fix: prevent NPE when creating init parameters (#19856)

ServletConfig might contain init parameter with null values. This is however not
supported by java Properties class.
This change adds a null check and logs offending keys for debugging purpose.

Fixes #19855

flow-server/src/main/java/com/vaadin/flow/server/DeploymentConfigurationFactory.java

@@ -21,6 +21,8 @@
 import java.util.Map;
 import java.util.Properties;
 
+import org.slf4j.LoggerFactory;
+
 import com.vaadin.flow.component.UI;
 import com.vaadin.flow.function.DeploymentConfiguration;
 import com.vaadin.flow.server.startup.AbstractConfigurationFactory;
@@ -94,8 +96,13 @@ protected Properties createInitParameters(Class<?> systemPropertyBaseClass,
  for (final Enumeration<String> e = vaadinConfig
  .getConfigParameterNames(); e.hasMoreElements();) {
  final String name = e.nextElement();
- initParameters.setProperty(name,
- vaadinConfig.getConfigParameter(name));
+ String value = vaadinConfig.getConfigParameter(name);
+ if (value != null) {
+ initParameters.setProperty(name, value);
+ } else {
+ LoggerFactory.getLogger(DeploymentConfigurationFactory.class)
+ .debug("Ignoring NULL init parameter {}", name);
+ }
  }
 
  readBuildInfo(initParameters, vaadinConfig.getVaadinContext());

flow-server/src/test/java/com/vaadin/flow/server/DeploymentConfigurationFactoryTest.java

@@ -2,6 +2,7 @@
 
 import jakarta.servlet.ServletConfig;
 import jakarta.servlet.ServletContext;
+
 import java.io.File;
 import java.io.IOException;
 import java.lang.reflect.Field;
@@ -20,12 +21,6 @@
 import java.util.Properties;
 import java.util.Set;
 
-import com.vaadin.flow.component.UI;
-import com.vaadin.flow.di.Lookup;
-import com.vaadin.flow.di.ResourceProvider;
-import com.vaadin.flow.function.DeploymentConfiguration;
-import com.vaadin.flow.server.frontend.FrontendUtils;
-import com.vaadin.flow.server.startup.ApplicationConfiguration;
 import org.apache.commons.io.FileUtils;
 import org.junit.After;
 import org.junit.AfterClass;
@@ -38,13 +33,19 @@
 import org.junit.rules.TemporaryFolder;
 import org.mockito.Mockito;
 
-import static java.util.Collections.emptyMap;
+import com.vaadin.flow.component.UI;
+import com.vaadin.flow.di.Lookup;
+import com.vaadin.flow.di.ResourceProvider;
+import com.vaadin.flow.function.DeploymentConfiguration;
+import com.vaadin.flow.server.frontend.FrontendUtils;
+import com.vaadin.flow.server.startup.ApplicationConfiguration;
 
 import static com.vaadin.flow.server.Constants.VAADIN_SERVLET_RESOURCES;
 import static com.vaadin.flow.server.InitParameters.SERVLET_PARAMETER_PRODUCTION_MODE;
 import static com.vaadin.flow.server.frontend.FrontendUtils.PARAM_TOKEN_FILE;
 import static com.vaadin.flow.server.frontend.FrontendUtils.TOKEN_FILE;
 import static com.vaadin.flow.server.startup.AbstractConfigurationFactory.DEV_FOLDER_MISSING_MESSAGE;
+import static java.util.Collections.emptyMap;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
@@ -186,6 +187,29 @@ public void servletConfigParametersOverrideServletContextParameters()
  config.getHeartbeatInterval());
  }
 
+ @Test
+ public void servletConfigParameters_nullValues_ignored() throws Exception {
+ Class<NoSettings> servlet = NoSettings.class;
+
+ Map<String, String> servletConfigParams = new HashMap<>(
+ defaultServletParams);
+ servletConfigParams.put("someKey", null);
+ servletConfigParams.put("someNotNullKey", "NOT_NULL");
+
+ Map<String, String> servletContextParams = new HashMap<>();
+
+ DeploymentConfiguration config = new DeploymentConfigurationFactory()
+ .createDeploymentConfiguration(servlet, createVaadinConfigMock(
+ servletConfigParams, servletContextParams));
+
+ Assert.assertFalse(
+ "Expecting null parameter to be ignored, but was in configuration",
+ config.getInitParameters().containsKey("someKey"));
+ Assert.assertTrue(
+ "Expecting not null parameter to be in configuration, but was not",
+ config.getInitParameters().containsKey("someNotNullKey"));
+ }
+
  @Test
  public void should_readConfigurationFromTokenFile() throws Exception {
  FileUtils.writeLines(tokenFile,