JDBC實現簡單增刪改查
1.資料庫驅動:Driver
載入mysql驅動:Class.forName("com.mysql.jdbc.Driver");
載入oracle驅動:Class.forName("oracle.jdbc.driver.OracleDriver");
否則無法正常執行。
2.獲取資料庫連結:Connection
DriverManager.getConnection()來獲取一個連線物件。
這裡有3個引數,分別是url,user,passwrod。對應的是要連結的資料庫,使用者名稱,密碼等。如:
url=jdbc:mysql://localhost:3306/jdbc?useUnicode=true&characterEncoding=utf-8
user=root
password=root
(2)PerparedStatement物件用於執行帶或不帶引數的預編譯SQL語句;
Statement的常用方法:
(2)executeUpdata()方法:執行增,刪,改操作,返回更新的行數。
(3)addBatch(Stringsql) :把多條sql語句放到一個批處理中。
(4)executeBatch():向資料庫傳送一批sql語句執行。
executeQuery()方法後返回的結果集
常用方法:
(1)getString(String columnName):獲得當前行的某一string型別的欄位
(6)next():移動到下一行
實際程式碼
資料庫驅動 driver=com.mysql.jdbc.Driver #連線資料庫的URL url=jdbc:mysql://localhost:3306/jdbc?useUnicode=true&characterEncoding=utf-8 #使用者名稱 user=root #密碼 password=root
接著寫一個連線資料庫的通用工具類:
public class DBUtil { private static String driver; private static String url; private static String user; private static String password; static{ try { //讀取配置檔案 InputStream in = DBUtil.class.getResourceAsStream("db.properties"); Properties properties = new Properties(); //載入配置檔案 properties.load(in); //獲取配置檔案中的資料 driver = properties.getProperty("driver"); url = properties.getProperty("url"); user = properties.getProperty("user"); password = properties.getProperty("password"); //載入資料庫連結驅動 Class.forName(driver); } catch (Exception e) { e.printStackTrace(); } } /** * 獲取一個數據庫連結 */ public static Connection getConnection() throws SQLException{ return DriverManager.getConnection(url, user, password); } }
實現簡單的增刪改查:
public class jdbcTest {
/**
* 建立表
*/
public static void createTable() throws SQLException{
String sql = "CREATE TABLE IF NOT EXISTS `user`("
+"`id` INT UNSIGNED AUTO_INCREMENT,"
+" `user_name` VARCHAR(100),"
+" `user_password` VARCHAR(100),"
+" `user_age` INT(11),"
+"PRIMARY KEY ( `id` )"
+")ENGINE=InnoDB DEFAULT CHARSET=utf8;";
Connection conn = DBUtil.getConnection();
//開啟事務
conn.setAutoCommit(false);
PreparedStatement preparedStatement = conn.prepareStatement(sql);
preparedStatement.executeUpdate();
//提交事務
conn.commit();
//要注意關閉連線(在實際中最好不要像這樣關閉,最好標準一點)
conn.close();
}
/**
* 增加資料
*/
public static void add() throws SQLException{
String sql = "INSERT INTO USER (user_name,user_password,user_age) VALUES('老王','123456',18)";
Connection conn = DBUtil.getConnection();
conn.setAutoCommit(false);
PreparedStatement preparedStatement = conn.prepareStatement(sql);
preparedStatement.executeUpdate();
conn.commit();
conn.close();
}
/**
* 刪除資料
*/
public static void delete() throws SQLException{
String sql = "DELETE FROM USER WHERE USER.user_name = '老王'";
Connection conn = DBUtil.getConnection();
conn.setAutoCommit(false);
PreparedStatement preparedStatement = conn.prepareStatement(sql);
preparedStatement.executeUpdate();
conn.commit();
conn.close();
}
/**
* 修改資料
*/
public static void updata() throws SQLException{
String sql = "UPDATE USER SET USER.user_name = '老李'";
Connection conn = DBUtil.getConnection();
conn.setAutoCommit(false);
PreparedStatement preparedStatement = conn.prepareStatement(sql);
preparedStatement.executeUpdate();
conn.commit();
conn.close();
}
/**
* 查詢資料
*/
public static void query() throws SQLException{
String sql = "SELECT * FROM USER";
Connection conn = DBUtil.getConnection();
conn.setAutoCommit(false);
PreparedStatement preparedStatement = conn.prepareStatement(sql);
//執行查詢語句並返回結果集
ResultSet resultSet = preparedStatement.executeQuery();
while (resultSet.next()) {
//注意:這裡要與資料庫裡的欄位對應
String username = resultSet.getString("user_name");
String password = resultSet.getString("user_password");
String age = resultSet.getString("user_age");
System.out.println(username + " " + password + " " + age);
}
conn.commit();
conn.close();
}
}