opendap.dts

Class DTSServlet

java.lang.Object

javax.servlet.GenericServlet

javax.servlet.http.HttpServlet

opendap.servlet.AbstractServlet

opendap.dts.DTSServlet

All Implemented Interfaces:

Serializable, javax.servlet.Servlet, javax.servlet.ServletConfig

public class DTSServlet
extends AbstractServlet

Purpose:
This is the OPeNDAP Test servlet (dts). It allows the owner of the server to deliver data in ANY valid DDS to a client. This DDS will be filled with invented data if the client requests a DataDDS. This kind of test fixture is useful for evaluating a clients ability to handle the various complexities of the OPeNDAP data types.

Configuration:
The AbstractServlet relies on the javax.servlet.ServletConfig interface (in particular the getInitParameter() method) to retrieve configuration information used by the servlet. InitParameters:

• DebugOn - This controls ouput to the terminal from which the servlet engine was launched. The value is a list of flags that turn on debugging instrumentation in different parts of the code. Values are:
  • showRequest - Show information about the clients request.
  • showResponse - Show information about the servlets response.
  • probeRequest - Show an exhaustive amount of information about the clients request object.


• INFOcache - This is should be set to the directory containing the files used by the ".info" service for the servlet. This directory should contain any dataset specific "over-ride" files (see below), any dataset specific additional information files (see below), and any servlet specific information files(see below).


• DDScache - This is should be set to the directory containing the DDS files for the datasets used by the servlet. Some servlets have been developed that do not use DDS's that are cached on the disk, however the default behaviour is for the servlet to load DDS images from disk.


• DAScache - This is should be set to the directory containing the DAS files for the datasets used by the servlet. Some servlets have been developed that do not use DAS's that are cached on the disk, however the default behaviour is for the servlet to load DAS images from disk.

Here is an example entry from the web.xml file (for tomcat3.3a) for the OPeNDAP Test Server (DTS):

         <servlet>
            <servlet-name>
                dts
            </servlet-name>
 

            <servlet-class>
                opendap.servers.dts
            </servlet-class>
 

            <init-param>
                <param-name>DebugOn</param-name>
                <param-value>showRequest showResponse </param-value>
            </init-param>
 

            <init-param>
                <param-name>INFOcache</param-name>
                <param-value>/usr/Java-OPeNDAP/sdds-testsuite/info/</param-value>
            </init-param>
 

            <init-param>
                <param-name>DDScache</param-name>
                <param-value>/usr/Java-OPeNDAP/sdds-testsuite/dds/</param-value>
            </init-param>
 

            <init-param>
                <param-name>DAScache</param-name>
                <param-value>/usr/Java-OPeNDAP/sdds-testsuite/das/</param-value>
            </init-param>
        </servlet>
 

Version:

$Revision: 16122 $

Author:

Nathan David Potter

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	allowDeflate Support compressions or not
static org.slf4j.Logger	log

Constructor Summary

Constructors

Constructor and Description
DTSServlet() ************************************************************************ Intitializes the servlet.

Method Summary

Methods

Modifier and Type	Method and Description
void	anyExceptionHandler(Throwable e, ReqState rs) Sends an error to the client.
void	badURL(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) Sends an html document to the client explaining that they have used a poorly formed URL and then the help page...
void	dap2ExceptionHandler(DAP2Exception de, javax.servlet.http.HttpServletResponse response) Sends a OPeNDAP DAP2 error to the client.
void	doDebug(ReqState rs) Handler for debug requests;
protected boolean	doDebugCmd(String cmd, StringTokenizer tz, PrintStream pw)
void	doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) Handles incoming requests from clients.
void	doGetASC(ReqState rs) Handler for OPeNDAP ascii data requests.
void	doGetBLOB(ReqState rs) Handler for the client's data request.
void	doGetCatalog(ReqState rs) Handler for OPeNDAP catalog.xml requests.
void	doGetDAP2Data(ReqState rs) Handler for the client's data request.
void	doGetDAS(ReqState rs) Handler for the client's DAS request.
void	doGetDDS(ReqState rs) Handler for the client's DDS request.
void	doGetDDX(ReqState rs) Handler for the client's DDX request.
void	doGetDIR(ReqState rs) Handler for the client's directory request.
void	doGetHELP(ReqState rs) Handler for the client's help request.
void	doGetHTML(ReqState rs) Handler for OPeNDAP .html requests.
void	doGetINFO(ReqState rs) Handler for OPeNDAP info requests.
void	doGetStatus(ReqState rs) Handler for OPeNDAP status requests; not publically available, used only for debugging
void	doGetSystemProps(ReqState rs) Handler for OPeNDAP status requests; not publically available, used only for debugging
void	doGetVER(ReqState rs) Handler for the client's version request.
protected GuardedDataset	getDataset(ReqState rs) ************************************************************************ This method must be implemented locally for each OPeNDAP server.
String	getDefaultContextPath()
protected ReqState	getRequestState(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response)
String	getRootPath() Getter function for rootpath
String	getServerName() In this (default) implementation of the getServerName() method we just get the name of the servlet and pass it back.
String	getServerVersion() This method returns a String containing the OPeNDAP Server Version...
void	init()
void	IOExceptionHandler(IOException e, ReqState rs) Sends an error to the client.
void	parseExceptionHandler(ParseException pe, javax.servlet.http.HttpServletResponse response) Turns a ParseException into a OPeNDAP DAP2 error and sends it to the client.
protected void	printCatalog(ReqState rs, PrintWriter os)
protected void	printStatus(PrintWriter os)
void	probeRequest(PrintStream ps, ReqState rs) This is a bit of instrumentation that I kept around to let me look at the state of the incoming HttpServletRequest from the client.
void	sendDODSError(ReqState rs, String clientMsg, String serverMsg) Sends a OPeNDAP DAP2 error (type UNKNOWN ERROR) to the client and displays a message on the server console.

