JavaWeb(三)servlet
时间:2022-04-29
本文章向大家介绍JavaWeb(三)servlet,主要内容包括例子:、使用Servlet+JDBC实现登录注册、基本概念、基础应用、原理机制和需要注意的事项等,并结合实例形式分析了其使用技巧,希望通过本文能帮助到大家理解应用这部分内容。
Servlet
* 什么是Servlet
是运行在web服务器端的Java应用程序,它使用JAVA语言编写,具有Java语言的优点。与Java程序的区别:Servlet对象主要封装了对Http请求的处理,并且他的运行需要Servlet容器的支持。
Servlet实质上就是按Servlet规范编写的Java类,他可以处理Web应用中的相关请求。Servlet是一个标准,由Sun公司定义,具体实现细节由Servlet容器进行实现,如Tomcat,JBoss等。
Servlet和JSP的区别:
1, 角色不同(视图层和控制层) 2, 编程方法不同 3, 是否需要重新编译 4, 运行速度不同
Servlet代码结构
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
<body>
<a href="TestServlet2?username=aaaa">测试Servlet链接</a><br>
<form action="TestServlet" method="post">
<input type="submit" value="aaa">
</form>
</body>
</html>
Servlet类作为处理层
package com.hanqi.servlet;
import java.io.IOException;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("")
public class TestServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//get方法接受的请求传到这里
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//post方法接受的请求传到这里
}
@Override
public void init(ServletConfig config) throws ServletException {
String username = config.getInitParameter("username");
String password = config.getInitParameter("password");
System.out.println(username);
System.out.println(password);
}
/* @Override
public void destroy() {
System.out.println("servlet被销毁");
}
@Override
public void init() throws ServletException {
System.out.println("初始化servlet");
}*/
}
web.xml配置,服务器启动先加载
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
id="WebApp_ID" version="3.0">
<servlet>
<servlet-name>TestServlet</servlet-name>
<servlet-class>com.hanqi.servlet.TestServlet</servlet-class>
<!-- 当这个标签中的数字是0或者不配置这个标签的时候, servlet默认使用的时候加载 -->
<!-- 数字不是0的时候, 为启动服务器时加载, 数字越小, 优先级越高 -->
<load-on-startup>1</load-on-startup>
<init-param>
<param-name>username</param-name>
<param-value>admin</param-value>
</init-param>
<init-param>
<param-name>password</param-name>
<param-value>123456</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>TestServlet</servlet-name>
<url-pattern>/TestServlet</url-pattern>
</servlet-mapping>
</web-app>
用Servlet传入信息并打印
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
<body>
<form action="TestServlet2" method="post">
<input name="username" type="text" /><br>
<input name="password" type="text" /><br>
<input name="realname" type="text" /><br>
<input type="submit" value="提交" />
</form>
</body>
</html>
package com.hanqi.servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class TestServlet2
*/
@WebServlet("/TestServlet2")
public class TestServlet2 extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public TestServlet2() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
* response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//String name = request.getParameter("username");
//request.getServletContext();
//request.getSession();
//request.getpagecontext
out response.getWriter();
System.out.println(name);
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
response.setContentType("text/html; charset=utf-8");
String username = request.getParameter("username");
String password = request.getParameter("password");
String realname = request.getParameter("realname");
response.getWriter()
.append("username: " + username + "npassword: "
+ password + "nrealname: " + realname);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
* response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
例子:
使用Servlet+JDBC实现登录注册
首先准备页面
注册页面:
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
<body>
<form action="ZhueServlet" method="post">
用户名:<input type="text" name="username"><br>
密码:<input type="password" name="password"><br>
确认密码:<input type="password" name="password1"><br>
真实姓名:<input type="text" name="realname"><br>
<input type="submit" value="提交"><br>
</form>
</body>
</html>
登录页面:
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
<body>
<form action="DengluServlet" method="post">
用户名:<input type="text" name="username"><br>
密码:<input type="password" name="password"><br>
<input type="submit" value="提交"><br>
</form>
</body>
</html>
主页:
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
<body>
电话本
</body>
</html>
提示页面:
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
<body>
<%
String code=request.getParameter("code");
if("1".equals(code)){
out.print("<h1>注册成功</h1><br>");
out.print("<a href=denglu.jsp >登录</a><br>");
out.print("<a href=zhuce.jsp >注册</a><br>");
}
if("2".equals(code)){
out.print("<h1>密码不一致</h1>");
out.print("<a href=denglu.jsp >登录</a><br>");
out.print("<a href=zhuce.jsp >注册</a><br>");
}
if("3".equals(code)){
out.print("<h1>输入有误</h1>");
out.print("<a href=denglu.jsp >登录</a><br>");
out.print("<a href=zhuce.jsp >注册</a><br>");
}
if("4".equals(code)){
out.print("<h1>用户名已存在</h1>");
out.print("<a href=denglu.jsp >登录</a><br>");
out.print("<a href=zhuce.jsp >注册</a><br>");
}
if("5".equals(code)){
out.print("<h1>用户名不存在</h1>");
out.print("<a href=denglu.jsp >登录</a><br>");
out.print("<a href=zhuce.jsp >注册</a><br>");
}
if("6".equals(code)){
out.print("<h1>登录成功</h1>");
out.print("<a href=index.jsp >查看电话本</a>");
out.print("<a href=denglu.jsp >登录</a><br>");
out.print("<a href=zhuce.jsp >注册</a><br>");
}
if(" ".equals(code)){
out.print("<h1>注册成功</h1>");
out.print("<a href=denglu.jsp >登录</a><br>");
out.print("<a href=zhuce.jsp >注册</a><br>");
}
if(" ".equals(code)){
out.print("<h1>注册成功</h1>");
out.print("<a href=denglu.jsp >登录</a><br>");
