星期四, 十二月 17, 2015 ?20:53:26
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一、servlet生命周期
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? ? 1.生命全过程
? ? ? ? ?加载 ClassLoader
? ? ? ? ?实例化 new
? ? ? ? ?初始化 init(ServletConfig)
? ? ? ? ?处理请求 service doGet doPost
? ? ? ? ?退出服务 destroy()
? 2.只有一个对象
? ?3.API中的过程
? ? ? init()//只执行一次，第一次初始化的时候
? ? ?service()
? ? ?destroy()//webapp退出的时候
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二、代码案例
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servlet类
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 ServletLifeCycle extends HttpServlet {
/**
* Constructor of the object.
*/
public ServletLifeCycle() {
System.out.println("construct");
}
/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
System.out.println("init");
}
/**
* Destruction of the servlet. <br>
*/
public void destroy() {
System.out.print("destroy");
}
/**
* 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("doGet");
}
}
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?
web.xml
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<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<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>HelloServlet</servlet-name>
<servlet-class>HelloServlet</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>ServletLifeCycle</servlet-name>
<servlet-class>ServletLifeCycle</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>HelloServlet</servlet-name>
<url-pattern>/httpServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>ServletLifeCycle</servlet-name>
<url-pattern>/ServletLifeCycle</url-pattern>
</servlet-mapping>
</web-app>
?访问url
? ?http://localhost:8080/TestServlet01/ServletLifeCycle
?
运行结果:
信息: Server startup in 866 ms
construct
init
doGet
doGet
2015-12-17 21:26:10 org.apache.coyote.http11.Http11Protocol pause
信息: Pausing Coyote HTTP/1.1 on http-8080
2015-12-17 21:26:11 org.apache.catalina.core.StandardService stop
信息: Stopping service Catalina
destroy2015-12-17 21:26:11 org.apache.catalina.core.ApplicationContext log
信息: SessionListener: contextDestroyed()
2015-12-17 21:26:11 org.apache.catalina.core.ApplicationContext log
信息: ContextListener: contextDestroyed()
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从结果可以看出，先调用construct，然后init且只初始化一次
doGet..doGet可多次调用，最后在tomcat退出的时候，才执行destroy
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二_servlet编程接口
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1.GenericServlet是所有Servlet的鼻祖
2.用户HTTP的Servlet编程都通过继承。
? ?javax.servlet.http.HttpServlet 实现
3.请求处理方法:
? ?分别对应http协议的7种请求
? ? 3.1 doGet 响应Get请求，常用
? ? 3.2 doPost 响应Post请求，常用
? ? 3.3 doPut 用户http1.1协议
? ? 3.4 doDelete 用户http1.1协议
? ? 3.5 doHead 仅响应Get请求头部
? ? 3.6 doOptions 用户http1.1协议
? ? 3.7 doTrace 用于http1.1协议
4.实例个数
? ?在非分布式的情况下，通常一个Servlet在服务器中一个实例
?
?
?
实现3个参数通过doGet()和doPost()传递
代码案例:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>MyHtml.html</title>
</head>
<body>
<form method="post" action = "servlet/ThreeParams">
<table>
<tr>
<tb width="93">param1</tb>
<tb width="94">
<input name="param1" type="text" id="param1"/>
</tb>
</tr>
<tr>
<tb width="93">param2</tb>
<tb width="94">
<input name="param2" type="text" id="param2"/>
</tb>
</tr>
<tr>
<tb width="93">param3</tb>
<tb width="94">
<input name="param3" type="text" id="param3"/>
</tb>
</tr>
<br/>
<tr>
<tb width="94">
<input type="submit"/>
</tb>
</tr>
</table>
</form>
</body>
</html>
/TestServlet01/src/ThreeParams.java
servlet类
ThreeParams.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 ThreeParams extends HttpServlet {
/**
* 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 {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println(request.getParameter("param1"));
out.println("<br/>");
out.println(request.getParameter("param2"));
out.println("<br/>");
out.println(request.getParameter("param3"));
}
/**
* 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 {
System.out.print("doPost");
doGet(request,response);
}
}
?运行结果:
http://localhost:8080/TestServlet01/MyHtml.html
提交后post
http://localhost:8080/TestServlet01/servlet/ThreeParams
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console展示
doPost
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星期四, 十二月 17, 2015 ?22:36:55
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今天了解了servlet的生命周期
和 使用页面进行传参给servlet
day_03 servlet生命周期+servlet编程接口
原文：http://yuzhouxiner.iteye.com/blog/2264902