Java JDBC

JDBC（Java DataBase Connection）

// 加载驱动
Class.forName("com.mysql.jdbc.Driver");

// 建立数据库连接
Connection = DriverManager.getConnection("jdbc；mysql://localhost:3306/Demo?useUnicode=true&characterEncoding=UTF8");

// 创建执行SQL的对象
Statement st = conn.createStatement();

// 提交 SQL 语句，并处理结果集
st.executeUpdate("SQL code");  //增删改
st.executeQuery("SQL code");   //查询

// 关闭数据库连接
st.close();
conn.close();

DBHelper 数据库连接类

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

/**
 * JDBC Utils
 * @author
 */
public class DBHelper {

    // 定义常量字符串存放数据库连接的信息
    private static final String USER = "root", PASSWORD = "root";
    private static final String URL = "jdbc:mysql://localhost:3306/Demo?useUnicode=true&characterEncoding=UTF8";

    /**
     * 连接数据库 Connection database
     * @return
     */
    public static Connection init() {
        Connection conn = null;
        try {
            // 加载驱动
            Class.forName("com.mysql.jdbc.Driver");         
            // 在驱动管理器的基础上获得连接
            conn = DriverManager.getConnection(URL, USER, PASSWORD);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return conn;
    }

    /**
     * 关闭连接  Close database
     * @param conn
     */
    public static void close(Connection conn) {
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * 设置SQL语句中不定量传参 
     * @param ps
     * @param values
     */
    private static void setParam(PreparedStatement ps, Object... values) {
        // 判断SQL语句中是否有条件
        if (values != null && values.length > 0) {
            // 循环设置参数
            for (int i = 0; i < values.length; i++) {
                try {
                    ps.setObject(i + 1, values[i]);
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    /**
     * 执行 insert delete update
     * @param conn
     * @param sql
     * @param values
     * @return
     */
    public static int executeUpdate(Connection conn, String sql, Object... values) {
        int alter = 0;
        try {
            // 编写SQL语句
            PreparedStatement ps = conn.prepareStatement(sql);
            // 设置参数
            setParam(ps, values);
            // 执行SQL语句
            alter = ps.executeUpdate();         
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return alter;
    }

    /**
     * 执行 select
     * @param conn
     * @param sql
     * @param values
     * @return
     */
    public static ResultSet executeQuery(Connection conn, String sql, Object... values) {
        ResultSet rs = null;
        try {
            PreparedStatement ps = conn.prepareStatement(sql);
            setParam(ps, values);
            rs = ps.executeQuery();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return rs;
    }
}

使用示例

• insert

Connection conn = DBUtils.init();
String sql = "insert into user(account,password) values (?,?);";
DBHelper.executeUpdate(conn, sql, "account", "password")

• delete

Connection conn = DBUtils.init();
String sql = "delete from user where id = ?";
DBUtils.executeUpdate(conn, sql, id);

• select

Connection conn = DBUtils.init();
String sql = "select * from user where account = ?";
ResultSet rs = DBHelper.executeQuery(conn, sql, "account")

• update

Connection conn = DBUtils.init();
String sql = "update user set account = ?,password = ? where id = ?";
DBUtils.executeUpdate(conn, sql, "account", "password");