Refactor DAP4 CDM file reading

dap4/d4servlet/src/main/java/dap4/servlet/DapController.java

@@ -130,14 +130,16 @@ public DapController() {}
   abstract protected String getWebContentRoot(DapRequest drq) throws DapException;
 
   /**
-   * Convert a URL path for a dataset into an absolute file path
-   *
-   * @param drq dap request
-   * @param location suffix of url path
-   * @return path in a string builder so caller can extend.
-   * @throws IOException
+   * Obtain a wrapped CDM source (NetcdfDataset) to Provide a DAP4 API
+   * <p>
+   * This method assumes a resource on the local filesystem. Override
+   * this method to provide other request/dataset location mappings. *
+   * </p>
+   * 
+   * @param drq DapRequest
+   * @throws IOException error obtaining the dataset described by the DapRequest
    */
-  abstract protected String getResourcePath(DapRequest drq, String location) throws DapException;
+  abstract protected CDMWrap getCDMWrap(DapRequest drq) throws IOException;
 
   //////////////////////////////////////////////////////////
 
@@ -257,10 +259,8 @@ protected void doDSR(DapRequest drq, DapContext cxt) throws IOException {
    */
 
   protected void doDMR(DapRequest drq, DapContext cxt) throws IOException {
-    // Convert the url to an absolute path
-    String realpath = drq.getResourcePath(drq.getDatasetPath());
 
-    CDMWrap c4 = new CDMWrap().open(realpath); // Create the wrapper
+    CDMWrap c4 = getCDMWrap(drq);
     DapDataset dmr = c4.getDMR();
     CEConstraint ce = constrainDapContext(cxt, dmr);
     ChecksumMode csummode = (ChecksumMode) cxt.get(DapConstants.CHECKSUMTAG);
@@ -310,12 +310,9 @@ protected void doDMR(DapRequest drq, DapContext cxt) throws IOException {
    */
 
   protected void doData(DapRequest drq, DapContext cxt) throws IOException {
-    // Convert the url to an absolute path
-    String realpath = drq.getResourcePath(drq.getDatasetPath());
-
-    CDMWrap c4 = new CDMWrap().open(realpath);
+    CDMWrap c4 = getCDMWrap(drq);
     if (c4 == null)
-      throw new DapException("No such file: " + realpath);
+      throw new DapException("Unknown resource");
 
     DapDataset dmr = c4.getDMR();
     CEConstraint ce = constrainDapContext(cxt, dmr);

dap4/d4servlet/src/main/java/dap4/servlet/DapRequest.java

@@ -205,17 +205,6 @@ public String getServletID() throws DapException {
     return controller.getServletID();
   }
 
-  /**
-   * Convert a URL path for a dataset into an absolute file path
-   *
-   * @param location suffix of url path
-   * @return path in a string builder so caller can extend.
-   * @throws IOException
-   */
-  public String getResourcePath(String location) throws DapException {
-    return controller.getResourcePath(this, location);
-  }
-
   /**
    * Convert a URL path for a web-content related file into an absolute file path
    *

dap4/d4ts/build.gradle

@@ -7,6 +7,7 @@ dependencies {
 
   implementation 'edu.ucar:dap4'
   implementation project(":dap4:d4servlet")
+  implementation 'edu.ucar:cdm-core'
 
   providedCompile "jakarta.servlet:jakarta.servlet-api:${depVersion.jakartaServletApi}"
 

dap4/d4ts/src/main/java/dap4/d4ts/D4TSServlet.java

@@ -69,7 +69,7 @@ protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws Se
   @Override
   protected void doFavicon(String icopath, DapContext cxt) throws IOException {
     DapRequest drq = (DapRequest) cxt.get(DapRequest.class);
-    String favfile = drq.getResourcePath(icopath);
+    String favfile = getResourcePath(drq, icopath);
     if (favfile != null) {
       try (FileInputStream fav = new FileInputStream(favfile);) {
         byte[] content = DapUtil.readbinaryfile(fav);
@@ -113,7 +113,7 @@ protected FrontPage getFrontPage(DapRequest drq, DapContext cxt) throws DapExcep
     if (this.defaultroots == null) {
       // Figure out the directory containing
       // the files to display.
-      String testroot = drq.getResourcePath("/");
+      String testroot = getResourcePath(drq, "/");
       if (testroot == null)
         throw new DapException("Cannot locate dataset  directory");
       this.defaultroots = new ArrayList<>();
@@ -141,6 +141,16 @@ public String getWebContentRoot(DapRequest drq) throws DapException {
     }
   }
 
