利用反射实现Servlet公共类的抽取
2024-08-27 23:20:54
一次请求的执行过程:
请求:发送请求地址-->到达web.xml中,找到地址对应的servlet类-->通过反射调用该类的构造函数,创建该servlet类的对象-->通过当前对象调用该servlet的init方法-->发现没有-->从其父类HttpServlet找init,还是没有-->再找其父类GenericServlet,有init,调用该init方法加载当前servlet类-->调用当前servlet的service方法-->发现没有,找父类HttpServlet-->父类有该方法,调用它,service中获取请求方式-->然后调用do post()方法,当前servlet的do post()方法-->最后销毁,调用disdroy。嗯,其实调用父类的init,service方法这种说貌似不妥,应该是调用继承自父类的这两个方法
对原本的service方法进行重写,利用反射调用子类的具体执行方法
package com.jixh.ss.web.base; import java.io.IOException;
import java.lang.reflect.Method; import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; public class BaseServlet extends HttpServlet { private static final long serialVersionUID = 1L; @Override
public void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // localhost:8080/store/productServlet?method=updateUser,url中必须带有所要调用的子类具体方法的方法名
String method = req.getParameter("method"); if (null == method || "".equals(method) || method.trim().equals("")) {
method = "execute";
} // 注意:此处的this代表的是子类的对象
// System.out.println(this);
// 子类对象字节码对象
@SuppressWarnings("rawtypes")
Class clazz = this.getClass(); try {
// 查找子类对象对应的字节码中的名称为method的方法.这个方法的参数类型是:HttpServletRequest.class,HttpServletResponse.class
@SuppressWarnings("unchecked")
Method md = clazz.getMethod(method, HttpServletRequest.class, HttpServletResponse.class);
if(null!=md){
String jspPath = (String)md.invoke(this, req, resp);
if (null != jspPath) {
req.getRequestDispatcher(jspPath).forward(req, resp);
}
}
} catch (Exception e) {
e.printStackTrace();
} } // 默认方法
public String execute(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
return null;
} }
子类Servlet只进行具体的业务处理
package com.jixh.ss.web.servlet; import java.util.List; import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; import com.jixh.peanut.domian.FirstMenu;
import com.jixh.peanut.domian.User;
import com.jixh.peanut.domian.UserPower;
import com.jixh.peanut.service.MenueService;
import com.jixh.peanut.service.UserService;
import com.jixh.peanut.service.impl.MenueServiceImpl;
import com.jixh.peanut.service.impl.UserServiceImpl;
import com.jixh.peanut.util.DateUtils;
import com.jixh.peanut.util.UUIDUtils;
import com.jixh.peanut.web.base.BaseServlet; import net.sf.json.JSONObject; public class userServlet extends BaseServlet {
private static final long serialVersionUID = 1L; // 修改用户
public String updateUser(HttpServletRequest request, HttpServletResponse response) {
try {
// 允许跨域访问的响应头
response.setHeader("Access-Control-Allow-Origin", "*"); String username = request.getParameter("username");
String password = request.getParameter("password");
// 验证用户名密码
UserService userService = new UserServiceImpl();
User user = userService.userLoging(username, password);
if (user != null) {
// 验证通过,进行下一步
String uid = (String) request.getSession().getAttribute("thisUser");
String utype = request.getParameter("utype");
int ustate = Integer.parseInt(request.getParameter("ustate"));
String powerIdArray = request.getParameter("powerIdArray");
System.out.println(uid+"=="+username + "==" + password + "==" + utype + "==" + ustate + "==" + powerIdArray);
//修改用户表
boolean result = userService.updateUser(uid, utype, ustate);
System.out.println("修改用户结果为"+result);
if(result) {
response.getWriter().write("success");
}else {
response.getWriter().write("faild");
}
} else {
// 直接响应
response.getWriter().write("error");
}
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
}
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