Servlet入门第二个例子

ServletContext

package com.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class AServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
/*
* 1. 获取ServletContext对象
* 2. 调用其setAttribute()方法完成保存数据
*/

ServletContext application =this.getServletContext();
application.setAttribute("name", "张三");
}

}

package com.servlet;

import java.io.IOException;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class BServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

/*
* 1. 获取ServletContext对象
* 2. 调用其getAttribute()方法完成获取数据
*/
ServletContext application=this.getServletContext();
String name=(String) application.getAttribute("name");
System.out.println(name);
}

}

<?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>Servlet02</display-name>
<servlet>
<servlet-name>AServlet</servlet-name>
<servlet-class>com.servlet.AServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>BServlet</servlet-name>
<servlet-class>com.servlet.BServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>CServlet</servlet-name>
<servlet-class>com.servlet.CServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>DServlet</servlet-name>
<servlet-class>com.servlet.DServlet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>AServlet</servlet-name>
<url-pattern>/AServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>BServlet</servlet-name>
<url-pattern>/BServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>CServlet</servlet-name>
<url-pattern>/CServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>DServlet</servlet-name>
<url-pattern>/DServlet</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
<!-- 公共的参数 -->
<context-param>
<param-name>context-name</param-name>
<param-value>context-value</param-value>
</context-param>
</web-app>

servlet 获取初始化参数

package com.servlet;

import java.io.IOException;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class CServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
/*
* 1. 得到ServletContext
* 2. 调用它getInitParameter(String)得到初始化参数
*/
ServletContext application=this.getServletContext();
String value=application.getInitParameter("context-name");
System.out.println(value);
}

}

Servlet获取资源真实路径

package com.servlet;

import java.io.IOException;
import java.io.InputStream;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class DServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
/*
* 它得到的是有盘符的路径：
*D:\apache-tomcat\webapps\Servlet02\index.jsp
*/
String path=this.getServletContext().getRealPath("/index.jsp");
System.out.println(path);
/*
* 获取资源的路径后，再创建出输入流对象！
*/
InputStream input=this.getServletContext().getResourceAsStream("index.jsp");
/*
* 获取当前路径下所有资源的路径！
*  D:\apache-tomcat\webapps\Servlet02\WEB-INF
D:\apache-tomcat\webapps\Servlet02\index.jsp
D:\apache-tomcat\webapps\Servlet02\WEB-INF
*/
String paths=this.getServletContext().getRealPath("/WEB-INF");
System.out.println(paths);
}

}