做个简单的Java学生考勤系统02--工具类

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工欲善其事，必先利其器。完成Java学生考勤的下一步是要有其相关的工具类作为考勤系统的辅助工具，下来列出有哪些相关的工具类。
工具类：

1、DB工具类

是连接数据库的工具类，数据库的用户名，密码，数据库驱动名称，url（JDBC+数据库库名的地址）。将数据保存到数据库里，也可以从数据库读取数据

package util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class DB
{
	private Connection con;

	private PreparedStatement pstm;

	private String user = "root";

	private String password = "123456";

	private String className = "com.mysql.jdbc.Driver";

	private String url = "jdbc:mysql://localhost:3306/db_kaoqin";

	public DB()
	{
		try
		{
			Class.forName(className);
		} catch (ClassNotFoundException e)
		{
			System.out.println("加载数据库驱动失败！");
			e.printStackTrace();
		}
	}

	/** 创建数据库连接 */
	public Connection getCon()
	{
		try
		{
			con = DriverManager.getConnection(url, user, password);
		} catch (SQLException e)
		{
			System.out.println("创建数据库连接失败！");
			con = null;
			e.printStackTrace();
		}
		return con;
	}

	public void doPstm(String sql, Object[] params)
	{
		if (sql != null && !sql.equals(""))
		{
			if (params == null)
				params = new Object[0];

			getCon();
			if (con != null)
			{
				try
				{
					System.out.println(sql);
					pstm = con.prepareStatement(sql,
							ResultSet.TYPE_SCROLL_INSENSITIVE,
							ResultSet.CONCUR_READ_ONLY);
					for (int i = 0; i < params.length; i++)
					{
						pstm.setObject(i + 1, params[i]);
					}
					pstm.execute();
				} catch (SQLException e)
				{
					System.out.println("doPstm()方法出错！");
					e.printStackTrace();
				}
			}
		}
	}

	public ResultSet getRs() throws SQLException
	{
		return pstm.getResultSet();
	}

	public int getCount() throws SQLException
	{
		return pstm.getUpdateCount();
	}

	public void closed()
	{
		try
		{
			if (pstm != null)
				pstm.close();
		} catch (SQLException e)
		{
			System.out.println("关闭pstm对象失败！");
			e.printStackTrace();
		}
		try
		{
			if (con != null)
			{
				con.close();
			}
		} catch (SQLException e)
		{
			System.out.println("关闭con对象失败！");
			e.printStackTrace();
		}
	}
}

2、配置filter

配置EncodingFilter过滤器，用来处理请求编码问题，解决Java中文乱码问题。

package util;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class EncodingFilter implements Filter {
	protected String encoding = "";

	protected FilterConfig filterConfig = null;

	public void destroy() {
		this.encoding = null;
		this.filterConfig = null;
	}

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		// Select and set (if needed) the character encoding to be used
		String encoding = selectEncoding(request);
		if (encoding != null) {
			request.setCharacterEncoding(encoding);
			response.setCharacterEncoding(encoding);
		}
		// Pass control on to the next filter
		chain.doFilter(request, response);
	}

	public void init(FilterConfig filterConfig) throws ServletException {
		this.filterConfig = filterConfig;
		this.encoding = filterConfig.getInitParameter("encoding");
	}

	protected String selectEncoding(ServletRequest request) {
		return (this.encoding);
	}
}

3、其他工具类

包含了时间转换，截取时间，将字符串截短等方法

package util;

import java.text.ParseException;
import java.util.Date;
import java.util.GregorianCalendar;

public class Util {
	public static Date newDate(String s) throws ParseException {
		java.text.SimpleDateFormat sdf = new java.text.SimpleDateFormat(
				"yyyy-MM-dd");
		Date date = new Date();
		date = sdf.parse(s);
		return date;
	}

	public static Date newDate1(String s) throws ParseException {
		java.text.SimpleDateFormat sdf = new java.text.SimpleDateFormat(
				"yyyy-MM-dd HH:mm");
		Date date = new Date();
		date = sdf.parse(s);
		return date;
	}

	public static Date FormatFullDate(String s) throws ParseException {
		java.text.SimpleDateFormat sdf = new java.text.SimpleDateFormat(
				"yyyy-MM-dd HH:mm:ss");
		Date date = new Date();
		date = sdf.parse(s);
		return date;

	}

	public static String splitDate(Date d) {
		java.text.SimpleDateFormat sdf = new java.text.SimpleDateFormat(
				"yyyy-MM-dd");
		return sdf.format(d);
	}

	public static String splitDate1(Date d) {
		java.text.SimpleDateFormat sdf = new java.text.SimpleDateFormat(
				"yyyy年MM月dd日");
		return sdf.format(d);
	}

	/**
	 * 将字符串截短，取前n个字符，英文算半个字符。
	 * 
	 * @param orignalString
	 *            原字符串
	 * @param length
	 *            长度
	 * @param chopedString
	 *            超过部分的表示字符串
	 * @return 截取的字符串
	 */
	public static String chop(String orignalString, double length,
			String chopedString) {
		if (orignalString == null || orignalString.length() == 0) {
			return orignalString;
		}
		orignalString = orignalString.replaceAll(" ", " ");
		if (orignalString.length() < length) {
			return orignalString;
		}
		StringBuffer buffer = new StringBuffer((int) length);
		length = length * 2;
		int count = 0;
		int stringLength = orignalString.length();
		int i = 0;
		for (; count < length && i < stringLength; i++) {
			char c = orignalString.charAt(i);
			if (c < '\u00ff') {
				count++;
			} else {
				count += 2;
			}
			buffer.append(c);
		}
		if (i < stringLength) {
			buffer.append(chopedString);
		}
		return buffer.toString();
	}

	public static long getPrimeKey() {
		GregorianCalendar calendar = new GregorianCalendar();
		return calendar.getTimeInMillis();
	}

	public static long stringToLong(String source) {
		return Long.parseLong(source);
	}
}

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