标签：his config 存在 程序 generics display eal end except
ServletContext:
ServletContext表示Servlet应用程序。每个Web应用程序只有一个上下文。在将一个应用程序同时部署到多个容器的分布式环境中，每台Java虚拟机上的Web应用都会有一个ServletContext对象。
通过在ServletConfig中调用getServletContext方法，可以获得ServletContext。
有了ServletContext,就可以共享从应用程序中的所有资料处访问到的信息，并且可以动态注册Web对象。前者将对象保存到ServletContext中的一个内部的Map中。保存在ServletContext中的对象被称作属性。
1：实现数据共享 setAttribute(key,value) getAttribute(key) ，获取域对象
2：获取全局配置信息: getInitParameter()
3：获得应用下任何资源的路径
例一：通过调用GenericServlet的 getServletContext对象得到ServletContext对象，获取域对象
先运行myservlet1.java，在运行myservlet2.java
myservlet1.java
public class myservlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//通过调用GenericServlet的 getServletContext对象得到ServletContext对象
//先访问demo1,在访问demo2
ServletContext application=this.getServletContext();
application.setAttribute("name", "tom");
System.out.println(application.getClass().getName());
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request,response);
}
}
myservlet2.java
public class myservlet2 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String name=(String) this.getServletContext().getAttribute("name");
if(name==null){
System.out.println("你不能直接访问这个类");
}
System.out.println(name);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request,response);
}
}
运行效果图：
例二：获取全局配置信息
获取encoding的配置信息
myservlet3.java
public class myservlet3 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String encoding=this.getServletContext().getInitParameter("encoding");
System.out.println(encoding);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request,response);
}
}
web.xml
<?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">
<display-name></display-name>
<context-param>
<param-name>encoding</param-name>
<param-value>utf-8</param-value>
</context-param>
<servlet>
<servlet-name>myservlet</servlet-name>
<servlet-class>com.zk.myservlet.myservlet</servlet-class>
</servlet>
<servlet>
<servlet-name>myservlet2</servlet-name>
<servlet-class>com.zk.myservlet.myservlet2</servlet-class>
</servlet>
<servlet>
<servlet-name>myservlet3</servlet-name>
<servlet-class>com.zk.myservlet.myservlet3</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>myservlet</servlet-name>
<url-pattern>/demo1</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>myservlet2</servlet-name>
<url-pattern>/demo2</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>myservlet3</servlet-name>
<url-pattern>/demo3</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
例三：获取资源路径
使用this.getServletContext().getRealPath获取文件的资源路径
public class myservlet1 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String apath=this.getServletContext().getRealPath("/WEB-INF/a.properties");//参数一定要以斜杠开头
System.out.println(apath);
//创建一个properties
Properties pro=new Properties();
pro.load(new FileInputStream(apath));
System.out.println(pro.getProperty("akey"));
String bpath=this.getServletContext().getRealPath("/WEB-INF/classes/b.properties");
System.out.println(bpath);
Properties pro2=new Properties();
pro2.load(new FileInputStream(bpath));
System.out.println(pro2.getProperty("key"));
String cpath=this.getServletContext().getRealPath("/WEB-INF/classes/com/zk/myservlet/c.properties");
System.out.println(cpath);
Properties pro3=new Properties();
pro3.load(new FileInputStream(cpath));
System.out.println(pro3.get("ckey"));
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request,response);
}
}
运行结果图:
标签：his config 存在 程序 generics display eal end except
原文地址：https://www.cnblogs.com/longlyseul/p/9943030.html
