Improve null-safety of module/spring-boot-devtools

See gh-46926

module/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/autoconfigure/ConditionEvaluationDeltaLoggingListener.java

@@ -27,6 +27,7 @@ import org.springframework.boot.context.event.ApplicationReadyEvent;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
 import org.springframework.context.ApplicationListener;
+import org.springframework.util.Assert;
 
 /**
  * An {@link ApplicationListener} that logs the delta of condition evaluation across
@@ -50,7 +51,8 @@ class ConditionEvaluationDeltaLoggingListener
 			return;
 		}
 		ConditionEvaluationReport report = event.getApplicationContext().getBean(ConditionEvaluationReport.class);
-		ConditionEvaluationReport previousReport = previousReports.get(event.getApplicationContext().getId());
+		String contextId = event.getApplicationContext().getId();
+		ConditionEvaluationReport previousReport = previousReports.get(contextId);
 		if (previousReport != null) {
 			ConditionEvaluationReport delta = report.getDelta(previousReport);
 			if (!delta.getConditionAndOutcomesBySource().isEmpty() || !delta.getExclusions().isEmpty()
@@ -64,7 +66,8 @@ class ConditionEvaluationDeltaLoggingListener
 				logger.info("Condition evaluation unchanged");
 			}
 		}
-		previousReports.put(event.getApplicationContext().getId(), report);
+		Assert.state(contextId != null, "'contextId' must not be null");
+		previousReports.put(contextId, report);
 	}
 
 	@Override

module/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/livereload/Connection.java

@@ -87,7 +87,9 @@ class Connection {
 			runWebSocket();
 		}
 		if (lowerCaseHeader.contains("get /livereload.js")) {
-			this.outputStream.writeHttp(getClass().getResourceAsStream("livereload.js"), "text/javascript");
+			InputStream stream = getClass().getResourceAsStream("livereload.js");
+			Assert.state(stream != null, "Resource 'livereload.js' not found");
+			this.outputStream.writeHttp(stream, "text/javascript");
 		}
 	}
 

module/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/classloader/ClassLoaderFileURLStreamHandler.java

@@ -23,6 +23,8 @@ import java.net.URL;
 import java.net.URLConnection;
 import java.net.URLStreamHandler;
 
+import org.springframework.util.Assert;
+
 /**
  * {@link URLStreamHandler} for the contents of a {@link ClassLoaderFile}.
  *
@@ -54,7 +56,9 @@ public class ClassLoaderFileURLStreamHandler extends URLStreamHandler {
 
 		@Override
 		public InputStream getInputStream() throws IOException {
-			return new ByteArrayInputStream(ClassLoaderFileURLStreamHandler.this.file.getContents());
+			byte[] contents = ClassLoaderFileURLStreamHandler.this.file.getContents();
+			Assert.state(contents != null, "'contents' must not be null");
+			return new ByteArrayInputStream(contents);
 		}
 
 		@Override