The first parameter is number one
A easy Java puzzle in the sql and jdbc mistakes family. One line below contains a real bug. Try to spot it first, then read why it fails and how to fix it.
Highlighted: line 6. Play this one as a puzzle without the answer.
What is wrong
JDBC parameter and column indexes start at 1, not 0. setString(0, ...) throws an SQLException about an invalid parameter index.
The fix
How to avoid it next time
JDBC is one-based, unlike arrays and lists. Named parameters in Spring JdbcTemplate avoid the counting.
Want the background? Read JDBC and prepared statements in the Java concepts library.
About sql and jdbc mistakes
Building SQL by string concatenation invites injection, and a handful of subtle JDBC habits leak connections, load too much data or commit half a change.
In code review: Search for plus signs inside strings passed to executeQuery, createQuery or createNativeQuery. Parameters belong in placeholders, never in the text.
More puzzles in this family
Frequently asked questions
What is the bug in "The first parameter is number one"?
JDBC parameter and column indexes start at 1, not 0. setString(0, ...) throws an SQLException about an invalid parameter index. The faulty line is line 6: ps.setString(0, status);
How do I fix it?
Replace it with: ps.setString(1, status);. JDBC is one-based, unlike arrays and lists. Named parameters in Spring JdbcTemplate avoid the counting.
How do I catch sql and jdbc mistakes in code review?
Search for plus signs inside strings passed to executeQuery, createQuery or createNativeQuery. Parameters belong in placeholders, never in the text.
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