What causes "msg == null ? e.getClass().getSimpleName() : msg" in MyCATApache/Mycat-Server?

Read the server log (LOGGER.warn prints this + sql + full stack trace) to find the real underlying exception and its cause.

MyCATApache/Mycat-Server · error

ER_PARSE_ERROR

ER_PARSE_ERROR

Error message

msg == null ? e.getClass().getSimpleName() : msg

What it means

ServerConnection.routeSQL() wraps SQL routing in a catch-all: any exception raised while parsing/routing a query through the RouterService is converted to a MySQL ER_PARSE_ERROR packet sent back to the client. The message is the exception's getMessage(), or the exception class's simple name when the message is null. It is a generic 'your SQL could not be routed/parsed by Mycat' reply rather than a true MySQL parser error.

Solutions

Read the server log (LOGGER.warn prints this + sql + full stack trace) to find the real underlying exception and its cause.
Fix the SQL to use syntax supported by Mycat's router, or adjust schema/rule configuration for the referenced tables.
If the message is just a class name (null message), inspect the stack trace for an NPE from missing schema/rule config and complete schema.xml/rule.xml.

Example fix

// before: incomplete sharding config causes NPE inside route()
SELECT * FROM order_detail WHERE id=1  // table missing in schema.xml -> NPE -> ER_PARSE_ERROR 'NullPointerException'
// after
<!-- schema.xml: declare the table so routing succeeds -->
<table name="order_detail" dataNode="dn1" />

Defensive patterns

Strategy: try-catch

Validate before calling

// before sending: check the statement is non-empty and table is declared in schema
String sql = "SELECT * FROM order_detail WHERE id=1";
if (sql == null || sql.trim().isEmpty()) throw new IllegalArgumentException("empty SQL");
// verify table exists in Mycat schema config (e.g. via SHOW TABLES on manager port)
boolean declared = mycatSchemaTables.contains(resolveTableName(sql));
if (!declared) { /* fix schema.xml before routing */ }

Try / catch

try {
    routeSQL(sql, type);
} catch (Exception e) {
    // client sees ER_PARSE_ERROR; consult server log for the real cause
    LOGGER.error("route failed for sql: " + sql, e);
    String detail = (e.getMessage() != null) ? e.getMessage() : e.getClass().getSimpleName();
    throw new RuntimeException("SQL routing failed: " + detail, e);
}

Prevention

Always check the Mycat server log, not just the client error packet, since ER_PARSE_ERROR masks the real exception.
Keep schema.xml/rule.xml in sync with every table referenced by application SQL.
Test new SQL against Mycat with EXPLAIN via the manager port before deploying.
Avoid syntax known to be unsupported by Mycat's Druid-based parser.

When it happens

Trigger: Any Exception thrown inside routeSQL while calling MycatServer.getInstance().getRouterservice().route(...), e.g. syntax Mycat's SQL parser cannot handle, unknown table/schema in sharding rules, or a routing rule throwing; also when e.getMessage() is null (e.g. NPE) the client sees just the class name like 'NullPointerException'.

Common situations: Mycat-specific or non-standard SQL syntax the embedded Druid parser rejects; queries against tables lacking schemaConfig/sharding config; NPEs from incomplete schema.xml configuration being surfaced as parse errors; version upgrades where the router became stricter.

Understand the failure class

Background: "query failed", "%w: SQL error" — wrapped database query errors in Go libraries explained — this error's family across 3 libraries.

Related errors

AI-assisted analysis of MyCATApache/Mycat-Server@65f8d8beb7 (2026-09-11). Data as JSON: /api/errors/eb36eb30a3d205bc. Report an issue: GitHub.

Appendix: source

Thrown at src/main/java/io/mycat/server/ServerConnection.java:328

			writeErrMessage(ErrorCode.ERR_BAD_LOGICDB,
					"Unknown MyCAT Database '" + db + "'");
			return null;
		}

		// 路由计算
		RouteResultset rrs = null;
		try {
			rrs = MycatServer
					.getInstance()
					.getRouterservice()
					.route(MycatServer.getInstance().getConfig().getSystem(),
							schema, type, sql, this.charset, this);

		} catch (Exception e) {
			StringBuilder s = new StringBuilder();
			LOGGER.warn(s.append(this).append(sql).toString() + " err:" + e.toString(),e);
			String msg = e.getMessage();
			writeErrMessage(ErrorCode.ER_PARSE_ERROR, msg == null ? e.getClass().getSimpleName() : msg);
			return null;
		}
		return rrs;
	}




	public void routeEndExecuteSQL(String sql, final int type, final SchemaConfig schema) {
		// 路由计算
		RouteResultset rrs = null;
		try {
			rrs = MycatServer
					.getInstance()
					.getRouterservice()
					.route(MycatServer.getInstance().getConfig().getSystem(),
							schema, type, sql, this.charset, this);

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