+  public CDMWrap getCDMWrap(DapRequest drq) throws IOException {
+    // Convert the url to an absolute path
+    String realpath = getResourcePath(drq, drq.getDatasetPath());
+
+    CDMWrap c4 = new CDMWrap().open(realpath); // Create the wrapper
+    if (c4 == null)
+      DapLog.debug("No such file: " + realpath);
+    return c4;
+  }
+
   /**
    * Convert a URL path for a dataset into an absolute file path
    *

tds/src/main/java/thredds/server/dap4/Dap4Controller.java

@@ -9,8 +9,11 @@
 import dap4.core.util.DapException;
 import dap4.core.util.DapUtil;
 import dap4.dap4lib.DapCodes;
+import dap4.servlet.CDMWrap;
 import dap4.servlet.DapController;
 import dap4.servlet.DapRequest;
+import java.util.EnumSet;
+import java.util.Set;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Controller;
 import org.springframework.web.bind.annotation.RequestMapping;
@@ -20,6 +23,9 @@
 import jakarta.servlet.http.HttpServletRequest;
 import jakarta.servlet.http.HttpServletResponse;
 import java.io.*;
+import ucar.nc2.NetcdfFile;
+import ucar.nc2.dataset.NetcdfDataset;
+import ucar.nc2.dataset.NetcdfDataset.Enhance;
 
 @Controller
 @RequestMapping("/dap4")
@@ -35,7 +41,8 @@ public class Dap4Controller extends DapController {
   static final String SERVICEID = "/dap4";
 
   // NetcdfDataset enhancement to use: need only coord systems
-  // static Set<NetcdfDataset.Enhance> ENHANCEMENT = EnumSet.of(NetcdfDataset.Enhance.CoordSystems);
+  // match dap4.servlet.CDMWrap.ENHANCEMENT
+  static Set<Enhance> ENHANCEMENT = EnumSet.of(NetcdfDataset.Enhance.CoordSystems);
 
   //////////////////////////////////////////////////
   // Instance variables
@@ -104,26 +111,16 @@ public String getWebContentRoot(DapRequest drq) throws DapException {
     return DapUtil.canonicalpath(rootpath);
   }
 
-  /**
-   * Convert a URL path for a dataset into an absolute file path
-   *
-   * @param location suffix of url path
-   * @return path in a string builder so caller can extend.
-   * @throws IOException
-   */
-  public String getResourcePath(DapRequest drq, String location) throws DapException {
-    assert (location.charAt(0) == '/');
-    // Remove the leading service name, if any
-    if (location.startsWith(SERVICEID))
-      location = location.substring(SERVICEID.length());
-    String path = TdsRequestedDataset.getLocationFromRequestPath(location);
-    if (path == null || path.length() == 0)
-      throw new DapException(String.format("getLocationFromRequestPath: location=|%s| path=null", location, path))
-          .setCode(DapCodes.SC_NOT_FOUND);
-    File f = new File(path);
-    if (!f.exists() || !f.canRead() || !f.isFile())
-      throw new DapException("Cannot locate resource: " + location).setCode(DapCodes.SC_NOT_FOUND);
-    return DapUtil.canonicalpath(path);
+  public CDMWrap getCDMWrap(DapRequest drq) throws IOException {
+    String datasetPath = drq.getDatasetPath();
+    String prefix = SERVICEID + "/";
+    if (datasetPath.startsWith(prefix)) {
+      datasetPath = datasetPath.substring(prefix.length());
+    }
+    NetcdfFile ncf = TdsRequestedDataset.getNetcdfFile(drq.getRequest(), drq.getResponse(), datasetPath);
+    NetcdfDataset ncd;
+    ncd = NetcdfDataset.wrap(ncf, ENHANCEMENT);
+    return new CDMWrap().open(ncd);
   }
 
 }