JavaWeb学习笔记——HelloWord Servlet
1.实现servlet打印日志
开发一个动态web资源，即开发一个Java程序向浏览器输出数据，需要完成以下2个步骤：
1.编写一个Java类，实现Servlet接口
开发一个动态web资源必须实现javax.servlet.Servlet接口，Servlet接口定义了Servlet引擎与Servlet程序之间通信的协议约定
以下是MyServlet.java文件中的代码（写的这个类的名字叫做MyServlet）：
package org.MyServlet.MyServlet;
import java.io.IOException;
import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
//开发一个动态web资源必须实现javax.servlet.Servlet接口
//Servlet接口定义了Servlet引擎与Servlet程序之间通信的协议约定
//Q:MyServlet完成了一个动态网页程序，或者说是一个功能，如何让客户端能否准确得找到我们得这个Servlet服务
//A:服务器需要预先为我们预留出扩展接口，我们只需要按照一定的规则去提供相应的扩展功能
//Q:如何和服务器进行通讯
//A:web.xml就是服务器提供给我们的完成功能的地方
public class MyServlet implements Servlet{
@Override
public void destroy() {
// TODO Auto-generated method stub
}
@Override
public ServletConfig getServletConfig() {
// TODO Auto-generated method stub
return null;
}
@Override
public String getServletInfo() {
// TODO Auto-generated method stub
return null;
}
@Override
public void init(ServletConfig arg0) throws ServletException {
// TODO Auto-generated method stub
}
//所有客户端请求会自动调用Service方法进行处理
//ServletRequest 是一个对象，封装所有HTTP请求信息
//ServletResponse 是一个对象，封装所有HTTP响应信息
//这两个对象是Tomcat服务器给我们的
@Override
public void service(ServletRequest arg0, ServletResponse arg1)
throws ServletException, IOException {
// TODO Auto-generated method stub
System.out.println("执行 MyServlet 的 service() 方法。。。。。");
}
}
关于其中的Service方法的一些Tip：
//所有客户端请求会自动调用Service方法进行处理 //ServletRequest 是一个对象，封装所有HTTP请求信息 //ServletResponse 是一个对象，封装所有HTTP响应信息 //这两个对象是Tomcat服务器给我们的 此外，如果是只实现service方法，则称为适配器模式
以下是web.xml文件中的代码：
<?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">
<display-name>MyServlet</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
//定义一个Servlet服务
//Servlet服务的名字叫做aaa
<servlet>
<servlet-name>aaa</servlet-name>
<servlet-class>org.MyServlet.MyServlet.MyServlet</servlet-class>
</servlet>
//定义一个Servlet服务的映射关系
//Servlet服务的名字叫做aaa
//请求的路径是/myServlet.do
//1.服务器启动模式加载webapps下面所有的应用，加载web应用的时候会读取每个应用的web。xml文件
//2.客户单发送请求http://127.0.0.1:8080/MyServlet/myServlet.do
//3.请求就找到http://127.0.0.1:8080，找到MyServlet(Context)
//去mapping里面查找/myServlet.do,如果找到，定位到<servlet-name>aaa</servlet-name>
//4.去Servlet的定义里面查找Servlet-name是aaa的Servlet服务
//然后定位到org.MyServlet.MyServlet.MyServlet,执行该class的service方法
<servlet-mapping>
<servlet-name>aaa</servlet-name>
<url-pattern>/myServlet.do</url-pattern>
</servlet-mapping>
</web-app>
然后在浏览器中输入
http://127.0.0.1:8080/MyServlet/myServlet.do
便可以在Tomcat中看到
执行 MyServlet 的 service() 方法。。。。。
2.把开发好的Java类部署到web服务器中
2.实现servlet打印HelloWorld
该工程的功能是在页面上输出一段话
首先在src里面新建一个class,在interface里面添加javax.servlet.Servlet
以下是HelloServlet.java中的代码：
package org.common.Servlet; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.Servlet; import javax.servlet.ServletConfig; import javax.servlet.ServletException; import javax.servlet.ServletRequest; import javax.servlet.ServletResponse; public class HelloServlet implements Servlet { @Override public void destroy() { // TODO Auto-generated method stub } @Override public ServletConfig getServletConfig() { // TODO Auto-generated method stub return null; } @Override public String getServletInfo() { // TODO Auto-generated method stub return null; } @Override public void init(ServletConfig arg0) throws ServletException { // TODO Auto-generated method stub } //开发完成之后要告诉服务器我的存在，就要在web。xml里面继续写代码 @Override public void service(ServletRequest arg0, ServletResponse arg1) throws ServletException, IOException { // TODO Auto-generated method stub //获取一个输出流，就可以对页面写出内容 PrintWriter pw = arg1.getWriter(); pw.println("终于成功了！"); pw.close(); } }
