Following syntax defines a file appender −

# Define the file appender
log4j.Appender.FILE=org.Apache.Log4j.FileAppender
log4j.Appender.FILE.File=$log/log.Out

JUnit Tutorial
Question 20. How Will You Define The Layout Of File Appender Using Log4j.Properties?

Answer :

Following syntax defines the layout of document appender −

# Define the format for document appender
log4j.Appender.FILE.Format=org.Apache.Log4j.PatternLayout
log4j.Appender.FILE.Format.ConversionPattern=%m%n

Eclipse (software program) Interview Questions
Question 21. How Will You Create A Logger In Any Class?

Answer :

Any other named Logger object example is received via the second one approach by way of passing the name of the logger. The name of the logger can be any string you may bypass, generally a class or a package deal call as we have used in the remaining bankruptcy and it's far referred to under −

static Logger log = Logger.GetLogger(log4jExample.Magnificence.GetName());

Question 22. How Will You Print A Log Message In Debug Mode?

Answer :

public void debug(Object message) of Logger class prints messages with the level Level.DEBUG.

Apache Ant Tutorial
Question 23. How Will You Print A Log Message In Error Mode?

Answer :

public void mistakes(Object message) of Logger elegance prints messages with the level Level.ERROR.

Apache Ant Interview Questions
Question 24. How Will You Print A Log Message In Fatal Mode?

Answer :

public void deadly(Object message) of Logger elegance prints messages with the extent Level.FATAL.

AJAX Interview Questions
Question 25. How Will You Print A Log Message In Info Mode?

Answer :

public void info(Object message) of Logger class prints messages with the extent Level.INFO.

Spring MVC Framework Tutorial
Question 26. How Will You Print A Log Message In Warn Mode?

Answer :

public void warn(Object message) of Logger magnificence prints messages with the extent Level.WARN.

Spring MVC Framework Interview Questions
Question 27. How Will You Print A Log Message In Trace Mode?

Answer :

public void trace(Object message) of Logger class prints messages with the level Level.TRACE.

JSP Interview Questions
Question 28. What Is Purpose Of All Log Level?

Answer :

ALL − All ranges such as custom levels.

JAVA Persistence API (JPA) Tutorial
Question 29. What Is Purpose Of Debug Log Level?

Answer :

DEBUG − Designates satisfactory-grained informational activities which can be maximum beneficial to debug an software.

Structural Analysis Interview Questions
Question 30. What Is Purpose Of Error Log Level?

Answer :

ERROR − Designates error occasions that would nevertheless allow the utility to keep running.

Question 31. What Is Purpose Of Fatal Log Level?

Answer :

FATAL − Designates very excessive blunders activities on the way to presumably lead the application to abort.

Question 32. What Is Purpose Of Info Log Level?

Answer :

INFO − Designates informational messages that highlight the progress of the application at coarse-grained level.

Question 33. What Is Purpose Of Off Log Level?

Answer :

OFF − The maximum viable rank and is supposed to turn off logging.

Quark Xpress Interview Questions
Question 34. What Is Purpose Of Trace Log Level?

Answer :

TRACE − Designates finer-grained informational events than the DEBUG.

Question 35. What Is Purpose Of Warn Log Level?

Answer :

WARN − Designates potentially harmful conditions.

Question 36. How Do Levels Works?

Answer :

A log request of degree p in a logger with degree q is enabled if p >= q. This rule is on the heart of log4j. It assumes that levels are ordered. For the same old stages, we have ALL < DEBUG < INFO < WARN < ERROR < FATAL < OFF.

JavaMail API Interview Questions
Question 37. How Will You Define A Root Logger Turning Debug Mode Off?

Answer :

Following syntax defines the basis logger with WARN mode turning DEBUG mode off.

# Define the basis logger with appender file
log = /usr/domestic/log4j
log4j.RootLogger = WARN, FILE

Question 38. What Is The Purpose Of Patternlayout Object?

Answer :

If you want to generate your logging records in a specific layout based on a sample, then you may use org.Apache.Log4j.PatternLayout to format your logging information.

The PatternLayout magnificence extends the summary org.Apache.Log4j.Layout class and overrides the format() method to structure the logging statistics according to a furnished sample.

