JDBC操作封裝實例

JDBCUtile.properties

drv=com.mysql.jdbc.Driver
url=jdbc:mysql:///myHomePage
uid=root
pwd=root

JDBCUtile

/**
 * JDBC工具類
 * @author leex
 *
 */
public class JDBCUtils {
    //創建Properties文件對象
    private static Properties prop = new Properties();
    //創建ThreadLocal線程鎖
    private static ThreadLocal<Connection> treadLocal = new ThreadLocal<Connection>();
    
    static {
        //TWR語法創建Properties文件輸入流
        //JDBCUtils.class.getClassLoader().getResourceAsStream("JDBC.properties")通過類加載器獲取文件完全路徑
        try (InputStream in = JDBCUtils.class.getClassLoader().getResourceAsStream("JDBC.properties")){
            //加載Properties文件
            prop.load(in);
            //加載數據庫驅動
            Class.forName(prop.getProperty("drv"));
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
    
    /**
     * 獲取Connection對象的方法
     * @return  Connection對象
     * @throws SQLException
     */
    public static Connection getConnection() throws SQLException {
        //獲取與此線程綁定的Connection
        Connection conn = treadLocal.get();
        //如果不為空返回
        if(null != conn) {
            return conn;
        }
        //如果為空創建新的
        conn = DriverManager.getConnection(
                prop.getProperty("url"), prop.getProperty("uid"), prop.getProperty("pwd"));
        //把創建的線程綁定到線程
        treadLocal.set(conn);
        return conn;
    }
    
    /**
     * 關閉Connection
     * @throws SQLException
     */
    public static void close() throws SQLException {
        Connection conn = treadLocal.get();
        if(null != conn) {
            conn.close();
            //從線程綁定中移除
            treadLocal.remove();
        }
    }
}

BaseDao

/**
 * 封裝的JDBC基礎操作類
 * @author leex
 *
 */
public class BaseDao {
    
    /**
     * 更新方法
     * @param sql       sql語句
     * @param paramers  占位符的值
     * @return
     * @throws SQLException
     */
    public int update(String sql ,Object...paramers) throws SQLException {
        //通過JDBCUtils獲取Connection連接
        Connection conn = JDBCUtils.getConnection();
        //創建PreparedStatement對象
        PreparedStatement statm = conn.prepareStatement(sql);
        //創建PreparedStatement元數據
        ParameterMetaData parameterMetaData = statm.getParameterMetaData();
        //通過PreparedStatement元數據獲取數據庫中的字段數
        int count = parameterMetaData.getParameterCount();
        //判斷輸入的值數量是否正確(提高程序健壯性)
        if(null != paramers) {
            if(count != paramers.length) {
                throw new RuntimeException("傳入的參數有錯誤....");
            }
        }
        //給sql語句中的占位符賦值
        for (int i = 0; i < paramers.length; i++) {
            statm.setObject(i + 1, paramers[i]);
        }
        //更新
        int executeUpdate = statm.executeUpdate();
        //關閉connection
        JDBCUtils.close();
        //返回收影響的行數
        return executeUpdate;
    }
    
    /**
     * 通用查詢方法
     * @param sql           sql語句   
     * @param clazz         返回的封裝類
     * @param paramers      sql占位符值
     * @return
     * @throws SQLException
     * @throws InstantiationException
     * @throws IllegalAccessException
     * @throws InvocationTargetException
     */
    public <T> List<T> queryList(String sql, Class clazz, Object... paramers ) throws SQLException, InstantiationException, IllegalAccessException, InvocationTargetException {
        List<T> list = new ArrayList<>();
        
        //通過JDBCUtils獲取Connection連接
        Connection conn = JDBCUtils.getConnection();
        //創建PreparedStatement對象
        PreparedStatement statm = conn.prepareStatement(sql);
        //創建PreparedStatement元數據
        ParameterMetaData parameterMetaData = statm.getParameterMetaData();
        //通過PreparedStatement元數據獲取數據庫中的字段數
        int count = parameterMetaData.getParameterCount();
        //判斷輸入的值數量是否正確(提高程序健壯性)
        if(null != paramers) {
            if(count != paramers.length) {
                throw new RuntimeException("傳入的參數有錯誤....");
            }
        }
        if(0 != paramers.length)
        for (int i = 0; i < paramers.length; i++) {
            statm.setObject(i + 1, paramers[i]);
        }
        //獲取結果集
        ResultSet result = statm.executeQuery();
        //創建結果集元數據
        ResultSetMetaData metaData = result.getMetaData();
        //獲取結果集的列數
        int columnCount = metaData.getColumnCount();
        //遍歷結果集
        while(result.next()) {
            //創建對象
            T t = (T) clazz.newInstance();
            //給對象賦值
            for (int i = 0; i < columnCount; i++) {
                //獲取結果集的列名(有別名則就是別名)
                String columnName = metaData.getColumnLabel(i+1);
                //獲取值
                Object value = result.getObject(columnName);
                //通過BeanUtils匹配賦值
                BeanUtils.copyProperty(t, columnName, value);
            }
            //加入列表
            list.add(t);
        }
        //關閉connection
        JDBCUtils.close();
        //返回list
        return list;
    }
}