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refactor: log dynamic-theme initialization #144

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refactor: log dynamic-theme initialization #144

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49 changes: 41 additions & 8 deletions src/main/java/com/flowingcode/vaadin/addons/demo/DynamicThemeInitializer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,12 @@
import com.vaadin.flow.server.communication.IndexHtmlRequestListener;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.Enumeration;
import java.util.Optional;
import java.util.Properties;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
* Service initialization listener that automatically applies a dynamic theme.
Expand All @@ -19,23 +24,51 @@
@SuppressWarnings("serial")
public class DynamicThemeInitializer implements VaadinServiceInitListener {

private static final Logger logger = LoggerFactory.getLogger(DynamicThemeInitializer.class);

private static final String PROPERTIES_PATH = "META-INF/dynamic-theme.properties";

@Override
public void serviceInit(ServiceInitEvent event) {
if (DynamicTheme.isFeatureSupported()) {
try (InputStream in = getClass().getResourceAsStream("/META-INF/dynamic-theme.properties")) {
if (in != null) {
Properties props = new Properties();
props.load(in);
String themeName = props.getProperty("theme");
if (themeName != null) {
DynamicTheme theme = DynamicTheme.valueOf(themeName.trim());
try {
Enumeration<URL> resources = getClass().getClassLoader().getResources(PROPERTIES_PATH);
while (resources.hasMoreElements()) {
URL url = resources.nextElement();
String source = getSourceName(url);
readTheme(url).ifPresent(theme -> {
logger.info("Applying dynamic theme '{}' from {}", theme, source);
event.addIndexHtmlRequestListener(theme::initialize);
}
});
}
} catch (IOException e) {
throw new RuntimeException("Error reading dynamic-theme.properties", e);
}
}
}

private Optional<DynamicTheme> readTheme(URL url) throws IOException {
try (InputStream in = url.openStream()) {
Properties props = new Properties();
props.load(in);
String themeName = props.getProperty("theme");
return Optional.ofNullable(themeName).map(String::trim).map(DynamicTheme::valueOf);
}
}
Comment on lines +50 to +57
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@coderabbitai coderabbitai bot Feb 7, 2026

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⚠️ Potential issue | 🟡 Minor

Silent skip when theme property is missing from a discovered file.

If a dynamic-theme.properties file is found but doesn't contain the theme key (e.g., typo like themes=LUMO), readTheme returns an empty Optional and nothing is logged. Given that this class now explicitly scans for these files, a missing property is likely a configuration error and should at least be logged as a warning.

Proposed fix 
   private Optional<DynamicTheme> readTheme(URL url) throws IOException {
     try (InputStream in = url.openStream()) {
       Properties props = new Properties();
       props.load(in);
       String themeName = props.getProperty("theme");
+      if (themeName == null || themeName.trim().isEmpty()) {
+        logger.warn("No 'theme' property found in {}", url);
+        return Optional.empty();
+      }
-      return Optional.ofNullable(themeName).map(String::trim).map(DynamicTheme::valueOf);
+      return Optional.of(DynamicTheme.valueOf(themeName.trim()));
     }
   }
🤖 Prompt for AI Agents 
In
`@src/main/java/com/flowingcode/vaadin/addons/demo/DynamicThemeInitializer.java`
around lines 50 - 57, The readTheme method currently returns empty silently when
the "theme" property is missing or invalid; update readTheme to (1) after
loading props check if props.getProperty("theme") is null or blank and log a
warning including the URL to indicate a misconfigured dynamic-theme.properties,
and (2) when mapping to DynamicTheme via DynamicTheme.valueOf, catch
IllegalArgumentException, log an error mentioning the invalid value and the URL,
and return Optional.empty; use the class logger (e.g., LOGGER or logger) for
these messages and keep the method signature and stream handling as-is.


// Extracts a short, readable source name from the URL.
private String getSourceName(URL url) {
String path = url.getPath();
// JAR URLs look like: file:/path/to/file.jar!/META-INF/...
int jarSeparator = path.indexOf("!/");
if (jarSeparator > 0) {
path = path.substring(0, jarSeparator);
int lastSlash = path.lastIndexOf('/');
if (lastSlash >= 0) {
return path.substring(lastSlash + 1);
}
}
return url.toString();
}

}