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");
			}
		}
	}
}

 

 

转载于:https://www.cnblogs.com/Laupaul/archive/2012/02/04/2338286.html