Package thredds.server.opendap.servlet

Class AbstractServlet

java.lang.Object

javax.servlet.GenericServlet

javax.servlet.http.HttpServlet

thredds.server.opendap.servlet.AbstractServlet

All Implemented Interfaces:

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

Direct Known Subclasses:

OpendapServlet

public abstract class AbstractServlet
extends javax.servlet.http.HttpServlet

AbstractServlet is the base servlet class for an OPeNDAP servers. Default handlers for all of the acceptable OPeNDAP client requests are here.

Each of the request handlers appears as an adjunct method to the doGet() method of the base servlet class. In order to reduce the bulk of this file, many of these methods have been in wrapper classes in this package (opendap.servlet).

This is an abstract class because it is left to the individual server development efforts to write the getDDS() and getServerVersion() methods. The getDDS() method is intended to be where the server specific OPeNDAP server data types are used via their associated class factory.

This code relies on the javax.servlet.ServletConfig interface (in particular the getInitParameter() method) to record detailed configuration information used by the servlet and it's children.

The servlet should be started in the servlet engine with the following initParameters for the tomcat servlet engine:

    <servlet>
        <servlet-name>
            dts
        </servlet-name>
        <servlet-class>
            opendap.servers.test.dts
        </servlet-class>
        <init-param>
            <param-name>INFOcache</param-name>
            <param-value>/home/Datasets/info</param-value>
        </init-param>
        <init-param>
            <param-name>DDScache</param-name>
            <param-value>/home/Datasets/dds</param-value>
        </init-param>
        <init-param>
            <param-name>DAScache</param-name>
            <param-value>/home/Datasets/das</param-value>
        </init-param>
        <init-param>
            <param-name>DDXcache</param-name>
            <param-value>/home/Datasets/ddx</param-value>
        </init-param>
    </servlet>

 

Obviously the actual values of these parameters will depend on your particular file system.

See the file SERVLETS in the top level directory of the software distribution for more detailed information about servlet configuration.

Also, the method processDodsURL() could be overloaded if some kind of special processing of the incoming request is needed to ascertain the OPeNDAP URL information.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
protected boolean	allowDeflate
static org.slf4j.Logger	log

Constructor Summary

Constructors

Constructor	Description
AbstractServlet()

Method Summary

Modifier and Type	Method	Description
void	anyExceptionHandler(Throwable e, ReqState rs)	Sends an error to the client.
void	badURL(ReqState rs)	Sends an html document to the client explaining that they have used a poorly formed URL and then the help page...
void	dap2ExceptionHandler(opendap.dap.DAP2Exception de, javax.servlet.http.HttpServletResponse response)	Sends a OPeNDAP DAP2 error to the client.
void	doDebug(ReqState rs)	Default handler for debug requests;
protected boolean	doDebugCmd(String cmd, StringTokenizer tz, PrintWriter pw)
void	doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response)	Handles incoming requests from clients.
void	doGetASC(ReqState rs)	Default handler for OPeNDAP ascii data requests.
void	doGetBLOB(ReqState rs)	Default handler for the client's data request.
void	doGetCatalog(ReqState rs)	Default handler for OPeNDAP catalog.xml requests.
void	doGetDAP2Data(ReqState rs)	Default handler for the client's data request.
void	doGetDAS(ReqState rs)	Default handler for the client's DAS request.
void	doGetDDS(ReqState rs)	Default handler for the client's DDS request.
void	doGetDDX(ReqState rs)	Default handler for the client's DDS request.
void	doGetDIR(ReqState rs)	Default handler for the client's directory request.
void	doGetHELP(ReqState rs)	Default handler for the client's help request.
void	doGetHTML(ReqState rs)	Default handler for OPeNDAP .html requests.
void	doGetINFO(ReqState rs)	Default handler for OPeNDAP info requests.
void	doGetStatus(ReqState rs)	Default handler for OPeNDAP status requests; not publically available, used only for debugging
void	doGetSystemProps(ReqState rs)	Default handler for OPeNDAP status requests; not publically available, used only for debugging
void	doGetVER(ReqState rs)	Default handler for the client's version request.
protected abstract GuardedDataset	getDataset(ReqState rs)	This method must be implemented locally for each OPeNDAP server.
protected ReqState	getRequestState(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response)
String	getServerName()	In this (default) implementation of the getServerName() method we just get the name of the servlet and pass it back.
abstract String	getServerVersion()	This function must be implemented locally for each OPeNDAP server.
void	IOExceptionHandler(IOException e, ReqState rs)	Sends an error to the client.
protected static void	parseConstraint(CEEvaluator ce, ReqState rs)
void	parseExceptionHandler(opendap.dap.parsers.ParseException pe, javax.servlet.http.HttpServletResponse response)	Turns a ParseException into a OPeNDAP DAP2 error and sends it to the client.
protected void	printBadURLPage(PrintWriter pw)	Prints the Bad URL Page page to the passed PrintWriter
protected void	printCatalog(ReqState rs, PrintWriter os)
protected void	printStatus(PrintWriter os)
static void	printThrowable(Throwable t)
void	probeRequest(PrintWriter 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(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response, String clientMsg, String serverMsg)	Sends a OPeNDAP DAP2 error (type UNKNOWN ERROR) to the client and displays a message on the server console.
static void	setLog(Class<?> cl)

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, 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

Constructor Detail

AbstractServlet

public AbstractServlet()

Method Detail

setLog

public static void setLog(Class<?> cl)

printThrowable

public static void printThrowable(Throwable t)

getServerVersion

public abstract String getServerVersion()

This function must be implemented locally for each OPeNDAP server. It should return a String containing the OPeNDAP Server Version...

