反射实现增删改查（DAO层）——修改数据

Posted 2020-11-07 云中志

先贴出代码，后续补充自己的思路、配置文件、使用方式：

/**
     * 
     * 修改数据
     * 
     */
    @Override
    public void updateObject(Object object, String tableName) {
        StringBuilder sql = new StringBuilder("UPDATE " + tableName + " SET ");
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        // 用于存放传入的对象的参数，默认将id值（主键）的key设为0，方便条件设置
        Map<Integer, Object> fieldsValues = new HashMap<Integer, Object>();
        try {
            for (int i = 0; i < fields.length; i++) {
                fields[i].setAccessible(true);

                if (i == 0) {
                    fieldsValues.put(fields.length - 1, fields[i].get(object));
                    continue;
                }
                sql.append(fields[i].getName());
                sql.append("=?");
                fieldsValues.put(i - 1, fields[i].get(object));
                if (i < (fields.length - 1))
                    sql.append(", ");
                if (i == (fields.length - 1)) {
                    sql.append(" WHERE ");
                    sql.append(fields[0].getName());
                    sql.append("=?");
                }

            }
            connection = DBConnection.getConnection();

            preparedStatement = connection.prepareStatement(sql.toString());
            Class<?> fieldClass = null;
            for (int i = 1; i <= fieldsValues.size(); i++) {
                /**
                 * 获取存入map中对象的参数的类类型，根据类类型选择preparedStatement的set方法
                 */
                fieldClass = fieldsValues.get(i - 1).getClass();
                // 如果类类型为String.class，则执行setString
                if (fieldClass.equals(String.class)) {
                    preparedStatement.setString(i,
                            (String) fieldsValues.get(i - 1));
                }
                // 如果类类型为Float.class，则执行setString
                if (fieldClass.equals(Float.class)) {
                    preparedStatement.setFloat(i,
                            (Float) fieldsValues.get(i - 1));
                }
                // 如果类类型为Integer.class，则执行setString
                if (fieldClass.equals(Integer.class)) {
                    preparedStatement.setInt(i,
                            (Integer) fieldsValues.get(i - 1));
                }
                // 如果类类型为Timestamp.class，则执行setString
                if (fieldClass.equals(Timestamp.class)) {
                    preparedStatement.setTimestamp(i, new Timestamp(
                            ((Date) fieldsValues.get(i - 1)).getTime()));
                }

            }
            // 执行sql语句，返回更新参数
            int columnsCount = preparedStatement.executeUpdate();
            System.out.println("有" + columnsCount + "条数据被更新！");

        } catch (SQLException e) {
            e.printStackTrace();
        } catch (SecurityException e) {
            e.printStackTrace();
        } catch (NumberFormatException e) {
            e.printStackTrace();
        } catch (IllegalArgumentException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } finally {
            DBConnection.close(connection, preparedStatement, null);
        }

    }