Troubleshooting

When the driver misbehaves, the issue is almost always one of a small set of recurring patterns: a TLS configuration mismatch, a batched operation that fills both ends of the TCP socket, a stale prepared statement, or similar. Each page below is keyed by the user-visible symptom (the error message or behaviour) rather than by the internal component at fault, so it should be searchable from a stack trace.

The pages cite source: exception strings as they appear in org.postgresql.util.PSQLException, the connection-property table at Connection properties , and the inline rationale in the driver’s bytecode. Anything that sounds like generic advice (“try restarting”, “check the network”) is out of scope; the goal is concrete, code-anchored guidance.

• executeBatch hangs without an error A large PreparedStatement.executeBatch() blocks indefinitely with no exception: both client and server are waiting on a full TCP buffer to drain. Tune the socket buffers or break the batch into smaller chunks.
• SSL / TLS connection errors Common TLS failure messages (PKIX path building failed, hostname mismatch, sslmode confusion, key-file format issues), with the cause and the exact connection-property fix for each.
• SCRAM authentication failed SCRAM-SHA-256 and channel-binding failures: what each error message means, and which server or channelBinding / requireAuth change resolves it.
• No suitable driver found DriverManager.getConnection throws SQLException: No suitable driver found for jdbc:postgresql://…. The four ways the driver can be unreachable to DriverManager, with a one-line diagnostic for each.
• org.postgresql.Driver not found The classic ClassNotFoundException / NoClassDefFoundError on org.postgresql.Driver from legacy Class.forName code: what it means in 2026 and why the call almost always belongs in the bin.
• Connection closed unexpectedly Idle connections die between checkout and use because of load-balancer timeouts, server idle limits, or OS keepalive defaults. Which mitigation (pool validation, tcpKeepAlive, socketTimeout, tcp_user_timeout) applies.
• cached plan must not change result type The two server-prepared-statement errors a JDBC client sees when the catalogue or backend session moves under a cached plan, with the flushCacheOnDdl, autosave, prepareThreshold, and PgBouncer settings that resolve them.
• Character encoding errors pgJDBC hard-requires client_encoding=UTF8. Errors that surface when the server tries to change that, when the database is SQL_ASCII, or when the byte stream is not what UTF-8 expects, with the fix and workaround for each.