黑马程序员_javaweb(servletcontext)

----------------------------android培训、java培训、期待与您交流！----------------------------------






1.两种获取servletContext对象的方式

ServletContext context = this.getServletConfig().getServletContext();
		ServletContext context1 = this.getServletContext();

2.用context对象实现数据共享

context.setAttribute("data", "aaaaaaaaaa");

3.获取ServletContext的共享数据

context.getAttribute("data")

4.通过servletContext,获取为web应用配置的初始化参数

		String url = this.getServletContext().getInitParameter("url");
		String username = this.getServletContext().getInitParameter("username");
		String password = this.getServletContext().getInitParameter("password");

  <context-param>
  	<param-name>url</param-name>
  	<param-value>jdbc:mysql://localhost:3306/test</param-value>
  </context-param>
  
  <context-param>
  	<param-name>username</param-name>
  	<param-value>root</param-value>
  </context-param>
  
  <context-param>
  	<param-name>password</param-name>
  	<param-value>root</param-value>
  </context-param>

5.通过servletContext获取文件的mime类型

String filename = "1.jpg";
		
		ServletContext context = this.getServletContext();
		System.out.println(context.getMimeType(filename));

6.通过servletContext 实现请求转发

//servlet收到请求产生数据，然后转交给jsp显示
		String data = "aaaaaa";
		this.getServletContext().setAttribute("data", data);
		RequestDispatcher rd = this.getServletContext().getRequestDispatcher("/view.jsp");
		rd.forward(request, response);

读取配置文件的各种方法：
方法一：

		ServletContext context = this.getServletContext();
		InputStream in = context.getResourceAsStream("/db.properties");
		
		Properties prop = new Properties();  //map
		prop.load(in);
		
		
		String url = prop.getProperty("url");
		String username = prop.getProperty("username");
		String password = prop.getProperty("password");
		
		System.out.println(url);
		System.out.println(username);
		System.out.println(password);

方法二：

ServletContext context = this.getServletContext();
		String realpath = context.getRealPath("/db.properties");  //c:\\sdsfd\sdf\db.properties
		
		//获取到操作文件名   realpath=abc.properties
		String filename = realpath.substring(realpath.lastIndexOf("\\")+1);
		System.out.println("当前读到的文件是：" + filename);
		
		
		FileInputStream in = new FileInputStream(realpath);
		Properties prop = new Properties();
		prop.load(in);
		
		String url = prop.getProperty("url");
		String username = prop.getProperty("username");
		String password = prop.getProperty("password");
		
		System.out.println("文件中有如下数据：");
		System.out.println(url);
		System.out.println(username);
		System.out.println(password);

方法三：

ServletContext context = this.getServletContext();
		URL url = context.getResource("/resource/db.properties");
		InputStream in = url.openStream();

方法四：

InputStream in = this.getServletContext().getResourceAsStream("/WEB-INF/classes/db.properties");
		Properties prop = new Properties();  //map
		prop.load(in);
		
		
		String url = prop.getProperty("url");
		String username = prop.getProperty("username");
		String password = prop.getProperty("password");
		
		System.out.println(url);
		System.out.println(username);
		System.out.println(password);