Java -- JDBC 学习--PreparedStatement

3、PreparedStatement 可以防止 SQL 注入。

例子：

@Test
    public void testPreparedStatement() {
        Connection connection = null;
        PreparedStatement preparedStatement = null;

        try {
            connection = JDBCTools.getConnection();
            String sql = "INSERT INTO customers (name, email, birth) "
                    + "VALUES(?,?,?)";

            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setString(1, "soyoungboy");
            preparedStatement.setString(2, "soyoungboy@163.com");
            preparedStatement.setDate(3,
                    new Date(new java.util.Date().getTime()));

            preparedStatement.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JDBCTools.releaseDB(null, preparedStatement, connection); 
        }
    }

SQL 注入攻击

概念：

SQL 注入是利用某些系统没有对用户输入的数据进行充分的检查，而在用户输入数据中注入非法的 SQL 语句段或命令，从而利用系统的 SQL 引擎完成恶意行为的做法。

对于 Java 而言，要防范 SQL 注入，只要用 PreparedStatement 取代 Statement 就可以了。

sql注入例子：

/**
     * SQL 注入.
     */
    @Test
    public void testSQLInjection() {
        String username = "a‘ OR PASSWORD = ";
        String password = " OR ‘1‘=‘1";

        String sql = "SELECT * FROM users WHERE username = ‘" + username
                + "‘ AND " + "password = ‘" + password + "‘";

        System.out.println(sql);

        Connection connection = null;
        Statement statement = null;
        ResultSet resultSet = null;

        try {
            connection = JDBCTools.getConnection();
            statement = connection.createStatement();
            resultSet = statement.executeQuery(sql);

            if (resultSet.next()) {
                System.out.println("登录成功!");
            } else {
                System.out.println("用户名和密码不匹配或用户名不存在. ");
            }

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JDBCTools.releaseDB(resultSet, statement, connection);
        }
    }

使用PreparedStatement 解决sql注入例子：

/**
     * 使用 PreparedStatement 将有效的解决 SQL 注入问题.
     */
    @Test
    public void testSQLInjection2() {
        String username = "a‘ OR PASSWORD = ";
        String password = " OR ‘1‘=‘1";

        String sql = "SELECT * FROM users WHERE username = ? "
                + "AND password = ?";

        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;

        try {
            connection = JDBCTools.getConnection();
            preparedStatement = connection.prepareStatement(sql);

            preparedStatement.setString(1, username);
            preparedStatement.setString(2, password);

            resultSet = preparedStatement.executeQuery();

            if (resultSet.next()) {
                System.out.println("登录成功!");
            } else {
                System.out.println("用户名和密码不匹配或用户名不存在. ");
            }

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JDBCTools.releaseDB(resultSet, preparedStatement, connection);
        }
    }

Java -- JDBC 学习--PreparedStatement

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