checker.java

一个简单的网上订书系统 java的课程设计

package proxy;

import java.sql.Date;

public class Checker {

	public static final String nullStr = "null";

	public static final String comma = ",";

	private static final String datePattern = "[0-9]{4}-[0-9]{2}-[0-9]{2}";

	public static String checkNull(String s) {
		if (s == null || s.trim().length() == 0)
			return nullStr;
		else
			return "'" + s.trim() + "'";
	}

	public static String isDate(String date) {
		if (date == null || date.trim().length() == 0)
			return nullStr;
		String t = date.trim();
		if (t.matches(datePattern)) {
			date = "'" + t + "'";
		} else {
			System.err.println("Date Format error : " + t);
			date = nullStr;
		}
		return date;
	}

	public static String updateOnNull(String s) {
		if (s == null || s.trim().length() == 0)
			return null;
		String t = s.trim();
		if (t.equals("null"))
			return t;
		return "'" + t + "'";
	}

	public static String addComma(String front, String back) {

		if (checkNull(front) != nullStr && checkNull(back) != nullStr
				&& (!front.equals("0.0")) && (!back.equals("0.0")))
			return comma;
		return "";
	}

	public static String argsInsert(String query, String[] args) {
		for (int i = 0; i < args.length; i++) {
			if (i == args.length - 1)
				query += checkNull(args[i]) + ");";
			else
				query += checkNull(args[i]) + comma;
		}
		return query;
	}

}