alibaba/druid · critical · SQLException

connect error, url {}, driverClass {}

Error message

connect error, url {}, driverClass {}

What it means

Thrown by createPhysicalConnection when DriverManager/Driver.connect returns null instead of a Connection object. Per the JDBC contract, Driver.connect returns null when the driver does not understand the given URL (it does NOT throw). Druid treats a null connection as a hard failure and reports the URL and driverClass to help diagnose the mismatch.

Source

Thrown at core/src/main/java/com/alibaba/druid/pool/DruidAbstractDataSource.java:1815

        long connectStartNanos = System.nanoTime();
        long connectedNanos, initedNanos, validatedNanos;

        Map<String, Object> variables = initVariants
                ? new HashMap<String, Object>()
                : null;
        Map<String, Object> globalVariables = initGlobalVariants
                ? new HashMap<String, Object>()
                : null;

        createStartNanosUpdater.set(this, connectStartNanos);
        creatingCountUpdater.incrementAndGet(this);
        try {
            conn = createPhysicalConnection(url, physicalConnectProperties);
            connectedNanos = System.nanoTime();

            if (conn == null) {
                throw new SQLException("connect error, url " + url + ", driverClass " + this.driverClass);
            }

            initPhysicalConnection(conn, variables, globalVariables);
            initedNanos = System.nanoTime();

            boolean skipSocketTimeout = "odps".equals(dbTypeName);
            if (socketTimeout > 0 && !netTimeoutError && !skipSocketTimeout) {
                try {
                    // As SQLServer-jdbc-driver 6.1.7 can use this, see https://github.com/microsoft/mssql-jdbc/wiki/SocketTimeout
                    conn.setNetworkTimeout(netTimeoutExecutor, socketTimeout); // here is milliseconds defined by JDBC
                } catch (SQLFeatureNotSupportedException | AbstractMethodError e) {
                    netTimeoutError = true;
                } catch (Exception ignored) {
                    // ignored
                }
            }

            // call initSqls after completing socketTimeout setting.

View on GitHub (pinned to fa8dc99126)

Solutions

1. Inspect the printed url and driverClass in the message: confirm the url scheme matches the driver (e.g. 'jdbc:mysql://' with com.mysql.cj.jdbc.Driver).
2. Ensure the correct JDBC driver JAR is on the classpath at runtime.
3. If specifying driverClass explicitly, make sure it is the class whose acceptsURL(jdbcUrl) returns true.
4. Let Druid auto-resolve the driver by setting only jdbcUrl and leaving driverClass null, or vice-versa consistently.

Example fix

// before
dataSource.setUrl("jdbc:mysqql://localhost:3306/db");
dataSource.setDriverClassName("com.mysql.cj.jdbc.Driver");
// after
dataSource.setUrl("jdbc:mysql://localhost:3306/db");
dataSource.setDriverClassName("com.mysql.cj.jdbc.Driver");

// Verify the driver accepts the url before init
java.sql.Driver d = dataSource.getDriver() != null ? dataSource.getDriver()
    : java.sql.DriverManager.getDriver(dataSource.getUrl());
if (!d.acceptsURL(dataSource.getUrl())) {
    throw new IllegalStateException("driver " + d.getClass().getName() + " does not accept url " + dataSource.getUrl());
}

try {
    dataSource.init();
} catch (SQLException e) {
    if (e.getMessage() != null && e.getMessage().startsWith("connect error, url")) {
        // url/driver mismatch or missing driver jar
        throw new IllegalStateException("Driver/URL mismatch or missing driver JAR", e);
    }
    throw e;
}

When it happens

Trigger: createPhysicalConnection(url, physicalConnectProperties) returns null at line 1811, hitting the conn==null check at 1814. This occurs when no registered Driver accepts the jdbcUrl prefix, or when driverClass points at a driver that does not handle the supplied url scheme.

Common situations: jdbcUrl typo or wrong scheme (e.g. 'jdbc:mysqql://...'); driverClass set to a driver whose acceptsURL returns false for the url; the JDBC driver JAR missing from the classpath so DriverManager hands back null; mixing url and driverClass from different databases.

Related errors

• check connection info failed
• url not set
• driverClassName length > 256.
• validationQuery didn't return a row
• dataSource inited.

AI-assisted analysis of alibaba/druid@fa8dc99126 (2026-08-14). Data as JSON: /api/errors/b9650651babf800b. Report an issue: GitHub.