Returns:

The Server Version String

getDataset

protected abstract GuardedDataset getDataset(ReqState rs)
                                      throws Exception

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.)

Parameters:

rs - The ReqState object for this particular client request.

Returns:

A GuardedDataset object cintaininb the parsed DAS and DDS.

Throws:

Exception

parseExceptionHandler

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

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

Parameters:

pe - The ParseException that caused the problem.

response - The HttpServletResponse for the client.

dap2ExceptionHandler

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

Sends a OPeNDAP DAP2 error to the client.

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. LOOK: The problem is that if the message is already committed when the IOException occurs, the headers dont get set.

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.

Parameters:

e - The exception that caused the problem.

rs - The ReqState for the client.

sendDODSError

public void sendDODSError(javax.servlet.http.HttpServletRequest request,
                          javax.servlet.http.HttpServletResponse response,
                          String clientMsg,
                          String serverMsg)
                   throws IOException,
                          javax.servlet.ServletException

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

Parameters:

request - The client's HttpServletRequest request object.

response - The server's HttpServletResponse response object.

clientMsg - Error message String to send to the client.

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

Throws:

IOException

javax.servlet.ServletException

doGetDAS

public void doGetDAS(ReqState rs)
              throws Exception

Default 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.

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

Default 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.

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

Default 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.

Parameters:

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

Throws:

Exception

See Also:

ReqState

parseConstraint

protected static void parseConstraint(CEEvaluator ce,
                                      ReqState rs)
                               throws opendap.dap.parsers.ParseException,
                                      opendap.dap.DAP2Exception

Throws:

opendap.dap.parsers.ParseException

opendap.dap.DAP2Exception

doGetBLOB

public void doGetBLOB(ReqState rs)
               throws Exception

Default 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.

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

Default 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.

Parameters:

rs - The ReqState of this client request.

Throws:

Exception

doGetDIR

public void doGetDIR(ReqState rs)
              throws Exception

Default 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.

Parameters:

rs - The client's ReqState

Throws:

Exception

See Also:

GetDirHandler

doGetVER

public void doGetVER(ReqState rs)
              throws Exception

Default handler for the client's version request.

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

Parameters:

rs - The client's ReqState

Throws:

Exception

doGetHELP

public void doGetHELP(ReqState rs)
               throws Exception

Default handler for the client's help request. Returns an html page of help info for the server

Parameters:

rs - The client's ReqState

Throws:

Exception

badURL

public void badURL(ReqState rs)
            throws Exception

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

Parameters:

rs - The client's ReqState

Throws:

Exception

doGetASC

public void doGetASC(ReqState rs)
              throws Exception

Default 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

Parameters:

rs - the decoded Request State

Throws:

Exception

doGetINFO

public void doGetINFO(ReqState rs)
               throws Exception

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

Parameters:

rs - The client's ReqState

Throws:

Exception

See Also:

GetInfoHandler

doGetHTML

public void doGetHTML(ReqState rs)
               throws Exception

Default 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.

Parameters:

rs - The client's ReqState

Throws:

Exception

See Also:

GetHTMLInterfaceHandler

doGetCatalog

public void doGetCatalog(ReqState rs)
                  throws Exception

Default handler for OPeNDAP catalog.xml requests.

Parameters:

rs - The client's ReqState

Throws:

Exception

See Also:

GetHTMLInterfaceHandler

printCatalog

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

Throws:

IOException

doDebug

public void doDebug(ReqState rs)
             throws IOException

Default handler for debug requests;

Parameters:

rs - The client's ReqState object.

Throws:

IOException

doDebugCmd

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

doGetSystemProps

public void doGetSystemProps(ReqState rs)
                      throws Exception

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

Parameters:

rs - The client's ReqState

Throws:

Exception

See Also:

GetHTMLInterfaceHandler

doGetStatus

public void doGetStatus(ReqState rs)
                 throws Exception

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

Parameters:

rs - The client's ReqState

Throws:

Exception

See Also:

GetHTMLInterfaceHandler

printStatus

protected void printStatus(PrintWriter os)
                    throws IOException

Throws:

IOException

probeRequest

public void probeRequest(PrintWriter 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.

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().

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 AbstractServlet.

Overrides:

doGet in class javax.servlet.http.HttpServlet

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)
                            throws opendap.dap.DAP2Exception

Parameters:

request -

Returns:

the request state

Throws:

opendap.dap.DAP2Exception

printBadURLPage

protected void printBadURLPage(PrintWriter pw)

Prints the Bad URL Page page to the passed PrintWriter

Parameters:

pw - PrintWriter stream to which to dump the bad URL page.