Log formatting configuration in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the log pattern to include timestamp and log level.

Spring Boot

logging.pattern.console=[1]

Drag options to blanks, or click blank then click option'

A%logger{36} - %msg%n

B%msg%n

C%d{yyyy-MM-dd HH:mm:ss} %-5level - %msg%n

D%thread %msg%n

Attempts:

3 left

💡 Hint

Common Mistakes

Using only %msg%n without timestamp or level

Forgetting to include the newline %n at the end

The pattern %d{yyyy-MM-dd HH:mm:ss} %-5level - %msg%n includes the timestamp and log level in the log output.

2fill in blank

medium

Complete the code to configure the log pattern to show thread name and logger name.

Spring Boot

logging.pattern.console=[1]

Drag options to blanks, or click blank then click option'

A%level %msg%n

B%thread %logger - %msg%n

C%msg%n

D%d{HH:mm:ss} [%thread] %-5level %logger{36} - %msg%n

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the thread name

Not limiting logger name length with {36}

The pattern %d{HH:mm:ss} [%thread] %-5level %logger{36} - %msg%n shows time, thread, level, logger name, and message.

3fill in blank

hard

Fix the error in the log pattern to correctly display the log level padded to 5 characters.

Spring Boot

logging.pattern.console=%d{HH:mm:ss} [1] - %msg%n

Drag options to blanks, or click blank then click option'

A%-5level

B%level

C%5level

D%lev

Attempts:

3 left

💡 Hint

Common Mistakes

Using %level without padding

Using %lev which is invalid

The correct syntax to pad the log level to 5 characters is %-5level.

4fill in blank

hard

Fill the blanks to create a log pattern that shows date, thread, log level, and message.

Spring Boot

logging.pattern.console=[1] [2] [3] - %msg%n

Drag options to blanks, or click blank then click option'

A%d{yyyy-MM-dd HH:mm:ss}

B%thread

C%-5level

D%logger

Attempts:

3 left

💡 Hint

Common Mistakes

Putting log level before date

Omitting thread name

The pattern starts with date %d{yyyy-MM-dd HH:mm:ss} and thread name %thread, followed by level and message.

5fill in blank

hard

Fill all three blanks to create a log pattern with logger name, log level, and message.

Spring Boot

logging.pattern.console=%d{HH:mm:ss} [[1]] [2] - [3]%n

Drag options to blanks, or click blank then click option'

A%logger{36}.toUpperCase()

B%-5level

C%msg

D%logger{36}

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to use Java methods like toUpperCase() in pattern

Omitting the message placeholder

The correct pattern uses %logger{36} for logger name, %-5level for padded log level, and %msg for the message.

Note: Spring Boot's default pattern does not support toUpperCase() directly.

Practice

1. What is the purpose of configuring log formatting in a Spring Boot application?

easy

A. To disable logging completely

B. To increase the size of log files automatically

C. To make logs easier to read and understand by customizing their appearance

D. To encrypt log messages for security

Solution

1. Step 1: Understand the role of log formatting

   Log formatting controls how log messages appear, making them clearer and easier to read.

2. Step 2: Identify the main goal of formatting

   The main goal is to customize the log output for better readability, not to disable or encrypt logs.

3. Final Answer:

   To make logs easier to read and understand by customizing their appearance -> Option C

4. Quick Check:

   Log formatting = Customize log appearance [OK]

Hint: Log formatting improves readability, not disables logging [OK]

Common Mistakes:

• Thinking log formatting disables logs
• Confusing formatting with log encryption
• Assuming formatting increases log file size

2. Which of the following is the correct way to set a simple console log pattern in application.properties?

easy

A. console.logging.pattern=%date %level %logger %message

B. logging.pattern.console=%d{HH:mm:ss} %-5level %logger{36} - %msg%n

C. logging.console.pattern=%d{HH:mm:ss} %level %logger - %msg

D. logging.pattern=%d %level %logger %msg

Solution

1. Step 1: Identify the correct property key for console log pattern

   The correct key is logging.pattern.console in Spring Boot.

2. Step 2: Check the pattern syntax

   The pattern uses placeholders like %d for date, %-5level for log level, %logger{36} for logger name, and %msg for message, ending with %n for newline.

