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'Snoop' Sample Code

This page contains the venerable snoop servlet code (provided with most servlet containers as an example), broken into fragments.

Servlet init parameters

out.println("<h3>Servlet init parameters</h3>");
java.util.Enumeration e = getInitParameterNames();
while (e.hasMoreElements()) {
    String key = (String)e.nextElement();
    String value = getInitParameter(key);
    out.println("   " + key + " = " + value); 
}

Sample output:
No output by default.

Servlet Context Initialization Parameters

out.println("<h3>Context init parameters</h3>");
ServletContext context = getServletContext();
java.util.Enumeration enum = context.getInitParameterNames();
while (enum.hasMoreElements()) {
    String key = (String)enum.nextElement();
    Object value = context.getInitParameter(key);
    out.println("   " + key + " = " + value);
}

Sample output:
No output by default.

Servlet Context Attributes (Application Scope Variables)

out.println("<h3>Context attributes</h3>");
ServletContext context = getServletContext();
java.util.Enumeration enum = context.getAttributeNames();
while (enum.hasMoreElements()) {
    String key = (String)enum.nextElement();
    Object value = context.getAttribute(key);
    out.println("   " + key + " = " + value);
}

Sample output:

   javax.servlet.context.tempdir = D:\Java\jakarta-tomcat-3.2.1\work\127.0.0.2_8080
   sun.servlet.workdir = D:\Java\jakarta-tomcat-3.2.1\work\127.0.0.2_8080

Request Attributes (Page Scope Variables)

out.println("Request attributes:");
java.util.Enumeration e = request.getAttributeNames();
while (e.hasMoreElements()) {
    String key = (String)e.nextElement();
    Object value = request.getAttribute(key);
    out.println("   " + key + " = " + value);
}

Sample output:

Request attributes:
   javax.servlet.include.servlet_path = /sessions/9597eukak1.jsp
   javax.servlet.include.context_path =
   javax.servlet.include.request_uri = /sessions/9597eukak1.jsp

Request Headers

Enumeration e = request.getHeaderNames();
while (e.hasMoreElements()) {
    String key = (String)e.nextElement();
    String value = request.getHeader(key);
    out.println("   <b>" + key + "</b>: " + value);
}

Sample output (long lines are folded for clarity):

   Cookie: JSESSIONID=9597eukak1
   Cache-Control: no-cache
   Host: 127.0.0.2:8080
   Accept: application/vnd.ms-powerpoint, application/vnd.ms-excel, 
   application/msword, application/pdf, image/gif, image/x-xbitmap, 
   image/jpeg, image/pjpeg, */*
   User-Agent: Mozilla/4.0 (compatible; MSIE 5.5; Windows NT 4.0)
   Content-Length: 363
   Accept-Language: en-us
   Accept-Encoding: gzip, deflate
   Content-Type: application/x-www-form-urlencoded
   Connection: Keep-Alive
   Referer: http://127.0.0.2:8080/JspIn.jsp

Mostly Request Information

out.println("Servlet Name: " + getServletName());
out.println("Protocol: " + request.getProtocol().trim());
out.println("Scheme: " + request.getScheme());
out.println("Server Name: " + request.getServerName());
out.println("Server Port: " + request.getServerPort());
out.println("Server Info: " + getServletContext().getServerInfo());
out.println("Remote Addr: " + request.getRemoteAddr());
out.println("Remote Host: " + request.getRemoteHost());
out.println("Character Encoding: " + request.getCharacterEncoding());
out.println("Content Length: " + request.getContentLength());
out.println("Content Type: "+ request.getContentType());
out.println("Locale: "+ request.getLocale());
out.println("Default Response Buffer: "+ response.getBufferSize());
out.println("Request Is Secure: " + request.isSecure());
out.println("Auth Type: " + request.getAuthType());
out.println("HTTP Method: " + request.getMethod());
out.println("Remote User: " + request.getRemoteUser());
out.println("Request URI: " + request.getRequestURI());
out.println("Context Path: " + request.getContextPath());
out.println("Servlet Path: " + request.getServletPath());
out.println("Path Info: " + request.getPathInfo());
out.println("Path Trans: " + request.getPathTranslated());
out.println("Query String: " + request.getQueryString());