out.print("<a href=zhuce.jsp >注册</a><br>");
}
%>
</body>
</html>
然后准备工具:
JDBC初始化数据库类:
package com.util;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import com.util.JdbcConnectionUtil;
public class JdbcConnectionUtil {
private static final String USERNAME = "test";
private static final String PASSWORD = "test";
private static final String URL = "jdbc:oracle:thin:@localhost:1521:xe";
private static final String DRIVERCLASSNAME = "oracle.jdbc.OracleDriver";
public static Connection getConnection(){
Connection conn=null;
try {
Class.forName(DRIVERCLASSNAME);
conn=DriverManager.getConnection(URL,USERNAME,PASSWORD);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
return conn;
}
public static void destroy(Connection conn){
if(conn!=null){
try {
conn.close();
conn=null;
} catch (SQLException e) {
e.printStackTrace();
}
}
}
public static void main(String[] args) {
System.out.println(JdbcConnectionUtil.getConnection());
}
}
数据库操作类:
package com.util;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Date;
import com.util.JdbcConnectionUtil;
import com.util.User;
public class MethodDal {
private Connection con;
private PreparedStatement pste;
private ResultSet rs;
//向表中添加数据
public int insertData(){
init();
int i=-1;
String sql="insert into puser values('c','c')";
try {
pste=con.prepareStatement(sql);
i=pste.executeUpdate();//针对于增删改数据吗,返回受影响的行数
} catch (SQLException e) {
e.printStackTrace();
}
return i;
}
//向表中添加数据
public int insertData(User user){
init();
int i=-1;
String sql="insert into puser values(?,?)";
try {
pste=con.prepareStatement(sql);
pste.setString(1,user.getUsername());
pste.setString(2, user.getPassword());
i=pste.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}
return i;
}
//删除记录
public int deleteDate(int id){
return 0;
}
//查现有姓名
public String selectName(String name){
init();
String sql="select * from puser p where p.pname=?";
try {
pste=con.prepareStatement(sql);
pste.setString(1,name);
rs = pste.executeQuery();
while(rs.next()) {
String pname=rs.getString("pname");
if(pname!=null){
return pname;
}
}
} catch (SQLException e) {
e.printStackTrace();
}
return "no";
}
//根据姓名查密码
public String selectPwd(String name){
init();
String sql="select * from puser p where p.pname=?";
try {
pste=con.prepareStatement(sql);
pste.setString(1,name);
rs = pste.executeQuery();
while(rs.next()) {
String pwd=rs.getString("ppassword");
return pwd;
}
} catch (SQLException e) {
e.printStackTrace();
}
return "wu";
}
public void init(){
con=JdbcConnectionUtil.getConnection();
}
}
用户类:
package com.util;
public class User {
private String username;
private String password;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
然后准备逻辑处理Servlet页面:
注册的Servlet页面:
package com.servlet;
import java.io.IOException;
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 com.util.MethodDal;
import com.util.User;
/**
* Servlet implementation class ZhueServlet
*/
@WebServlet("/ZhueServlet")
public class ZhueServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public ZhueServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
response.setContentType("text/html; charset=utf-8");
String username=request.getParameter("username");
String password=request.getParameter("password");
String password1=request.getParameter("password1");
String realname=request.getParameter("realname");
//调用方法判断传入的参数有没有空,都不为空才可以执行下去
if(checkParam(username,password,password1)){
if(password.equals(password1)){
MethodDal m=new MethodDal();
if(m.selectName(username).equals("no")){//调用方法根据用户名查询,如果返回no说明数据库没有此用户名,可以注册
User user=new User();//实例化用户类并添加信息
user.setUsername(username);
user.setPassword(password);
m.insertData(user);//将实例化的用户传到添加用户的方法
response.sendRedirect("message.jsp?code=1");
}else{
response.sendRedirect("message.jsp?code=4");
}
}else{
response.sendRedirect("message.jsp?code=2");
}
}else{
response.sendRedirect("message.jsp?code=3");
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
//判断传入的参数有没有空的方法,只要有空的就返回false
public boolean checkParam(String... args){//这样传参数代表参数个数不确定,传几个都可以
for(String s : args){
if("".equals(s)||s==null){
return false;
}
}
return true;
}
}
登陆的Servlet页面:
package com.servlet;
import java.io.IOException;
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 com.util.MethodDal;
import com.util.User;
/**
* Servlet implementation class DengluServlet
*/
@WebServlet("/DengluServlet")
public class DengluServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public DengluServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
response.setContentType("text/html; charset=utf-8");
String username=request.getParameter("username");
String password=request.getParameter("password");
MethodDal m=new MethodDal();
//调用方法判断传入的参数有没有空,都不为空才可以执行下去
if(checkParam(username,password)){
if(!(m.selectName(username).equals("no"))){//调用方法根据用户名查询,如果返回不为no说明数据库有此用户
if((m.selectPwd(username)).equals(password)){//根据用户名查询密码,并对比输入的密码和数据库的密码
response.sendRedirect("message.jsp?code=6");
}else{
response.sendRedirect("message.jsp?code=4");
}
}else{
response.sendRedirect("message.jsp?code=5");
}
}else{
response.sendRedirect("message.jsp?code=3");
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
//判断传入的参数有没有空的方法,只要有空的就返回false
public boolean checkParam(String... args){//这样传参数代表参数个数不确定,传几个都可以
for(String s : args){
if("".equals(s)||s==null){
return false;
}
}
return true;
}
}
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