Unidata · lesserwhirls · Dec 20, 2025 · Dec 20, 2025 · Dec 20, 2025 · Dec 20, 2025
@@ -15,24 +15,24 @@ jobs:
           ubuntu-24.04,
           ubuntu-24.04-arm,
           windows-2022,
-          macos-13,
           macos-14,
-          macos-15
+          macos-15,
+          macos-15-intel
         ]
     name: netCDF-Java Native Compression Tests
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v4
       - name: Setup JDK 8, 17
-        if: ${{ matrix.os == 'ubuntu-24.04' || matrix.os == 'macos-13' }}
+        if: ${{ matrix.os == 'ubuntu-24.04' || matrix.os == 'macos-15-intel' }}
         uses: actions/setup-java@v5
         with:
           distribution: 'temurin'
           java-version: |
             8
             17
       - name: Setup JDK 21
-        if: ${{ matrix.os != 'ubuntu-24.04' && matrix.os != 'macos-13' }}
+        if: ${{ matrix.os != 'ubuntu-24.04' && matrix.os != 'macos-15-intel' }}
         uses: actions/setup-java@v5
         with:
           distribution: 'temurin'
@@ -47,12 +47,12 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-gradle-
       - name: Run libaec JNA tests
-        if: ${{ matrix.os == 'ubuntu-24.04' || matrix.os == 'macos-13'  }}
+        if: ${{ matrix.os == 'ubuntu-24.04' || matrix.os == 'macos-15-intel'  }}
         run: ./gradlew -Dorg.gradle.java.installations.auto-detect=true clean :libaec-jna:test
         env:
           JDK8: /usr/thredds-test-environment/temurin8
       - name: Run libaec JNA tests (JDK 21 tests)
-        if: ${{ matrix.os != 'ubuntu-24.04' && matrix.os != 'macos-13' }}
+        if: ${{ matrix.os != 'ubuntu-24.04' && matrix.os != 'macos-15-intel' }}
         run: ./gradlew clean :libaec-jna:test21
       - uses: actions/upload-artifact@v4
         if: failure()

@@ -48,6 +48,8 @@ val publicArtifacts =
     ":legacy",
     ":libaec-jna",
     ":libaec-native",
+    ":libblosc2-jna",
+    ":libblosc2-native",
     ":netcdf4",
     ":opendap",
     ":udunits",

@@ -1,4 +1,3 @@
-ucar.nc2.filter.Blosc$Provider
 ucar.nc2.filter.Deflate$Provider
 ucar.nc2.filter.Checksum32$Fletcher32Provider
 ucar.nc2.filter.Checksum32$Adler32Provider

@@ -20,6 +20,8 @@ dependencies {
   implementation(libs.jackson.databind)
   implementation(libs.slf4j.api)
 
+  runtimeOnly(project(":libblosc2-jna"))
+
   testImplementation(platform(project(":netcdf-java-testing-platform")))
 
   testImplementation(project(":cdm-s3"))
@@ -38,6 +40,8 @@ dependencies {
 
   testCompileOnly(libs.junit4)
 
+  testRuntimeOnly(project(":libblosc2-native"))
+
   testRuntimeOnly(libs.junit5.platformLauncher)
   testRuntimeOnly(libs.junit5.vintageEngine)
 }
@@ -15,6 +15,8 @@
 import ucar.ma2.ArrayLong;
 import ucar.ma2.DataType;
 import ucar.ma2.InvalidRangeException;
+import ucar.ma2.MAMath;
+import ucar.ma2.MAMath.MinMax;
 import ucar.ma2.Section;
 import ucar.nc2.*;
 
@@ -399,4 +401,24 @@ public void testGeozarrSharedDimension() throws IOException {
       }
     }
   }
+
+  @Test
+  public void testBloscCompressedData() throws IOException {
+    NetcdfFile ncfile = NetcdfFiles.open(SCALAR_GEOZARR_DATA);
+    Variable bloscVariable = ncfile.findVariable("temperature");
+    assertThat(bloscVariable != null).isTrue();
+    Attribute compressor = bloscVariable.findAttribute("_Compressor");
+    assertThat(compressor).isNotNull();
+    assertThat(compressor.getStringValue()).isEqualTo("blosc");
+    Array data = bloscVariable.read();
+    assertThat(data).isNotNull();
+    MinMax mm = MAMath.getMinMax(data);
+    assertThat(mm).isNotNull();
+    // values from python zarr implementation
+    double expectedMin = 1.9752643660053693e-05;
+    double expectedMax = 0.9999808929333684;
+    assertThat(mm.min).isWithin(1e-9).of(expectedMin);
+    assertThat(mm.max).isWithin(1e-7).of(expectedMax);
+  }
+
 }
@@ -64,7 +64,7 @@ sidebars:
 - netcdfJavaTutorial_sidebar
 