Sample Output (long lines are folded for clarity):

Servlet Name: jsp
Protocol: HTTP/1.1
Scheme: http
Server Name: 127.0.0.2
Server Port: 8080
Server Info: Tomcat Web Server/3.2.1 (JSP 1.1; Servlet 2.2; Java 1.3.0; 
Windows NT 4.0 x86; java.vendor=Sun Microsystems Inc.)
Remote Addr: 127.0.0.2
Remote Host: 127.0.0.2
Character Encoding: null
Content Length: 1968
Content Type: application/x-www-form-urlencoded
Locale: en_US
Default Response Buffer: 8192
Request Is Secure: false
Auth Type: null
HTTP Method: POST
Remote User: null
Request URI: /servlet/com.mslinn.JspExplorer
Context Path:
Servlet Path: /servlet/com.mslinn.JspExplorer
Path Info: null
Path Trans: null
Query String: null

Request Parameters

out.println("Parameter names in this request:");
java.util.Enumeration e = request.getParameterNames();
while (e.hasMoreElements()) {
    String key = (String)e.nextElement();
    String[] values = request.getParameterValues(key);
    out.print("   " + key + " = ");
    for(int i = 0; i < values.length; i++) {
        out.print(values[i] + " ");
    }
    out.println();
}

Sample Output

This output can be a bit confusing until you realize that Zamples uses request parameters to perform its magic.

Parameter names in this request:
   imports =
   stylesheet = on
   cmd = out.println("Parameter names in this request:");
java.util.Enumeration e = request.getParameterNames();
while (e.hasMoreElements()) {
    String key = (String)e.nextElement();
    String[] values = request.getParameterValues(key);
    out.print("   " + key + " = ");
    for(int i = 0; i < values.length; i++) {
        out.print(values[i] + " ");
    }
    out.println();
}
   applet =
   format = Java
   pre = on

Request Headers

out.println("<h3>Request Headers</h3>");
java.util.Enumeration e = request.getHeaderNames();
while (e.hasMoreElements()) {
    String key = (String)e.nextElement();
    String value = request.getHeader(key);
    out.println("   " + key + ": " + value);
}

Sample Output (long lines are folded for clarity):

   Cookie: JSESSIONID=9597eukak1
   Cache-Control: no-cache
   Host: 127.0.0.2:8080
   Accept: application/vnd.ms-powerpoint, application/vnd.ms-excel, 
   application/msword, application/pdf, image/gif, image/x-xbitmap, 
   image/jpeg, image/pjpeg, */*
   User-Agent: Mozilla/4.0 (compatible; MSIE 5.5; Windows NT 4.0)
   Content-Length: 418
   Accept-Language: en-us
   Accept-Encoding: gzip, deflate
   Content-Type: application/x-www-form-urlencoded
   Connection: Keep-Alive
   Referer: http://127.0.0.2:8080/JspIn.jsp

Request Cookies

Cookie[] cookies = request.getCookies();
for (int i = 0; i < cookies.length; i++) {
    Cookie cookie = cookies[i];
    out.println("   " + cookie.getName() + " = " + cookie.getValue());
}

Sample Output

JSESSIONID = 9597eukak1

Session Information

out.println("Requested Session Id: " + request.getRequestedSessionId());
HttpSession session = request.getSession();
out.println("Current Session Id: " + session.getId());
out.println("Session Created Time: " + session.getCreationTime());
out.println("Session Last Accessed Time: " + session.getLastAccessedTime());
out.println("Session Max Inactive Interval Seconds: " + session.getMaxInactiveInterval());
out.println("Session scoped attributes:");
java.util.Enumeration names = session.getAttributeNames();
while (names.hasMoreElements()) {
    String name = (String) names.nextElement();
    out.println("   " + name + " = " + session.getAttribute(name));
}

Sample Output

Requested Session Id: 9597eukak1
Current Session Id: 9597eukak1
Session Created Time: 985054073972
Session Last Accessed Time: 985057437578
Session Max Inactive Interval Seconds: 1800
Session scoped attributes:
   javax.security.auth.subject = Subject:

Add New Code Samples Here

If you have code samples that don't fit into any of the topics above which you would like to contribute, please put them here. We'll sort them out into their own sections as appropriate later.

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