🎨 Rename cache control properties, and better tolerate cache creation failures

Author: pmonks

README.md

@@ -40,8 +40,8 @@ There are a couple of static classes that help common usage scenarios:
 `Spdx-Java-Library` is configured using Java system properties, as those allow both human operator configuration (via JVM `-D` command line options) as well as programmatic configuration by downstream code that needs automated control.
 
 Currently the library offers these configuration options:
-1. `org.spdx.storage.listedlicense.SpdxListedLicenseWebStore.enableCache` - a boolean that enables or disables the WebStore's local cache. Defaults to `false` (the cache is disabled). The cache location is determined as per the [XDG Base Directory Specification](https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html) i.e. `${XDG_CACHE_HOME}/Spdx-Java-Library` or `${HOME}/.cache/Spdx-Java-Library`).
-2. `org.spdx.storage.listedlicense.SpdxListedLicenseWebStore.cacheCheckIntervalSecs` - a long that controls how often each cache entry is rechecked for staleness, in units of seconds. Defaults to 86,400 seconds (24 hours). Set to 0 (zero) to have each cache entry checked every time (note: this will result in a lot more network I/O and negatively impact performance, albeit there is still a substantial performance saving vs not using the cache at all).
+1. `org.spdx.storage.listedlicense.enableCache` - a boolean that enables or disables the WebStore's local cache. Defaults to `false` (the cache is disabled). The cache location is determined as per the [XDG Base Directory Specification](https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html) i.e. `${XDG_CACHE_HOME}/Spdx-Java-Library` or `${HOME}/.cache/Spdx-Java-Library`).
+2. `org.spdx.storage.listedlicense.cacheCheckIntervalSecs` - a long that controls how often each cache entry is rechecked for staleness, in units of seconds. Defaults to 86,400 seconds (24 hours). Set to 0 (zero) to have each cache entry checked every time (note: this will result in a lot more network I/O and negatively impact performance, albeit there is still a substantial performance saving vs not using the cache at all).
 
 Note that both of these configuration options can only be modified prior to initialization of Spdx-Java-Library. Once the library is initialized, subsequent changes to either or both of these Java properties will have no effect.
 

src/main/java/org/spdx/storage/listedlicense/SpdxListedLicenseWebStore.java

@@ -76,8 +76,9 @@ public class SpdxListedLicenseWebStore extends SpdxListedLicenseModelStore {
 			System.getenv("XDG_CACHE_HOME")) +
 			"/Spdx-Java-Library";
 
-	private final boolean cacheEnabled = Boolean.parseBoolean(
-			System.getProperty("org.spdx.storage.listedlicense.SpdxListedLicenseWebStore.enableCache"));
+	private final String JAVA_PROPERTY_CACHE_ENABLED = "org.spdx.storage.listedlicense.enableCache";
+	private final String JAVA_PROPERTY_CACHE_CHECK_INTERVAL_SECS = "org.spdx.storage.listedlicense.cacheCheckIntervalSecs";
+	private final boolean cacheEnabled;
 	private final long cacheCheckIntervalSecs;
 
 	private final DateTimeFormatter iso8601 = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.000'Z'").withZone(ZoneOffset.UTC);
@@ -87,18 +88,22 @@ public class SpdxListedLicenseWebStore extends SpdxListedLicenseModelStore {
 	 */
 	public SpdxListedLicenseWebStore() throws InvalidSPDXAnalysisException {
 		super();
-		if (cacheEnabled) {
+
+		// Initialise cache
+		boolean tmpCacheEnabled = Boolean.parseBoolean(System.getProperty(JAVA_PROPERTY_CACHE_ENABLED));
+		if (tmpCacheEnabled) {
 			try {
 				final File cacheDirectory = new File(cacheDir);
 				Files.createDirectories(cacheDirectory.toPath());
 			} catch (IOException ioe) {
-				throw new InvalidSPDXAnalysisException("Unable to create cache directory: " + cacheDir, ioe);
+				logger.warn("Unable to create cache directory '" + cacheDir "'; continuing with cache disabled.", ioe);
+				tmpCacheEnabled = false;
 			}
 		}
+		cacheEnabled = tmpCacheEnabled;
 		long tmpCacheCheckIntervalSecs = DEFAULT_CACHE_CHECK_INTERVAL_SECS;
 		try {
-			tmpCacheCheckIntervalSecs = Long.parseLong(
-					System.getProperty("org.spdx.storage.listedlicense.SpdxListedLicenseWebStore.cacheCheckIntervalSecs"));
+			tmpCacheCheckIntervalSecs = Long.parseLong(System.getProperty(JAVA_PROPERTY_CACHE_CHECK_INTERVAL_SECS));
 		} catch(NumberFormatException nfe) {
 			// Ignore parse failures - in this case we use the default value of 24 hours
 		}