servelt相关的一些例子
总的项目结构图如下：
配置文件web.xml
1，第一个servlet例子
index.jsp
执行结果：
如果输入不是数字，最后一行显示： 对不起，输入不是数字
2，购物车的例子，用session保存信息
showcart.jsp
执行结果：
选择后点击“加入购物篮”
如果点击链接“继续购物”，返回showcart.jsp页面，选择“电脑”加入购物车
3，servlet通过jdbc链接数据库
结果：
4，把链接数据库的参数配置在web.xml中的servlet初始参数中，见web.xml
结果就是显示数据库中Loginuser表格的内容
源码见附件
配置文件web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<!-- 配置servlet -->
<servlet>
<!--servlet名称，必须唯一-->
<servlet-name>Firstservlet</servlet-name>
<!--对应的servlet类-->
<servlet-class>firstservlet.FirstServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Firstservlet</servlet-name>
<!--访问的URL地址： http://localhost:8080/servlet/firstservlet-->
<!-- 对应index.jsp中的表单动作<form action="firstservlet"> -->
<url-pattern>/firstservlet</url-pattern>
</servlet-mapping>
<!-- 配置servlet -->
<servlet>
<servlet-name>testservlet</servlet-name>
<servlet-class>servletAPI.TestServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>testservlet</servlet-name>
<url-pattern>/testservlet</url-pattern>
</servlet-mapping>
<!-- 配置servlet -->
<servlet>
<description>
This is the description of my J2EE component
</description>
<display-name>
This is the display name of my J2EE component
</display-name>
<servlet-name>initservlet</servlet-name>
<servlet-class>servletAPI.InitServlet</servlet-class>
<!-- 连接数据库的初始化参数 -->
<init-param>
<param-name>driver</param-name>
<param-value>
com.microsoft.jdbc.sqlserver.SQLServerDriver
</param-value>
</init-param>
<init-param>
<param-name>URL</param-name>
<param-value>
jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=login
</param-value>
</init-param>
<init-param>
<param-name>username</param-name>
<param-value>sa</param-value>
</init-param>
<init-param>
<param-name>password</param-name>
<param-value>sa</param-value>
</init-param>
</servlet>
<!-- 建立servlet自动生成的 -->
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>ShowCart</servlet-name>
<servlet-class>shoppingCart.ShowCart</servlet-class>
</servlet>
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>ShortMessage</servlet-name>
<servlet-class>ch05shortmessage.ShortMessage</servlet-class>
</servlet>
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>ProductList</servlet-name>
<servlet-class>ch06servletJDBC.ProductList</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>initservlet</servlet-name>
<url-pattern>/initservlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>ShowCart</servlet-name>
<url-pattern>/ShowCart</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>ShortMessage</servlet-name>
<url-pattern>/shortmessage</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>ProductList</servlet-name>
<url-pattern>/productlist</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
1，第一个servlet例子
package firstservlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Date;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class FirstServlet extends HttpServlet {
private int stringtoint(String str)throws NumberFormatException{
int i = Integer.parseInt(str);
return i;
}
//覆盖父类的方法doGet，doPost， doPost不会显示传递的参数
public void doGet(HttpServletRequest request,HttpServletResponse response)throws ServletException,IOException{
String str;
int inputNum;
String outputstring;
response.setContentType("text/html;charset=gb2312");
PrintWriter out = response.getWriter();
Cookie cookies[]=request.getCookies();
//输出网页
out.println("<HTML>");
out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");
out.println(" <BODY>");
out.println("<h1>servlet例子</h1>");
if((cookies==null)||(cookies.length==0)){
out.println("没有Cookies！");
}
else{
out.println("<center><h1>响应消息中的Cookies的信息</h1>");
out.println("<table border=2>");
out.println("<tr><th>Name</th><th>value</th><th>comment</th><th>max age</th></tr>");//表头
for(int i=0;i<cookies.length;i++){
Cookie c = cookies[i];
