ServletConfig和ServletContext对象

1由于一个WEB应用程序中的所有Servlet都共享同一个对应的ServletContext对象，所以ServletContext对象被称为application对象。是当前web应用的大管家，可以获取到web应用的各个信息

package servlet;

import java.io.IOException;
import java.io.InputStream;
import java.util.Enumeration;

import javax.servlet.ServletConfig;
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 HelloServlet extends HttpServlet {

/**
* Constructor of the object.
*/
public HelloServlet() {
super();
System.out.println("constructor");
}

public void init(ServletConfig servletconfig) throws ServletException {
// ServletConfig常用方法
String v = servletconfig.getInitParameter("user:");
// String v = this.getInitParameter("user:");
// //也行，因为HttpServlet是ServletConfig的实现类，所以可以用this调用该方法
System.out.println("method1:" + v);
System.out.println("init");

// Enumeration<String> en = this.getInitParameterNames();
Enumeration<String> en = servletconfig.getInitParameterNames();
while (en.hasMoreElements()) {
String names = en.nextElement();
String values = servletconfig.getInitParameter(names);
System.out.println(names + "-->" + values);
}
System.out.println("");
// ServletContext常用方法
ServletContext sct = servletconfig.getServletContext();
String svalue = sct.getInitParameter("driver");
System.out.println(svalue);
// 获取当前文件在web服务器上的绝对路径
String str = sct.getRealPath("/file1.txt");
System.out.println(str);
// 获取当前web应用名称
String conp = sct.getContextPath();
System.out.println(conp);
try {
InputStream is = sct
.getResourceAsStream("/WEB-INF/classes/xml.properties"); // 路径是相对当前web应用的路径
System.out.println(is);
} catch (Exception ex) {
ex.printStackTrace();
}
}

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
System.out.println("doGet");
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
System.out.println("dopost");
}

public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
System.out.println("destroy");
}

}

<?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"> <context-param>
<param-name>driver</param-name>
<param-value>jdbc.odbc</param-value>
</context-param>
<servlet>
<servlet-name>HelloServlet</servlet-name>
<servlet-class>servlet.HelloServlet</servlet-class>
<!--设置局部初始化参数  -->
<init-param>
<param-name>user:</param-name>
<param-value>wuyj</param-value>
</init-param>
<init-param>
<param-name>password:</param-name>
<param-value>123</param-value>
</init-param>
<load-on-startup>3</load-on-startup>

</servlet>

<servlet-mapping>
<servlet-name>HelloServlet</servlet-name>
<url-pattern>/servlet/HelloServlet</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>

结果：

constructor

method1:wuyj

init

password:-->123

user:-->wuyj

jdbc.odbc

C:\Program Files\Apache Software Foundation\Tomcat 6.0\webapps\sdf\file1.txt

/sdf

java.io.FileInputStream@1a3551c