servlet编程基本流程
好久没有写servlet—jsp类型的web开发了，今天做了一个简单的开发流程。废话不多说上代码。
1.创建一个web项目
2.创建包：

3.在index.jsp页面增加一个表单

<h3>增加</h3>    <form action="addStudentAction" method="post">        用户名：<input type="text" name="addname"/>      密码:<input type="text" name="pwd"/>    <input type="submit" value="提交"/>    </form>

4.在com.arz.action包中创建一个action也就是一个servlet

package com.arz.action;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.arz.dao.StudentDao;public class AddStudentAction extends HttpServlet {StudentDao dao = new StudentDao();@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {String name = req.getParameter("addname");System.out.println(name);String pwd = req.getParameter("pwd");dao.add(name, pwd);req.getRequestDispatcher("stu/ok.jsp").forward(req, resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {doGet(req,resp);}}

5.创建dao

package com.arz.dao;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import java.util.ArrayList;import java.util.List;import com.arz.po.Student;import com.arz.util.JDBCUtil;public class StudentDao {private static Connection conn = null;private static PreparedStatement ps = null;public void add(String name , String pwd){try{conn = JDBCUtil.getConn();String sql = "insert into student(name,pwd)values(?,?)";ps = conn.prepareStatement(sql);ps.setString(1, name);ps.setString(2, pwd);ps.execute();}catch(SQLException e){e.printStackTrace();}finally{JDBCUtil.close(null, ps, conn);}}public void del(String name){try{conn = JDBCUtil.getConn();String sql = "delete from student where name = ?";ps = conn.prepareStatement(sql);ps.setString(1, name);System.out.println(ps.execute()); }catch(SQLException e){e.printStackTrace();}finally{JDBCUtil.close(null, ps, conn);}}public List<Student> sel(String name){List<Student> list = new ArrayList<Student>();ResultSet rs = null;try{conn = JDBCUtil.getConn();String sql = "select name,pwd from student where name = ?";ps = conn.prepareStatement(sql);ps.setString(1, name);rs = ps.executeQuery();while(rs.next()){String sultName = rs.getString(1);String sultPwd = rs.getString(2);list.add(new Student(sultName,sultPwd));}}catch(SQLException e){e.printStackTrace();}finally{JDBCUtil.close(rs, ps, conn);}return list;}public static void main(String[] args){StudentDao dao = new StudentDao();List<Student> list = dao.sel("123123");System.out.println(list.size());for(int i = 0;i<list.size();i++){System.out.println(list.get(i).getName());}}}

6.创建po

package com.arz.po;public class Student {private int id ;private String name ;private String pwd;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getPwd() {return pwd;}public void setPwd(String pwd) {this.pwd = pwd;}public Student(){}public Student(String name,String pwd){this.name = name;this.pwd = pwd;}}

7.创建工具包，可以方便得到连接和关闭连接

package com.arz.util;import java.sql.Connection;import java.sql.DriverManager;import java.sql.Statement;import java.sql.ResultSet;public class JDBCUtil {private static Connection conn; private static String url = "jdbc:mysql://localhost:3306/test";private static String user = "root";private static String password = "root";public static Connection getConn() {try{Class.forName("com.mysql.jdbc.Driver");conn = DriverManager.getConnection(url,user,password);}catch(Exception e){e.printStackTrace();}return conn;}public static void close(ResultSet rs , Statement sta , Connection conn ){if(rs != null){try{rs.close();}catch(Exception e){e.printStackTrace();}}if(sta != null){try{sta.close();}catch(Exception e){e.printStackTrace();}}if(conn != null){try{conn.close();}catch(Exception e){e.printStackTrace();}}}}

8.做完这些别忘了导如Mysql的包
9.然后是配置web.xml

<?xml version="1.0" encoding="UTF-8"?><web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">  <welcome-file-list>    <welcome-file>index.jsp</welcome-file>  </welcome-file-list>  <servlet>  <servlet-name>student</servlet-name>  <servlet-class>com.arz.action.AddStudentAction</servlet-class>  </servlet>  <servlet-mapping>  <servlet-name>student</servlet-name>  <url-pattern>/addStudentAction</url-pattern>  </servlet-mapping></web-app>

基本上代码写完了。现在我们要走一下servlet的请求过程
1．首先是在index页面输入用户名和密码。
2．From发出请求（action=” addStudentAction”）
3．Web容器接受到请求后解析web.xml找到了url-pattern这个元素解析之后就可以找到对应的servlet类。在这个如果不太清楚web容器的可以看看我的“浅析Tomcat”这篇文章里面讲解了tomcat的原理。
4．在servlet里面在去寻找对应的方法（get/post）