Fix: Resolve Thymeleaf 3.1.4+ TemplateProcessingException in variables.css (Issue #5251) by EIHEI2 · Pull Request #5264 · codecentric/spring-boot-admin

EIHEI2 · 2026-04-15T02:04:57Z

Description

This PR fixes the TemplateProcessingException that occurs with Thymeleaf 3.1.4.RELEASE when processing the variables.css template.

Problem

Thymeleaf 3.1.4+ introduced stricter security restrictions that forbid bean references (@cssColorUtils) in CSS templates, causing the following error:

Solution

Added a model attribute to that pre-computes RGB values from the theme palette
Updated template to use the pre-computed map instead of calling directly
Added bean configuration for better compatibility

Changes

: Added dependency and model attribute method
: Updated template expressions to use instead of bean method calls
: Added bean configuration

Testing

The fix avoids bean references in the template while maintaining the same functionality. The RGB values are computed once per request in the controller instead of per-variable in the template.

Fixes #5251

…estriction - Add cssColors model attribute to UiController with pre-computed RGB values - Update variables.css template to use cssColors instead of @cssColorUtils bean reference - Add SpringStandardDialect bean configuration for compatibility This fixes the TemplateProcessingException caused by Thymeleaf 3.1.4.RELEASE which forbids bean references (@cssColorUtils) in CSS templates.

cdprete · 2026-04-15T12:12:01Z

+	@ModelAttribute(value = "cssColors", binding = false)
+	public Map<String, String> getCssColors() {
+		var palette = uiSettings.getTheme().getPalette();
+		return Map.of(


Given that the values here come from the configuration, I would personally just compute this map once in the constructor when the controller is created and just reuse that value every time the endpoint gets called.

That's just a small optimisation :)

As the properties may be changed at runtime (via Spring Boot Admin's Properties UI + Spring Cloud mechanisms), i tend to have it in a method instead of a constructor.

Ah ok. I was not aware of this possibility.
Makes sense then.

SteKoe · 2026-04-17T07:04:25Z

-	public UiController(String publicUrl, UiExtensions uiExtensions, Settings uiSettings) {
+	private final CssColorUtils cssColorUtils;
+
+	public UiController(String publicUrl, UiExtensions uiExtensions, Settings uiSettings, CssColorUtils cssColorUtils) {


Since you have extended/changed the controller constructor, check all parts where this is used. I guess that at least the tests are broken.

@EIHEI2

Error: Failed to execute goal io.spring.javaformat:spring-javaformat-maven-plugin:0.0.47:validate (default) on project spring-boot-admin-server-ui: Formatting violations found in the following files:
Error: * /home/runner/work/spring-boot-admin/spring-boot-admin/spring-boot-admin-server-ui/src/main/java/de/codecentric/boot/admin/server/ui/web/UiController.java

I try to build this PR locally ... compile error:

