Improve performance of ContainerProperties and ConsumerProperties toString() methods using StringBuilder #4013

cwangg897 · 2025-07-24T05:08:33Z

Improve toString() performance with StringBuilder

This commit improves the performance of toString() methods in
ContainerProperties and ConsumerProperties classes by replacing
string concatenations with StringBuilder usage.

Motivation:
The ContainerProperties.toString() method is frequently used in
Spring Boot applications for debugging Kafka container configuration
issues. With 40+ properties being concatenated using the + operator,
the original implementation created excessive temporary String
objects, leading to:

Memory allocation overhead
Performance degradation in logging-heavy scenarios
Increased GC pressure

Changes:

ContainerProperties:

Replaced string concatenation with StringBuilder in toString()
method
Added helper methods for consistent formatting:
- appendProperty(): for regular non-null properties
- appendEnabledProperty(): for properties with "enabled/not enabled"
  formatting
Improved organization with logical property grouping and
descriptive comments
Enhanced maintainability through reduced code duplication

ConsumerProperties:

Updated renderProperties() method to use StringBuilder instead of
string concatenations
Modified renderTopics() to accept StringBuilder parameter for
efficiency
Applied ContainerProperties improvements

Performance Impact:

Reduced memory allocations during toString() operations
Improved performance in logging-heavy scenarios
Better scalability for applications with frequent container
configuration logging

Backward Compatibility:

No breaking changes
Output format unchanged
All existing functionality preserved

Resolves: #4012

Signed-off-by: Choi Wang Gyu dhkdrb897@gmail.com

artembilan

Please, add your name to the @author list of the affected classes.
I wonder if your English name could be added to the commit message, like you have mentioned in the PR description:

Signed-off-by: [Choi Wang Gyu] [dhkdrb897@gmail.com](mailto:dhkdrb897@gmail.com)

I also believe in the power of the commit message.
The PR is going to be lost eventually, but commit with stay in the history.
Therefore I anticipate to move all of your PR description to the final commit.

More info about commit importance here: https://cbea.ms/git-commit/

I also think that it is safe to back-port your change to the previous version.

Thank you so far!

artembilan · 2025-07-25T14:54:40Z

spring-kafka/src/main/java/org/springframework/kafka/listener/ContainerProperties.java

+
+	/**
+	 * Append an optional property only if it's not null.
+	 *


No blank lines in JavaDocs, please.

artembilan · 2025-07-25T14:55:42Z

spring-kafka/src/main/java/org/springframework/kafka/listener/ContainerProperties.java

+	 * @param name  the property name
+	 * @param value the property value (nullable)
+	 */
+	private void appendOptionalProperty(StringBuilder sb, String name, @Nullable Object value) {


I don't think we need separate methods for the logic.
Just one appendProperty() with @Nullable Object value and that if is enough.

artembilan · 2025-07-28T14:16:19Z

spring-kafka/src/main/java/org/springframework/kafka/listener/ContainerProperties.java

+	 * @param name  the property name
+	 * @param value the property value
+	 */
+	private void appendProperty(StringBuilder sb, String name, Object value) {


Well, actually my last review has asked to keep only one method, but have that value as @Nullable and perform not null check exactly in this method.
This way that toString() would be much simpler, without all those if.

That's a good idea. I misunderstood it at first, but thank you — I've applied the change now.

This commit improves the performance of toString() methods in ContainerProperties and ConsumerProperties classes by replacing string concatenations with StringBuilder usage. Motivation: The ContainerProperties.toString() method is frequently used in Spring Boot applications for debugging Kafka container configuration issues. With 40+ properties being concatenated using the + operator, the original implementation created excessive temporary String objects, leading to: - Memory allocation overhead - Performance degradation in logging-heavy scenarios - Increased GC pressure Changes: ContainerProperties: - Replaced string concatenation with StringBuilder in toString() method - Added helper methods for consistent formatting: - appendProperty(): for regular non-null properties - appendEnabledProperty(): for properties with "enabled/not enabled" formatting - Improved organization with logical property grouping and descriptive comments - Enhanced maintainability through reduced code duplication ConsumerProperties: - Updated renderProperties() method to use StringBuilder instead of string concatenations - Modified renderTopics() to accept StringBuilder parameter for efficiency - Applied ContainerProperties improvements Performance Impact: - Reduced memory allocations during toString() operations - Improved performance in logging-heavy scenarios - Better scalability for applications with frequent container configuration logging Backward Compatibility: - No breaking changes - Output format unchanged - All existing functionality preserved Resolves: spring-projects#4012 Signed-off-by: Choi Wang Gyu <dhkdrb897@gmail.com>

artembilan · 2025-07-28T14:25:14Z

You don't need to squash commits all the time.
It is better to preserve history for review traceability.
We will squash them on merge then.
Thanks

artembilan · 2025-07-28T14:29:42Z

spring-kafka/src/main/java/org/springframework/kafka/listener/ContainerProperties.java

+	 * @param value the property value
+	 */
+	private void appendProperty(StringBuilder sb, String name, @Nullable Object value) {
+		sb.append("\n ").append(name).append("=").append(value);


Thanks, but why no if(value!=null) any more?

mistake sorry

Still not resolved.

