JDBC 完整封装（二）

小咪咪 2022-05-20 06:26 182阅读 0赞

![JDBCUtil 文件结构][JDBCUtil]

## JDBCUtil 工具类 ##

*  使用properties加载属性文件
 *  获取数据库连接
 *  释放资源（重载释放资源方法）

## 实现代码 ##

*  main 测试类
 *  JDBCUtil 工具类
 *  jdbc.properties 配置类

`/demo1/src/MainTest.java`

import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Statement;
    
    import com.mysql.jdbc.Driver;
    
    public class MainTest { 
    
        public static void main(String[] args) {
            // TODO Auto-generated method stub
            Connection conn  = null;
            Statement stmt   = null;
            ResultSet rs     = null;
            try {
    
                conn = JDBCUtil.getConnection();
                // 3. 创建连接对象
                stmt = conn.createStatement();
                String sql = "select * from student";
                // 4. 执行sql，获得查询结果
                rs = stmt.executeQuery(sql);
                // 5. 循环遍历，处理每一条结果
                while (rs.next()) {
                    int id = rs.getInt("studentNo");
                    String name = rs.getString("name");
                    System.out.println("id :" + id + ", name : " + name);
                }
    
    
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } finally {
                JDBCUtil.close(conn, stmt, rs);
            }
    
        }
    
    }

`/demo1/src/jdbc.properties`

driverClassName=com.mysql.jdbc.Driver
    url=jdbc:mysql://localhost/myschool
    user=root
    password=103013

`/demo1/src/JDBCUtil.java`

import java.io.InputStream;
    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Statement;
    import java.util.Properties;
    
    public class JDBCUtil { 
        private static String url;
        private static String user;
        private static String password;
    
        static {
    
            // 使用properties加载属性文件
            Properties prop = new Properties();
            try {
                InputStream is = JDBCUtil.class.getClassLoader().getResourceAsStream("jdbc.properties");
                prop.load(is);
                // 注册驱动（获取属性文件中的数据）
                String driverClassName = prop.getProperty("driverClassName");
                Class.forName(driverClassName);
                // 获取属性文件中的url,username,password
                url = prop.getProperty("url");
                user = prop.getProperty("user");
                password = prop.getProperty("password");
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    
        // 获取数据库连接
        public static Connection getConnection() {
            Connection conn = null;
            try {
                conn = DriverManager.getConnection(url, user, password);
            } catch (SQLException e) {
                e.printStackTrace();
            }
            return conn;
        }
    
        // 释放资源
        public static void close(Connection conn, Statement stat, ResultSet rs) {
            close(conn, stat);
            if (rs != null) {
                try {
                    rs.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    
        // 释放资源
        public static void close(Connection conn, Statement stat) {
            if (conn != null) {
                try {
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (stat != null) {
                try {
                    stat.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }

[JDBCUtil]: /images/20220520/69387cf401984f439264f5278aa0a14d.png