一、servlet相關的包
tomcat8.0裏面的servlet-api.jar在tomcat安裝目錄下的lib目錄下;在寫部署在tomcat8.0下的servlet時,要引入該jar包。二、servlet包介紹
1.所有的servlet必須實現Servlet接口。2.servlet是可以在任何服務器端運行的小程序,且主要用servlet的service函數。所以寫web端的servlet時,不直接實現servlet接口,而是從它的實現類HTTPservlet繼承並重寫相應的方法。
3.一個servlet被調用時,實際上是調用它的service方法,我們不重寫service方法,因爲它會自己去調用其他的方法。
4.HttpServlet()是當客戶端去請求url地址時被容器調用;針對不同的請求調用不同的方法。
5.Httpservlet最重要的是doGet和doPost方法;在地址欄直接敲地址時,是get方式;只有在form裏點提交時,form的method是post時,爲post方式。
//get方式,參數列表跟在url地址後面;post方式,參數列表不跟在url地址後面。
6.HttpServletRequest對象:封裝了客戶端到服務端的請求;HttpServletResponse對象:從服務器端返回給客戶端的對象(只要給這個對象裏寫東西,就會發送給客戶端)。
7.本節總結:理解servlet,Genericservlet,HttpServlet之間的關係;理解爲什麼要從HttpServlet繼承;爲什麼要寫doGet方法;這個方法的兩個參數的意思。
三、servlet開發和部署:
servlet要正常運行1.首先要copy它的class文件到WEB-INF下的classes文件夾下;
2.必須把servlet部署到容器裏面(在web.xml中用xml標籤部署);
<servlet>
<servlet-name>HW</servlet-name> //servlet名,可任意取
<servlet-class>HelloWorldServlet</servlet-class> //對應的class名
</servlet>
<servlet-mapping> //servlet映射
<servlet-name>HW</servlet-name> //找該文件中有沒有定義名爲HW的servlet;
<url-pattern>/abc</url-pattern> //訪問這個地址時,調用HW;
</servlet-mapping>
Tomcat 查找web.xml的過程 -->找其中的與輸入的相對應的urlpattern-->servlet的名字-->對應的class-->new一對象-->調用Doget/Post
(放在包裏面的servlet的配置:連文件夾一起copy到classes文件夾下;servlet-class標籤裏寫class全名。)
四、servlet的生命週期
1.加載 ClassLoader2.實例化 new
3.初始化 init(ServletConfig) //servlet的配置信息,在講給servlet傳參數的時候會再講。
4.處理請求 service doGet doPost
5.退出服務 destroy() //在整個webapp退出的時候
只有一個對象
init()只執行一次,在第一次被訪問時。
測試代碼:
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Date;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class TestLifeCycle extends HttpServlet {
public TestLifeCycle() {
System.out.println("constructor");
}
@Override
public void destroy() {
PrintWriter pw = null;
try {
pw = new PrintWriter(new BufferedWriter(new FileWriter("d:\\destroy.txt",true)));
pw.println("destroy at");
pw.println(new Date().toString());
pw.println("___________________");
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
if (pw != null) {
pw.close();
}
}
}
@Override
public void init(ServletConfig config) throws ServletException {
System.out.println("init");
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
System.out.println("doGet!");
}
}
五、servlet編程接口和例子程序
GenericServlet是所有Servlet的鼻祖用於HTTP的Servlet編程都通過繼承 javax.servlet.http.HttpServlet 實現
請求處理方法:(分別對應http協議的7種請求)
1、doGet 響應Get請求,常用
2、doPost 響應Post請求,常用
3、doPut 用於http1.1協議
4、doDelete 用於http1.1協議
5、doHead 僅響應Get請求的頭部。
6、doOptions 對webserver進行配置
7、doTrace 用於http1.1協議進行跟蹤(調試用)
實例的個數: 在非分佈式的情況下,通常一個Servlet在服務器中有一個實例
html頁面:
<form id="form1" name="form1" method="post" action="servlet/ThreePrams">
<table width="400" cellpadding="6" cellspacing="1" bgcolor="#999999">
<tr>
<td bgcolor="#FFFFFF">參數一</td>
<td bgcolor="#FFFFFF"><input type="text" name="pram1" id="pram1" />
</td>
</tr>
<tr>
<td bgcolor="#FFFFFF">參數二</td>
<td bgcolor="#FFFFFF"><input type="text" name="pram2" id="pram2" />
</td>
</tr>
<tr>
<td bgcolor="#FFFFFF">參數三</td>
<td bgcolor="#FFFFFF"><input type="text" name="pram3" id="pram3" />
</td>
</tr>
<tr>
<td bgcolor="#FFFFFF"> </td>
<td bgcolor="#FFFFFF"><label>
<input type="submit" name="bt1" id="bt1" value="提交" />
</label></td>
</tr>
</table>
</form>
ThreePrams.java:
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;
public class ThreePrams extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
resp.setContentType("text/html");
PrintWriter pr = resp.getWriter();
pr.println(req.getParameter("pram1"));
