简封为HttpServlet的用户登录例子、结合jdbc的用户登录例子
我们先看简封为HttpServlet的用户登录例子
这个小例子对servlet、request进行了小小的封装
需求是：在web.xml中进行配置用户名、密码，然后通过html进行登录，跳转到servlet，通过getServletContext().getInitParameter获取配置信息，然后通过req.getParameter获取请求信息，如果用户名、密码配对正确那么就输出成功即可
首先看配置文件：
<context-param>
<param-name>userparam-name>
<param-value>wyfparam-value>
context-param>
<context-param>
<param-name>passwordparam-name>
<param-value>123456param-value>
context-param>
<servlet>
<servlet-name>loginServletservlet-name>
<servlet-class>com.safly.LoginServlet2servlet-class>
servlet>
<servlet-mapping>
<servlet-name>loginServletservlet-name>
<url-pattern>/loginServleturl-pattern>
servlet-mapping>
然后看一个简单的html界面login.html
<html>
<head>
<meta charset="UTF-8">
<title>Insert title heretitle>
head>
<body>
<form action="loginServlet" method="post">
user:<input type="text" name="user" />
password:<input type="text"
<input type="submit" value="Submit" />
form>
body>
html>MyGenericServlet
package com.safly;
import java.io.IOException;
import java.util.Enumeration;
import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
public abstract class MyGenericServlet implements Servlet, ServletConfig {
public void destroy() {
}
public ServletConfig getServletConfig() {
return servletConfig;
}
public String getServletInfo() {
return null;
}
private ServletConfig servletConfig;
public void init(ServletConfig config) throws ServletException {
this.servletConfig = config;
init();
}
private void init() throws ServletException {
}
public abstract void service(ServletRequest req, ServletResponse res)
throws ServletException, IOException;
//以下是ServletConfig的实现方法
public String getInitParameter(String arg0) {
return servletConfig.getInitParameter(arg0);
}
public Enumeration getInitParameterNames() {
return servletConfig.getInitParameterNames();
}
public ServletContext getServletContext() {
return servletConfig.getServletContext();
}
public String getServletName() {
return servletConfig.getServletName();
}
}MyHttpServlet
package com.safly;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class MyHttpServlet extends MyGenericServlet {
public void service(ServletRequest req, ServletResponse res)
throws ServletException, IOException {
if (req instanceof HttpServletRequest) {
HttpServletRequest request = (HttpServletRequest) req;
if (res instanceof HttpServletResponse) {
HttpServletResponse response = (HttpServletResponse) res;
service(request, response);
}
}
}
public void service(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
String method = req.getMethod();
if ("GET".equalsIgnoreCase(method)) {
doGet(req, res);
} else if ("POST".equalsIgnoreCase(method)) {
doPost(req, res);
}
}
public void doPost(HttpServletRequest req, HttpServletResponse res)
throws IOException {
}
public void doGet(HttpServletRequest req, HttpServletResponse res)
throws IOException {
}
}LoginServlet2
package com.safly;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LoginServlet2 extends MyHttpServlet {
public void doPost(HttpServletRequest req, HttpServletResponse res)
throws IOException {
String username = req.getParameter("user");
String password = req.getParameter("password");
String initUser = getServletContext().getInitParameter("user");
String initPassword = getServletContext().getInitParameter("password");
PrintWriter pw = res.getWriter();
if (initUser.equals(username) && initPassword.equals(password)) {
pw.print("Helloo:" + username);
} else {
pw.print("Sorryy:" + username);
}
}
}
进行调试：
http://localhost:8080/day01/login.html
输入wyf,123456
然后浏览器输出 Helloo:wyf 说明校验正确
如果输出错误输出 Sorryy:www（用户名输入的是www）
http://localhost:8080/day01/loginServlet
结合jdbc的用户登录例子
总体流程就是创建一个user数据库，里面存有用户登录的姓名、密码
然后通过html页面进行登录，跳转到servlet，通过req.getParameter获取对应的值，构建sql语句，jdbc进行数据库链接，去查询数据库是否有用户信息，如果有的话，就输出登录成功即可
以上就是创建mydatabase数据库，然后创建user表，字段有username、password
再看代码之前，由于jdbc是数据库连接池，所以有些方法需要用到mysql-connector-java-5.1.7-bin.jar
直接丢在WEB-INF-lib下即可
我们还是先来看web.xml配置信息：
<servlet>
<servlet-name>loginServletservlet-name>
<servlet-class>com.safly.LoginServelt3servlet-class>
servlet>
<servlet-mapping>
<servlet-name>loginServletservlet-name>
<url-pattern>/loginServleturl-pattern>
servlet-mapping>接下来就就看html界面的东东，就一个用户名，密码框
然后就是servlet了
package com.safly;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LoginServelt3 extends HttpServlet {
public void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
String username = req.getParameter("username");
String password = req.getParameter("password");
System.out.println("username:"+username+",password:"+password);
java.sql.Connection connection = null;
java.sql.PreparedStatement statement = null;
ResultSet resultSet = null;
PrintWriter pw = resp.getWriter();
try {
Class.forName("com.mysql.jdbc.Driver");
String url = "jdbc:mysql://127.0.0.1:3306/mydatabase";
String user = "root";
String password2 = "root";
connection = DriverManager.getConnection(url, user, password2);
String sql = "select count(id) from user where username=? and password=?";
statement = connection.prepareStatement(sql);
statement.setString(1, username);
statement.setString(2, password);
resultSet = statement.executeQuery();
if (resultSet.next()) {
int count = resultSet.getInt(1);
System.out.println("resultSet.count1:"+count);
if (count == 1) {
pw.print("hello" + username);
} else {
pw.print("sorry" + username);
}
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (resultSet != null) {
try {
resultSet.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (statement != null) {
try {
statement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}浏览器调试：
http://localhost:8080/day01/login.html
输入wyff、wyf
这说明wyff、wyf在数据库中存在2条记录
这里判断的不严禁
if (count == 1) {
pw.print("hello" + username);
} else {
pw.print("sorry" + username);
}就输出 sorrywyff