conndb.java

利用Mysql数据库、struts框架实现的web系统开发

package com.dao.conn;

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

public class ConnDB {
	public ConnDB() {
	}

	// 如何从配置文件里读出来的信息
	private static Connection conn = null;

	private static String driverName = "com.mysql.jdbc.Driver"; // JDBC驱动

	private static String userName = "root"; // 数据库登录用户名

	private static String password = "lxj504241"; // 数据库登录密码(如果没有设置，可以为空)

	private static String dbName = "officesystem"; // 数据库名称

	private Statement stmt; // 数据库管理员

	private ResultSet res; // 返回结果集

	private static String url = "jdbc:mysql://localhost:3306/" + dbName
			+ "?user=" + userName + "&password=" + password;

	public static Connection getConnection() {
		try {
			Class.forName(driverName);
			conn = DriverManager.getConnection(url);
		} catch (ClassNotFoundException ex) {
			ex.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return conn;
	}

	public ResultSet executeQuery(String sql) {
		// 对数据库进行查询操作

		try {
			conn = this.getConnection();
			stmt = conn.createStatement();
			try {
				res = stmt.executeQuery(sql);
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
				return null;
			}
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			return null;
		}
		return res;
	}

	public int update(String sql) {
		// 对数据库信息进行更新操作
		int count = 0;
		try {
			if (conn == null) {
				getConnection();
			}
			stmt = conn.createStatement();
			count = stmt.executeUpdate(sql);
			return count;
		} catch (SQLException e) {
			e.printStackTrace();
			return 0;
		} finally {
			this.close();
		}
	}

	public void close() {
		// 关闭数据库连接

		if (res != null) {
			try {
				res.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} finally {
				res = null;
			}
		}
		if (stmt != null) {
			try {
				stmt.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} finally {
				stmt = null;
			}
		}
		if (conn != null) {
			try {
				conn.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} finally {
				conn = null;
			}
		}
	}
}