使用PreparedStatement实现增删改、查操作

1. 获取数据库的连接

public static Connection getConnection() throws Exception {
        //1.加载配置文件
        InputStream is = ClassLoader.getSystemClassLoader().getResourceAsStream("jdbc.properties");
        Properties pros = new Properties();
        pros.load(is);

        //2.读取配置信息
        String user = pros.getProperty("user");
        String password = pros.getProperty("password");
        String url = pros.getProperty("url");
        String driverClass = pros.getProperty("driverClass");

        //3.加载驱动
        Class.forName(driverClass);

        //4.获取连接
        return DriverManager.getConnection(url,user,password);
    }

2. 关闭连接

//增删改！
public static void closeResource(Connection conn, Statement ps){
        try {
            if (ps != null) {
                ps.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        try {
            if (conn != null) {
                conn.close();
            }

        } catch (SQLException e) {
            e.printStackTrace();
        }

    }

//查询！
public static void closeResources(Connection conn, Statement ps, ResultSet rs) {

        try {
            if (ps != null) {
                ps.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        try {
            if (conn != null) {
                conn.close();
            }

        } catch (SQLException e) {
            e.printStackTrace();
        }
        try {
            if (rs != null) {
                rs.close();
            }

        } catch (SQLException e) {
            e.printStackTrace();
        }


    }

3. 通用的增删改操作

public int update(String sql, Object ...args){//sql中占位符的个数应与可变参数的长度相同
        Connection conn = null;
        PreparedStatement ps = null;
        try {
            //1.获取数据库的连接
            conn = JDBCUtils.getConnection();
            //2.预编译sql语句，返回实例
            ps = conn.prepareStatement(sql);
            //3.填充占位符
            for (int i = 0; i < args.length; i++) {
                ps.setObject(i + 1, args[i]);
            }
            //4.执行
            /*
            * 如果执行的是查询操作，有返回结果则返回true；
            * 如果是其他的操作，无返回结果则返回false
            */
            //ps.execute();

            return ps.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            //5.资源的关闭
            JDBCUtils.closeResource(conn,ps);
        }
        return 0;


    }

4. 通用查询操作

public <T> List<T> getForList(Class<T> clazz, String sql, Object... args){
	
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
		//获取数据库连接
            conn = JDBCUtils.getConnection();
			//预编译sql语句，得到PreparedStatement对象
            ps = conn.prepareStatement(sql);
			//填充占位符
            for (int i = 0; i < args.length; i++) {
                ps.setObject(i + 1, args[i]);
            }
			//执行excuteQuery()，得到结果集。

            rs = ps.executeQuery();
			//结果集的元数据
            ResultSetMetaData read = rs.getMetaData();
			//得到数据库的列数
            int columnCount = read.getColumnCount();
            //创建集合对象
            ArrayList<T> list = new ArrayList<>();
            while (rs.next()){
                T t = clazz.newInstance();
                for (int i = 0; i < columnCount; i++) {
                    Object columnValue = rs.getObject(i + 1);
					//获取列的别名
                    String columnLabel = read.getColumnLabel(i + 1);
					//使用反射，给对象的相应属性赋值
                    Field field = clazz.getDeclaredField(columnLabel);
                    field.setAccessible(true);
                    field.set(t, columnValue);
                }
                list.add(t);
            }
            return list;
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
		//关闭资源
            JDBCUtils.closeResources(conn, ps, rs);
        }
        return null;

    }

标签：ps,PreparedStatement,String,rs,try,增删,操作,null,conn
来源： https://www.cnblogs.com/ylxx-drizzle/p/16536496.html