Java获取数据库各种查询结果

在查询时候有时候要一条数据，有时候要的是一个结果集，然而有时候返回就是一个统计值，通过对ResultSet和ResultSetMetaData的变换得到各类所需的查询结果，因为没有利用连接池数据链接管理比较麻烦，所以谢了一个工具类，

package com.sky.connect;

import java.lang.reflect.InvocationTargetException;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.commons.beanutils.BeanUtils;

import com.mysql.jdbc.Connection;
import com.mysql.jdbc.PreparedStatement;
import com.mysql.jdbc.ResultSetMetaData;

/**
 * DAO设计模式
 * 
 * @author 潘琢文
 * 
 */
public class DAO {
	/**
	 * 更新数据库操作
	 * 
	 * @param sql
	 * @param args
	 */
	public void update(String sql, Object... args) {
		Connection connection = null;
		PreparedStatement preparedStatement = null;

		try {
			connection = JDBCTools.getConnection();
			preparedStatement = (PreparedStatement) connection
					.prepareStatement(sql);

			for (int i = 0; i < args.length; i++) {
				preparedStatement.setObject(i + 1, args[i]);
			}

			preparedStatement.executeUpdate();
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			JDBCTools.release(preparedStatement, connection);
		}
	}

	/**
	 * 通用查询方法，返回一条记录
	 * 
	 * @param clazz
	 * @param sql
	 * @param args
	 * @return
	 */
	public  T get(Class clazz, String sql, Object... args) {
		T entity = null;
		Connection connection = null;
		PreparedStatement preparedStatement = null;
		ResultSet result = null;

		try {
			connection = JDBCTools.getConnection();
			preparedStatement = (PreparedStatement) connection
					.prepareStatement(sql);
			for (int i = 0; i < args.length; i++) {
				preparedStatement.setObject(i + 1, args[i]);
			}

			result = preparedStatement.executeQuery();

			Map map = new HashMap();

			ResultSetMetaData rsmd = (ResultSetMetaData) result.getMetaData();
			if (result.next()) {
				for (int i = 0; i < rsmd.getColumnCount(); i++) {
					String columnLabel = rsmd.getColumnLabel(i + 1);
					Object value = result.getObject(i + 1);
					map.put(columnLabel, value);
				}
			}
			if (map.size() > 0) {
				entity = clazz.newInstance();
				for (Map.Entry entry : map.entrySet()) {
					String filedName = entry.getKey();
					Object filedObject = entry.getValue();
					BeanUtils.setProperty(entity, filedName, filedObject);
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			JDBCTools.release(result, preparedStatement, connection);
		}
		return entity;
	}

	/**
	 * 通用查询方法，返回一个结果集
	 * 
	 * @param clazz
	 * @param sql
	 * @param args
	 * @return
	 */
	public  List getForList(Class clazz, String sql, Object... args) {
		List list = new ArrayList();
		Connection connection = null;
		PreparedStatement preparedStatement = null;
		ResultSet result = null;
		try {
			connection = JDBCTools.getConnection();
			preparedStatement = (PreparedStatement) connection
					.prepareStatement(sql);
			for (int i = 0; i < args.length; i++) {
				preparedStatement.setObject(i + 1, args[i]);
			}

			result = preparedStatement.executeQuery();

			List> values = handleResultSetToMapList(result);
			list = transfterMapListToBeanList(clazz, values);
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			JDBCTools.release(result, preparedStatement, connection);
		}
		return list;
	}

	/**
	 * 
	 * @param clazz
	 * @param values
	 * @return
	 * @throws InstantiationException
	 * @throws IllegalAccessException
	 * @throws InvocationTargetException
	 */
	public  List transfterMapListToBeanList(Class clazz,
			List> values) throws InstantiationException,
			IllegalAccessException, InvocationTargetException {

		List result = new ArrayList();

		T bean = null;

		if (values.size() > 0) {
			for (Map m : values) {
				bean = clazz.newInstance();
				for (Map.Entry entry : m.entrySet()) {
					String propertyName = entry.getKey();
					Object value = entry.getValue();

					BeanUtils.setProperty(bean, propertyName, value);
				}
				// 13. 把 Object 对象放入到 list 中.
				result.add(bean);
			}
		}

		return result;
	}

	/**
	 * 
	 * @param resultSet
	 * @return
	 * @throws SQLException
	 */
	public List> handleResultSetToMapList(
			ResultSet resultSet) throws SQLException {
		List> values = new ArrayList>();

		List columnLabels = getColumnLabels(resultSet);
		Map map = null;

		while (resultSet.next()) {
			map = new HashMap();

			for (String columnLabel : columnLabels) {
				Object value = resultSet.getObject(columnLabel);
				map.put(columnLabel, value);
			}
			values.add(map);
		}
		return values;
	}