artembilan

 Error: eckstyle] [ERROR] /home/runner/work/spring-kafka/spring-kafka/spring-kafka/src/main/java/org/springframework/kafka/listener/ContainerProperties.java:1200:9: '/*' has more than 1 empty lines before. [EmptyLineSeparator]
Error: eckstyle] [ERROR] /home/runner/work/spring-kafka/spring-kafka/spring-kafka/src/main/java/org/springframework/kafka/listener/ConsumerProperties.java:517: Line matches the illegal pattern 'Trailing whitespace'. [Regexp]
Error: eckstyle] [ERROR] /home/runner/work/spring-kafka/spring-kafka/spring-kafka/src/main/java/org/springframework/kafka/listener/ConsumerProperties.java:533: Line matches the illegal pattern 'Trailing whitespace'. [Regexp]
Error: eckstyle] [ERROR] /home/runner/work/spring-kafka/spring-kafka/spring-kafka/src/main/java/org/springframework/kafka/listener/ConsumerProperties.java:535: Line matches the illegal pattern 'Trailing whitespace'. [Regexp]
Error: eckstyle] [ERROR] /home/runner/work/spring-kafka/spring-kafka/spring-kafka/src/main/java/org/springframework/kafka/listener/ConsumerProperties.java:542: Line matches the illegal pattern 'Trailing whitespace'. [Regexp]

Please, consider to run ./greadlew check locally before pushing to PR.
Thanks

artembilan · 2025-07-28T15:00:18Z

spring-kafka/src/main/java/org/springframework/kafka/listener/ContainerProperties.java

+	 * @param value the property value
+	 */
+	private void appendProperty(StringBuilder sb, String name, @Nullable Object value) {
+		sb.append("\n ").append(name).append("=").append(value);


Still not resolved.

Omit properties with null values from the toString() output by updating the appendProperty method. This improves readability and avoids clutter in logs by excluding unset configuration fields. Signed-off-by: Choi Wang Gyu <dhkdrb897@gmail.com>

artembilan · 2025-07-28T15:07:43Z

spring-kafka/src/main/java/org/springframework/kafka/listener/ContainerProperties.java

@@ -1193,7 +1192,9 @@ public String toString() {
 	 * @param value the property value
 	 */
 	private void appendProperty(StringBuilder sb, String name, @Nullable Object value) {
-		sb.append("\n ").append(name).append("=").append(value);
+		if(value != null){


Looks like you have not run check locally.
This is not a code style we follow.
See if you can apply src/idea/spring-framework.xml into your IntelliJ IDEA for our Spring-specific code style.

Sorry, I saw your comment after opening the PR.
I'll fix it locally and push the update soon.
Please wait a moment. Thank you!

@artembilan
I'm sorry for keeping you waiting.
This is my first time contributing to open source, so I was a bit clumsy.
Thanks to your help, I was able to resolve the issue and learned a lot.
If there's anything else I should fix, please feel free to let me know.
I really appreciate your time and guidance. Thank you!

No problem! All good.
We do have this guidance, though: https://github.com/spring-projects/spring-kafka/blob/main/CONTRIBUTING.adoc.

Please, let us know if that is good enough to make your contribution routine smooth.
I do see that we need to mention that src/idea/spring-framework.xml code style config over there.
Plus, we don't need to update Copyright anymore 😄 .

But who knows what else causes headache for you but we can help to avoid it with some simple improvement to the process.
Thank you!

Reformatted ContainerProperties.java to comply with the project's Spring-specific IntelliJ code style configuration. This ensures consistency and passes local style checks. Signed-off-by: Choi Wang Gyu <dhkdrb897@gmail.com>

Removed trailing spaces from lines 517, 533, 535, 542, and 546 in ConsumerProperties.java. This change ensures that `./gradlew check` passes successfully, addressing the reviewer's request for code style compliance. Signed-off-by: Choi Wang Gyu <dhkdrb897@gmail.com>

cwangg897 mentioned this pull request Jul 25, 2025

Performance: Optimize toString() methods with StringBuilder #4012

Closed

cwangg897 force-pushed the refactor-containerproperties-tostring branch from 45a6782 to d1e9c6f Compare July 25, 2025 09:12

artembilan requested changes Jul 25, 2025

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cwangg897 force-pushed the refactor-containerproperties-tostring branch from d1e9c6f to 505b828 Compare July 26, 2025 06:36

cwangg897 changed the base branch from main to 3.3.x July 28, 2025 08:32

cwangg897 changed the base branch from 3.3.x to main July 28, 2025 08:34

artembilan requested changes Jul 28, 2025

View reviewed changes

cwangg897 force-pushed the refactor-containerproperties-tostring branch from 505b828 to 797da20 Compare July 28, 2025 14:23

artembilan requested changes Jul 28, 2025

View reviewed changes

Skip null fields in toString() output

9e6c926

Omit properties with null values from the toString() output by updating the appendProperty method. This improves readability and avoids clutter in logs by excluding unset configuration fields. Signed-off-by: Choi Wang Gyu <dhkdrb897@gmail.com>

artembilan requested changes Jul 28, 2025

View reviewed changes

cwangg897 added 2 commits July 29, 2025 00:14

Apply Spring code style using spring-framework.xml

d81bdbb

Reformatted ContainerProperties.java to comply with the project's Spring-specific IntelliJ code style configuration. This ensures consistency and passes local style checks. Signed-off-by: Choi Wang Gyu <dhkdrb897@gmail.com>

artembilan enabled auto-merge (squash) July 28, 2025 15:44

artembilan merged commit 08985a3 into spring-projects:main Jul 28, 2025
3 checks passed

Improve performance of ContainerProperties and ConsumerProperties toString() methods using StringBuilder #4013

Improve performance of ContainerProperties and ConsumerProperties toString() methods using StringBuilder #4013

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cwangg897 commented Jul 24, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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artembilan commented Jul 28, 2025

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cwangg897 commented Jul 24, 2025 •

edited

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