How to Retrieve Auto-Generated Key After Row Insertion in Spring 3 with PostgreSQL

How can I successfully retrieve the auto-generated ID from a row insertion in Spring 3 using PostgreSQL?

long result = keyHolder.getKey().longValue();

Retrieving auto-generated keys in a Spring 3 application using PostgreSQL can be complex, particularly if you're running into NullPointerExceptions. This issue often arises due to improper handling of `KeyHolder` or the absence of a return value from the insert operation. Let's break down the approach step by step and identify typical pitfalls.

final String SQL = "INSERT INTO compte (prenom, nom, datenaissance, numtelephone) VALUES (?, ?, ?, ?)";
KeyHolder keyHolder = new GeneratedKeyHolder();
int rows = this.jdbcTemplate.update(connection -> {
    PreparedStatement ps = connection.prepareStatement(SQL, new String[] { "idcompte" });
    ps.setString(1, a.getSurname());
    ps.setString(2, a.getName());
    ps.setDate(3, a.getDob());
    ps.setString(4, a.getPhone());
    return ps;
}, keyHolder);

if (rows == 1) {
    result = keyHolder.getKey().longValue(); // Correct retrieval of auto-generated key
} else {
    throw new DataAccessException("No rows affected, insert may have failed.");
}

Causes

• The `KeyHolder` may not be populated if the insertion fails or no key is generated.
• Not using the correct sequence associated with the primary key.
• The `jdbcTemplate` operation might not be set correctly to retrieve keys due to missing options.

Solutions

• Ensure that you handle exceptions that may arise during the execution of the `update` method.
• Use `PreparedStatementCreator` correctly to pass the necessary parameters.
• Make sure you specify the generated keys when creating the PreparedStatement.

Mistake: Not specifying the returned column names in the PreparedStatement.

Solution: Use `new String[] { "idcompte" }` when preparing the statement.

Mistake: Trying to retrieve the key before confirming the insert was successful.

Solution: Check if the number of affected rows is greater than zero before accessing `keyHolder`.