以下是web.xml文件中的代码：
<?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">
<display-name>HelloApp</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
<!-- 定义Servlet服务 -->
<servlet>
<servlet-name>hello</servlet-name> <!--随便取-->
<servlet-class>org.common.Servlet.HelloServlet</servlet-class> <!--取包名。类名-->
</servlet>
<!-- 定义映射关系 -->
<servlet-mapping>
<!-- 注意：mapping里面的servlet-name在Servlet的定义里面一定要有匹配的，否则启动报错 -->
<servlet-name>hello</servlet-name>
<url-pattern>/hello</url-pattern>
</servlet-mapping>
</web-app>
访问的网址是
http://127.0.0.1:8080/Helloapp/hello
其中Helloapp是Tomcat里面的文件夹的名字，hello是url-pattern里面写的名字
3.实现servlet打印当前时间
该工程的功能是实现在页面中显示当前的时间
1.编写一个Java类，实现Servlet接口
以下的代码是HelloServlet.java中的代码
package helloapp2;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Date;
import javax.servlet.GenericServlet;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
public class HelloServlet extends GenericServlet {
@Override
public void service(ServletRequest arg0, ServletResponse arg1)
throws ServletException, IOException {
// TODO Auto-generated method stub
PrintWriter pw = arg1.getWriter();
pw.println("Hello");
pw.println(new Date().toLocaleString());
pw.close();
}
}
以下的代码是web.xml中的代码
<?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_2_5.xsd" id="WebApp_ID"
version="2.5">
<display-name>helloapp2</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>Hello</servlet-name>
<servlet-class>helloapp2.HelloServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Hello</servlet-name>
<url-pattern>/Hello</url-pattern>
</servlet-mapping>
</web-app>
2.把开发好的Java类部署到web服务器中
使用myeclipse自动部署的方法(使用myeclipse 2015自动部署有问题，待解决)(换成2014的便可以自动部署)：
1.Window->preferences->Myeclipse->Servers->Runtime Ecvironment->add->Tomcat 6.0，要选中添加local的那个选项
2.在manage deployment的module里面选择要部署的工程
3.重新安装Tomcat出现的问题解决，但是还是要手动部署
自动部署设置，参考：Eclipse中的Web项目自动部署到Tomcat
自动部署后要把网页的文件放在根目录下
该工程的名称是testhttp，功能是在页面中表格打印浏览过程中的相关头信息。
新建一个工程，然后在这个工程里面新建一个servlet，这样便可以省去编写web.xml的过程
3.实现servlet打印header
以下是TestHttpServlet.java中的代码
package org.common.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class TestHttpServlet extends HttpServlet {
/**
* Constructor of the object.
*/
public TestHttpServlet() {
super();
}
/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}
/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
//Servlet接口的参数service(ServletRequest arg0, ServletResponse arg1)
//HttpServletRequest封装了所有的请求信息，其实就是Tomcat将请求信息按照JAVA EE的Servlet的规范
//封装好给我们
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//设置返回类型
//response.setContentType("text/html;charset=GBK");
response.setContentType("text/html");
response.setCharacterEncoding("GBK");
//获取输出流
PrintWriter out = response.getWriter();
out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
out.println("<HTML>");
out.println(" <HEAD><TITLE>testhttp Servlet</TITLE></HEAD>");
out.println(" <BODY>");
out.print("<center>");
out.print(" <h2>请求头信息列表<h2> ");
out.print(" <table border=1> ");
out.print(" <tr><th>名字</th><th>值</th></tr> ");
//返回头消息名字集合，返回的是一个枚举
Enumeration enums = request.getHeaderNames();
//遍历获取所有头信息名和值
while(enums.hasMoreElements()){
//获取每一个头消息的名字
String headName = (String)enums.nextElement();
out.println(" <tr> ");
out.println(" <td> " + headName + " </td> ");
//getHeader(java.lang.String name)
//Returns the value of the specified request header as a String.
