java（JDBC连接数据库）[对PreparedStatement进行封装]

package com.iflytec.ex01;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class ConnectionDB {

	/**
	 * 数据库驱动类名称
	 */
	private static final String DRIVER = "com.microsoft.sqlserver.jdbc.SQLServerDriver";

	/**
	 * 连接字符串
	 */
	private static final String URLSTR = "jdbc:sqlserver://localhost:1433; databaseName=Northwind";

	/**
	 * 用户名
	 */
	private static final String USERNAME = "sa";

	/**
	 * 密码
	 */
	private static final String USERPASSWORD = "111111";

	/**
	 * 创建数据库连接类
	 */
	private Connection connnection = null;

	private PreparedStatement preparedStatement = null;

	/**
	 * 创建结果集对象
	 */
	private ResultSet resultSet = null;

	static {
		try {
			// 加载数据库驱动程序
			Class.forName(DRIVER);
		} catch (ClassNotFoundException e) {
			System.out.println("加载驱动错误");
			System.out.println(e.getMessage());
		}
	}

	/**
	 * 建立数据库连接
	 * 
	 * @return
	 */
	public Connection getConnection() {
		try {
			// 获取连接
			connnection = DriverManager.getConnection(URLSTR, USERNAME,
					USERPASSWORD);
		} catch (SQLException e) {
			System.out.println(e.getMessage());
		}
		return connnection;
	}

	public int executeUpdate(String sql, Object[] params) {
		int affectedLine = 0;
		try {
			connnection = this.getConnection();
			preparedStatement = connnection.prepareStatement(sql);
			for (int i = 0; i < params.length; i++) {
				preparedStatement.setObject(i + 1, params[i]);
			}

			affectedLine = preparedStatement.executeUpdate();

		} catch (SQLException e) {
			System.out.println(e.getMessage());
		} finally {
			closeAll();
		}
		return affectedLine;
	}
	

	private ResultSet executeQueryRS(String sql, Object[] params) {
		try {
			connnection = this.getConnection();
			preparedStatement = connnection.prepareStatement(sql);
			for (int i = 0; i < params.length; i++) {
				preparedStatement.setObject(i + 1, params[i]);
			}

			resultSet = preparedStatement.executeQuery();

		} catch (SQLException e) {
			System.out.println(e.getMessage());
		} 
		
		return resultSet;
	}
	
	/**
	 * 获取结果集，并将结果放在List中
	 * @param sql SQL语句
	 * @return List结果集
	 */
	public List<Object> excuteQuery(String sql, Object[] params) { 
		ResultSet rs = executeQueryRS(sql,params);
		ResultSetMetaData rsmd = null;
		int columnCount = 0;
		try {
			rsmd = rs.getMetaData();
			columnCount = rsmd.getColumnCount();
		} catch (SQLException e1) {
			System.out.println(e1.getMessage());
		}
		
		List<Object> list = new ArrayList<Object>();
		
		try {
			while(rs.next()) {
				Map<String, Object> map = new HashMap<String, Object>();
				for(int i = 1; i <= columnCount; i++) {
					map.put(rsmd.getColumnLabel(i), rs.getObject(i));				
				}
				list.add(map);
			}
		} catch (SQLException e) {
			System.out.println(e.getMessage());
		} finally {
			closeAll();
		}
		
		return list;
	}

	private void closeAll() {

		if (resultSet != null) {
			try {
				resultSet.close();
			} catch (SQLException e) {
				System.out.println(e.getMessage());
			}
		}

		if (preparedStatement != null) {
			try {
				preparedStatement.close();
			} catch (SQLException e) {
				System.out.println(e.getMessage());
			}
		}
		
		if (connnection != null) {
			try {
				connnection.close();
			} catch (SQLException e) {
				System.out.println(e.getMessage());
			}
		}
	}
}