Question 39. What Is The Purpose Of C Character Used In The Conversionpattern Of Patternlayout Object?

Answer :

c − Used to output the class of the logging occasion. For example, for the category name "a.B.C" the pattern %c2 will output "b.C".

Question forty. What Is The Purpose Of C Character Used In The Conversionpattern Of Patternlayout Object ?

Answer :

C − Used to output the completely certified magnificence call of the caller issuing the logging request. For instance, for the class name. "org.Apache.Xyz.SomeClass", the pattern %C1 will output "SomeClass".

JUnit Interview Questions
Question forty one. What Is The Purpose Of D Character Used In The Conversionpattern Of Patternlayout Object?

Answer :

d − Used to output the date of the logging occasion. For instance, %dHH:mm:ss,SSS or %ddd MMM yyyy HH:mm:ss,SSS.

Question forty two. What Is The Purpose Of F Character Used In The Conversionpattern Of Patternlayout Object?

Answer :

F − Used to output the file name wherein the logging request was issued.

Eclipse (software) Interview Questions
Question 43. What Is The Purpose Of L Character Used In The Conversionpattern Of Patternlayout Object?

Answer :

l − Used to output location facts of the caller which generated the logging occasion.

Question 44. What Is The Purpose Of L Character Used In The Conversionpattern Of Patternlayout Object ?

Answer :

L − Used to output the line wide variety from wherein the logging request became issued.

Question 45. What Is The Purpose Of M Character Used In The Conversionpattern Of Patternlayout Object?

Answer :

m − Used to output the software furnished message related to the logging event.

Question 46. What Is The Purpose Of M Character Used In The Conversionpattern Of Patternlayout Object ?

Answer :

M − Used to output the method name wherein the logging request become issued.

Question 47. What Is The Purpose Of N Character Used In The Conversionpattern Of Patternlayout Object?

Answer :

n − Outputs the platform established line separator man or woman or characters.

Question forty eight. What Is The Purpose Of P Character Used In The Conversionpattern Of Patternlayout Object?

Answer :

p − Used to output the concern of the logging event.

Question 49. What Is The Purpose Of R Character Used In The Conversionpattern Of Patternlayout Object?

Answer :

r − Used to output the wide variety of milliseconds elapsed from the development of the format until the introduction of the logging event.

Question 50. What Is The Purpose Of T Character Used In The Conversionpattern Of Patternlayout Object?

Answer :

t − Used to output the name of the thread that generated the logging event.

Question 51. What Is The Purpose Of X Character Used In The Conversionpattern Of Patternlayout Object?

Answer :

x − Used to output the NDC (nested diagnostic context) related to the thread that generated the logging event.

Question fifty two. What Is The Purpose Of X Character Used In The Conversionpattern Of Patternlayout Object ?

Answer :

X − The X conversion man or woman is followed by way of the important thing for the MDC. For example, XclientIP will print the data saved in the MDC in opposition to the important thing clientIP.

Question fifty three. What Is The Purpose Of % Character Used In The Conversionpattern Of Patternlayout Object?

Answer :

% − The literal percentage sign. %% will print a % sign.

Question 54. What Are Format Modifiers?

Answer :

By default, the applicable facts is displayed as output as is. However, with the resource of format modifiers, it is viable to trade the minimum discipline width, the maximum subject width, and justification.

Question fifty five. What Is The Intent Of %20c Format Modifier?

Answer :

%20c − Left pad with spaces if the class call is much less than 20 characters lengthy.

Question fifty six. What Is The Intent Of %-20c Format Modifier?

Answer :

%-20c − Right pad with spaces if the category call is less than 20 characters lengthy.

Question 57. What Is The Intent Of %.30c Format Modifier?

Answer :

%.30c − Truncate from the start if the category call is longer than 30 characters.

Question 58. What Is The Intent Of %20.30c Format Modifier?

Answer :

%20.30c − Left pad with spaces if the category name is shorter than 20 characters. However, if the category call is longer than 30 characters, then truncate from the beginning.

Question fifty nine. What Is The Intent Of %-20.30c Format Modifier?

