Allow ApplicationPid to write to a new file

Update `ApplicationPid` so that "canWrite" is only called for files
that already exist.

See gh-9922
Fixes gh-10784

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/ApplicationPid.java

@@ -89,7 +89,9 @@ public class ApplicationPid {
 	public void write(File file) throws IOException {
 		Assert.state(this.pid != null, "No PID available");
 		createParentFolder(file);
-		assertCanWrite(file);
+		if (file.exists()) {
+			assertCanOverwrite(file);
+		}
 		try (FileWriter writer = new FileWriter(file)) {
 			writer.append(this.pid);
 		}
@@ -102,7 +104,7 @@ public class ApplicationPid {
 		}
 	}
 
-	private void assertCanWrite(File file) throws IOException {
+	private void assertCanOverwrite(File file) throws IOException {
 		if (!file.canWrite() || !canWritePosixFile(file)) {
 			throw new FileNotFoundException(file.toString() + " (permission denied)");
 		}

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/ApplicationPidTests.java

@@ -68,6 +68,17 @@ public class ApplicationPidTests {
 		assertThat(actual).isEqualTo("123");
 	}
 
+	@Test
+	public void writeNewPid() throws Exception {
+		// gh-10784
+		ApplicationPid pid = new ApplicationPid("123");
+		File file = this.temporaryFolder.newFile();
+		file.delete();
+		pid.write(file);
+		String actual = FileCopyUtils.copyToString(new FileReader(file));
+		assertThat(actual).isEqualTo("123");
+	}
+
 	@Test
 	public void getPidFromJvm() throws Exception {
 		assertThat(new ApplicationPid().toString()).isNotEmpty();