RegisterServlet.java ~~~ package zyw.web; import zyw.service.UserService; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; @WebServlet(name = "RegisterServlet",urlPatterns = "/register") public class RegisterServlet extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String name = request.getParameter("name"); // String id = request.getParameter("id"); String password = request.getParameter("password"); String email = request.getParameter("email"); // User user=new User(); UserService userService=new UserService(); // boolean register = userService.register(user); boolean register = userService.register(name,password,email); if (register) { response.sendRedirect(request.getContextPath()+"login.jsp"); }else { response.setContentType("text/html;charset=utf-8"); response.getWriter().write("注册失败"); } } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } } ~~~ UserService.java ~~~ package zyw.service; import zyw.dao.UserDao; public class UserService { //1. 判断注册用户是否存在 public boolean register(String name,String password,String email) { boolean register=false; UserDao userDao = new UserDao(); boolean checkUser = userDao.checkUser(name); //2. 如果不存在就将用户信息添加到数据库 if (checkUser) { register = userDao.register(name,password,email); } return register; } } ~~~ UserDao.java ~~~ package zyw.dao; import com.mchange.v2.c3p0.ComboPooledDataSource; import org.apache.commons.dbutils.QueryRunner; import org.apache.commons.dbutils.handlers.BeanHandler; import zyw.bean.User; import java.sql.SQLException; public class UserDao { /** * 检查用户是否存在 * @param name * @return */ public boolean checkUser(String name){ try { ComboPooledDataSource dataSource=new ComboPooledDataSource(); QueryRunner queryRunner=new QueryRunner(dataSource); String sql="select name from user where name=?"; User user = queryRunner.query(sql, new BeanHandler<User>(User.class),name); //如果没有查询到数据 说明这个用户名没有注册过 if (user==null) { return true; }else { return false; } } catch (SQLException e) { e.printStackTrace(); return false; } } /** * 用户注册 * @param * @return */ public boolean register(String name,String password,String email) { try { ComboPooledDataSource dataSource=new ComboPooledDataSource(); QueryRunner queryRunner=new QueryRunner(dataSource); String sql="insert into user values(null,?,?,?)"; int row = queryRunner.update(sql, name,password, email); //行数大于零说明注册成功 if (row>0) { return true; }else { return false; } } catch (SQLException e) { e.printStackTrace(); return false; } } } ~~~ 运行结果，如果不存在名字，则注册名字并跳转登录页面，如果存在名字