Answer :

%-20.30c − Right pad with spaces if the class name is shorter than 20 characters. However, if category name is longer than 30 characters, then truncate from the beginning.

Question 60. If You Want To Generate Your Logging Information In An Html-formatted File, How Will You Proceed?

Answer :

If you need to generate your logging statistics in an HTML-formatted record, then you could use org.Apache.Log4j.HTMLLayout to layout your logging facts.

The HTMLLayout class extends the abstract org.Apache.Log4j.Layout elegance and overrides the layout() technique from its base magnificence to offer HTML-fashion formatting.

Question sixty one. What Kind Of Information Htmllayout Class Provides?

Answer :

It affords the subsequent statistics to be displayed −

The time elapsed from the begin of the software before a selected logging occasion turned into generated.
The name of the thread that invoked the logging request.
The level related to this logging request.
The call of the logger and logging message.
The non-obligatory vicinity information for the program document and the line variety from which this logging was invoked.
Question sixty two. How Will You Set The Content Type Of Html Generated Using Htmllayout?

Answer :

HTMLLayout.SetContentType(String) − Sets the content material form of the HTML content. Default is text/html.

Question sixty three. How Will You Set The Location Information For The Logging Event Using Htmllayout?

Answer :

HTMLLayout.SetLocationInfo(String) − Sets the region information for the logging occasion. Default is fake.

Question 64. How Will You Set The Title Of Html Page Generated Using Htmllayout?

Answer :

HTMLLayout.SetTitle(String) − Sets the title for the HTML file. Default is log4j Log Messages.

Question sixty five. What Is The Purpose Of Immediateflush Configuration Of Fileappender?

Answer :

immediateFlush − This flag is by way of default set to authentic, which means the output circulation to the document being flushed with each append operation.

Question 66. What Is The Purpose Of Encoding Configuration Of Fileappender?

Answer :

encoding − It is feasible to use any individual-encoding. By default, it's miles the platform-precise encoding scheme.

Question sixty seven. What Is The Purpose Of Threshold Configuration Of Fileappender?

Answer :

threshold − The threshold stage for this appender.

Question 68. What Is The Purpose Of Filename Configuration Of Fileappender?

Answer :

Filename − The name of the log report.

Question sixty nine. What Is The Purpose Of Fileappend Configuration Of Fileappender?

Answer :

fileAppend − This is by using default set to genuine, this means that the logging information being appended to the give up of the identical record.

Question 70. What Is The Purpose Of Bufferedio Configuration Of Fileappender?

Answer :

bufferedIO − This flag indicates whether or not we want buffered writing enabled. By default, it's far set to false.

Question seventy one. What Is The Purpose Of Buffersize Configuration Of Fileappender?

Answer :

bufferSize − If buffered I/O is enabled, it suggests the buffer length. By default, it's far set to 8kb.

Question seventy two. How Will You Configure Immediate Flush To True Using Log4j.Houses?

Answer :

Following code configures instantaneous flush to authentic −

# Set the immediately flush to proper (default)
log4j.Appender.FILE.ImmediateFlush=authentic

Question seventy three. How Will You Set The Threshold To Debug Mode Using Log4j.Houses?

Answer :

Following code sets the threshold to debug mode −

# Set the threshold to debug mode
log4j.Appender.FILE.Threshold=debug

Question 74. How Will You Set The Append To False, Overwrite Using Log4j.Properties?

Answer :

Following code units the append to fake, overwrite −

# Set the append to fake, overwrite
log4j.Appender.FILE.Append=fake

Question seventy five. If You Want To Write Your Logging Information Into Multiple Files Then How Will You Proceed?

Answer :

To write your logging records into multiple files, you'll should use org.Apache.Log4j.RollingFileAppender class which extends the FileAppender class and inherits all its homes.

Question seventy six. What Is The Purpose Of Maxfilesize Property Of Rollingfileappender Class?

Answer :

This is the vital size of the document above which the file might be rolled.

Question 77. What Is Default Value Of Maxfilesize Property Of Rollingfileappender Class?

Answer :

Default fee is 10 MB.

Question seventy eight. What Is The Purpose Of Maxbackupindex Property Of Rollingfileappender Class?

