database.java

完成图书管理系统的一些简单的功能

package util;

import java.sql.*;

public class Database {
	private static Connection conn = null;

	private static Statement stmt = null;

	private static ResultSet rs = null;

	private static String _dbDriver = "com.mysql.jdbc.Driver";

	private static String _dbUrl = "jdbc:mysql://localhost:3306/db_library";

	private static String _dbUser = "library";

	private static String _dbPassword = "library";

	public Database() {
	}

	public Database(String dbDriver, String dbUrl, String dbUser,
			String dbPassword) {
		_dbDriver = dbDriver;
		_dbUrl = dbUrl;
		_dbUser = dbUser;
		_dbPassword = dbPassword;
	}

	public static Connection getDbConnection() {
		try {
			Class.forName(_dbDriver).newInstance();
			conn = DriverManager.getConnection(_dbUrl, _dbUser, _dbPassword);
		} catch (Exception e) {
			e.getStackTrace();
		}
		// finally
		{
			if (conn == null) {
				System.err
						.println("警告：DbConnectionManager.getConnection()获得数据库链接失败。\r\n\r\n链接类型："
								+ _dbDriver
								+ "\r\n链接位置："
								+ _dbUrl
								+ "\r\n用户/密码：" + _dbUser + "/" + _dbPassword);
			}
			return conn;
		}
	}

	public static ResultSet executeQuery(String sql) {
		try {
			conn = Database.getDbConnection();
			stmt = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,
					ResultSet.CONCUR_READ_ONLY);
			rs = stmt.executeQuery(sql);
		} catch (Exception e) {
			System.err.println(e.getMessage());
		}
		if (rs == null) {
			System.err
					.println("execute query sql statement is error,please check!");
		}
		return rs;
	}

	public int executeUpdate(String sql) {// 返回更新的行数
		int result = 0;
		try {
			conn = Database.getDbConnection();
			stmt = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,
					ResultSet.CONCUR_READ_ONLY);
			result = stmt.executeUpdate(sql);
		} catch (SQLException e) {
			result = 0;
		}
		try {
			stmt.close();
		} catch (SQLException e) {
		}
		return result;
	}

	public int executeUpdate_id(String sql) {// 返回更新的字段编号
		int result = 0;
		try {
			conn = Database.getDbConnection();
			stmt = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,
					ResultSet.CONCUR_READ_ONLY);
			result = stmt.executeUpdate(sql);
			String ID = "select@@identity as id";
			rs = stmt.executeQuery(ID);
			if (rs.next()) {
				result = rs.getInt("id");
			}
		} catch (SQLException e) {
			result = 0;
		}
		return result;
	}

	public void close() {
		try {
			if (rs != null) {
				rs.close();
			}
		} catch (Exception e) {
			e.printStackTrace(System.err);
		}
		try {
			if (stmt != null) {
				stmt.close();
			}
		} catch (Exception e) {
			e.printStackTrace(System.err);
		}
		try {
			if (conn != null) {
				conn.close();
			}
		} catch (Exception e) {
			e.printStackTrace(System.err);
		}
	}

}