JDBC\u3092\u4f7f\u7528\u3057\u3066\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u304b\u3089\u30d5\u30a1\u30a4\u30eb\u3092\u691c\u7d22\u3059\u308b\u4e00\u822c\u7684\u306a\u624b\u9806\u306f\u6b21\u306e\u3068\u304a\u308a\u3067\u3059\u30021.\u5fc5\u8981\u306aJDBC\u30e9\u30a4\u30d6\u30e9\u30ea\u306e\u30a4\u30f3\u30dd\u30fc\u30c8:\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u30c9\u30e9\u30a4\u30d0\u30fc\u306eJAR\u30d5\u30a1\u30a4\u30eb\u3092\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u306e\u30af\u30e9\u30b9\u30d1\u30b9\u306b\u8ffd\u52a0\u3057\u307e\u3059\u30022.\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u63a5\u7d9a\u306e\u4f5c\u6210:JDBC\u306e`java.sql.Connection`\u30a4\u30f3\u30bf\u30fc\u30d5\u30a7\u30a4\u30b9\u3092\u4f7f\u7528\u3057\u3066\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u306b\u63a5\u7d9a\u3057\u307e\u3059\u3002\u3053\u308c\u306b\u306f\u3001\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u306eURL\u3001\u30e6\u30fc\u30b6\u30fc\u540d\u3001\u30d1\u30b9\u30ef\u30fc\u30c9\u304c\u5fc5\u8981\u3067\u3059\u30023.`java.sql.Statement`\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u307e\u305f\u306f`java.sql.PreparedStatement`\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306e\u4f5c\u6210:\u3053\u308c\u3089\u306e\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306f\u3001SQL\u30af\u30a8\u30ea\u30b9\u30c6\u30fc\u30c8\u30e1\u30f3\u30c8\u3092\u5b9f\u884c\u3059\u308b\u305f\u3081\u306b\u4f7f\u7528\u3055\u308c\u307e\u3059\u30024.SQL\u306e\u30af\u30a8\u30ea\u30b9\u30c6\u30fc\u30c8\u30e1\u30f3\u30c8\u306e\u4f5c\u6210:SELECT\u30b9\u30c6\u30fc\u30c8\u30e1\u30f3\u30c8\u3092\u4f7f\u7528\u3057\u3066\u30d5\u30a1\u30a4\u30eb\u306e\u30c7\u30fc\u30bf\u3092\u53d6\u5f97\u3057\u307e\u3059\u3002\u3053\u308c\u306b\u306f\u3001\u30c6\u30fc\u30d6\u30eb\u540d\u3001\u5217\u540d\u3001\u305d\u306e\u4ed6\u306e\u30af\u30a8\u30ea\u6761\u4ef6\u3092\u6307\u5b9a\u3059\u308b\u3053\u3068\u3082\u542b\u307e\u308c\u308b\u5834\u5408\u304c\u3042\u308a\u307e\u3059\u30025.\u30af\u30a8\u30ea\u306e\u306e\u5b9f\u884c:SQL\u30af\u30a8\u30ea\u30b9\u30c6\u30fc\u30c8\u30e1\u30f3\u30c8\u3092\u5b9f\u884c\u3059\u308b\u305f\u3081\u306b`Statement`\u307e\u305f\u306f`PreparedStatement`\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306e`executeQuery()`\u30e1\u30bd\u30c3\u30c9\u3092\u547c\u3073\u51fa\u3057\u307e\u3059\u30026.\u30af\u30a8\u30ea\u7d50\u679c\u306e\u51e6\u7406:`ResultSet`\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u304b\u3089\u30d5\u30a1\u30a4\u30eb\u306e\u30c7\u30fc\u30bf\u3092\u62bd\u51fa\u3057\u307e\u3059\u3002`getBinaryStream()`\u30e1\u30bd\u30c3\u30c9\u3092\u4f7f\u7528\u3057\u3066\u30d5\u30a1\u30a4\u30eb\u306e\u30d0\u30a4\u30ca\u30ea\u30b3\u30f3\u30c6\u30f3\u30c4\u3092\u53d6\u5f97\u3057\u3001\u30ed\u30fc\u30ab\u30eb\u30d5\u30a1\u30a4\u30eb\u306b\u4fdd\u5b58\u3059\u308b\u304b\u3001\u3055\u3089\u306b\u51e6\u7406\u3067\u304d\u307e\u3059\u30027.\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u63a5\u7d9a\u3068\u95a2\u9023\u30ea\u30bd\u30fc\u30b9\u306e\u30af\u30ed\u30fc\u30ba:\u30af\u30a8\u30ea\u306e\u5b8c\u4e86\u5f8c\u3001`ResultSet`\u3001`Statement`\u3001`Connection`\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306a\u3069\u3092\u30af\u30ed\u30fc\u30ba\u3057\u3066\u30ea\u30bd\u30fc\u30b9\u3092\u89e3\u653e\u3057\u3001\u30e1\u30e2\u30ea\u30ea\u30fc\u30af\u3092\u9632\u304e\u307e\u3059\u3002\u4ee5\u4e0b\u306fJDBC\u3092\u4f7f\u7528\u3057\u3066\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u304b\u3089\u30d5\u30a1\u30a4\u30eb\u3092\u691c\u7d22\u3059\u308b\u65b9\u6cd5\u3092\u793a\u3059\u7c21\u5358\u306a\u30b5\u30f3\u30d7\u30eb\u30b3\u30fc\u30c9\u3067\u3059\u3002“`javaimport java.io.FileOutputStream;
