Improper Resource Release

Overview

Improper resource release occurs when files, streams, sockets, database connections, or locks are not closed.

Impact

Leaked resources can exhaust memory, handles, connections, or locks and reduce availability.

Countermeasures

Use structured cleanup such as try-with-resources or finally blocks and verify cleanup on both success and failure paths.

Examples

try {
    OutputStream os = response.getOutputStream();
    FileInputStream fis = new FileInputStream(file);
    FileCopyUtils.copy(fis, os);
    fis.close();
    return true;
} catch (IOException e) {
    logger.error(e, e);
}

OutputStream os = null;
FileInputStream fis = null;
try {
    os = response.getOutputStream();
    fis = new FileInputStream(file);
    FileCopyUtils.copy(fis, os);
} catch (IOException e) {
    logger.error(e.getMessage());
} finally {
    try {
        fis.close();
        os.close();
    } catch (IOException e) {
        logger.error(e.getMessage());
    }
}

OutputStream os = null;
FileInputStream fis = null;
try {
    os = response.getOutputStream();
    fis = new FileInputStream(file);
    FileCopyUtils.copy(fis, os);
} catch (IOException e) {
    logger.error(e.getMessage());
} finally {
    try {
         if (fis =! null)
             fis.close();
    } catch (IOException e) {
        logger.error(e.getMessage());
    }
    try {
         if (os =! null)
             os.close();
    } catch (IOException e) {
        logger.error(e.getMessage());
    }    
}