- 创建Servlet、命名为BaseServlet继承HttpServlet，只需要覆写一个方法，即service方法
- 写你需要用到的Servlet，比方：UserServlet | DepartmentServlet | EmployeeServlet等
但是他们不用再去继承HttpServlet，而是要去继承BaseServlet
以下BaseServlet，没有采用注解。依旧是使用web.xml作为配置
package cn.javabs.commons; 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 java.io.IOException; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; //@WebServlet(name = "BaseServlet"，urlPatterns = {"/baseServlet"}) public class BaseServlet extends HttpServlet { @Override protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String uri = req.getRequestURI(); System.out.println("uri:" + uri);//uri: /userServlet/addUser int position = uri.lastIndexOf('/'); System.out.println("position:" + position); // position: 12 String methodName = uri.substring(position+1);//position+1: 最后一个斜线后的字母，也就是我们想要单词的首字母 System.out.println("methodName:" + methodName);// methodName: /addUser // ---- System.out.println("this代表的是："+this);//this代表的是：cn.javabs.commons.UserServlet@49220d try { // 不会忽略访问权限修饰符 只识别public修饰的方法 // method = this.getClass().getMethod(methodName, HttpServletRequest.class, HttpServletResponse.class); // 会忽略访问权限修饰符 Method method = this.getClass().getDeclaredMethod(methodName, HttpServletRequest.class, HttpServletResponse.class); System.out.println("method:"+ method); String pageName = (String) method.invoke(this,req,resp); System.out.println("pageName:" + pageName); if (pageName==null || pageName.equals("")){ resp.sendRedirect(req.getContextPath()+"/404.jsp"); }else{ // 判断 返回得字符串中是否又冒号存在！ if (pageName.contains(":")){ // 以冒号分割 pageName String[] datas = pageName.split(":"); System.out.println("数组的长度："+datas.length); System.out.println("冒号左边的数据："+datas[0]); System.out.println("冒号右边的数据："+datas[1]); // 进行判断 固定的字符串"forward" 与 我们得到的左侧数据 进行判断是否相同(忽略大小写) if("forward".equalsIgnoreCase(datas[0])){ req.getRequestDispatcher("/"+datas[1]+".jsp").forward(req,resp); } // 进行判断 固定的字符串"redirect" 与 我们得到的左侧数据 进行判断是否相同(忽略大小写) else if("redirect".equalsIgnoreCase(datas[0])){ resp.sendRedirect(req.getContextPath()+"/"+datas[1]+".jsp"); } }else{// 没有冒号，即代表没有指定是转发或者重定向、一律按照转发处理！ req.getRequestDispatcher("/"+pageName+".jsp").forward(req,resp); } } } catch (NoSuchMethodException e) { throw new RuntimeException("BaseServlet出现了NoSuchMethodException异常" + e); } catch (IllegalAccessException e) { throw new RuntimeException("BaseServlet出现了IllegalAccessException异常" + e); } catch (InvocationTargetException e) { throw new RuntimeException("BaseServlet出现了InvocationTargetException异常" + e); } } }
以下Servlet，全部是继承的BaseServlet，也可以理解为是测试使用的Servlet
页面
<%-- Created by IntelliJ IDEA. User: Mryang Date: 2019/4/26 Time: 14:01 To change this template use File | Settings | File Templates. --%> <%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>$Title$</title> </head> <body> <a href="${pageContext.request.contextPath}/userServlet/addUser">添加用户</a> <a href="${pageContext.request.contextPath}/userServlet/editUser">编辑用户</a> <a href="${pageContext.request.contextPath}/userServlet/delUser">删除用户</a> <a href="${pageContext.request.contextPath}/userServlet/findUser">查询用户</a> <hr/> <a href="${pageContext.request.contextPath}/userServlet/xxx">没有对应的方法</a> <hr/> <a href="${pageContext.request.contextPath}/departmentServlet/addDept">添加部门注解</a> <a href="${pageContext.request.contextPath}/bookServlet/addBook">添加图书配置文件</a> <hr/> </body> </html>
以下是测试的Servlet（有配置文件的，也有注解方式的）
第一个UserServlet
package cn.javabs.web.servlet; import cn.javabs.commons.BaseServlet; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; public class UserServlet extends BaseServlet { /** * 添加用户 * @param request * @param response * @throws ServletException * @throws IOException */ public String addUser(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("添加用户方法被index.jsp调用执行了"); // request.getRequestDispatcher("/main.jsp").forward(request,response); // 会将return的内容字符串发送给BaseServlet中得PageName 变量接受接受得 return "forward:main"; } /** * 编辑用户 * @param request * @param response * @throws ServletException * @throws IOException */ protected String editUser(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("编辑用户方法被index.jsp调用执行了"); // response.sendRedirect(request.getContextPath()+"/success.jsp"); // 会将return的内容字符串发送给BaseServlet中得PageName 变量接受接受得 return "redirect:success"; } /** * 删除用户 * @param request * @param response * @throws ServletException * @throws IOException */ protected String delUser(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("删除用户方法被index.jsp调用执行了"); return "right"; } /** * 查询用户 * @param request * @param response * @throws ServletException * @throws IOException */ protected String findUser(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("查询用户方法被index.jsp调用执行了"); return ""; } }
第二个BookServlet
package cn.javabs.web.servlet; import cn.javabs.commons.BaseServlet; import javax.servlet.ServletException; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; public class BookServlet extends BaseServlet { public String addBook(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("添加图书成功"); return "success"; } public String editBook(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { return "redirect:main"; } }
第三个测试Servlet，我们采用注解的方式：
package cn.javabs.web.servlet; import cn.javabs.commons.BaseServlet; 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 java.io.IOException; @WebServlet(urlPatterns = {"/departmentServlet/*"}) public class DepartmentServlet extends BaseServlet { public String addDept(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("添加部门成功"); return "success"; } public String editDept(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { return "redirect:main"; } }
配置文件 web.xml
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0"> <!--BaseServlet的配置--> <servlet> <servlet-name>BaseServlet</servlet-name> <servlet-class>cn.javabs.commons.BaseServlet</servlet-class> </servlet> <!--注意:没有使用通配符--> <servlet-mapping> <servlet-name>BaseServlet</servlet-name> <url-pattern>/baseServlet</url-pattern> </servlet-mapping> <!--UserServlet的配置--> <servlet> <servlet-name>UserServlet</servlet-name> <servlet-class>cn.javabs.web.servlet.UserServlet</servlet-class> </servlet> <!--注意:url中的属性值后需要有通配符--> <servlet-mapping> <servlet-name>UserServlet</servlet-name> <url-pattern>/userServlet/*</url-pattern> </servlet-mapping> <!--BookServlet的配置--> <servlet> <servlet-name>BookServlet</servlet-name> <servlet-class>cn.javabs.web.servlet.BookServlet</servlet-class> </servlet> <!--注意:url中的属性值后需要有通配符--> <servlet-mapping> <servlet-name>BookServlet</servlet-name> <url-pattern>/bookServlet/*</url-pattern> </servlet-mapping> </web-app>
图解
图1：
图2： 
图3： 
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