


Java: Error Using ResultSet after Connection Closure
When attempting to retrieve data from a MySQL database using JDBC, users may encounter the error: "java.sql.SQLException: Operation not allowed after ResultSet closed." This occurs when trying to use a ResultSet object after the underlying connection has been closed.
Explanation
JDBC operates on a concept of lazy loading, where the results of a query are not fully retrieved until requested. The ResultSet object provides a cursor over the results, allowing you to iterate through them. However, closing the connection that created the ResultSet also closes the cursor, making it unusable.
Solution
To avoid this error, one must either keep the connection open until the ResultSet is no longer needed or use a different approach.
One recommended approach is to use a row mapper to convert the result set into a collection of objects. This method encapsulates the conversion process and allows you to access the results even after the connection is closed:
<code class="java">public static List<t> sqlquery(String query, RowMapper<t> rowMapper) throws SQLException { try (Connection connection = DriverManager.getConnection(...); Statement st = connection.createStatement(); ResultSet rs = st.executeQuery(query)) { List<t> list = new ArrayList(); while (rs.next()) { list.add(rowMapper.mapRow(rs)); } return list; } }</t></t></t></code>
This modified code uses try-with-resources to ensure that the connection, statement, and result set are automatically closed when the method completes, eliminating the possibility of forgetting to close them manually. Additionally, it uses a row mapper to convert each row in the result set into a populated object, which can then be collected into a list.
Conclusion
By understanding the lazy loading mechanism of JDBC and utilizing row mappers, developers can effectively retrieve data from databases while avoiding errors related to closed ResultSets after connection closure.
The above is the detailed content of Why Am I Getting \'java.sql.SQLException: Operation not allowed after ResultSet closed\' in Java JDBC?. For more information, please follow other related articles on the PHP Chinese website!

This article explores optimizing MySQL memory usage in Docker. It discusses monitoring techniques (Docker stats, Performance Schema, external tools) and configuration strategies. These include Docker memory limits, swapping, and cgroups, alongside

This article addresses MySQL's "unable to open shared library" error. The issue stems from MySQL's inability to locate necessary shared libraries (.so/.dll files). Solutions involve verifying library installation via the system's package m

The article discusses using MySQL's ALTER TABLE statement to modify tables, including adding/dropping columns, renaming tables/columns, and changing column data types.

This article compares installing MySQL on Linux directly versus using Podman containers, with/without phpMyAdmin. It details installation steps for each method, emphasizing Podman's advantages in isolation, portability, and reproducibility, but also

This article provides a comprehensive overview of SQLite, a self-contained, serverless relational database. It details SQLite's advantages (simplicity, portability, ease of use) and disadvantages (concurrency limitations, scalability challenges). C

This guide demonstrates installing and managing multiple MySQL versions on macOS using Homebrew. It emphasizes using Homebrew to isolate installations, preventing conflicts. The article details installation, starting/stopping services, and best pra

Article discusses configuring SSL/TLS encryption for MySQL, including certificate generation and verification. Main issue is using self-signed certificates' security implications.[Character count: 159]

Article discusses popular MySQL GUI tools like MySQL Workbench and phpMyAdmin, comparing their features and suitability for beginners and advanced users.[159 characters]


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool

SublimeText3 Mac version
God-level code editing software (SublimeText3)

mPDF
mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),

Notepad++7.3.1
Easy-to-use and free code editor

Safe Exam Browser
Safe Exam Browser is a secure browser environment for taking online exams securely. This software turns any computer into a secure workstation. It controls access to any utility and prevents students from using unauthorized resources.