//返回这个名字的头信息的值
out.println(" <td> " + request.getHeaders(headName) + " </td> ");
out.println(" </tr> ");
}
out.println(" </table> ");
out.println(" <hr> ");
//测试HttpServletRequest的方法
out.println("Method： " + request.getMethod() + "<br>");
out.println("Request URI： " + request.getRequestURI() + "<br>");
out.println("Protocol： " + request.getProtocol() + "<br>");
out.println("PathInfo： " + request.getPathInfo() + "<br>");
out.println("Remote Address： " + request.getRemoteAddr() + "<br>");
out.println("ContextPath： " + request.getContextPath() + "<br>");
out.println("getScheme： " + request.getScheme() + "<br>");
out.println("getServerName： " + request.getServerName() + "<br>");
out.println("getServerPort： " + request.getServerPort() + "<br>");
out.println("getRequestURI： " + request.getRequestURI() + "<br>");
String path = request.getContextPath();
//请求全路径
String basePath
= request.getScheme() + "://" + request.getServerName() + ":"
+ request.getServerPort() + request.getRequestURI();
out.println(" path: " + path + "<br>");
out.println(" basePath: " + basePath + "<br>");
//out.print(this.getClass());
//out.println(", using the GET method");
out.print("</center>");
out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//调用doGet方法
this.doGet(request, response);
}
/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
}
}
然后部署并启动Tomcat服务器，在浏览器中输入
http://127.0.0.1:8080/testhttp/servlet/TestHttpServlet
4.使用servlet实现简单的login
本工程的功能是实现Javaweb的servlet身份验证
一下是login.html文件中的代码
<!DOCTYPE html>
<html>
<head>
<title>login.html</title>
<meta name="keywords" content="keyword1,keyword2,keyword3">
<meta name="description" content="this is my page">
<meta name="content-type" content="text/html; charset=GBK">
<!--<link rel="stylesheet" type="text/css" href="./styles.css">-->
<script type="text/javascript">
function check(){
//获取控件内容
var loginname = document.getElementById("loginname").value;
if(loginname == ""){
alert("用户名不能为空");
document.getElementById("loginname").focus();//获取焦点
return false;
}
var password = document.getElementById("password").value;
if(password == ""){
alert("密码不能为空");
document.getElementById("password").focus();
return false;
}
//验证成功
document.loginform.submit();
}
</script>
</head>
<body>
<center>
<h2>登陆页面</h2>
<br>
<!-- html数据由两种传输方式 1.get 从地址栏传递 2.form表单传输
form代表表单
--action属性代表提交的url
action="login.do",那么在web.xml里面定义<servlet-mapping>的<url-pattern>
的时候也是login.do
--method属性代表提交表单的方式，http里面重点是get和post，默认get方式提交
--name属性给表单其名字
--id属性代表唯一标示该表单的名字，主要是javascript脚本使用
-->
<form action="login.do" method="get" name="loginform" id="loginform">
<table>
<tr>
<td>登录名：</td>
<td><input type="text" name="loginname" id="loginname"/></td>
</tr>
<tr>
<td>密码：</td>
<td><input type="password" name="password" id="password"/></td>
</tr>
</table>
<table>
<tr>
<td><input type="button" value="提交" onclick="check();"></td>
<td><input type="reset" value="重置"></td>
</tr>
</table>
</form>
</center>
</body>
</html>
以下代码是LoginServlet.java中的代码
package org.common.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;
import java.util.Properties;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LoginServlet extends HttpServlet {
/**
* Constructor of the object.
*/
public LoginServlet() {
super();
}
/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}
/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
System.out.println("执行 doGet 方法...");
// //1.接收前台传递过来的参数
// Enumeration enums = request.getParameterNames();
// while(enums.hasMoreElements()){
// System.out.println(enums.nextElement());
//
// }
//转换编码的第2种方式，配合doPost()方法使用
request.setCharacterEncoding("GBK");
//提交的name可以在后台使用request.getParameter("loginname")获取值
String loginname = request.getParameter("loginname");
System.out.println("转换前loginname:" + loginname);
//String password = request.getParameter("password");
//把loginname这个字符串转成GBK，前提你要确定编码
loginname = new String(loginname.getBytes("iso-8859-1"),"GBK");
System.out.println("转换后loginname:" + loginname);
String password = request.getParameter("password");
//properties文件是java的默认配置文件，以key-value的形式存储数据
//增加了一个user.properties文件存储用户名密码
Properties pro = new Properties();
//load方法从输入流中读取属性列表（键和元素对）
pro.load(this.getClass().getResourceAsStream("/user.properties"));
//System.out.print(pro);
response.setContentType("text/html;charset=GBK");
PrintWriter out = response.getWriter();
out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
out.println("<HTML>");
out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");
out.println(" <BODY>");
//out.print(" loginname: " + loginname);
//out.print(" password: " + password);
if(loginname.equals(pro.getProperty("loginname"))
&& password.equals(pro.getProperty("password"))){
out.println(" 欢迎["+pro.getProperty("username")+"]登陆");
}else{
out.println("用户名密码错误");
}
out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doGet(request, response);
}
/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
}
}
doGet()方法不安全，所以尽量使用doPost()方法
本文只发表于博客园和tonglin0325的博客，作者：tonglin0325，转载请注明原文链接：https://www.cnblogs.com/tonglin0325/p/4607338.html
