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如何使用JDBC連接數(shù)據(jù)庫并執(zhí)行SQL語句

更新時(shí)間：2023年04月28日 11:12:57 作者：互聯(lián)小助手

JDBC是Java數(shù)據(jù)庫連接的縮寫，是Java程序與數(shù)據(jù)庫進(jìn)行交互的標(biāo)準(zhǔn)API。JDBC主要包括Java.sql和javax.sql兩個(gè)包，通過DriverManager獲取數(shù)據(jù)庫連接對(duì)象Connection，并通過Statement或PreparedStatement執(zhí)行SQL語句

1. JDBC入門

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();
        }
    }
}

2. 抽取工具類

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();
        }
    }
}

3. Statement CRUD

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);
        }
    }
}

4. 演練CRUD

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);
        }
    }
}

5. Dao模式(聲明與實(shí)現(xiàn)分開)

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
}

6. PrepareStatement CRUD

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);
        }
    }
}

以上就是關(guān)于JDBC入門、抽取工具類、Statement CRUD、演練CRUD、Dao模式（聲明與實(shí)現(xiàn)分開）、PrepareStatement CRUD的詳細(xì)介紹和代碼示例。通過學(xué)習(xí)這些內(nèi)容，可以讓我們更好地掌握J(rèn)DBC的使用和開發(fā)技巧，從而更好地應(yīng)用到實(shí)際的項(xiàng)目中。

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