> For the complete documentation index, see [llms.txt](https://sugar-at.gitbook.io/blog-article/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://sugar-at.gitbook.io/blog-article/examination/javaee.md).
# 1. java EE 复习
## 列举三种动态网页技术，并描述其特点
* ASP
* Active Server Pages 基于.Net实现的动态服务器页面
* JSP
* jAVA Server Page,基于Java实现的web页面模板引擎
* Django
* 基于Python语言实现的MVC设计模式的WEB框架
* PHP
* 主要应用于Web开发,服务端执行的脚本语言
## 描述你在使用某集成开发环境，进行JSP+JavaBean+Servelet编程时，遇到的一个故障，及最终的解决办法
使用IDEA 集成开发环境,在新建Servlet时会自动生成@WebServlet注解,避免了配置Web.xml的麻烦,但是启动项目后发现并没有起作用,原因是 @WebServlet("test")没有加 `/` 正确写法为WebServlet("/test)
## 编程题
> Servlet接收表单传递过来的数据 假定给你提供了一个HTML文件，用户在表单中输入某些信息(可能含有中文)，用户点提交按钮的时候，向Servlet提交。 你的Servlet的功能：对数据的合法性进行基本检验，如果有问题则给出错误消息。如果满足要求，则直接输出html到客户端，回显用户输入的每一项信息。要求：中文不能有乱码的情况。
```java
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//设置回调字符编码和文本格式
response.setCharacterEncoding("utf-8");
response.setContentType("text/html");
PrintWriter writer=response.getWriter();
//获取表单传递的参数
String username=request.getParameter("username");
String password=request.getParameter("password");
//数据校验
if(username==null||username.equals("")){
writer.println("用户名不能为空");
return;
}
if (password.length()<6||password.length()>12){
writer.println("密码长度不符合要求");
return;
}
//成功回调
writer.println("账号:"+username);
writer.println("密码:"+password);
}
```
> JSP输出基本信息创建一个Welcome.jsp，在页面上显示： 当前日期时间是2019-12-15 19:20:30， 欢迎你，来自210.41.240.254的朋友。 其中的日期时间和IP都是动态获取的，当前页面显示3秒后， 跳转到：
```
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
欢迎
<%
DateFormat df=new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
Date now =new Date();
String nowTime=df.format(now);
String ip=request.getRemoteAddr();
%>
当前日期时间是<%=nowTime %> ，欢迎你，来自 <%=ip%> 的朋友。
<%
response.setHeader("refresh","3;url=https://www.swpu.edu.cn/scs/");
%>
```
> 会话处理能力 用JSP或Servlet实现登录的表单界面。当用户成功登录后，将用户名存储在Cookie中，下一次打开此页面时，用户名可以自动显示在用户名文本框内。
* servlet
```java
//获取表单传递的参数
String username=request.getParameter("username");
String password=request.getParameter("password");
PrintWriter writer=response.getWriter();
//成功回调
writer.println("账号:"+username);
writer.println("密码:"+password);
//存储cookie
response.addCookie(new Cookie("username",username));
response.addCookie(new Cookie("password",password));
```
* jsp
\`\`\`jsp <% Cookie\[]cookies =request.getCookies(); String username=""; String password=""; for (Cookie k:cookies){ if(k.getName().equals("username")){ username=k.getValue(); } if(k.getName().equals("password"){ password=k.getValue(); } } %>
```
用户名：
密码：
```
\
````
---
>Java类封装数据库访问
编写一个名为DbHelper的类，此类能连接到SQL Server数据库中指定的数据库，并提供一个checkUser的方法，接收用户名和密码，到tblUser表中，检查此用户是否存在。方法返回int类型，返回1表示用户名和密码正确，返回-1表示不能成功登录。
```java
public class DbHelper {
private Connection connection=null;
/**
构造方法，尝试创建连接对象
*/
public DbHelper() throws Exception
{
String sJdbcURL="jdbc:sqlserver://localhost:1433;databaseName=sugar";
String sUser="sa";
String sPwd="123456";
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
connection= DriverManager.getConnection(sJdbcURL,sUser,sPwd);
}
public int checkUser(String username,String password)
{
try
{
CallableStatement call=connection.prepareCall("{call prjCheckUser(?,?)}");
call.setString(1,username);
call.setString(2,password);
ResultSet rs=call.executeQuery();
rs.next();
return rs.getString(1).equals("Y")?1:-1;
}
catch(Exception err)
{
return -1;
}
}
}
````
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