servlet中Java连接数据库后的基本操作

Posted 2020-08-10

servlet中Java连接数据库后的基本操作

 

1. 在eclipse中新建一个工程:login
2. 在Server中新建一个服务器,基本的操作不用说了,在前两天的笔记中可以找到;
3. 需要知道数据库的用户名和密码:用户名:user.密码:yufei
4. 需要改变的地方:

地方一:web.xml                        

   

         

<?xml version="1.0"     encoding="UTF-8"?>     <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"     xmlns="http://java.sun.com/xml/ns/javaee"     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee     http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">       <display-name>login</display-name>         <welcome-file-list>         <welcome-file>login.html</welcome-file>        </welcome-file-list>              <!-- 注册servlet -->      <servlet>       <!-- servlet的名字 (名字可以随便取)但是约定俗成的名字是开发的servlet的名字 -->         <servlet-name>LoginServlet</servlet-name>           <!-- 配置servlet的包名 (不要带上后缀) -->         <servlet-class>login.com.LoginServlet</servlet-class>      </servlet>             <!-- 映射servlet -->       <servlet-mapping>       <!-- 映射servlet的名字     必须和你注册的servlet的名字一样 -->         <servlet-name>LoginServlet</servlet-name>       <!-- 配置servlet处理的路径(路径可以随便取)但是约定俗成的名字是开发的servlet的名字 -->       <url-pattern>/LoginServlet</url-pattern>       </servlet-mapping>     </web-app>

 

地方二:在Java Resources 里面新建包和html文件比如:login.com(包),LoginServlet.java文件

 

下面是:LoginServlet.java里面的内容:

   

         

package     login.com; import     java.io.IOException;       import     java.io.PrintWriter; 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     javax.servlet.ServletException;    import     javax.servlet.http.HttpServlet; import     javax.servlet.http.HttpServletRequest; import     javax.servlet.http.HttpServletResponse; public class     LoginServlet extends HttpServlet{             @Override                 protected void     doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException,     IOException {                        // TODO     Auto-generated method stub                        //处理中文的乱码                           resp.setContentType("text/html;charset=utf-8");//响应                        req.setCharacterEncoding("utf-8");     //请求                           String name =     req.getParameter("username"); //username是输入框对应的name                          String pwd =     req.getParameter("pwd");                          try {                                       try {                                                   //表单填写的都是字符串                                                   Class.forName("com.mysql.jdbc.Driver");                                                    Connection     connection =     DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/login",     "root", "yufei");     //                                             System.out.println(connection);                                                    String     sql = "select * from conn where name=? and pwd=? ;";                                                    PreparedStatement     preparedStatement = connection.prepareStatement(sql);                                                    System.out.println("name:"+name+"============"     +"pwd" + pwd);                                                   preparedStatement.setString(1,     name);                                                   preparedStatement.setString(2,     pwd);                                                  ResultSet     re = preparedStatement.executeQuery();                                                   PrintWriter     out = resp.getWriter();                                                    out.print("<h1>==========</h1>");                                                   String     sql1 = "select * from student";                                                PreparedStatement     sprint = connection.prepareStatement(sql1);                                                    ResultSet     studinf = sprint.executeQuery();                                                                                                       while(re.next()){                                                                                                                 out.print("<h1>登录成功</h1>");                                                               out.print("<h5>学生的信息是:</h5>");                                                                                                                             while(studinf.next()){                                                                           out.print("<p>学生的姓名是:"+     studinf.getString("name")+"===id号:"+studinf.getString("id")+"===性别是:"+studinf.getString("gender")+"===年龄是:"+studinf.getString("age")+"</p>");                                                               }                                                               return;//终止程序                                                    }                                                    out.print("<h1>登录失败</h1>");                                        } catch     (SQLException e) {                                                    //     TODO Auto-generated catch block                                                    e.printStackTrace();                                        }                            } catch     (ClassNotFoundException e) {                                        // TODO     Auto-generated catch block                                        e.printStackTrace();                            }                 }                                 //form默认的提交方式是get                 @Override                 protected void doGet(HttpServletRequest     req, HttpServletResponse resp) throws ServletException, IOException {                            // TODO     Auto-generated method stub                            doPost(req,resp);                 }     }

 

地方三:在文件WebContent里面新建一个html文件,比如:login.html

 

下面是:login.html内容:

   

         

<!DOCTYPE html>     <html>     <head>     <meta charset="UTF-8">     <title>login</title>     </head>     <body>         <h1>&nbsp;welcome to login</h1>         <div style=‘outline:1px black solid;width:340px;  text-align: center;‘>             <h1>登录页面</h1>             <!--   <a href=‘HelloServer‘>获得连接</a>     -->             <!-- <%=request.getContextPath()%>/ -->             <form action=‘LoginServlet‘ method=‘post‘>             <p>用户名:<input type=‘text‘     name=‘username‘/></p>             <p>密码: <input type=‘password‘     name=‘pwd‘/></p>             <button>login</button>             </form>         </div>     </body>     </html>

 

地方四:添加夹包-在文件夹WEB-INF的lib里面加上夹包Server和mysql