./mvnw clean install -DskipTests -Dspring-javaformat.skip=true

INFO] ------------------------------------------------------------- [INFO] ------------------------------------------------------------- [ERROR] COMPILATION ERROR : [INFO] ------------------------------------------------------------- [ERROR] /D:/Dev/git/privat/spring-boot-admin/spring-boot-admin-server-ui/src/main/java/de/codecentric/boot/admin/server/ui/config/AdminServerUiAutoConfiguration.java:[135,24] constructor UiController in class de.codecentric.boot.admin.server.ui.web.UiController cannot be applied to given types; required: java.lang.String,de.codecentric.boot.admin.server.ui.extensions.UiExtensions,de.codecentric.boot.admin.server.ui.web.UiController.Settings,de.codecentric.boot.admin.server.ui.config.CssColorUtils found: java.lang.String,de.codecentric.boot.admin.server.ui.extensions.UiExtensions,de.codecentric.boot.admin.server.ui.web.UiController.Settings reason: actual and formal argument lists differ in length [INFO] 1 error [INFO] ------------------------------------------------------------- [INFO] ------------------------------------------------------------------------ [INFO] Reactor Summary for Spring Boot Admin 4.1.0-SNAPSHOT: [INFO] [INFO] Spring Boot Admin .................................. SUCCESS [ 4.128 s] [INFO] Spring Boot Admin Dependencies ..................... SUCCESS [ 0.292 s] [INFO] Spring Boot Admin Build ............................ SUCCESS [ 0.453 s] [INFO] Spring Boot Admin Server ........................... SUCCESS [01:18 min] [INFO] Spring Boot Admin Server UI ........................ FAILURE [02:41 min] [INFO] Spring Boot Admin Client ........................... SKIPPED [INFO] Spring Boot Admin Docs ............................. SKIPPED [INFO] Spring Boot Admin Server Cloud ..................... SKIPPED [INFO] Spring Boot Admin Server Starter ................... SKIPPED [INFO] Spring Boot Admin Client Starter ................... SKIPPED [INFO] Spring Boot Admin Samples .......................... SKIPPED [INFO] Spring Boot Admin Server custom UI ................. SKIPPED [INFO] Spring Boot Admin Sample Servlet ................... SKIPPED [INFO] Spring Boot Admin Sample Reactive .................. SKIPPED [INFO] Spring Boot Admin Sample War ....................... SKIPPED [INFO] Spring Boot Admin Sample Hazelcast ................. SKIPPED [INFO] Spring Boot Admin Sample Eureka .................... SKIPPED [INFO] Spring Boot Admin Sample Consul .................... SKIPPED [INFO] Spring Boot Admin Sample Zookeeper ................. SKIPPED [INFO] ------------------------------------------------------------------------ [INFO] BUILD FAILURE [INFO] ------------------------------------------------------------------------ [INFO] Total time: 04:05 min [INFO] Finished at: 2026-04-20T11:08:36+02:00 [INFO] ------------------------------------------------------------------------ [ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.15.0:compile (default-compile) on project spring-boot-admin-server-ui: Compilation failure [ERROR] /D:/Dev/git/privat/spring-boot-admin/spring-boot-admin-server-ui/src/main/java/de/codecentric/boot/admin/server/ui/config/AdminServerUiAutoConfiguration.java:[135,24] constructor UiController in class de.codecentric.boot.admin.server.ui.web.UiController cannot be applied to given types; [ERROR] required: java.lang.String,de.codecentric.boot.admin.server.ui.extensions.UiExtensions,de.codecentric.boot.admin.server.ui.web.UiController.Settings,de.codecentric.boot.admin.server.ui.config.CssColorUtils [ERROR] found: java.lang.String,de.codecentric.boot.admin.server.ui.extensions.UiExtensions,de.codecentric.boot.admin.server.ui.web.UiController.Settings [ERROR] reason: actual and formal argument lists differ in length [ERROR] [ERROR] -> [Help 1] [ERROR] [ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch. [ERROR] Re-run Maven using the -X switch to enable full debug logging. [ERROR] [ERROR] For more information about the errors and possible solutions, please read the following articles: [ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException [ERROR] [ERROR] After correcting the problems, you can resume the build with the command [ERROR] mvn <args> -rf :spring-boot-admin-server-ui AD001+hoehmann@dinmPF5F7PQ0 • 2026-04-20 • 11:08 • MINGW64 /d/Dev/git/privat/spring-boot-admin (fix-issue-47) •

Indeed the expectations from @SteKoe were correct then.

@ahoehma the bean is already registered in the context.
Therefore, for the sake of testing, you can just add it as parameter in https://github.com/codecentric/spring-boot-admin/blob/master/spring-boot-admin-server-ui/src/main/java/de/codecentric/boot/admin/server/ui/config/AdminServerUiAutoConfiguration.java#L100 and then pass that parameter to https://github.com/codecentric/spring-boot-admin/blob/master/spring-boot-admin-server-ui/src/main/java/de/codecentric/boot/admin/server/ui/config/AdminServerUiAutoConfiguration.java#L127.

Moreover, I would suggest you to run it with -Dmaven.test.skip=true instead of -DskipTests so that Maven doesn't even try to compile the tests (which maybe would fail as well).

I fixed the few compile errors by myself ... now I try to include the 4.1.0-SNAPSHOT into my project ... keep you informed asap :-)

Hmmm ... I'm using the snapshot now ... build is fine ... startup also fine .. but then when I try to open sba ...

2026-04-20 12:42:12 [ http-nio-9090-exec-9] ERROR - [] - org.apache.catalina.core.ContainerBase.[Tomcat].[localhost].[/].[dispatcherServlet]:170 - Servlet.service() for servlet [dispatcherServlet] threw exception org.thymeleaf.exceptions.ConfigurationException: Conflicting execution attribute. Two or more dialects specify an execution attribute with the same name "StandardExpressionParser". at org.thymeleaf.DialectSetConfiguration.build(DialectSetConfiguration.java:268) at org.thymeleaf.EngineConfiguration.<init>(EngineConfiguration.java:123) at org.thymeleaf.TemplateEngine.initialize(TemplateEngine.java:341) at org.thymeleaf.TemplateEngine.getConfiguration(TemplateEngine.java:411) at org.thymeleaf.spring6.view.ThymeleafView.renderFragment(ThymeleafView.java:265) at org.thymeleaf.spring6.view.ThymeleafView.render(ThymeleafView.java:193) at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1305) at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1042) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:980) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:866) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1000) at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:892) at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:622) at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:874) at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:710) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:128) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:107)

Can you please try removing the spring standard dialect bean which was added in the PR?
I suspect there is already one coming from Spring Boot itself, therefore now Thymeleaf doesn't know which one to use.

