HttpServletResponse obj lost after using System.getProperty

[Ian Yang]

In "MyServlet.java" 's doGet method, I called another class's method which utilizes the following codes
FileInputStream file = new FileInputStream("inputFile"); Properties p = System.getProperties();
p.load(file);
System.setProperties(p);
String var = System.getProperty("VAR");
...
....
Notice the above codes are in ANOTHER class's method and "MyServlet.java" just called it, but I found immediately after it calls this method, the HttpServletResponse object is no longer functioning properly. For example,
response.sendRedirect("URL");
has not ANY effect at all.
By the way, i found the "var" does get the correct results. So the "System.getProperty()" does get right result.
Do you know what's the reason for the response object's lost ?
Thanks lot,
Ian

[Mike Curwen]

My first thought was this:

The API for setProperties suggests that whatever is inside the System properties 'bag' is replaced (overwritten) by the one you are setting.

public static void setProperties(Properties props)
... snip ...
The argument becomes the current set of system properties for use by the getProperty(String) method. 
If the argument is null, then the current set of system properties is forgotten.

However, this doesn't appear to be the case, in fact, sending null into the setProperties method doesn't appear to make the current set of properties be forgotten.

I can't duplicate your condition. My property file contains one mapping hello=world. Here is my code for the 'helper' class

package scratch;
 
import java.util.*;
import java.io.*;
 
public class propertyStuff {
 
  Properties p = new Properties();
 
  public propertyStuff() {
  }
 
 
  public static void main(String[] args) {
    propertyStuff app = new propertyStuff();
    try {
      app.load(args);
    } catch (Exception e) {
      System.err.println("exception: " + e);
    }
 
  } //end main
 
  public void load(String args[]) throws Exception {
    if (args.length > 0) {
 
      FileInputStream file = new FileInputStream(args[0]);
      Properties p = System.getProperties();
 
      // output what is in system properties
      System.out.println("*********** System Properties ****************");
      System.out.println("os.name="  + System.getProperty("os.name"));
      System.out.println("java.version=" + System.getProperty("java.version"));
      System.out.println("hello=" + System.getProperty("hello"));
 
      // load the file
      p.load(file);
      System.setProperties(p);
 
      // output what is in system properties
      System.out.println("\n\n*********** System Properties ****************");
      System.out.println("os.name="  + System.getProperty("os.name"));
      System.out.println("java.version=" + System.getProperty("java.version"));
      System.out.println("hello=" + System.getProperty("hello"));
 
 
    }
    else {
      System.out.println("Usage: include a properties File as the first parameter!");
    }
  } //end load()
 
} //end class

Here is the servlet:

package scratch;
 
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
 
 
public class PropertyTester extends HttpServlet {
  private static final String CONTENT_TYPE = "text/html";
  //Initialize global variables
  public void init() throws ServletException {
  }
  //Process the HTTP Get request
  public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String fileName = request.getParameter("Propfile");
    if (fileName == null) {
      fileName = "d:/props.txt";
    }
    propertyStuff helper = new propertyStuff();
    try {
      helper.load(new String[] {fileName});
    } catch (Exception e) {
      System.err.println("exception: " + e);
    }
 
    response.sendRedirect("done.jsp");
  }
}

The output is:

*********** System Properties ****************
os.name=Windows 2000
java.version=1.3.1
hello=null

*********** System Properties ****************
os.name=Windows 2000
java.version=1.3.1
hello=world

And I get to done.jsp to boot.
[ February 26, 2002: Message edited by: Mike Curwen ]