MyCATApache/Mycat-Server · critical · RuntimeException

can't find class resource file

Error message

can't find class resource file {mapFile}

What it means

PartitionByRangeMod.initialize() loads the range-to-node map file from the classpath using ClassLoader.getResourceAsStream(mapFile) and throws this RuntimeException when the stream is null, i.e. the resource is not on the classpath. The failure happens during rule initialization, before any query is routed.

Solutions

1. Ensure the range-mod map file exists on the classpath (Mycat conf directory) with exactly the name given in mapFile.
2. Fix the mapFile property to a classpath-relative, case-correct resource name (no leading slash or filesystem path).
3. Repackage/redeploy so the resource is inside the artifact, then restart Mycat.
4. Add a filesystem fallback (FileInputStream(fileMapPath)) in initialize() if loading from disk is required.

Example fix

// before: file on disk only, referenced absolutely
<property name="mapFile">/opt/mycat/conf/range-mod.txt</property>
// after: file committed to classpath resources
<property name="mapFile">range-mod.txt</property>

java.io.InputStream s = PartitionByRangeMod.class.getClassLoader().getResourceAsStream(mapFile);
if (s == null) throw new IllegalStateException("mapFile missing from classpath: " + mapFile); else s.close();

try { rule.init(); } catch (RuntimeException e) { if (e.getMessage().contains("can't find class resource file")) { /* place the map file on the classpath */ } throw e; }

When it happens

Trigger: init() on a PartitionByRangeMod rule whose <mapFile> (e.g. partition-range-mod.txt) does not resolve to any classpath resource: file absent from conf/, wrong name/case, or an absolute path supplied instead of a resource name.

Common situations: New Mycat install missing the default map file; renaming the map file in schema.xml without renaming the actual file; building a custom distribution that excludes the resources directory; mixing up PartitionByFileMap vs PartitionByRangeMod map file formats and names.

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

• can't find class resource file
• can't find class resource file
• can't find class resource file
• Log already in use? in
• SelfCheck### user all node is empty!

AI-assisted analysis of MyCATApache/Mycat-Server@65f8d8beb7 (2026-09-11). Data as JSON: /api/errors/7c2954b643a62f71. Report an issue: GitHub.

Appendix: source

Thrown at src/main/java/io/mycat/route/function/PartitionByRangeMod.java:162

            for(int i =0;i<len;i++){
                re[i]=begin+i;
            }

            return re;
        }else{
            return null;
        }
	}



	private void initialize() {
		BufferedReader in = null;
		try {
			InputStream fin = this.getClass().getClassLoader()
					.getResourceAsStream(mapFile);
			if (fin == null) {
				throw new RuntimeException("can't find class resource file "
						+ mapFile);
			}
			in = new BufferedReader(new InputStreamReader(fin));
			LinkedList<LongRange> longRangeList = new LinkedList<LongRange>();

			for (String line = null; (line = in.readLine()) != null;) {
				line = line.trim();
				if (line.startsWith("#") || line.startsWith("//")) {
					continue;
				}
				int ind = line.indexOf('=');
				if (ind < 0) {
					System.out.println(" warn: bad line int " + mapFile + " :"
							+ line);
					continue;
				}
					String pairs[] = line.substring(0, ind).trim().split("-");
					long longStart = NumberParseUtil.parseLong(pairs[0].trim());

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