反射写的BaseDAO

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.util.ArrayList;

import java.util.Date;

import java.util.List;



public final class BaseDAO{	

	/**

	 * ------------- Oracle ---------------

	 * DB_DRIVER ="oracle.jdbc.driver.OracleDriver";

	 * DB_URL ="jdbc:oracle:thin:@localhost:1521:admin";

	 * DB_USERNAME ="root";

	 * DB_PASSWORD ="root";

	 * ------------------------------------

	 */

	

	/**

	 * ------------- Sql Server ---------------

	 * DB_DRIVER ="com.microsoft.sqlserver.jdbc.SQLServerDriver";

	 * DB_URL ="jdbc:sqlserver://localhost:1433;DatabaseName=bookinfo";

	 * DB_USERNAME ="root";

	 * DB_PASSWORD ="root";

	 * ----------------------------------------

	 */

		

	private static final String DB_DRIVER ="com.mysql.jdbc.Driver";

	private static final String DB_URL ="jdbc:mysql://localhost:3306/student";

	private static final String DB_USERNAME ="root";

	private static final String DB_PASSWORD ="root";

	

	private static Connection getConnection() throws SQLException{

		try {

			

			Class.forName(DB_DRIVER);

			return DriverManager.getConnection(DB_URL, DB_USERNAME,

					DB_PASSWORD);

		} catch (ClassNotFoundException e) {

			e.printStackTrace();

			throw new RuntimeException("无法找到对应的数据库驱动类");

		} 

	}	

	//增删改

	public static void executeUpdate(String sql,Object[] args){

		Connection con=null;

		PreparedStatement ps=null;

		System.out.println("准备执行："+sql);

		try {

			con=getConnection();

			ps= con.prepareStatement(sql);

			if(args!=null&&args.length>0){

				for(int i=0;i<args.length;i++){

					ps.setObject(i+1,args[i]);

				}

			}

			ps.executeUpdate();

		} catch (SQLException e) {

			e.printStackTrace();

			throw new RuntimeException("SQL语句执行失败:"+sql);

		}finally{

			closeAll(con,ps,null);

		}

	}

	

	//查询

	public static <T> List<T> executeQuery(Class<T> entityClass,String sql,Object[] args){

		Connection con=null;

		PreparedStatement ps=null;

		ResultSet rs=null;

		System.out.println("准备执行："+sql);

		try {

			con=getConnection();

			ps= con.prepareStatement(sql);

			if(args!=null&&args.length>0){

				for(int i=0;i<args.length;i++){

					ps.setObject(i+1,args[i]);

				}

			}

			rs=ps.executeQuery();

			List<T> list=new ArrayList<T>();

			while(rs.next()){

				T obj=fillDataFromResultSetToEntity(entityClass,rs);

				list.add(obj);

			}

			return list;

		} catch (SQLException e) {

			e.printStackTrace();

			throw new RuntimeException("SQL语句执行失败:"+sql);

		}finally{

			closeAll(con,ps,rs);

		}

	}

	private static<T> T fillDataFromResultSetToEntity(Class<T> entityClass, ResultSet rs)throws SQLException {

		try {

			//实例化对应实体类

			T entity = entityClass.newInstance();

			//获得该实体类的所有set方法

			Method[] methods=getAllSetMethods(entityClass);

			for(Method m:methods){

				try{ 

				//通过set方法名推算出属性名

				String fieldName=m.getName().substring(3,4).toLowerCase()+m.getName().substring(4);

				//获得要调用的ResultSet对象的方法名

				String rsMethodName = getResultSetMethod(m.getParameterTypes()[0]);

				//获得要调用的ResultSet对象的方法对象

				Method rsMethod=rs.getClass().getMethod(rsMethodName,String.class);

				//调用rs.getXXX方法获得对应列的数据

				Object fieldValue=rsMethod.invoke(rs,fieldName);

				//调用实体对象的set方法设值

				m.invoke(entity,fieldValue);

				}catch (SecurityException e) {

					System.out.println("[警告]:"+entityClass.getName()+"."+m.getName()+"无法访问，跳过..");

					continue;

				} catch (IllegalArgumentException e) {

					System.out.println("[警告]:"+entityClass.getName()+"."+m.getName()+"("+m.getParameterTypes()[0].getName()+")参数错误");

					continue;

				} catch (NoSuchMethodException e) {

					System.out.println("[警告]:找不到方法"+entityClass.getName()+"."+m.getName()+"("+m.getParameterTypes()[0].getName()+")");

					continue;

				} catch (InvocationTargetException e) {

					System.out.println("[警告]:调用"+entityClass.getName()+"."+m.getName()+"("+m.getParameterTypes()[0].getName()+")方法产生内部异常");

					continue;

				} 

			}

			return entity;

		} catch (InstantiationException e) {

			e.printStackTrace();

			throw new RuntimeException("无法实例化" + entityClass.getName());

		} catch (IllegalAccessException e) {

			e.printStackTrace();

			throw new RuntimeException("没有或无法访问["+entityClass.getName()+"]的无参构造函数");

		} 

	}

	private static Method[] getAllSetMethods(Class<?> entityClass){

		Method[] methods=entityClass.getMethods();

		List<Method> list=new ArrayList<Method>();

		for(Method m:methods){

			if(m.getName().indexOf("set")==0){

				list.add(m);

			}

		}

		return list.toArray(new Method[list.size()]);

	}

	

	private static String getResultSetMethod(Class<?> fieldType) {

		String rsMethodName = null;

		if (String.class.equals(fieldType)) {

			rsMethodName = "getString";

		}

		if (Long.class.equals(fieldType) || "long".equals(fieldType.getName())) {

			rsMethodName = "getLong";

		}

		if (Date.class.equals(fieldType)) {

			rsMethodName = "getDate";

		}

		if (Integer.class.equals(fieldType)

				|| "int".equals(fieldType.getName())) {

			rsMethodName = "getInt";

		}

		if (Double.class.equals(fieldType)

				|| "double".equals(fieldType.getName())) {

			rsMethodName = "getDouble";

		}

		if (Float.class.equals(fieldType)

				|| "float".equals(fieldType.getName())) {

			rsMethodName = "getFloat";

		}

		if (rsMethodName == null) {

			throw new RuntimeException("无法识别的属性类型:" + fieldType.getName()

					+ "目前支持的属性类型有[String,Integer,Long,Double,Float,Date]");

		}

		return rsMethodName;

	}

	private static void closeAll(Connection con, PreparedStatement ps,ResultSet rs) {

		if(rs!=null){

			try {

				rs.close();

			} catch (SQLException e) {

				e.printStackTrace();

				throw new RuntimeException("关闭数据集错误");

			}

		}

		if(ps!=null){

			try {

				ps.close();

			} catch (SQLException e) {

				e.printStackTrace();

				throw new RuntimeException("关闭数据访问对象错误");

			}

		}

		if(con!=null){

			try {

				con.close();

			} catch (SQLException e) {

				e.printStackTrace();

				throw new RuntimeException("关闭数据库连接错误");

			}

		}

	}

}