无法正常运行
来源：2-6 自由编程
光印
2020-07-01 07:24:34
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<form action="/add/add" method="get">
<input name="add">
<input type="submit" value="求累加和">
</form>
</body>
</html>
package homework.add;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class add
*/
@WebServlet("/add")
public class add extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public add() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#service(HttpServletRequest request, HttpServletResponse response)
*/
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
String add =request.getParameter("add");
int a=Integer.valueOf(add);
int sum=0;
for(int i=1;i<a;i++) {
sum+=i;
}
request.setAttribute("add", sum);
request.getRequestDispatcher("/add2").forward(request, response);
}
}
package homework.add;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class add2
*/
@WebServlet("/add2")
public class add2 extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public add2() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#service(HttpServletRequest request, HttpServletResponse response)
*/
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
int a = (int) request.getAttribute("a");
response.getWriter().println(a);
}
}
1回答
-
同学你好，经测试同学代码出现空指针异常：如下所示:
在add2页面接收转发带来的数据，同学传递有误，是add不是a。修改如下：
2、求累加和，同学的计算有问题，如下所示：
原因是for循环的条件有误，应该是<=。修改如下：
如果我的回答解决了你的疑惑，请采纳！祝学习愉快！
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