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今天小編給大家分享一下怎么使用JDBC連接數(shù)據(jù)庫并執(zhí)行SQL語句的相關(guān)知識(shí)點(diǎn),內(nèi)容詳細(xì),邏輯清晰,相信大部分人都還太了解這方面的知識(shí),所以分享這篇文章給大家參考一下,希望大家閱讀完這篇文章后有所收獲,下面我們一起來了解一下吧。
JDBC(Java Database Connectivity)是Java程序與數(shù)據(jù)庫進(jìn)行交互的一種標(biāo)準(zhǔn)接口,它提供了一種簡(jiǎn)單的方式來連接和操作數(shù)據(jù)庫。在使用JDBC之前,需要先了解以下幾個(gè)概念:
JDBC Driver:JDBC驅(qū)動(dòng)程序是一個(gè)Java類,用于將Java應(yīng)用程序與特定數(shù)據(jù)庫管理系統(tǒng)(DBMS)連接。JDBC驅(qū)動(dòng)程序分為四種類型:JDBC-ODBC橋接驅(qū)動(dòng)程序、本地API驅(qū)動(dòng)程序、網(wǎng)絡(luò)協(xié)議驅(qū)動(dòng)程序和本地協(xié)議驅(qū)動(dòng)程序。
Connection:Connection是一個(gè)JDBC接口,用于連接到數(shù)據(jù)庫。在Java程序中,通過Connection接口的實(shí)現(xiàn)類來實(shí)現(xiàn)與數(shù)據(jù)庫的連接。
Statement:Statement是一個(gè)JDBC接口,用于向數(shù)據(jù)庫發(fā)送SQL語句并執(zhí)行它們。在Java程序中,通過Connection對(duì)象創(chuàng)建Statement對(duì)象。
ResultSet:ResultSet是一個(gè)JDBC接口,用于表示從數(shù)據(jù)庫中檢索到的結(jié)果集。ResultSet對(duì)象通過Statement對(duì)象的executeQuery()方法返回。
下面是一個(gè)簡(jiǎn)單的JDBC連接示例:
import java.sql.*; public class JDBCDemo { public static void main(String[] args) { try { // 加載JDBC驅(qū)動(dòng)程序 Class.forName("com.mysql.cj.jdbc.Driver"); // 建立數(shù)據(jù)庫連接 Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "root", "password"); // 執(zhí)行SQL查詢 Statement stmt = conn.createStatement(); ResultSet rs = stmt.executeQuery("SELECT * FROM users"); while (rs.next()) { System.out.println(rs.getInt(1) + ", " + rs.getString(2) + ", " + rs.getString(3)); } // 關(guān)閉數(shù)據(jù)庫連接 rs.close(); stmt.close(); conn.close(); } catch (Exception e) { e.printStackTrace(); } } }
在實(shí)際開發(fā)中,我們通常會(huì)抽取出一個(gè)JDBC工具類來封裝JDBC相關(guān)操作,以方便代碼的重用和維護(hù)。下面是一個(gè)簡(jiǎn)單的JDBC工具類示例:
import java.sql.*; public class JDBCUtils { private static final String URL = "jdbc:mysql://localhost:3306/mydb"; private static final String USER = "root"; private static final String PASSWORD = "password"; static { try { // 加載JDBC驅(qū)動(dòng)程序 Class.forName("com.mysql.cj.jdbc.Driver"); } catch (ClassNotFoundException e) { e.printStackTrace(); } } public static Connection getConnection() { Connection conn = null; try { // 建立數(shù)據(jù)庫連接 conn = DriverManager.getConnection(URL, USER, PASSWORD); } catch (SQLException e) { e.printStackTrace(); } return conn; } public static void release(ResultSet rs, Statement stmt, Connection conn) { try { if (rs != null) rs.close(); if (stmt != null) stmt.close(); if (conn != null) conn.close(); } catch (SQLException e) { e.printStackTrace(); } } }
Statement是JDBC中最基本的操作方式,它用于向數(shù)據(jù)庫發(fā)送SQL語句并執(zhí)行它們。下面是一個(gè)使用Statement進(jìn)行CRUD操作的示例:
import java.sql.*; public class StatementCRUD { public static void main(String[] args) { Connection conn = null; Statement stmt = null; ResultSet rs = null; try { conn = JDBCUtils.getConnection(); stmt = conn.createStatement(); // 插入數(shù)據(jù) String sql = "INSERT INTO users (name, age) VALUES ('Tom', 18)"; stmt.executeUpdate(sql); // 更新數(shù)據(jù) sql = "UPDATE users SET age = 20 WHERE name = 'Tom'"; stmt.executeUpdate(sql); // 刪除數(shù)據(jù) sql = "DELETE FROM users WHERE age = 20"; stmt.executeUpdate(sql); // 查詢數(shù)據(jù) sql = "SELECT * FROM users"; rs = stmt.executeQuery(sql); while (rs.next()) { System.out.println(rs.getInt(1) + ", " + rs.getString(2) + ", " + rs.getInt(3)); } } catch (SQLException e) { e.printStackTrace(); } finally { JDBCUtils.release(rs, stmt, conn); } } }
下面是一個(gè)使用PreparedStatement進(jìn)行CRUD操作的示例:
import java.sql.*; public class PreparedStatementCRUD { public static void main(String[] args) { Connection conn = null; PreparedStatement pstmt = null; ResultSet rs = null; try { conn = JDBCUtils.getConnection(); // 插入數(shù)據(jù) String sql = "INSERT INTO users (name, age) VALUES (?, ?)"; pstmt = conn.prepareStatement(sql); pstmt.setString(1, "Tom"); pstmt.setInt(2, 18); pstmt.executeUpdate(); // 更新數(shù)據(jù) sql = "UPDATE users SET age = ? WHERE name = ?"; pstmt = conn.prepareStatement(sql); pstmt.setInt(1, 20); pstmt.setString(2, "Tom"); pstmt.executeUpdate(); // 刪除數(shù)據(jù) sql = "DELETE FROM users WHERE age = ?"; pstmt = conn.prepareStatement(sql); pstmt.setInt(1, 20); pstmt.executeUpdate(); // 查詢數(shù)據(jù) sql = "SELECT * FROM users"; pstmt = conn.prepareStatement(sql); rs = pstmt.executeQuery(); while (rs.next()) { System.out.println(rs.getInt(1) + ", " + rs.getString(2) + ", " + rs.getInt(3)); } } catch (SQLException e) { e.printStackTrace(); } finally { JDBCUtils.release(rs, pstmt, conn); } } }
