Package opendap.servlet

Class AbstractServlet

java.lang.Object
jakarta.servlet.GenericServlet
jakarta.servlet.http.HttpServlet
opendap.servlet.AbstractServlet
All Implemented Interfaces:
jakarta.servlet.Servlet, jakarta.servlet.ServletConfig, Serializable
public abstract class AbstractServlet extends jakarta.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 jakarta.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:

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    protected boolean
    allowDeflate
    ************************************************************************ Compression
    static org.slf4j.Logger
    log
     
    protected String
    rootpath
    path to the root of the servlet in tomcat webapps directory

  • 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, jakarta.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(jakarta.servlet.http.HttpServletRequest request, jakarta.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(jakarta.servlet.http.HttpServletRequest request, jakarta.servlet.http.HttpServletResponse response)
     
    String
    getServerName()
    ************************************************************************
    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.
    void
    parseExceptionHandler(opendap.dap.parsers.ParseException pe, jakarta.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)
     
    static void
    printDODSException(opendap.dap.DAP2Exception de)
     
    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(jakarta.servlet.http.HttpServletRequest request, jakarta.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)
     
    protected void
    setRootpath(String rootPath)
     

    Methods inherited from class jakarta.servlet.http.HttpServlet

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

    Methods inherited from class jakarta.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 Details

    • log

      public static org.slf4j.Logger log

    • allowDeflate

      protected boolean allowDeflate
      ************************************************************************ Compression

    • rootpath

      protected String rootpath
      path to the root of the servlet in tomcat webapps directory

  • Constructor Details

    • AbstractServlet

      public AbstractServlet()

  • Method Details

    • setLog

      public static void setLog(Class cl)

    • printDODSException

      public static void printDODSException(opendap.dap.DAP2Exception de)

    • printThrowable

      public static void printThrowable(Throwable t)

    • setRootpath

      protected void setRootpath(String rootPath)

    • 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:
      The ServerDDS object all parsed and ready to roll.
      Throws:
      opendap.dap.DAP2Exception
      IOException
      opendap.dap.parsers.ParseException
      Exception
      See Also:

    • parseExceptionHandler

      public void parseExceptionHandler(opendap.dap.parsers.ParseException pe, jakarta.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, jakarta.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(jakarta.servlet.http.HttpServletRequest request, jakarta.servlet.http.HttpServletResponse response, String clientMsg, String serverMsg) throws IOException, jakarta.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
      jakarta.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:

    • 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:

    • 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:

    • 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:

    • 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. Contains all kinds of important stuff.
      Throws:
      IOException
      jakarta.servlet.ServletException
      Exception
      See Also:

    • 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:

    • 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.

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

      Parameters:
      rs - The client's ReqState
      Throws:
      Exception
      See Also:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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(jakarta.servlet.http.HttpServletRequest request, jakarta.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 jakarta.servlet.http.HttpServlet
      Parameters:
      request - The client's HttpServletRequest request object.
      response - The server's HttpServletResponse response object.
      See Also:

    • getRequestState

      protected ReqState getRequestState(jakarta.servlet.http.HttpServletRequest request, jakarta.servlet.http.HttpServletResponse response) throws opendap.dap.DAP2Exception
      Parameters:
      request -
      Returns:
      the request state
      Throws:
      opendap.dap.DAP2Exception