三、通过ServletContext对象来获取web.xml文件中内容

1、该程序的作用：

1) 通过ServletContext对象来获取web.xml文件中内容
2) 在一个AServlet进行ServletContext属性的配置，在另外一个BServlet中进行读取
3) 修改欢迎页面的默认配置(默认配置在WEB-INF的跟目录下面)
4) 发生错误时如何进行统一的处理

AServlet类：

package com.bjpownernode.javaweb.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Date;
import java.util.Enumeration;

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

import entity.User;

public class AServlet implements Servlet {
private ServletConfig config;
@Override
public void init(ServletConfig config) throws ServletException {
this.config=config;

}

@Override
public ServletConfig getServletConfig() {
return config;
}

@Override
public void service(ServletRequest req, ServletResponse res)
   throws ServletException, IOException {
  ServletContext application=config.getServletContext();
  PrintWriter out=res.getWriter();
  out.print(application);
  out.print("<br>");
  Enumeration<String> names=application.getInitParameterNames();
  while(names.hasMoreElements()){
   String name=names.nextElement();
   String value=application.getInitParameter(name);
   out.print(name+":"+value);
   out.print("<br>");
  }
  String path=application.getRealPath("/index.html");
  out.println(path);
  User user=new User();
  user.setUserCode("12");
  user.setUserName("jason");
  //向ServletContext范围中存储User数据
  application.setAttribute("userObject", user);
  application.setAttribute("time",new Date());
}

@Override
public String getServletInfo() {
return null;
}

@Override
public void destroy() {

}

BServlet类

package com.bjpownernode.javaweb.servlet;

import java.io.IOException;

public class BServlet implements Servlet {

private ServletConfig config;
@Override
public void init(ServletConfig config) throws ServletException {
  this.config=config;
}
@Override
public void service(ServletRequest req, ServletResponse res)
   throws ServletException, IOException {
  ServletContext application= config.getServletContext();
  //从ServletContext范围中读取数据
  Object obj1=application.getAttribute("userObject");
  Object obj2=application.getAttribute("time");
  res.setContentType("text/html");
  res.getWriter().print("--->"+obj1);
  res.getWriter().print("--->"+obj2);
}
@Override
public ServletConfig getServletConfig() {
  // TODO Auto-generated method stub
  return config;
}

@Override
public String getServletInfo() {
// TODO Auto-generated method stub
return null;
}

@Override
public void destroy() {
// TODO Auto-generated method stub

}

User类

package entity;

public class User {
private String userName;
private String userCode;

public String getUserName() {
return userName;
}

public void setUserName(String userName) {
this.userName = userName;
}

public String getUserCode() {
return userCode;
}

public void setUserCode(String userCode) {
this.userCode = userCode;
}

@Override
public String toString() {
return "User [userName=" + userName + ", userCode=" + userCode + "]";
}

}

index.html

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>测试ServletContext接口</title>
</head>
<body>
<a href="/prj-servlet05/a">AServlet</a>
<a href="/prj-servlet05/b">BServlet</a>
</body>
</html>

web.xml

<?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"
xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
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>prj-servlet05</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>

<context-param>
<param-name>username</param-name>
<param-value>admin</param-value>
</context-param>
<context-param>
<param-name>password</param-name>
<param-value>123</param-value>
</context-param>
<servlet>
<servlet-name>a</servlet-name>
<servlet-class>com.bjpownernode.javaweb.servlet.AServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>a</servlet-name>
<url-pattern>/a</url-pattern>
</servlet-mapping>
    <servlet>
<servlet-name>b</servlet-name>
<servlet-class>com.bjpownernode.javaweb.servlet.BServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>b</servlet-name>
<url-pattern>/b</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>test</servlet-name>
<servlet-class>com.bjpownernode.javaweb.servlet.TestServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>test</servlet-name>
<url-pattern>/test01</url-pattern>
</servlet-mapping>
<error-page>
<error-code>404</error-code>
<location>/error/error.html</location>
</error-page>
</web-app>

error.html

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>错误提示</title>
</head>
<body>
亲出错了哦，联系管理员吧！
</body>
</html>

posted @ 2017-01-15 14:19 爱笑的berg 阅读(292) 评论(0) 收藏举报

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爱笑的berg

三、通过ServletContext对象来获取web.xml文件中内容

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