1. JDBC入門
JDBC（Java Database Connectivity）是Java程序與數(shù)據(jù)庫(kù)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(lái)連接和操作數(shù)據(jù)庫(kù)。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(kù)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(kù)。在Java程序中，通過(guò)Connection接口的實(shí)現(xiàn)類來(lái)實(shí)現(xiàn)與數(shù)據(jù)庫(kù)的連接。
- Statement：Statement是一個(gè)JDBC接口，用于向數(shù)據(jù)庫(kù)發(fā)送SQL語(yǔ)句并執(zhí)行它們。在Java程序中，通過(guò)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(kù)中檢索到的結(jié)果集。ResultSet對(duì)象通過(guò)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(kù)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(kù)連接
rs.close();
stmt.close();
conn.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
2. 抽取工具類
在實(shí)際開(kāi)發(fā)中，我們通常會(huì)抽取出一個(gè)JDBC工具類來(lái)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(kù)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(kù)發(fā)送SQL語(yǔ)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(kāi)）
Dao（Data Access Object）模式是一種用于封裝數(shù)據(jù)訪問(wèn)邏輯的設(shè)計(jì)模式。它將數(shù)據(jù)訪問(wèn)邏輯與業(yè)務(wù)邏輯分離開(kāi)來(lái)，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(guò)占位符的方式來(lái)替換SQL語(yǔ)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：文章來(lái)源：http://www.zghlxwxcb.cn/news/detail-425096.html
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(kāi)）、PrepareStatement CRUD的詳細(xì)介紹和代碼示例。通過(guò)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(kāi)發(fā)技巧，從而更好地應(yīng)用到實(shí)際的項(xiàng)目中。文章來(lái)源地址http://www.zghlxwxcb.cn/news/detail-425096.html
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