一个Servlet处理多个请求的方法

方法一:

可以在jsp中对一个变量赋予不同的值来实现不同的功能。

如下面这个例子。利用表单标签给op赋予不同的值findOne和findAll来实现根据id查询或者查所有的用户。

index.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html >
<html>
<head>
<meta  charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
	<form action="user.s" method="get">
			<input type="hidden" name="op" value="findOne"/>
			请输入你的id<input type="text" name="id"/><br/>
			<input type="submit" value="submit"/>
	</form>
	<br/>
	<form action="user.s" method="get">
			<input type="hidden" name="op" value="findAll"/>
			<input type="submit" value="submit"/>
	</form>
</body>
</html>

UserServlet.java

package cn.itcast.servlet;

import java.io.IOException;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import cn.itcast.bean.UserBean;
import cn.itcast.biz.UserBiz;
import cn.itcast.uitil.ServletUtil;

/**
 * Servlet implementation class UserServlet
 */
@WebServlet("/user.s")
public class UserServlet extends BasicServlet {
	
	private UserBiz ubiz = new UserBiz();
	
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		// TODO Auto-generated method stub
		String op = req.getParameter("op");
		if("findOne".equals(op)){
			try {
				findOne(req,resp);
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
				req.getRequestDispatcher("/WEB-INF/error.jsp").forward(req, resp);
			}
		}else if("findAll".equals(op)){
			try {
				findAll(req,resp);
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
				req.getRequestDispatcher("/WEB-INF/error.jsp").forward(req, resp);
			}
		}else if("delete".equals(op)){
			try {
				delete(req,resp);
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
				req.getRequestDispatcher("/WEB-INF/error.jsp").forward(req, resp);
			}
		}
		
		
	}
	
	/**
	 * 根据id值来删除指定用户
	 * @param req
	 * @param resp
	 * @throws Exception
	 * @throws Exception
	 */
	private void delete(HttpServletRequest req, HttpServletResponse resp) throws Exception {
		// TODO Auto-generated method stub
		System.out.println("delete");
		String id = req.getParameter("id");
		System.out.println(id);
		ubiz.delete(id);
		findAll(req,resp);
		
	}

	/**
	 * 查所有的用户
	 * @param req
	 * @param resp
	 * @throws Exception
	 * @throws Exception
	 */
	private void findAll(HttpServletRequest req, HttpServletResponse resp) throws Exception, Exception {
		// TODO Auto-generated method stub
		System.out.println("findAll");
		List<UserBean> list = ubiz.selectAll();
		req.setAttribute("list", list);
		req.getRequestDispatcher("user1.jsp").forward(req, resp);
		
	}

	/**
	 * 根据id查询指定用户
	 * @param req
	 * @param resp
	 * @throws ServletException
	 * @throws Exception
	 */
	private void findOne(HttpServletRequest req, HttpServletResponse resp) throws ServletException, Exception {
		// TODO Auto-generated method stub
		System.out.println("findOne");
		Integer id =  ServletUtil.getParamter(req, Integer.class, "id");
		UserBean ub = ubiz.selectByid(id);
		req.setAttribute("user", ub);
		req.getRequestDispatcher("user.jsp").forward(req, resp);
	}
	

}

方法二

在jsp中根据不同的后缀来区分即将跳转到的Servlet。在Servlet中获取ServletPath。如下

url: http://localhost:8080/MVC1/findOne.do?id=3

ServletPath：就为findOne

接下来就根据ServletPath来创建相应的方法例如(findOne).

之后利用反射机制获取Servlet中的findOne方法并执行这个findOne()方法

web.xml来配置Serclet(下面表示所有.do结尾的都跳转到com.atguigu.mvcapp.servlet.CustomerServlet进行处理)

<servlet>
    <description></description>
    <display-name>CustomerServlet</display-name>
    <servlet-name>CustomerServlet</servlet-name>
    <servlet-class>com.atguigu.mvcapp.servlet.CustomerServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>CustomerServlet</servlet-name>
    <url-pattern>*.do</url-pattern>
  </servlet-mapping>

CustomerServlet.java(下面是利用反射机制)

@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		
		//1. 获取 ServletPath: /edit.do 或 /addCustomer.do
		String servletPath = req.getServletPath();

		
		//2. 去除 / 和 .do, 得到类似于 edit 或 addCustomer 这样的字符串
		String methodName = servletPath.substring(1);
		
		methodName = methodName.substring(0, methodName.length() - 3);
		
		try {
			//3. 利用反射获取 methodName 对应的方法  后面两个参数是method.invoke需要携带的类型
			Method method = getClass().getDeclaredMethod(methodName, HttpServletRequest.class, 
					HttpServletResponse.class);
			//4. 利用反射调用对应的方法
			method.invoke(this, req, resp);
		} catch (Exception e) {
			e.printStackTrace();
			//可以有一些响应.
			resp.sendRedirect("error.jsp");
		}
		
	}

findOne方法

	private void findOne(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
		//1. 获取表单参数: name, address, phone
		String name = request.getParameter("name");
		String address = request.getParameter("address");
		String phone = request.getParameter("phone");
		
		//2. 检验 name 是否已经被占用:
		
		//2.1 调用 CustomerDAO 的 getCountWithName(String name) 获取 name 在数据库中是否存在
		long count = customerDAO.getCountWithName(name);
		
		//2.2 若返回值大于 0, 则响应 newcustomer.jsp 页面: 
		//通过转发的方式来响应 newcustomer.jsp
		if(count > 0){
			//2.2.1 要求再 newcustomer.jsp 页面显示一个错误消息: 用户名 name 已经被占用, 请重新选择!
			//在 request 中放入一个属性 message: 用户名 name 已经被占用, 请重新选择!, 
			//在页面上通过 request.getAttribute("message") 的方式来显示
			request.setAttribute("message", "用户名" + name + "已经被占用, 请重新选择!");
			
			//2.2.2 newcustomer.jsp 的表单值可以回显. 
			//通过 value="<%= request.getParameter("name") == null ? "" : request.getParameter("name") %>"
			//来进行回显
			//2.2.3 结束方法: return 
			request.getRequestDispatcher("/newcustomer.jsp").forward(request, response);
			return;
		}
		
		//3. 若验证通过, 则把表单参数封装为一个 Customer 对象 customer
		Customer customer = new Customer(name, address, phone);
		
		//4. 调用 CustomerDAO 的  save(Customer customer) 执行保存操作
		customerDAO.save(customer);
		
		//5. 重定向到 success.jsp 页面: 使用重定向可以避免出现表单的重复提交问题.  
		response.sendRedirect("success.jsp");
		//request.getRequestDispatcher("/success.jsp").forward(request, response);
	}

index.jsp

<form action="findOne.do" method="post">
		<table>
			<tr>
				<td>CustomerName:</td>
				<td><input type="text" name="name" value="${param.name }"/></td>
			</tr>
			<tr>
				<td>Address:</td>
				<td><input type="text" name="address" value="${param.address }"/></td>
			</tr>
			<tr>
				<td>Phone:</td>
				<td><input type="text" name="phone" value="${param.phone }"/></td>
			</tr>
			<tr>
				<td colspan="2"><input type="submit" value="Submit"/></td>
			</tr>
		</table>
	</form>

一个Servlet处理多个请求的方法

方法一:

方法二

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