后台简单的MVC模式以及前台显示
- 需要使用jstl的jar包，mysql-connector-java-5.1.39-bin的jar包，MySQL5.5
- myeclipse2014版在建立web项目时可自动选择添加jstl的jar包，然而，我用的时候在<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>这句就报错了，也许是前面什么地方设置有问题，要是没遇到报错后面的步骤可以忽略。所以又导入了一次jstl的jar包，先点开JSTL 1.2.1Library然后就能看到那两个jar包的位置，把他们复制到WEB-INF下面的lib文件夹下。
再到myeclipse，右击项目，点击属性，Java Build Path->Add External JARs...，添加WEB-INF下lib中那两个jar包。
-
数据库操作：我还是把mysql-connector-java-5.1.39-bin复制到WEB-INF lib下，然后和上面的步骤一样添加jar包(复制到lib文件夹下是想着项目拿到别的电脑上也能运行，但是没试过)。然后Class.forName("com.mysql.jdbc.Driver"); 遇到报错java.lang.ClassNotFoundException: com.mysql.jdbc.Driver,解决办法看http://blog.csdn.net/woaixiaozhe/article/details/7326915
- 最后
- MVC大概流程目测都差不多，复杂的也只是加了点别的设计模式：
- 所有的后台代码都放一个packet my里了，因为是个简单的mvc
-
- index.jsp
<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%> <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <base href="<%=basePath%>"> <title>My JSP 'index.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> --> </head> <body> This is my JSP page. <br> <a href="controller?action=display">display</a><br> <a href="controller?action=add">add</a> </body> </html>index中href="controller?***”对应了后台
，相应web.xml里代码
index页面
- 点击index页面display后，后台执行相应的程序，代码如下：
package my; import java.io.IOException; import java.io.PrintWriter; import java.util.List; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.RequestDispatcher;//要导入此包！！！ public class Simplecontroller extends HttpServlet { /** * Constructor of the object. */ public Simplecontroller() { super(); } /** * Destruction of the servlet. <br> */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request,response); } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String action = request.getParameter("action"); String jspPage = "/index.jsp"; if("display".equals(action)){ DataDao Datadao = new DataDao(); List<DataBean> datalist= Datadao.getAll(); request.setAttribute("datalist",datalist); jspPage = "/display.jsp"; } dispatch(jspPage,request,response);//自定义的转发函数 } protected void dispatch(String jspPage,HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{ if(jspPage!=null){ RequestDispatcher rd = request.getRequestDispatcher(jspPage); rd.forward(request, response); } } /** * Initialization of the servlet. <br> * * @throws ServletException if an error occurs */ public void init() throws ServletException { // Put your code here } }
，相应web.xml里代码
里面没写点击add应该执行的代码。
dispatch(jspPage,request,response);将请求转发到display.jsp页面(能转发大概是因为jsp就是个servlet，猜的)，点击index.jsp中display后会产生跳转，会跳到display页面，猜是
dispatch(jspPage,request,response);中response是display.jsp页面，没去仔细看dispatch函数功能了。
DataDao Datadao = new DataDao();List<DataBean> datalist= Datadao.getAll();request.setAttribute("datalist",datalist);这部分暂时不用管，返回数据的。
3.display.jsp代码
<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'display.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<h>display pageee</h><br>
<% /* List<DataBean> data*/// = (List<DataBean>) request.getAttribute("datalist") ;%>
<c:forEach var="data" items="${requestScope.datalist}">
<tr>
<td>${data.name}</td>
<td>${data.id}</td>
</tr>
</c:forEach>
</body>
</html>
这里可以不用jstl,但是没用jstl时候，
<% /* List<DataBean> data*/// = (List<DataBean>) request.getAttribute("datalist") ;%>报错说解析不了List<DataBean>，目测需要把DataBean给import进来(没试)，觉得麻烦所以就改用jstl,也
不清楚为什么用jstl时候不用把javaBean导入进来就可以用了javaBean了，是因为var这种变量很强大？还是前面想的都错了？还有<c:>里面不要乱加空格。
4.SimpleController.java中
DataDao Datadao = new DataDao();List<DataBean> datalist= Datadao.getAll();request.setAttribute("datalist",datalist);对应的程序是
用来产生对象的，
DataBean.java
package my;
public class DataBean {
private Integer id;
private String name;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getname() {
return name;
}
public void setname(String name) {
this.name = name;
}
public DataBean(Integer id, String name) {
super();
this.id = id;
this.name = name;
}
}
DataDao.java(类名起的也许不太对)
package my;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
//import mvctest.DataBean;
import my.DataBean;
public class DataDao {
public List<DataBean> getAll(){
List<DataBean> DataBeans = new ArrayList<DataBean>();
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
try {
Class.forName("com.mysql.jdbc.Driver");
String url = "jdbc:mysql://localhost:3306/databean";
String user = "root";
String password = "123";
String sql = "select * from data";
conn = DriverManager.getConnection(url, user, password);
if(conn!=null)
{ ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
while(rs.next()){
int id = rs.getInt(1);
String DataBeanName = rs.getString(2);
System.out.print(id);
System.out.println(DataBeanName);
//int id = 1;
//String DataBeanName = "i";
System.out.print(id);
System.out.println(DataBeanName);
DataBean DataBean = new DataBean(id, DataBeanName);
DataBeans.add(DataBean);
} }else{System.out.println("数据库连接失败");}
}catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
try {
if(rs != null)
rs.close();
if(ps != null)
ps.close();
if(conn != null)
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return DataBeans;
}
/*public void main(){
DataDao A = new DataDao();
A.getAll();
}*/
}
Class.forName("com.mysql.jdbc.Driver");
String url = "jdbc:mysql://localhost:3306/databean";
String user = "root";
String password = "123";
String sql = "select * from data";
conn = DriverManager.getConnection(url, user, password); ，databean是用mysql新建的数据库的名字，
Class.forName("com.mysql.jdbc.Driver");是固定的语句，里面不要乱加空格。
最后，整个项目结构;
testmysql.java，JdbcUnits.java是空的，用不着。
数据库
index页面
点击display后
本来是觉得在浏览器中直接输入http://localhost:8080/mvc/controller?action=display时候打不开的，因为找不到他对应哪个后台，后来发现能正常显示，大概是根据controller就找到了对应的后台程序，所以还是要试下才知道的...
