详细讲解各版本Java Servlet的使用,这次哥哥讲细节 (✪ω✪) !
Servlet 2.5 : 通过配置web.xml文件来映射Servlet ( 示例代码如下 )
Servlet program
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42public class FirstServlet extends HttpServlet {
private static final long serialVersionUID = -7228095681625205247L;
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("This is doGet ..");
}
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doGet(req, resp);
System.out.println("This is doPost ..");
}
}
/*
* #(doGet)The result be shown as followed :
*
* Apr 05, 2019 10:15:33 AM org.apache.catalina.core.StandardContext reload INFO: Reloading Context with
* name [/Servlet_basic] is completed
* This is doGet ..
*/
/*
* #(doPost)The result be shown as followed :
*
* Apr 05, 2019 10:57:08 AM org.apache.catalina.core.StandardContext reload INFO: Reloading Context with
* name [/Servlet_basic] is completed
* This is doPost ..
*
*/
/*
* #(doPost —> doGet)The result be shown as followed :
*
* Apr 05, 2019 11:22:21 AM org.apache.catalina.core.StandardContext reload NFO: Reloading Context with
* name [/Servlet_basic] is completed
* This is doGet ..
* This is doPost ..
*
*/JSP Progarm
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27<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Servlet 2.5</title>
</head>
<body>
<!--
href same as : http://localhost:8080/Servlet_basic_version_2.5/FirstServlet
注意: 构建路径及`WebContent`都属于 : 根目录.
JSP中的'/'表示服务器的跟路径.如 : http://localhost:8080/
web.xml中的'/'表示项目的根路径.如 : http://localhost:8080/Servlet_basic_version_2.5/
-->
<a href="/Servlet_basic_version_2.5/FirstServlet">doGet : FirstServlet</a>
<!-- 注意 : `form`的默认提交方式为`get`,所以修改为: method="post" -->
<div>
<form action="FirstServlet" method="get"><hr>
<input type="submit" value="doGet " />
</form>
<form action="FirstServlet" method="post"><br>
<input type="submit" value="doPost" />
</form>
</div>
</body>
</html>web.xml
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<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
id="WebApp_ID" version="4.0">
<display-name>Servlet_basic</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>
<!--
当程序运行后,点击`HiServlet.jsp`页面中的`url`请求时`web.xml`配置文件中的映射关系如下:
1.<servlet-mapping>
↓
↓
2.请求被根目录(src/WebContent是根目录)下<url-pattern>标签中的Servlet程序拦截.
↓
↓
3.(寻找Servlet.class的桥梁) 匹配与其<servlet-name>名称相同的<servlet>.
↓
↓
4.通过<servlet-class>标签中的`Servlet.class`响应用户的请求.
可此得知标签<servlet-name>是<servlet>和<servlet-mapping>之间沟通的桥梁( 其名称任意,但其两者间的名称必须相同 ! )
如不同`Tomcat`则会抛出如下异常信息:
error..Caused by: java.lang.IllegalArgumentException: Servlet mapping specifies an unknown servlet name [sameName]..
-->
<servlet>
<servlet-name>sameName</servlet-name>
<servlet-class>pers.huangyuhui.servlet.test.FirstServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>sameName</servlet-name>
<url-pattern>/FirstServlet</url-pattern>
</servlet-mapping>
</web-app>
Servlet 3.0 : 通过注解来映射相应的Servlet.
Servlet program
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47/*
1.Servlet 3.0 与 Servlet 2.5 的区分 :
Servlet 3.0 : 较`Servlet 2.0`不需要在web.xml中配置Servlet映射,但需在Servlet类的定义处上编写注解: @WenServlet("/Servlet url..")其中"/Servlet url.."与Servlet 2.0在web.xml配置文件中<url-pattern>标签中的内容原理是相同的.
2.Servlet3.0 响应请求的路线 :
如: 当点击`HiServlet.jsp`中的url链接时其先与@WebServlet中的值进行匹配,如果匹配成功,则说明请求的就是该注解所对应的类.
*/
public class ServletTest extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public ServletTest() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
//response.getWriter().append("Served at: ").append(request.getContextPath());
System.out.println("This is doGet ..");
}
/**
* @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);
System.out.println("This is doPost ..");
}
}
/*#The result be shown as followed :
*
* Apr 05, 2019 12:06:08 PM org.apache.catalina.startup.Catalina start
* INFO: Server startup in [3,425] milliseconds
* This is doGet .. <— 点击`url`链接时`Servlet`触发的响应.
* This is doPost .. <— 点击`doPost`按钮时`Servlet`触发的响应.
* This is doGet .. <— 点击`doGet`按钮时`Servlet`触发的响应.
*
*/JSP Program
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19<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Servlet 3.0</title>
</head>
<body>
<a href="ServletTest">doGet : Servlet 3.0</a>
<div>
<form action="ServletTest" method="get"><hr>
<input type="submit" value="doGet " />
</form>
<form action="ServletTest" method="post"><br>
<input type="submit" value="doPost" />
</form>
</div>
</body>
</html>web.xml
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13<!-- 无需任何修改 -->
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd" id="WebApp_ID" version="4.0">
<display-name>Servlet_basic_version_3.0</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>
</web-app>JSP运行效果示例图
- 常被问到 : 辉仔啊,都
大二下学期了呀,怎还是没有女朋友哟 ! 心想 : 是不是太爱Coding了呢 (灬°ω°灬) ~
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