	/**
	 * 
	 * @param resultSet
	 * @return
	 * @throws SQLException
	 */
	private List getColumnLabels(ResultSet resultSet)
			throws SQLException {
		List labels = new ArrayList();

		ResultSetMetaData rsmd = (ResultSetMetaData) resultSet.getMetaData();
		for (int i = 0; i < rsmd.getColumnCount(); i++) {
			labels.add(rsmd.getColumnLabel(i + 1));
		}

		return labels;
	}

	/**
	 * 通用查询方法，返回一个值（可能是统计值）
	 * 
	 * @param sql
	 * @param args
	 * @return
	 */
	@SuppressWarnings("unchecked")
	public  E getForValue(String sql, Object... args) {
		Connection connection = null;
		PreparedStatement preparedStatement = null;
		ResultSet resultSet = null;
		try {
			connection = JDBCTools.getConnection();
			preparedStatement = (PreparedStatement) connection
					.prepareStatement(sql);
			for (int i = 0; i < args.length; i++) {
				preparedStatement.setObject(i + 1, args[i]);
			}
			resultSet = preparedStatement.executeQuery();
			if (resultSet.next()) {
				return (E) resultSet.getObject(1);
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			JDBCTools.release(resultSet, preparedStatement, connection);
		}
		return null;
	}
}

package com.sky.connect;

import java.io.IOException;
import java.io.InputStream;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;

import com.mysql.jdbc.Connection;
import com.mysql.jdbc.Driver;
import com.mysql.jdbc.PreparedStatement;
import com.mysql.jdbc.Statement;

/**
 * JDBC操作的工具类 版本 1.0
 * 
 * @author 潘琢文
 * 
 */
public class JDBCTools {
	/**
	 * 使用preparedStatement进行数据更新
	 * 
	 * @param sql
	 * @param args
	 */
	public static void update(String sql, Object ... args) {
		Connection connection = null;
		PreparedStatement preparedStatement = null;
		try {
			connection = JDBCTools.getConnection();
			preparedStatement = (PreparedStatement) connection
					.prepareStatement(sql);
			for (int i = 0; i < args.length; i++) {
				preparedStatement.setObject(i + 1, args[i]);
			}
			preparedStatement.executeUpdate();
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			JDBCTools.release(preparedStatement, connection);
		}
	}

	/**
	 * 结果查询关闭
	 * 
	 * @param rs
	 * @param statement
	 * @param conn
	 */
	public static void release(ResultSet rs, Statement statement,
			Connection conn) {
		if (rs != null) {
			try {
				rs.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
		if (statement != null) {
			try {
				statement.close();
			} catch (Exception e2) {
				e2.printStackTrace();
			}
		}

		if (conn != null) {
			try {
				conn.close();
			} catch (Exception e2) {
				e2.printStackTrace();
			}
		}
	}

	/**
	 * 数据库更新方法
	 * 
	 * @param sql
	 */
	public void uodate(String sql) {
		Connection connection = null;
		Statement statement = null;
		try {
			connection = JDBCTools.getConnection();
			statement = (Statement) connection.createStatement();
			statement.executeUpdate(sql);
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			JDBCTools.release(statement, connection);
		}
	}

	/**
	 * 关闭数据库连接的方法
	 * 
	 * @param statement
	 * @param conn
	 */
	public static void release(Statement statement, Connection conn) {
		if (statement != null) {
			try {
				statement.close();
			} catch (Exception e2) {
				e2.printStackTrace();
			}
		}

		if (conn != null) {
			try {
				conn.close();
			} catch (Exception e2) {
				e2.printStackTrace();
			}
		}
	}

	/**
	 * 编写通用方法获取任意数据库链接，不用修改源程序
	 * 
	 * @return
	 * @throws ClassNotFoundException
	 * @throws IllegalAccessException
	 * @throws InstantiationException
	 * @throws SQLException
	 * @throws IOException
	 */
	public static Connection getConnection() throws InstantiationException,
			IllegalAccessException, ClassNotFoundException, SQLException,
			IOException {
		String driverClass = null;
		String jdbcUrl = null;
		String user = null;
		String password = null;
		// 读取properties文件
		InputStream in = JDBCTools.class.getClassLoader().getResourceAsStream(
				"jdbc.properties");
		Properties properties = new Properties();
		properties.load(in);
		driverClass = properties.getProperty("driver");
		jdbcUrl = properties.getProperty("url");
		user = properties.getProperty("user");
		password = properties.getProperty("password");
		Class.forName(driverClass);
		Connection connection = (Connection) DriverManager.getConnection(
				jdbcUrl, user, password);
		return connection;
	}
}