Why Does My Java Code Throw a 'java.sql.SQLException: Operation not allowed after ResultSet closed' Exception?

Understanding the "Operation Not Allowed After ResultSet Closed" Exception

When executing SQL statements in Java, it is essential to manage ResultSet objects properly to avoid exceptions. One common exception encountered is "java.sql.SQLException: Operation not allowed after ResultSet closed."

This exception occurs when an operation (such as fetching data from a ResultSet) is attempted after the ResultSet has been closed. The code snippet you provided illustrates this issue.

Root Cause of the Exception

In your code, you create a statement object and use it to execute two queries: one to fetch the user's name and another to retrieve IDs from the "profiles" table. You then attempt to create a PreparedStatement using the same connection object and prepare an update statement.

The problem arises when you access the "getStuff()" method within the while loop iterating over the results of the "profiles" table. Inside this method:

1. You execute a query and obtain a ResultSet (rs).
2. You fail to close the ResultSet before returning.

This violates the requirement that only one ResultSet per Statement object can be open at a time. As a result, the ResultSet from the "getStuff()" method conflicts with the ResultSet object (rs2) created in the main code.

Solution

To resolve this exception, you must properly manage the ResultSet objects:

1. Close the ResultSet (rs) obtained from the "getStuff()" method before returning.
2. Ensure that the ResultSet (rs) in the main code is also closed once it is no longer needed.

Additionally, you may consider creating a new Statement object for the "getStuff()" method to avoid any potential conflicts with the Statement object used in the main code.

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