木舟0基础学习Java的第二十六天(JavaWeb)

设置响应头

resp.setHeader("key","nihao");//推荐使用英文中文会乱码

案例：模拟登录

jdbc.properties

driverClass=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/test?verifyServerCertificate=false&useSSL=false
name=root
password=123456

JDBCUtil

public class JDBCUtil {static String driverClass=null;static String url=null;static String name=null;static String password=null;static{Properties properties=new Properties();InputStream is=null;try {is=JDBCUtil.class.getClassLoader().getResourceAsStream("jdbc.properties");properties.load(is);driverClass=properties.getProperty("driverClass");url=properties.getProperty("url");name=properties.getProperty("name");password=properties.getProperty("password");} catch (IOException e) {throw new RuntimeException(e);}}public static Connection getConn(){Connection conn=null;try {Class.forName(driverClass);conn= DriverManager.getConnection(url,name,password);} catch (Exception e) {throw new RuntimeException(e);}return conn;}private static void closeConn(Connection conn){if(conn!=null){try {conn.close();} catch (SQLException e) {throw new RuntimeException(e);}finally{conn=null;}}}private static void closePs(PreparedStatement ps){if(ps!=null){try {ps.close();} catch (SQLException e) {throw new RuntimeException(e);}finally{ps=null;}}}private static void closeRs(ResultSet rs){if(rs!=null){try {rs.close();} catch (SQLException e) {throw new RuntimeException(e);}finally{rs=null;}}}public static void release(Connection conn,PreparedStatement ps,ResultSet rs){closeRs(rs);closePs(ps);closeConn(conn);}public static void release(Connection conn,PreparedStatement ps){closePs(ps);closeConn(conn);}
}

T_user

需要实现序列化 Serializable接口

public class T_user implements Serializable{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;}@Overridepublic String toString() {return "T_user{" +"id=" + id +", name='" + name + '\'' +", pwd='" + pwd + '\'' +'}';}
}

UserDao

public interface UserDao {public T_user login(String uname, String pwd);
}

UserDaoImpl

public class UserDaoImpl implements UserDao {//处理数据连接数据库Connection conn=null;PreparedStatement ps=null;ResultSet rs=null;T_user user=null;@Overridepublic T_user login(String uname, String pwd) {try {conn= JDBCUtil.getConn();String sql="select * from t_user where uname=? and pwd=?";ps=conn.prepareStatement(sql);ps.setString(1,uname);ps.setString(2,pwd);rs=ps.executeQuery();while(rs.next()){String uname1 = rs.getString("uname");String pwd1 = rs.getString("pwd");user=new T_user();user.setName(uname1);user.setPwd(pwd1);}} catch (SQLException e) {throw new RuntimeException(e);}finally{JDBCUtil.release(conn,ps,rs);}return user;}
}

LoginService

@WebServlet("/LoginService")
public class LoginService extends HttpServlet {private UserDao UserDao;public LoginService() {UserDao=new UserDaoImpl();}@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {req.setCharacterEncoding("utf-8");resp.setContentType("text/html;charset=utf-8");String uname = req.getParameter("uname");String pwd = req.getParameter("pwd");System.out.println("uname:" + uname + "\tpwd:" + pwd);T_user user=UserDao.login(uname,pwd);if(user!=null){resp.getWriter().write("<font color='red' size=30>登录成功，欢迎"+user.getName()+"回来！</font>");}else{resp.getWriter().write("<font color='red' size=30>登录失败，账号或密码错误！</font>");}}
}

login.html

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title>
</head>
<body>
<form action="LoginService" method="post">用户名:<input type="text" name="uname">密码:<input type="password" name="pwd">爱好:<input type="checkbox" name="hobby" value="抽烟">抽烟<input type="checkbox" name="hobby" value="喝酒">喝酒<input type="checkbox" name="hobby" value="烫头">烫头<input type="checkbox" name="hobby" value="蹦迪">蹦迪<input type="submit" value="提交">
</form>
</body>
</html>

请求转发与重定向

请求转发

特点：路径不会发生改变

缺点：每次刷新页面就相当于重新提交

请求转发 在登录场景 和 转账场景不能使用

req.getRequestDispatcher("success.html").forward(req,resp);

重定向

缺点：不能携带数据

 resp.sendRedirect("success.html");

servlet跳转servlet

//将数据以键值对的方式存入req.setAttribute("user", user);//key,valuereq.getRequestDispatcher("HanderServlet").forward(req, resp);

@WebServlet("/HanderServlet")
public class HanderServlet extends HttpServlet {@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {T_user user = (T_user)req.getAttribute("user");//利用getAttribute获取值resp.getWriter().write("<h1>系统提示</h1>");resp.getWriter().write("<hr/>");resp.getWriter().write("<font color='red'>欢迎，"+user.getUname()+"登录成功！</font>");}
}

