What is the equivalent of PHP's $_SERVER['DOCUMENT_ROOT'] in Java

I need to know the Java equivalent of PHP's $_SERVER['DOCUMENT_ROOT'].

I am writing a Java backend program that will take an uploaded image as a byte[] and save the image to the server where my Java program is running. Then I want to send the image url to the user (front-end) or as email; so that the user can click on the url I send to view the image.

In PHP, I use $_SERVER['DOCUMENT_ROOT'] plus the relative path of the file. How do I do that in Java?

I am not using servet. I am using Jersey to return the url. (If that's impo开发者_运维百科rtant)

I need the returned path to be "http://localhost:8080/mypics/pic1.jpg" when the server is localhost and "http://www.mysite.com/mypics/pic1.jpg" when running on a live server. The new File("./") code is not returning "http..."; netbeans cannot find the method ServletContext.getContextPath(), after importing

import javax.servlet.ServletContext;

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You can use ServletContext.getContextPath() to get context path or use ServletContext.getRealPath(String path) to get real path for a given virtual path.

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The simplest way if you not use servlet API is to create File object point to the ./:

System.out.println(new File("./").getAbsolutePath());

In this case you should see in console path to your application directory. This could be your $_SERVER['DOCUMENT_ROOT'] for this application.