JDBC工具类

package com.demo.util;

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.util.Properties;

public class DBHelper {

	private static String driver;
	private static String url;
	private static String username;
	private static String password;
	private static Connection conn;

	private static void init() {

		Properties props = new Properties();
		InputStream fis = DBHelper.class
				.getResourceAsStream("/jdbc.properties");
		try {
			props.load(fis);
		} catch (IOException e) {
			e.printStackTrace();
		}
		driver=props.getProperty("jdbc.driver");
		url=props.getProperty("jdbc.url");
		username=props.getProperty("jdbc.username");
		password=props.getProperty("jdbc.password");
	}
	
	//获取数据库连接
	public static Connection getConn(){
		init();
		try{
			Class.forName(driver);
			conn=DriverManager.getConnection(url,username,password);
		}catch(Exception e){
			e.printStackTrace();
		}
		return conn;
	}
	
	//关闭连接
	public static void closeConn(){
		try{
			if(conn!=null){
				conn.close();
				conn=null;
			}
		}catch(Exception e){
			e.printStackTrace();
		}
	}
}

package com.demo.util;

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.Iterator;
import java.util.List;
import java.util.Map;

public class DBCommand {

	private static ResultSet rs;

	private DBCommand() {
	}

	public static int execUpdate(PreparedStatement pstm,
			Map<Object, Object> paramsMap) {
		try {
			Iterator<Object> it=paramsMap.keySet().iterator();
			int i=1;
			while(it.hasNext()){
				pstm.setObject(i++, paramsMap.get(it.next()));
			}
			return pstm.executeUpdate();
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			close(pstm);
		}
		return -1;
	}

	public static List<Map<String, Object>> execQuery(PreparedStatement pstm,
			Map<Object, Object> paramsMap) {
		try {
			Iterator<Object> it = paramsMap.keySet().iterator();
			int i = 1;
			while (it.hasNext()) {
				pstm.setObject(i++, paramsMap.get(it.next()));
			}
			rs = pstm.executeQuery();
			return readRs(rs);
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			close(rs);
			close(pstm);
		}
		return null;
	}

	public static List<Map<String, Object>> execQuery(PreparedStatement pstm) {
		try {
			rs=pstm.executeQuery();
			return readRs(rs);
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			close(rs);
			close(pstm);
		}
		return null;
	}

	public static List<Map<String, Object>> readRs(ResultSet rs) {
		List<Map<String, Object>> data = new ArrayList<Map<String, Object>>();
		ResultSetMetaData rsmd;
		int columnCount;
		try {
			rsmd = rs.getMetaData();
			columnCount = rsmd.getColumnCount();
			while (rs.next()) {
				Map<String, Object> row = new HashMap<String, Object>();
				for (int index = 1; index <= columnCount; index++) {
					String columnName = rsmd.getColumnName(index);
					row.put(columnName, rs.getObject(columnName));
				}
				data.add(row);
			}
		} catch (SQLException e) {
			
			e.printStackTrace();
		}

		return data;
	}

	public static void close(ResultSet rs) {
		try {
			if (rs != null) {
				rs.close();
				rs = null;
			}
		} catch (Exception ex) {
			ex.printStackTrace();
		}
	}

	public static void close(PreparedStatement pstm) {
		try {
			if (pstm != null) {
				pstm.close();
				pstm = null;
			}
		} catch (Exception ex) {
			ex.printStackTrace();
		}
	}
}

package com.demo.dao;

import java.sql.PreparedStatement;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

import com.demo.entity.User;
import com.demo.util.BaseDAO;
import com.demo.util.DBCommand;

public class UserDaoImpl extends BaseDAO {

	private PreparedStatement pstm;

	public User getUser(String name, String password) {
		User user = null;
		String sqlStr="select * from t_user where name=? and password=?";
		try {
			pstm = this.getConn().prepareStatement(sqlStr);
			Map<Object,Object> paramsMap=new LinkedHashMap<Object,Object>();
			paramsMap.put("name", name);
			paramsMap.put("password", password);
			List<Map<String,Object>> userList=DBCommand.execQuery(pstm,paramsMap);
			if(userList.size()!=0){
				user=new User();
				Map<String,Object> row=userList.get(0);
				user.setId(new Integer(row.get("id").toString()));
				user.setName(row.get("name").toString());
				user.setPassword(row.get("password").toString());
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
		return user;
	}
}