dbutil运用于反射与普通反射机制

其他 2018-08-12 04:19:41 阅读次数: 0 
自写数据库dbUtil
public List<Student> getAllStus(){
	List<Student> stuList = new ArrayList<Student>();
	
	Connection conn = DBUtil.getDBConn();
	
	String sql = "select * from stu_info";
	
	QueryRunner qr = new QueryRunner();
	
	try{
			stuList = qr.execute(conn,sql,new ResultSetHandler(){
				public List<Student> stuList = new ArrayList<Student>();
				Student stu = null;
				
				try{
					while(rs.next()){
						stu...... = rs....
						
						数据输入
					}
				}catch(final SQLException e){
			e.printStackTrace();
		}
		return stuList;
		
		

},null)
}catch(final SQLException e){
			e.printStackTrace();
		}
		return stuList;

写的过程可能会遇到这样遇到一个问题：

java.lang.NumberFormatException: For input string: "stuName"
	at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
	at java.lang.Integer.parseInt(Integer.java:580)
	at java.lang.Integer.parseInt(Integer.java:615)
	at javax.el.ListELResolver.coerce(ListELResolver.java:157)
	at javax.el.ListELResolver.getValue(ListELResolver.java:70)
	at org.apache.jasper.el.JasperELResolver.getValue(JasperELResolver.java:110)
	at org.apache.el.parser.AstValue.getValue(AstValue.java:169)
	at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:184)
	at org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:943)
	at org.apache.jsp.start_jsp._jspx_meth_c_005fforEach_005f0(start_jsp.java:248)
	at org.apache.jsp.start_jsp._jspService(start_jsp.java:158)
	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:438)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
	at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:716)
	at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:466)
	at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:391)
	at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:318)
	at com.zzxtit.java.action.operateServlet.searchStuList(operateServlet.java:235)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at com.zzxtit.java.service.databaseOpe.doPost(databaseOpe.java:33)
	at com.zzxtit.java.service.databaseOpe.doGet(databaseOpe.java:17)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:94)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
	at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:620)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:502)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1132)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:684)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1533)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1489)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:745)

java.lang.reflect.InvocationTargetException
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at com.zzxtit.java.service.databaseOpe.doPost(databaseOpe.java:33)
	at com.zzxtit.java.service.databaseOpe.doGet(databaseOpe.java:17)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:94)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
	at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:620)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:502)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1132)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:684)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1533)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1489)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.jasper.JasperException: java.lang.NumberFormatException: For input string: "stuName"
	at org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:560)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:476)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
	at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:716)
	at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:466)
	at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:391)
	at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:318)
	at com.zzxtit.java.action.operateServlet.searchStuList(operateServlet.java:235)
	... 29 more
Caused by: java.lang.NumberFormatException: For input string: "stuName"
	at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
	at java.lang.Integer.parseInt(Integer.java:580)
	at java.lang.Integer.parseInt(Integer.java:615)
	at javax.el.ListELResolver.coerce(ListELResolver.java:157)
	at javax.el.ListELResolver.getValue(ListELResolver.java:70)
	at org.apache.jasper.el.JasperELResolver.getValue(JasperELResolver.java:110)
	at org.apache.el.parser.AstValue.getValue(AstValue.java:169)
	at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:184)
	at org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:943)
	at org.apache.jsp.start_jsp._jspx_meth_c_005fforEach_005f0(start_jsp.java:248)
	at org.apache.jsp.start_jsp._jspService(start_jsp.java:158)
	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:438)
	... 42 more

这好像是数据除了为题引起的invoke方法出错，具体的改正方法，还没有写出，但是另一种反射机制却能成功实现搜索学生列表


public void searchStuList(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
			//throws ServletException, IOException {
		/*
		Connection conn = null;
		Statement stat = null;
		ResultSet rs = null;
		
		String sql = "select * from stu_infom";
		
		
		//System.out.println("+++>1"+sql);
		List<Student> stuList = new ArrayList<Student>();
		Student stu = null;
		
		conn = DBUtil.getDBConn();
		try {
			stat = conn.createStatement();
			rs = stat.executeQuery(sql); 
			
			while(rs.next()){
				stu = new Student();
				stu.setId(rs.getInt("id"));
				stu.setStuName(rs.getString("stuName"));
				stu.setStuNo(rs.getString("stuNo"));
				stu.setGender(rs.getString("gender"));
				stu.setBirthday(rs.getDate("birthday"));
				stuList.add(stu);	
			}
			System.out.println("-----"+stuList);
			request.setAttribute("stuInfo",stuList);
			
			
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
			DBUtil.closeRes(rs);
			DBUtil.closeStatet(stat);
			DBUtil.closeCon(conn);}
           request.getRequestDispatcher("start.jsp").forward(request, response);
}

以我现在的认知觉得dbuti并没有普通的那么好用经查询得知dbutil有以下几的好处：

1.对于数据表的读操作，他可以把结果转换成List，Array，Set等java集合，便于程序员操作；
2.对于数据表的写操作，也变得很简单（只需写sql语句）
3.可以使用数据源，使用JNDI， 数据库连接池等技术来优化性能--重用已经构建好的数据库连接对象，而不像php，asp那样，费时费力的不断重复的构建和析构这样的对象。

而对于本也例子中试用到的QueryRunner:

Queryrunner.query    —————只可以执行select语句。
Queryrunner.update  —————只可以接收update,delte,insert语句
BeanHandler          ——————返回一个 Bean，结果封装到Bean。只查询第一行。适合根据id查询唯一的一行
BeanListHandler     ——————返回List<Bean>所有行，都封装到List，适合于查询多个结果
MapHandler           ——————与BeanHandler应，只返回第一行，封装成Map类型　－　也适合于查询一个结果集的    适合于关联查询，且没有匹配的Bean。
MapListHandler      ——————与BeanListHandler对应，返回所有，封装成List<Map>类型

ScalarHandler        ——————标量- 用于select count(1)|sum|avg|max …一些聚合函数

......

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