Methods inherited from class opendap.servlet.AbstractServlet

badURL, printDODSException, printThrowable, sendDODSError, setLog

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doHead, doOptions, doPost, doPut, doTrace, getLastModified, service, service

Methods inherited from class javax.servlet.GenericServlet

destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, log, log

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

log

public static org.slf4j.Logger log

allowDeflate

protected boolean allowDeflate

Support compressions or not

Constructor Detail

DTSServlet

public DTSServlet()

************************************************************************ Intitializes the servlet. Init (at this time) basically sets up the object opendap.util.util.Debug from the debuggery flags in the servlet InitParameters. The Debug object can be referenced (with impunity) from anywhere in the VM.

Method Detail

getDefaultContextPath

public String getDefaultContextPath()

Specified by:

getDefaultContextPath in class AbstractServlet

getRootPath

public String getRootPath()

Getter function for rootpath

Overrides:

getRootPath in class AbstractServlet

Returns:

rootpath

getServerVersion

public String getServerVersion()

This method returns a String containing the OPeNDAP Server Version...

Specified by:

getServerVersion in class AbstractServlet

getDataset

protected GuardedDataset getDataset(ReqState rs)
                             throws DAP2Exception,
                                    IOException,
                                    ParseException

************************************************************************ This method must be implemented locally for each OPeNDAP server. The local implementation of this method is the key piece for connecting any localized data types that are derived from the opendap.Server types back into the running servlet.

This method should do the following:

• Make a new ServerFactory (aka BaseTypeFactory) for the dataset requested.
• Instantiate a ServerDDS using the ServerFactory and populate it (this could be accomplished by just opening a (cached?) DDS in a file and parsing it)
• Return this freshly minted ServerDDS object (to the servlet code where it is used.)

Specified by:

getDataset in class AbstractServlet

Parameters:

rs - The ReqState object for this particular client request.

Returns:

The ServerDDS object all parsed and ready to roll.

Throws:

DAP2Exception

IOException

ParseException

init

public void init()
          throws javax.servlet.ServletException

Overrides:

init in class AbstractServlet

Throws:

javax.servlet.ServletException

parseExceptionHandler

public void parseExceptionHandler(ParseException pe,
                         javax.servlet.http.HttpServletResponse response)

Turns a ParseException into a OPeNDAP DAP2 error and sends it to the client.

Overrides:

parseExceptionHandler in class AbstractServlet

Parameters:

pe - The ParseException that caused the problem.

response - The HttpServletResponse for the client.

dap2ExceptionHandler

public void dap2ExceptionHandler(DAP2Exception de,
                        javax.servlet.http.HttpServletResponse response)

Sends a OPeNDAP DAP2 error to the client.

Overrides:

dap2ExceptionHandler in class AbstractServlet

Parameters:

de - The OPeNDAP DAP2 exception that caused the problem.

response - The HttpServletResponse for the client.

IOExceptionHandler

public void IOExceptionHandler(IOException e,
                      ReqState rs)

Sends an error to the client. fix: The problem is that if the message is already committed when the IOException occurs, the headers dont get set.