Cookie

cookie技术是浏览器端的数据存储技术解决了同一个工程下不同请求需要使用相同数据的问题我们把请求需要共享的请求数据存储在浏览器端避免用户进行重复书写请求数据

特点：适合少量数据键值对不安全

注意：一个cookie对象存储一条数据多条数据可以创建多个cookie对象进行存储

作用：Cookie技术解决不同请求发送之间的数据共享问题

Cookie的使用

@WebServlet("/LoginSerlet")
public class LoginUser extends HttpServlet {private com.dao.UserDao UserDao;public LoginUser() {UserDao = new UserDaoImpl();}@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {req.setCharacterEncoding("UTF-8");resp.setContentType("text/html;charset=UTF-8");String uname = req.getParameter("uname");String pwd = req.getParameter("pwd");System.out.println("uname:" + uname + "\tpwd:" + pwd);T_user user=UserDao.login(uname,pwd);if(user!=null){//将数据存储到Cookie当中Cookie c1=new Cookie("name",user.getUname());Cookie c2=new Cookie("pwd",user.getPwd());//设置三天免登录 默认不设置时间 关闭浏览器立即失效c1.setMaxAge(24*3600*3);//把存储了登录信息的Cookie 通过响应resp 响应到浏览器中resp.addCookie(c1);resp.addCookie(c2);resp.sendRedirect("success");}else{req.getRequestDispatcher("login.html").forward(req, resp);}}
}

@WebServlet("/success")
public class LoginServlet extends HttpServlet {@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {req.setCharacterEncoding("UTF-8");resp.setContentType("text/html;charset=UTF-8");//通过浏览器携带的cookie name=admin pwd=123456 找tomcat中cookie对象的数据//获取cookieCookie[] cookies = req.getCookies();//键值对String value=null;//遍历所有cookie 找cookie的key是user的cookie对象for (Cookie c : cookies) {if("name".equals(c.getName())) {value = c.getValue();System.out.println("name:"+value);}if("pwd".equals(c.getName())) {value = c.getValue();System.out.println("pwd:"+value);}}resp.getWriter().write("<h1>系统提示</h1>");resp.getWriter().write("<hr/>");resp.getWriter().write("<font color='red'>欢迎，"+value+"登录成功！</font>");}
}

中央仓库（jar包下载）

Maven Repository: Central (mvnrepository.com)https://mvnrepository.com/repos/central

Session

首先创建Session Session在tomcat容器中 有且只有一个

Session默认时间30分钟在开发中一般都使用Session存储用户登录信息

@WebServlet("/SessionLogin")
public class SessionLogin extends HttpServlet {UserService service;public SessionLogin() {service = new UserServiceImpl();}@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {req.setCharacterEncoding("UTF-8");resp.setContentType("text/html;charset=UTF-8");String uname = req.getParameter("uname");String pwd = req.getParameter("pwd");T_stu stu = service.login(uname, pwd);if(stu!=null){//创建sessionHttpSession session = req.getSession();//将数据以键值对的方式存入session.setAttribute("stu", stu);resp.sendRedirect("SessionUser");}else{req.getRequestDispatcher("login.html").forward(req, resp);}}
}

@WebServlet("/SessionUser")
public class SessionUser extends HttpServlet {@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {req.setCharacterEncoding("UTF-8");resp.setContentType("text/html;charset=UTF-8");//创建sessionHttpSession session = req.getSession();//获取数据T_stu stu =(T_stu)session.getAttribute("stu");resp.getWriter().write("<h1>系统提示</h1>");resp.getWriter().write("<hr/>");resp.getWriter().write("<h1>登录成功，欢迎"+stu.getUname()+"登录！</h1>");resp.getWriter().write("<a href='exit'>退出</a>");}
}

@WebServlet("/exit")
public class SessionExit extends HttpServlet {@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {req.setCharacterEncoding("UTF-8");resp.setContentType("text/html;charset=UTF-8");HttpSession session = req.getSession();//关闭sessionsession.invalidate();resp.sendRedirect("login.html");}
}

ServletContext(上下文对象携带数据)

生命周期程序启动到结束

作用域在项目内

创建

        //第一种创建方式 有就创建 没有就获取ServletContext sc1= this.getServletContext();//第二种ServletContext sc2=req.getSession().getServletContext();//第三种ServletContext c3=this.getServletConfig().getServletContext();

得到

 ServletContext sc = this.getServletContext();String a =(String) sc.getAttribute("a");String b =(String) sc.getAttribute("b");String c =(String) sc.getAttribute("c");resp.getWriter().write("a:"+a+"b:"+b+"c:"+c);

删除

ServletContext sc = this.getServletContext();//删除bsc.removeAttribute("b");

读取配置文件的配置信息

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"version="4.0"><context-param><param-name>name</param-name><param-value>木舟</param-value></context-param>
</web-app>

String city = sc.getInitParameter("city");System.out.println(city);