Yep. Now its up and running - CSS issues gone! 👍

fix-issue-47-followup.patch

cdprete · 2026-04-17T19:07:40Z

@EIHEI2 please fix as well your commit message since it's referencing another PR (i.e.: #47) instead of your issue.

cdprete · 2026-04-20T12:50:13Z

@SteKoe given we're getting no fixes here, I've collected and applied all the findings (plus more) in #5285 instead.
/cc @ahoehma maybe you can test that one shortly too. Just to be doubly sure ;)

ahoehma · 2026-04-20T13:27:11Z

@SteKoe given we're getting no fixes here, I've collected and applied all the findings (plus more) in #5285 instead. /cc @ahoehma maybe you can test that one shortly too. Just to be doubly sure ;)

Branch: fix/5251

[INFO] --- checkstyle:3.6.0:check (checkstyle-validation) @ spring-boot-admin-server-ui ---
[INFO] Beginne PrÃ¼fung...
[ERROR] D:\Dev\git\privat\spring-boot-admin\spring-boot-admin-server-ui\src\test\java\de\codecentric\boot\admin\server\ui\web\UiControllerTest.java:28:1: Wrong order for 'de.codecentric.boot.admin.server.ui.config.AdminServerUiProperties' import. [SpringImportOrder]
PrÃ¼fung beendet.
[INFO] There is 1 error reported by Checkstyle 12.3.1 with src/checkstyle/checkstyle.xml ruleset.
[ERROR] src\test\java\de\codecentric\boot\admin\server\ui\web\UiControllerTest.java:[28,1] (extension) SpringImportOrder: Wrong order for 'de.codecentric.boot.admin.server.ui.config.AdminServerUiProperties' import.

./mvnw clean install -DskipTests -Dspring-javaformat.skip=true -Dcheckstyle.skip=true

Green ... and inside my app the CSS still fixed 👍

cdprete · 2026-04-20T14:00:48Z

@SteKoe given we're getting no fixes here, I've collected and applied all the findings (plus more) in #5285 instead. /cc @ahoehma maybe you can test that one shortly too. Just to be doubly sure ;)

Branch: fix/5251
[INFO] --- checkstyle:3.6.0:check (checkstyle-validation) @ spring-boot-admin-server-ui ---
[INFO] Beginne PrÃ¼fung...
[ERROR] D:\Dev\git\privat\spring-boot-admin\spring-boot-admin-server-ui\src\test\java\de\codecentric\boot\admin\server\ui\web\UiControllerTest.java:28:1: Wrong order for 'de.codecentric.boot.admin.server.ui.config.AdminServerUiProperties' import. [SpringImportOrder]
PrÃ¼fung beendet.
[INFO] There is 1 error reported by Checkstyle 12.3.1 with src/checkstyle/checkstyle.xml ruleset.
[ERROR] src\test\java\de\codecentric\boot\admin\server\ui\web\UiControllerTest.java:[28,1] (extension) SpringImportOrder: Wrong order for 'de.codecentric.boot.admin.server.ui.config.AdminServerUiProperties' import.
./mvnw clean install -DskipTests -Dspring-javaformat.skip=true -Dcheckstyle.skip=true

Green ... and inside my app the CSS still fixed 👍

Thanks for checking it, @ahoehma.
I've fixed the checkstyle violation(s) in the meantime and the build passes.
So, now it's up to @SteKoe and the team to decide how to proceed.

SteKoe · 2026-04-20T14:42:53Z

Hey there, thanks for your hard work! That's much appreciated! I will close this PR as it is superseeded by the new PR created by you, @cdprete.

EIHEI2 requested a review from a team as a code owner April 15, 2026 02:04

cdprete reviewed Apr 15, 2026

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SteKoe requested changes Apr 17, 2026

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This was referenced Apr 19, 2026

org.thymeleaf.exceptions.TemplateProcessingException in variables.css #5251

Closed

fix(#5251): expose the colors configured in the settings directly rather then calling a method which is not allowed from Thymeleaf 3.1.4 #5285

Merged

SteKoe closed this Apr 20, 2026

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EIHEI2 commented Apr 15, 2026

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