Overrides:

IOExceptionHandler in class AbstractServlet

Parameters:

e - The exception that caused the problem.

rs - The ReqState for the client.

anyExceptionHandler

public void anyExceptionHandler(Throwable e,
                       ReqState rs)

Sends an error to the client.

Overrides:

anyExceptionHandler in class AbstractServlet

Parameters:

e - The exception that caused the problem.

rs - The ReqState for the client.

sendDODSError

public void sendDODSError(ReqState rs,
                 String clientMsg,
                 String serverMsg)
                   throws Exception

Sends a OPeNDAP DAP2 error (type UNKNOWN ERROR) to the client and displays a message on the server console.

Parameters:

rs - The client's ReqState object.

clientMsg - Error message String to send to the client.

serverMsg - Error message String to display on the server console.

Throws:

Exception

doGetDAS

public void doGetDAS(ReqState rs)
              throws Exception

Handler for the client's DAS request. Operates on the assumption that the DAS information is cached on a disk local to the server. If you don't like that, then you better override it in your server :)

Once the DAS has been parsed it is sent to the requesting client.

Overrides:

doGetDAS in class AbstractServlet

Parameters:

rs - The ReqState of this client request. Contains all kinds of important stuff.

Throws:

Exception

See Also:

ReqState

doGetDDS

public void doGetDDS(ReqState rs)
              throws Exception

Handler for the client's DDS request. Requires the getDDS() method implemented by each server localization effort.

Once the DDS has been parsed and constrained it is sent to the requesting client.

Overrides:

doGetDDS in class AbstractServlet

Parameters:

rs - The ReqState of this client request. Contains all kinds of important stuff.

Throws:

Exception

See Also:

ReqState

doGetDDX

public void doGetDDX(ReqState rs)
              throws Exception

Handler for the client's DDX request. Requires the getDDX() method implemented by each server localization effort.

Once the DDX has been parsed and constrained it is sent to the requesting client.

Overrides:

doGetDDX in class AbstractServlet

Parameters:

rs - The ReqState of this client request. Contains all kinds of important stuff.

Throws:

Exception

See Also:

ReqState

doGetBLOB

public void doGetBLOB(ReqState rs)
               throws Exception

Handler for the client's data request. Requires the getDDS() method implemented by each server localization effort.

Once the DDS has been parsed, the data is read (using the class in the localized server factory etc.), compared to the constraint expression, and then sent to the client.

Overrides:

doGetBLOB in class AbstractServlet

Parameters:

rs - The ReqState of this client request. Contains all kinds of important stuff.

Throws:

Exception

See Also:

ReqState

doGetDAP2Data

public void doGetDAP2Data(ReqState rs)
                   throws Exception

Handler for the client's data request. Requires the getDDS() method implemented by each server localization effort.

Once the DDS has been parsed, the data is read (using the class in the localized server factory etc.), compared to the constraint expression, and then sent to the client.

Overrides:

doGetDAP2Data in class AbstractServlet

Parameters:

rs - The ReqState of this client request. Contains all kinds of important stuff.

Throws:

IOException

javax.servlet.ServletException

Exception

See Also:

ReqState

doGetDIR

public void doGetDIR(ReqState rs)
              throws Exception

Handler for the client's directory request.

Returns an html document to the client showing (a possibly pseudo) listing of the datasets available on the server in a directory listing format.

The bulk of this code resides in the class opendap.servlet.GetDirHandler and documentation may be found there.

Overrides:

doGetDIR in class AbstractServlet

Parameters:

rs - The client's ReqState

Throws:

Exception

See Also:

GetDirHandler

doGetVER

public void doGetVER(ReqState rs)
              throws Exception

Handler for the client's version request.

Returns a plain text document with server version and OPeNDAP core version #'s

Overrides:

doGetVER in class AbstractServlet

Parameters:

rs - The client's ReqState

Throws:

Exception

doGetHELP

public void doGetHELP(ReqState rs)
               throws Exception

Handler for the client's help request.

Returns an html page of help info for the server

Overrides:

doGetHELP in class AbstractServlet

Parameters:

rs - The client's ReqState

Throws:

Exception

badURL

public void badURL(javax.servlet.http.HttpServletRequest request,
          javax.servlet.http.HttpServletResponse response)
            throws Exception

Sends an html document to the client explaining that they have used a poorly formed URL and then the help page...