3. Final Answer:

   logging.pattern.console=%d{HH:mm:ss} %-5level %logger{36} - %msg%n -> Option B

4. Quick Check:

   Correct property and pattern syntax = logging.pattern.console=%d{HH:mm:ss} %-5level %logger{36} - %msg%n [OK]

Hint: Use logging.pattern.console for console logs in application.properties [OK]

Common Mistakes:

• Using wrong property keys like logging.console.pattern
• Missing newline %n at the end
• Incorrect placeholder syntax

3. Given this configuration in application.properties:

logging.pattern.console=%d{yyyy-MM-dd HH:mm:ss} [%thread] %-5level %logger{10} - %msg%n

What will be the output format of a log message?

medium

A. 2024-06-01 14:30:00 [main] INFO MyApp - Application started

B. [main] 2024-06-01 14:30:00 INFO MyApp - Application started

C. INFO 2024-06-01 14:30:00 [main] MyApp - Application started

D. MyApp INFO [main] 2024-06-01 14:30:00 - Application started

Solution

1. Step 1: Analyze the pattern placeholders

   %d{yyyy-MM-dd HH:mm:ss} prints date/time, [%thread] prints thread in brackets, %-5level prints log level left-aligned in 5 spaces, %logger{10} prints logger name truncated to 10 chars, %msg prints the message, %n adds newline.

2. Step 2: Match the pattern to the output options

   2024-06-01 14:30:00 [main] INFO MyApp - Application started matches the exact order and format: date, thread in brackets, level padded, logger, dash, message.

3. Final Answer:

   2024-06-01 14:30:00 [main] INFO MyApp - Application started -> Option A

4. Quick Check:

   Pattern placeholders = Output format [OK]

Hint: Match placeholders order exactly to output format [OK]

Common Mistakes:

• Mixing order of thread and date
• Ignoring padding in log level
• Confusing logger truncation

4. You set this in application.properties:

logging.pattern.file=%d{HH:mm:ss} %level %logger - %msg%n

But your log file shows no timestamps. What is the likely cause?

medium

A. The timestamp format %d{HH:mm:ss} is invalid and causes logs to skip it

B. The pattern uses %level instead of %-5level, causing timestamp omission

C. The property key should be logging.pattern.file instead of logging.pattern.file

D. The logging system ignores the pattern if the file appender is not configured properly

Solution

1. Step 1: Verify property key correctness

   The property key logging.pattern.file is correct for file log pattern in Spring Boot.

2. Step 2: Consider logging system configuration

   If the file appender is not properly set up, the pattern may be ignored, causing missing timestamps.

3. Final Answer:

   The logging system ignores the pattern if the file appender is not configured properly -> Option D

4. Quick Check:

   File appender config missing = pattern ignored [OK]

Hint: Check file appender setup if pattern changes don't appear [OK]

Common Mistakes:

• Assuming %level causes timestamp issues
• Thinking property key is wrong
• Believing timestamp format is invalid

5. You want to configure your Spring Boot app to log to both console and file with different formats. Which configuration snippet correctly sets a detailed file log pattern and a simple console pattern?

hard

A. logging.pattern.console=%d{HH:mm:ss} %-5level %msg%n
logging.pattern.file=%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n

B. logging.pattern.console=%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger - %msg%n
logging.pattern.file=%d{HH:mm:ss} %-5level %msg%n

C. logging.pattern.console=%msg%n
logging.pattern.file=%msg%n

D. logging.console.pattern=%d{HH:mm:ss} %level %msg
logging.file.pattern=%d{yyyy-MM-dd} %level %logger %msg

Solution

1. Step 1: Identify correct property keys for console and file patterns

   Spring Boot uses logging.pattern.console and logging.pattern.file keys.

2. Step 2: Check pattern details for console and file

   Console pattern is simple with time, level, and message. File pattern is detailed with full timestamp, thread, level, logger, and message.

3. Step 3: Match options to correct keys and patterns

   logging.pattern.console=%d{HH:mm:ss} %-5level %msg%n logging.pattern.file=%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n correctly sets simple console and detailed file patterns with proper keys and placeholders.

4. Final Answer:

   logging.pattern.console=%d{HH:mm:ss} %-5level %msg%n logging.pattern.file=%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n -> Option A

5. Quick Check:

   Correct keys and patterns for console and file = logging.pattern.console=%d{HH:mm:ss} %-5level %msg%n logging.pattern.file=%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n [OK]

Hint: Use logging.pattern.console and logging.pattern.file keys for different formats [OK]

Common Mistakes:

• Swapping console and file property keys
• Using incorrect property keys like logging.console.pattern
• Using overly simple patterns for file logs