out.println("<tr><td>"+c.getName()+"</td><td>"+c.getValue()+"</td><td>"+c.getComment()+"</td><td>"+c.getMaxAge()+"</td><td>");
}//maxage为cookie的过期时间，过期的cookie就不会往服务器端发送了
out.println("</table></center>");
}
out.println("<h1>httpsession接口</h1>");
HttpSession session = request.getSession();
long time = session.getCreationTime();
Date createDate = new Date(time);
out.println("seesion创建的时间："+createDate+"<br>");
out.println("seesion的ID："+session.getId()+"<br>");
//第一次执行为null，后面的为12，重启Tomcat后为null，或者关闭浏览器重启为null
out.println("session的getValue:"+session.getValue("item1")+"<br>");
Integer sessionItem = new Integer(12);
session.putValue("item1", sessionItem); //保存到session中
str = request.getParameter("txtInputNum"); //取得请求参数,txtInputNum为index.jsp中设置的参数名称
try {
inputNum = stringtoint(str);
outputstring = "你输入的数字为："+inputNum;
} catch (NumberFormatException e) {
outputstring = "对不起，输入不是数字";
}
out.println("<h1>表单传递参数</h1>");
out.println(outputstring);
out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
public void doPost(HttpServletRequest request,HttpServletResponse response)throws ServletException,IOException{
doGet(request,response);
}
}
index.jsp
<%@ page language="java" contentType = "text/html;charset=gb2312"%>
<%
//String path = request.getContextPath();
//String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<!-- <base href="<%//=basePath
%>"> -->
<title>servlet处理异常</title>
</head>
<body>
<form action="firstservlet">
请输入一个数字:
<input type="text" name="txtInputNum" />
<input type="submit" value="submit" />
</form>
</body>
</html>
执行结果：
如果输入不是数字，最后一行显示： 对不起，输入不是数字
2，购物车的例子，用session保存信息
package shoppingCart;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class ShowCart extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=gb2312"); // 设置返回的MIME类型，只能设置一次，为纯html文件
PrintWriter out = response.getWriter();
out.println("<HTML>");
out.println(" <HEAD><TITLE>购物车实例</TITLE></HEAD>");
out.println(" <BODY>");
String[] items = { "电视机", "电冰箱", "电脑" };
HttpSession session = request.getSession(); //取得会话
Integer itemCount = (Integer) session.getValue("itemCount");
if (itemCount == null) {
itemCount = new Integer(0);
}
String[] itemSelected;
String itemName;
itemSelected = request.getParameterValues("item");// 取得表单中的checkbox的值
if (itemSelected != null) {
for (int i = 0; i < itemSelected.length; i++) {
itemName = itemSelected[i]; // 对应于checkbox的value
itemCount = new Integer(itemCount.intValue() + 1);
session.putValue("Item" + itemCount, itemName); // 商品名称为ItemX
session.putValue("itemCount", itemCount); // 商品数量保存到session中
}
}
out.println("<h3>购物篮中的物品：</h3>");
for (int i = 1; i <= itemCount.intValue(); i++) {
String item = (String) session.getValue("Item" + i); // 取出商品名称在checkbox对应的数值
out.println(items[Integer.parseInt(item)]);
out.println("<br>");
}
out.println("<hr>");
out.println("<a href='showcart.jsp'>继续购物</a>");
out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
}
showcart.jsp
<%@ page language="java" contentType = "text/html;charset=gb2312"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>购物车</title>
</head>
<body>
<form action="ShowCart" method="post">
选购商品:<br>
<input type="checkbox" name="item" value="0" />
第一种:电视机<br>
<input type="checkbox" name="item" value="1" />
第二种:电冰箱<br>
<input type="checkbox" name="item" value="2" />
第三种:电脑<br>
<hr>
<input type="submit" name ="addtocart" value="加入购物篮" />
</form>
</body>
</html>
执行结果：
选择后点击“加入购物篮”
如果点击链接“继续购物”，返回showcart.jsp页面，选择“电脑”加入购物车
3，servlet通过jdbc链接数据库
package ch06servletJDBC;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Properties;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
public class ProductList extends HttpServlet {
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
}
private boolean query(String driverName, String connectionURL, Properties pro,