Dao(Data Access Object)模式是一種用于封裝數(shù)據(jù)訪問邏輯的設(shè)計(jì)模式。它將數(shù)據(jù)訪問邏輯與業(yè)務(wù)邏輯分離開來,使得代碼更易于維護(hù)和擴(kuò)展。下面是一個(gè)使用Dao模式進(jìn)行CRUD操作的示例:
import java.sql.*; public class UserDAO { private static final String INSERT_SQL = "INSERT INTO users (name, age) VALUES (?, ?)"; private static final String UPDATE_SQL = "UPDATE users SET age = ? WHERE name = ?"; private static final String DELETE_SQL = "DELETE FROM users WHERE age = ?"; private static final String SELECT_SQL = "SELECT * FROM users"; public void insert(User user) { Connection conn = null; PreparedStatement pstmt = null; try { conn = JDBCUtils.getConnection(); pstmt = conn.prepareStatement(INSERT_SQL); pstmt.setString(1, user.getName()); pstmt.setInt(2, user.getAge()); pstmt.executeUpdate(); } catch (SQLException e) { e.printStackTrace(); } finally { JDBCUtils.release(null, pstmt, conn); } } public void update(User user) { Connection conn = null; PreparedStatement pstmt = null; try { conn = JDBCUtils.getConnection(); pstmt = conn.prepareStatement(UPDATE_SQL); pstmt.setInt(1, user.getAge()); pstmt.setString(2, user.getName()); pstmt.executeUpdate(); } catch (SQLException e) { e.printStackTrace(); } finally { JDBCUtils.release(null, pstmt, conn); } } public void delete(int age) { Connection conn = null; PreparedStatement pstmt = null; try { conn = JDBCUtils.getConnection(); pstmt = conn.prepareStatement(DELETE_SQL); pstmt.setInt(1, age); pstmt.executeUpdate(); } catch (SQLException e) { e.printStackTrace(); } finally { JDBCUtils.release(null, pstmt, conn); } } public List<User> selectAll() { Connection conn = null; PreparedStatement pstmt = null; ResultSet rs = null; List<User> userList = new ArrayList<>(); try { conn = JDBCUtils.getConnection(); pstmt = conn.prepareStatement(SELECT_SQL); rs = pstmt.executeQuery(); while (rs.next()) { User user = new User(); user.setId(rs.getInt(1)); user.setName(rs.getString(2)); user.setAge(rs.getInt(3)); userList.add(user); } } catch (SQLException e) { e.printStackTrace(); } finally { JDBCUtils.release(rs, pstmt, conn); } return userList; } } public class User { private int id; private String name; private int age; // 省略getter、setter方法 }
PreparedStatement是一種預(yù)編譯的Statement,它可以通過占位符的方式來替換SQL語句中的參數(shù),避免了SQL注入的危險(xiǎn)。下面是一個(gè)使用PreparedStatement進(jìn)行CRUD操作的示例:
import java.sql.*; public class PrepareStatementCRUD { public static void main(String[] args) { Connection conn = null; PreparedStatement pstmt = null; ResultSet rs = null; try { conn = JDBCUtils.getConnection(); // 插入數(shù)據(jù) String sql = "INSERT INTO users (name, age) VALUES (?, ?)"; pstmt = conn.prepareStatement(sql); pstmt.setString(1, "Tom"); pstmt.setInt(2, 18); pstmt.executeUpdate(); // 更新數(shù)據(jù) sql = "UPDATE users SET age = ? WHERE name = ?"; pstmt = conn.prepareStatement(sql); pstmt.setInt(1, 20); pstmt.setString(2, "Tom"); pstmt.executeUpdate(); // 刪除數(shù)據(jù) sql = "DELETE FROM users WHERE age = ?"; pstmt = conn.prepareStatement(sql); pstmt.setInt(1, 20); pstmt.executeUpdate(); // 查詢數(shù)據(jù) sql = "SELECT * FROM users"; pstmt = conn.prepareStatement(sql); rs = pstmt.executeQuery(); while (rs.next()) { System.out.println(rs.getInt(1) + ", " + rs.getString(2) + ", " + rs.getInt(3)); } } catch (SQLException e) { e.printStackTrace(); } finally { JDBCUtils.release(rs, pstmt, conn); } } }
以上就是“怎么使用JDBC連接數(shù)據(jù)庫并執(zhí)行SQL語句”這篇文章的所有內(nèi)容,感謝各位的閱讀!相信大家閱讀完這篇文章都有很大的收獲,小編每天都會(huì)為大家更新不同的知識(shí),如果還想學(xué)習(xí)更多的知識(shí),請(qǐng)關(guān)注億速云行業(yè)資訊頻道。
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