pr.println("<br />");
pr.println(req.getParameter("pram2"));
pr.println("<br />");
pr.println(req.getParameter("pram3"));
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
this.doGet(req,resp);
}
}
web.xml配置: <servlet>
<servlet-name>ThreePrams</servlet-name>
<servlet-class>ThreePrams</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ThreePrams</servlet-name>
<url-pattern>/servlet/ThreePrams</url-pattern>
</servlet-mapping>
總結:1)熟悉所有HttpServletRequest和HttpServletResponse的方法。
2)如果method=“get”,提交後的鏈接地址後面會跟參數列表;而method=“post”,提交後的鏈接地址後面不會跟參數。
六、servlet通過request讀取所有參數
效果:
提交之後顯示:
HTML代碼:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>無標題文檔</title>
</head>
<body>
<h1>A Sample FORM using POST
</h1>
<form id="form1" name="form1" method="post" action="servlet/ShowPrams">
<table width="600" border="1" cellpadding="3" cellspacing="1" bordercolor="#999999">
<tr>
<td width="200">Item Number:</td>
<td width="400">
<input type="text" name="itemnum" id="itemnum" /> </td>
</tr>
<tr>
<td>Quantity:</td>
<td><input type="text" name="quan" /></td>
</tr>
<tr>
<td>Price Each:</td>
<td><input type="text" name="price" /></td>
</tr>
<tr>
<td>Frist Name:</td>
<td><input type="text" name="fn" /></td>
</tr>
<tr>
<td>Last Name:</td>
<td><input type="text" name="ln" /></td>
</tr>
<tr>
<td>Middle Initial:</td>
<td><input type="text" name="mn" /></td>
</tr>
<tr>
<td>Shipping Address:</td>
<td><textarea name="address" id="address" cols="45" rows="4"></textarea></td>
</tr>
<tr>
<td>Credit Card:</td>
<td><p>
<label>
<input type="radio" name="RadioGroup1" value="visa" id="RadioGroup1_0" />
Visa</label>
<br />
<label>
<input type="radio" name="RadioGroup1" value="master" id="RadioGroup1_1" />
Master Card</label>
<br />
<label>
<input type="radio" name="RadioGroup1" value="express" id="RadioGroup1_2" />
American Express</label>
<br />
<label>
<input type="radio" name="RadioGroup1" value="discover" id="RadioGroup1_3" />
Discover</label>
<br />
<label>
<input type="radio" name="RadioGroup1" value="java" id="RadioGroup1_4" />
Java SmartCard</label>
<br />
</p></td>
</tr>
<tr>
<td>Credit Card Number:</td>
<td><input type="password" name="cardnum" /></td>
</tr>
<tr>
<td>Repeat Credit Card Number:</td>
<td><input type="password" name="cardnum" /></td>
</tr>
<tr>
<td> </td>
<td><input type="submit" name="submit" id="submit" value="Submit Order!" /></td>
</tr>
</table>
</form>
</body>
</html>
ShowPrams.java代碼:
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 ShowPrams extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
resp.setContentType("text/html");
PrintWriter pr = resp.getWriter();
pr.println("<html><head><title>無標題文檔</title></head>"+
"<body><h1>Reading All Request Parameters</h1><table width='500' border='1' cellspacing='1' cellpadding='6'>"+
"<tr><td>Paramaters Name</td><td>Paramaters Value(s)</td></tr>");
Enumeration<String> paramName = req.getParameterNames();
while(paramName.hasMoreElements()) {
String name = paramName.nextElement();
pr.print("<tr><td>" + name + "</td><td>");
String[] paramValues = req.getParameterValues(name);
if(paramValues.length == 1) {
if(paramValues[0].length() == 0) {
pr.print("no value");
}else {
pr.print(paramValues[0]);
}
} else {
for(int i=0;i<paramValues.length;i++){
pr.print("<li>" + paramValues[i] + "</li>");
}
}
pr.print("</td></tr>");
}
pr.print("</table></body></html>");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
doGet(req,resp);
}
}