\nimport java.io.IOException;
\nimport java.io.InputStream;
\nimport java.sql.Connection;
\nimport java.sql.DriverManager;
\nimport java.sql.PreparedStatement;
\nimport java.sql.ResultSet;
\nimport java.sql.SQLException;<\/p>\n
public class RetrieveFileFromDatabase {<\/p>\n
public static void main(String[] args) {
\nString url = “jdbc:mysql:\/\/localhost:3306\/mydatabase”;
\nString username = “root”;
\nString password = “password”;
\nString query = “SELECT file_data FROM files WHERE id = ?”;
\nint fileId = 1;<\/p>\n
try (Connection conn = DriverManager.getConnection(url, username, password);
\nPreparedStatement pstmt = conn.prepareStatement(query)) {
\npstmt.setInt(1, fileId);<\/p>\n
try (ResultSet rs = pstmt.executeQuery()) {
\nif (rs.next()) {
\nInputStream fileData = rs.getBinaryStream(“file_data”);
\nsaveToFile(fileData, “output.txt”);
\nSystem.out.println(“File retrieved successfully.”);
\n} else {
\nSystem.out.println(“File not found with id: ” + fileId);
\n}
\n}
\n} catch (SQLException | IOException e) {
\ne.printStackTrace();
\n}
\n}<\/p>\n
private static void saveToFile(InputStream inputStream, String filePath) throws IOException {
\ntry (FileOutputStream outputStream = new FileOutputStream(filePath)) {
\nbyte[] buffer = new byte[4096];
\nint bytesRead;
\nwhile ((bytesRead = inputStream.read(buffer)) != -1) {
\noutputStream.write(buffer, 0, bytesRead);
\n}
\n}
\n}
\n}
\n“`\u4e0a\u8a18\u306e\u30b3\u30fc\u30c9\u3067\u306f\u3001MySQL\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u3092\u4f7f\u7528\u3057\u3066\u304a\u308a\u3001`files`\u3068\u3044\u3046\u540d\u524d\u306e\u30c6\u30fc\u30d6\u30eb\u304c\u3042\u308a\u3001\u30d5\u30a1\u30a4\u30eb\u30c7\u30fc\u30bf\u3092\u683c\u7d0d\u3059\u308b\u305f\u3081\u306b`file_data`\u3068\u3044\u3046BLOB\u5217\u304c\u542b\u307e\u308c\u3066\u3044\u308b\u3053\u3068\u3092\u60f3\u5b9a\u3057\u3066\u3044\u307e\u3059\u3002\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u306eURL\u3001\u30e6\u30fc\u30b6\u30fc\u540d\u3001\u30d1\u30b9\u30ef\u30fc\u30c9\u3001\u30af\u30a8\u30ea\u3001\u30d5\u30a1\u30a4\u30ebID\u3092\u74b0\u5883\u306b\u5408\u308f\u305b\u3066\u7f6e\u304d\u63db\u3048\u308b\u3053\u3068\u3067\u3001\u81ea\u5206\u306e\u74b0\u5883\u306b\u9069\u7528\u3067\u304d\u307e\u3059\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
JDBC\u3092\u4f7f\u7528\u3057\u3066\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u304b\u3089\u30d5\u30a1\u30a4\u30eb\u3092\u691c\u7d22\u3059\u308b\u4e00\u822c\u7684\u306a\u624b\u9806\u306f\u6b21\u306e\u3068\u304a\u308a\u3067\u3059\u30021.\u5fc5\u8981\u306aJDBC\u30e9\u30a4\u30d6\u30e9\u30ea\u306e\u30a4\u30f3\u30dd\u30fc\u30c8:\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u30c9\u30e9\u30a4\u30d0\u30fc\u306eJAR\u30d5\u30a1\u30a4\u30eb\u3092\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u306e\u30af\u30e9\u30b9\u30d1\u30b9\u306b\u8ffd\u52a0\u3057\u307e\u3059\u30022.\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u63a5 […]<\/p>\n","protected":false},"author":8,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-122203","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"yoast_head":"\n