How to Resolve the \'Operation Not Allowed After ResultSet Closed\' MySQL Exception in Java JDBC?

MySQL Exception: "Operation Not Allowed After ResultSet Closed" in Java JDBC

When working with databases, it's crucial to understand the state of data objects to prevent errors. One common exception in JDBC is the "Operation not allowed after ResultSet closed" error. Let's explore the cause and solution for this issue.

Cause:

In JDBC, a ResultSet represents the result set of a database query. Once you execute a query and obtain a ResultSet, you must iterate through it and close it explicitly to release system resources. If you attempt to perform any operations on a closed ResultSet, you'll encounter the "Operation not allowed after ResultSet closed" exception.

Solution:

In the provided code, the error occurs in the MySQLDonation class while iterating through the ResultSet returned by the query that retrieves donation records. Specifically, the issue arises because the same Statement object is used both to execute the Select query and to execute the subsequent Delete query.

Recommended Approach:

To resolve this issue, create a new Statement object each time you execute a query, rather than reusing the same statement. Here are the steps to implement this approach:

1. Remove the statement = connection.createStatement(); line from the connect() method in the MySQLDatabase class.
2. Replace all instances of statement in the MySQLDatabase class with connection.createStatement(). Alternatively, you can delete the private statement variable altogether.

By following these steps, you ensure that each operation on a ResultSet is performed using a newly created Statement object, thus preventing premature closing of the ResultSet. This approach will allow the code to process donation records correctly and avoid the "Operation not allowed after ResultSet closed" exception.

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