登陆页面的搭建

首先仍然是javaScript的处理

function login(){
var th=document.form1;
if(th.username.value==""){
alert("用户名不能为空！");
th.username.focus();
return;
}
if(th.pswd.value==""){
alert("密码不能为空！");
th.pswd.focus();
return;
}
th.action="<%=path%>/servlet/LoginAction";
th.submit();

}

新建一个接口 来处理用户登陆

package com.servlet.login.service;

import java.util.List;
import java.util.Map;

public interface LoginService {
public boolean userLogin(List<Object> params);
}

新建一个类 继承接口 完成对数据的访问

package com.servlet.login.dao;

import java.sql.SQLException;
import java.util.List;
import java.util.Map;

import com.jdbc.util.MySqlConnect;
import com.servlet.login.service.LoginService;

public class LoginDao implements LoginService {
private MySqlConnect conn = null;

public LoginDao() {
conn = new MySqlConnect();
}

public boolean userLogin(List<Object> params) {
//连接数据库
conn.getConnect();
boolean flag = false;
String sql = "select * from userinfo where username= ? and password=? ";
try {
Map<String, Object> map = conn.queryBySimpleResult(sql, params);
flag = !map.isEmpty() ? true : false;
} catch (SQLException e) {
e.printStackTrace();
}finally{
conn.releaseConnect();
}
return flag;
}

}

再新建一个类 完成对业务逻辑的处理

package com.servlet.login.action;

import java.io.IOException;
import java.io.PrintWriter;
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;

import com.servlet.login.dao.LoginDao;
import com.servlet.login.service.LoginService;

public class LoginAction extends HttpServlet {

private static final long serialVersionUID = 1L;
private LoginService service;

public LoginAction() {
service=new LoginDao();
}

public void destroy() {
super.destroy();
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String path=request.getContextPath();
response.setContentType("text/html;charset=utf-8");

String username=request.getParameter("username");
String password=request.getParameter("pswd");
List<Object>params=new ArrayList<Object>();
params.add(username);
params.add(password);
boolean flag=service.userLogin(params);
if(flag){
request.getSession().setAttribute("username",username);
response.sendRedirect(path+"/main.jsp");
}

}

public void init() throws ServletException {
}

}

为了防止直接从登陆页面跳转页面直接登陆 还需要添加一个过滤器

package com.servlet.login.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class MyFilter implements Filter {

public MyFilter() {
}

public void destroy() {

}

public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest httpServletRequest = (HttpServletRequest) request;
HttpServletResponse httpServletResponse = (HttpServletResponse) response;
String path = httpServletRequest.getContextPath();
httpServletRequest.setCharacterEncoding("utf-8");
httpServletResponse.setCharacterEncoding("utf-8");
String username = (String) httpServletRequest.getSession()
.getAttribute("username");
if (username == null) {
httpServletResponse.sendRedirect(path + "/index.jsp");
}
chain.doFilter(httpServletRequest, httpServletResponse);
}

public void init(FilterConfig arg0) throws ServletException {

}

}

web.xml中配置一下

<filter>
<filter-name>MyFilter</filter-name>
<filter-class>com.servlet.login.filter.MyFilter</filter-class>
</filter>

<filter-mapping>
<filter-name>MyFilter</filter-name>
<url-pattern>/main.jsp</url-pattern>
</filter-mapping>