String sql, PrintWriter out) {
boolean rc = true;
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
long startMS = System.currentTimeMillis();
int rowCount = 0;
try {
System.out.println("begin to load class");
Class.forName(driverName).newInstance();
conn = DriverManager.getConnection(connectionURL, pro);
System.out.println(conn==null);
stmt = conn.createStatement();
System.out.println(stmt==null);
rs = stmt.executeQuery(sql);
rowCount = formatTable(rs, out);
} catch (Exception e) {
e.printStackTrace();
rc = false;
return false;
} finally {
try {
if (rs != null) {
rs.close();
}
if (stmt != null) {
stmt.close();
}
if (conn != null) {
conn.close();
}
} catch (Exception e) {
}
}
if (rc) {
long elapsed = System.currentTimeMillis() - startMS;
out.println("<br>共" + rowCount + "记录，耗时" + elapsed + "毫秒！");
}
return true;
}
private int formatTable(ResultSet rs, PrintWriter out) throws SQLException {
int rowCount = 0;
out.println("<center><table border=2>");
ResultSetMetaData rsmd = rs.getMetaData();
int columnCount = rsmd.getColumnCount();
out.println("<tr>");
for (int i = 0; i < columnCount; i++) {
out.println("<th>" + rsmd.getColumnLabel(i + 1) + "</th>");// 字段名作为表头
}
out.println("</tr>");
while(rs.next()){
rowCount++;
out.println("<tr>");
for (int i = 0; i < columnCount; i++) {
out.println("<td>" + rs.getString(i+1) + "</td>");// 字段名作为表头
}
out.println("</tr>");
}
out.println("</table></center>");
return rowCount;
}
public void init(ServletConfig cfg) throws ServletException{
super.init(cfg);
}
public void destroy(){
super.destroy();
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException{
response.setContentType("text/html;charset=gb2312");
// PrintWriter out = response.getWriter();
PrintWriter out = new PrintWriter(response.getOutputStream());
Properties pro = new Properties(); // 用属性的数据结构存储用户名和密码
pro.put("user", "sa");
pro.put("password", "sa");
String sql;
sql = "select * from productlist"; //数据库中的productlist表格
String connectionURL = "jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=login";
out.println("<HTML>");
out.println(" <HEAD><TITLE>产品列表</TITLE></HEAD>");
out.println("<h1>产品信息列表</h1>");
out.println(" <BODY>");
// 需要有mssql的三个数据库驱动jar包
boolean r = query("com.microsoft.jdbc.sqlserver.SQLServerDriver", connectionURL,
pro, sql, out);
out.println("查询结果："+r);
out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
}
结果：
4，把链接数据库的参数配置在web.xml中的servlet初始参数中，见web.xml
package servletAPI;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class InitServlet extends HttpServlet {
private String driver = "";
private String URL = "";
private String username = "";
private String password = "";
// 获取web.xml中的init-param参数
public void init() throws ServletException { //自动执行
driver = getInitParameter("driver"); //参数"driver" 为param-name，返回的是param-value
URL = getInitParameter("URL");
username = getInitParameter("username");
password = getInitParameter("password");
}
//获得数据库连接的方法
public Connection getConnection() {
Connection con = null;
try {
Class.forName(driver);
con = DriverManager.getConnection(URL, username, password);
return con;
} catch (Exception e) {
}
return con;
}
//通过doGet()方法实现数据查询功能
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=gb2312");
PrintWriter out = response.getWriter();
Connection con = this.getConnection();
try {
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery("select * from Loginuser");
while (rs.next()) {
out.print(rs.getString("username"));
out.print(" ");
out.print(rs.getString("password"));
out.print(" ");
out.print(rs.getString("gender"));
out.print(" ");
out.print(rs.getInt("age"));
out.print(" ");
out.print(rs.getDate("logintime"));
out.print("<br>");
}
} catch (SQLException e) {
e.printStackTrace();
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
结果就是显示数据库中Loginuser表格的内容
源码见附件