Answer :

This belongings denotes the wide variety of backup files to be created.

Question seventy nine. What Is Default Value Of Maxbackupindex Property Of Rollingfileappender Class?

Answer :

Default cost is 1.

Question eighty. How Will You Configure A Rollingfileappender Using Log4j.Residences?

Answer :

Following code configures a RollingFileAppender −

# Define the root logger with appender document
log4j.RootLogger = DEBUG, FILE
# Define the document appender
log4j.Appender.FILE=org.Apache.Log4j.RollingFileAppender

Question eighty one. How Will You Configure Maximum File Size Before Rollover Using Log4j.Residences?

Answer :

Following code configures most document length earlier than rollover −

# Set the maximum file size earlier than rollover
log4j.Appender.FILE.MaxFileSize=5KB

Question 82. How Will You Configure Maximum Files To Be Used To Log Data Using Log4j.Residences?

Answer :

Following code configures most documents to be used −

# Set the the backup index
log4j.Appender.FILE.MaxBackupIndex=2

Question eighty three. What Happens If Logs Exceeding The Maximum Size While Using Rollingfileappender?

Answer :

A new log record may be created.

Question 84. What Happens If Last Log File Reaches The Maximum Size While Using Rollingfileappender?

Answer :

Once the remaining log document reaches the most size, the first log report can be erased and thereafter, all the logging information may be rolled returned to the first log report.

Question eighty five. How Will You Generate Your Log Files On A Daily Basis?

Answer :

To write your logging statistics into files on a day by day basis, you would have to use org.Apache.Log4j.DailyRollingFileAppender elegance which extends the FileAppender magnificence and inherits all its residences.

Question 86. What Is The Purpose Of Datepattern Property Of Dailyrollingfileappender Class?

Answer :

This suggests while to roll over the report and the naming convention to be followed. By default, roll over is carried out at nighttime every day.

Question 87. How Will You Configure Your Log To Roll Over At The End Of Each Month And At The Beginning Of The Next Month?

Answer :

'.' yyyy-MM − Roll over on the quit of each month and at the start of the next month.

Question 88. How Will You Configure Your Log To Roll Over At Midnight Each Day?

Answer :

'.' yyyy-MM-dd − Roll over at the hours of darkness each day. This is the default value.

Question 89. How Will You Configure Your Log To Roll Over At Midday And Midnight Of Each Day?

Answer :

'.' yyyy-MM-dd-a − Roll over at midday and middle of the night of each day.

Question ninety. How Will You Configure Your Log To Roll Over At The Top Of Every Hour?

Answer :

'.' yyyy-MM-dd-HH − Roll over on the top of every hour.

Question ninety one. How Will You Configure Your Log To Roll Over Every Minute?

Answer :

'.' yyyy-MM-dd-HH-mm − Roll over every minute.

Question ninety two. How Will You Configure Your Log To Roll Over On The First Day Of Each Week Depending Upon The Locale?

Answer :

'.' yyyy-ww − Roll over on the primary day of every week relying upon the locale.

Question 93. How Will You Configure A Dailyrollingfileappender Using Log4j.Homes?

Answer :

Following code configures a DailyRollingFileAppender −

# Define the root logger with appender record
log4j.RootLogger = DEBUG, FILE
# Define the file appender
log4j.Appender.FILE = org.Apache.Log4j.DailyRollingFileAppender

Question 94. How Will You Set The Datepattern Using Log4j.Homes?

Answer :

Following code configures a DatePattern −

# Set the DatePattern
log4j.Appender.FILE.DatePattern = '.' yyyy-MM-dd-a

Question ninety five. How Will You Put The Logs In Database Using Log4j?

Answer :

The log4j API offers the org.Apache.Log4j.Jdbc.JDBCAppender object, which can put logging data in a exact database.

Question ninety six. What Is The Purpose Of Driver Configuration Of Jdbcappender?

Answer :

motive force − Sets the driver elegance to the specified string. If no motive force elegance is exact, it defaults to sun.Jdbc.Odbc.JdbcOdbcDriver.

Question ninety seven. What Is The Purpose Of Password Configuration Of Jdbcappender?

Answer :