Parameters:

request - The client's request

response - The client response

Throws:

Exception

doGetASC

public void doGetASC(ReqState rs)
              throws Exception

Handler for OPeNDAP ascii data requests. Returns the request data as a comma delimited ascii file. Note that this means that the more complex OPeNDAP structures such as Grids get flattened...

Modified 2/8/07 jcaron to not make a DConnect2 call to itself

Overrides:

doGetASC in class AbstractServlet

Parameters:

rs - the decoded Request State

Throws:

Exception

doGetINFO

public void doGetINFO(ReqState rs)
               throws Exception

Handler for OPeNDAP info requests. Returns an HTML document describing the contents of the servers datasets.

The bulk of this code resides in the class opendap.servlet.GetInfoHandler and documentation may be found there.

Overrides:

doGetINFO in class AbstractServlet

Parameters:

rs - The client's ReqState

Throws:

Exception

See Also:

GetInfoHandler

doGetHTML

public void doGetHTML(ReqState rs)
               throws Exception

Handler for OPeNDAP .html requests. Returns the OPeNDAP Web Interface (aka The Interface From Hell) to the client.

The bulk of this code resides in the class opendap.servlet.GetHTMLInterfaceHandler and documentation may be found there.

Overrides:

doGetHTML in class AbstractServlet

Parameters:

rs - The client's ReqState

Throws:

Exception

See Also:

GetHTMLInterfaceHandler

doGetCatalog

public void doGetCatalog(ReqState rs)
                  throws Exception

Handler for OPeNDAP catalog.xml requests.

Overrides:

doGetCatalog in class AbstractServlet

Parameters:

rs - The client's ReqState

Throws:

Exception

See Also:

GetHTMLInterfaceHandler

printCatalog

protected void printCatalog(ReqState rs,
                PrintWriter os)
                     throws IOException

Overrides:

printCatalog in class AbstractServlet

Throws:

IOException

doDebug

public void doDebug(ReqState rs)

Handler for debug requests;

Overrides:

doDebug in class AbstractServlet

Parameters:

rs - The client's ReqState object.

doDebugCmd

protected boolean doDebugCmd(String cmd,
                 StringTokenizer tz,
                 PrintStream pw)

Overrides:

doDebugCmd in class AbstractServlet

doGetSystemProps

public void doGetSystemProps(ReqState rs)
                      throws Exception

Handler for OPeNDAP status requests; not publically available, used only for debugging

Overrides:

doGetSystemProps in class AbstractServlet

Parameters:

rs - The client's ReqState

Throws:

Exception

See Also:

GetHTMLInterfaceHandler

doGetStatus

public void doGetStatus(ReqState rs)
                 throws Exception

Handler for OPeNDAP status requests; not publically available, used only for debugging

Overrides:

doGetStatus in class AbstractServlet

Parameters:

rs - The client's ReqState

Throws:

Exception

See Also:

GetHTMLInterfaceHandler

printStatus

protected void printStatus(PrintWriter os)

Overrides:

printStatus in class AbstractServlet

probeRequest

public void probeRequest(PrintStream ps,
                ReqState rs)

This is a bit of instrumentation that I kept around to let me look at the state of the incoming HttpServletRequest from the client. This method calls the get* methods of the request and prints the results to standard out.

Overrides:

probeRequest in class AbstractServlet

Parameters:

ps - The PrintStream to send output.

rs - The ReqState object to probe.

getServerName

public String getServerName()

In this (default) implementation of the getServerName() method we just get the name of the servlet and pass it back. If something different is required, override this method when implementing the getDDS() and getServerVersion() methods.

This is typically used by the getINFO() method to figure out if there is information specific to this server residing in the info directory that needs to be returned to the client as part of the .info rs.getResponse().

Overrides:

getServerName in class AbstractServlet

Returns:

A string containing the name of the servlet class that is running.

doGet

public void doGet(javax.servlet.http.HttpServletRequest request,
         javax.servlet.http.HttpServletResponse response)

Handles incoming requests from clients. Parses the request and determines what kind of OPeNDAP response the client is requesting. If the request is understood, then the appropriate handler method is called, otherwise an error is returned to the client.

This method is the entry point for DTSServlet.

Overrides:

doGet in class AbstractServlet

Parameters:

request - The client's HttpServletRequest request object.

response - The server's HttpServletResponse response object.

See Also:

ReqState

getRequestState

protected ReqState getRequestState(javax.servlet.http.HttpServletRequest request,
                       javax.servlet.http.HttpServletResponse response)

Overrides:

getRequestState in class AbstractServlet

Parameters:

request -

Returns:

the request state