- 一、什么是mvc
- 二、目前增删改查的代码的问题以及解决方法
- 三、自定义mvc的工作原理和打印
什么是mvc
m:model
v:view
c:controller-
优点：分工明确，各司其职j,降低代码的耦合度
最主要的问题：关于单个实体/表操作场景越多，需要新建的类也就越多，造成了项目中类的数量过于庞大
如何解决：写一个stuservlet，实现doget和dopost方法，然后拿到前台要调用的方法名传递到后台,前台传递说明方法，就调用当前类的对应方法，对应的方法里面调用biz里面的dao方法；
如何传递方法名href=“${pageContext.request.contextPath }/stu.action?mothodName=add”
下面展示 servlet代码。
package com.yzp.servlet;
import java.io.IOException;
import java.lang.reflect.Method;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
//@WebServlet("/order.action")
public class OrderServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//为了区分当前请求的目的：增删改查的目的，就从前台讲要调用的方法名传递到后台
String methodName = request.getParameter("mothodName");
//methodName可可以是add/del/edit/list/load/xxxx/yyy/aaa....
//前台传递说明方法，就调用当前类的对应方法
try {
Method m = this.getClass()//stuservlet
.getDeclaredMethod(methodName,HttpServletRequest.class,HttpServletResponse.class );
m.setAccessible(true);
m.invoke(this, request,response);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// if("add".equals(methodName)) {
// //如果前台传递到后台的是一个新增的请求，那么后台就调用新增方法
// Add(request,response);
// }else if("del".equals(methodName)) {
// del(request,response);
// }else if("edit".equals(methodName)) {
// edit(request,response);
// }else if("list".equals(methodName)) {
// list(request,response);
// }else if("load".equals(methodName)) {
// load(request,response);
// }
}
private void load(HttpServletRequest request, HttpServletResponse response) {
System.out.println("在同一个orderservlet中调用load方法");
}
private void del(HttpServletRequest request, HttpServletResponse response) {
System.out.println("在同一个orderservlett中调用del方法");
}
private void Add(HttpServletRequest request, HttpServletResponse response) {
System.out.println("在同一个orderservlet中调用add方法");
}
private void edit(HttpServletRequest request, HttpServletResponse response) {
System.out.println("在同一个orderservlet中调用edit方法");
}
private void list(HttpServletRequest request, HttpServletResponse response) {
System.out.println("在同一个orderservlet中调用list方法");
}
}
下面展示jsp代码。
类数量过多问题的优化 增加 修改 删除 查询 回显三、自定义mvc的工作原理和打印
先建一个DispatcherServlet：中央控制器
然后再建一个子控制器：Action；写一个void execute(HttpServletRequest request, HttpServletResponse response);方法
写一个stuaction用来放对应的方法
然后再写一个ActionSupport类实现Action类，然后实现execute方法；将String methodName = request.getParameter(“mothodName”);
//methodName可可以是add/del/edit/list/load/xxxx/yyy/aaa…
//前台传递说明方法，就调用当前类的对应方法
try {
Method m = this.getClass()//stuservlet
.getDeclaredMethod(methodName,HttpServletRequest.class,HttpServletResponse.class );
m.setAccessible(true);
m.invoke(this, request,response);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
放进去
下面展示 DispatcherServlet代码：中央控制器。
package com.yzp.framework;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("*.action")
public class DispatcherServlet extends HttpServlet{
private Map actions = new HashMap();
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doPost(req, resp);
}
//程序启动时，只会加载一次
@Override
public void init() throws ServletException {
actions.put("/order", new StuAction());
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//http://localhost:8080/mvc/stu.action?methodName=list
String uri = req.getRequestURI();
//拿到/book，最后一个/最后一个点的位置
uri=uri.substring(uri.lastIndexOf("/"),uri.lastIndexOf("."));
Action action = actions.get(uri);
action.execute(req, resp);
}
}
下面展示 action类代码：写一个方法。
package com.yzp.framework;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public interface Action {
void execute(HttpServletRequest request, HttpServletResponse response);
}
下面展示 ActionSupport类。保存共同代码
package com.yzp.framework;
import java.lang.reflect.Method;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ActionSupport implements Action {
@Override
public void execute(HttpServletRequest request, HttpServletResponse response) {
String methodName = request.getParameter("mothodName");
//methodName可可以是add/del/edit/list/load/xxxx/yyy/aaa....
//前台传递说明方法，就调用当前类的对应方法
try {
Method m = this.getClass()//stuservlet
.getDeclaredMethod(methodName,HttpServletRequest.class,HttpServletResponse.class );
m.setAccessible(true);
m.invoke(this, request,response);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
下面展示一些 stuaction类：用来放方法。
package com.yzp.framework;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class StuAction extends ActionSupport {
private void load(HttpServletRequest request, HttpServletResponse response) {
System.out.println("在同一个servlet中调用load方法");
}
private void del(HttpServletRequest request, HttpServletResponse response) {
System.out.println("在同一个servlet中调用del方法");
}
private void Add(HttpServletRequest request, HttpServletResponse response) {
System.out.println("在同一个servlet中调用add方法");
}
private void edit(HttpServletRequest request, HttpServletResponse response) {
System.out.println("在同一个servlet中调用edit方法");
}
private void list(HttpServletRequest request, HttpServletResponse response) {
System.out.println("在同一个servlet中调用list方法");
}
}