 # project logo (32x32), name, main landing page  (currently used in the footer)
-project_logo: https://www.unidata.ucar.edu/images/logos/thredds_netcdf-32x32.png
+project_logo: https://assets.unidata.ucar.edu/images/logos/thredds_netcdf-32x32.png
 project_name: netCDF-Java
 project_landing_page: https://unidata.ucar.edu/software/netcdf-java/
 
@@ -74,3 +74,9 @@ description: "This is a documentation site for the netCDF-Java, which is part of
 # needed for sitemap.xml file only
 # must include trailing slash, leave off the version :-)
 base_docs_url: https://docs.unidata.ucar.edu/netcdf-java/
+
+# these will appear in various doc pages
+java_version_build: 17
+java_version_runtime: 8
+libaec_version: 1.1.3.0
+cblosc2_version: 2.22.0.0
@@ -8,8 +8,8 @@ permalink: upgrade.html
 
 ## Requirements
 
-* Java 8 or later is required to use the library.
-* Starting with version 5.10.0, Java 17 is required to build the library.
+* Java {{ site.java_version_runtime }} or later is required to use the library.
+* Java {{ site.java_version_build }} is required to build the library.
 
 ## Quick Navigation
 * [Summary of changes for v5.10.x](#netcdf-java-api-changes-510x)
@@ -29,10 +29,23 @@ permalink: upgrade.html
 Point release notes:
 * [5.10.0](https://github.com/Unidata/netcdf-java/releases/tag/v5.10.0){:target="_blank"} (_yyyy-mm-dd, unreleased_)
 
-Starting with 5.10.x, the netCDF-Java library requires Java 17 to build (although the build will produce Java 8 bytecode, so the minimum supported version is still Java 8).
+Starting with 5.10.0, the netCDF-Java library requires Java 17 to build (although the build will produce Java 8 bytecode, so the minimum supported version is still Java 8).
 Note: we are looking to update the minimum version of the JVM we support for the project.
 Please consider taking a moment to participate in the [poll on GitHub](https://github.com/Unidata/netcdf-java/discussions/1468){:target="_blank"}.
 
+The 5.10.0 release adds support for reading blosc compressed data using the C-Blosc2 native library.
+The new artifact for JNA support is `edu.ucar.unidata:libblosc2-jna` (the current version is `2.22.0.0`).
+
+### Native jar group name changes
+
+Going forard, all native jars will be published under the `edu.ucar.unidata` group.
+Their version will match the version of the native library that they contain, plus a build number.
+This is to help make clear which version of the native library is being used by the jar.
+Starting with this release, `libaec-native` will be published under the `edu.ucar.unidata` group as well.
+Consider using the netcdf-java-bom artifact to manage your netCDF-Java dependencies, as it will always contain the latest versions of the native jars.
+The new `edu.ucar.unidata:libaec-native:1.1.3.0` is equivalent to the previous `edu.ucar:libaec-native:5.9.1`.
+Please use the new group name for any `*-native` artifacts going forward.
+
 ## netCDF-Java API Changes (5.9.x)
 
 Point release notes:

@@ -8,7 +8,7 @@ toc: false
 
 {% include image.html file="netcdf-java/tutorial/coordsystems/CoordSys.png" alt="Coordinate Systems UML" caption="Coordinate Systems UML" %}
 
-For an overview, see: [CDM Object Model]( /common_data_model_overview.html). The Coordinate Axes for a Variable must use a subset of the Variables's dimensions.
+For an overview, see: [CDM Object Model](common_data_model_overview.html). The Coordinate Axes for a Variable must use a subset of the Variables's dimensions.
 
 ## Goals of _Coordinate Attribute Convention
 

@@ -152,7 +152,7 @@ java -Xmx1g -classpath netcdfAll-<version>.jar ucar.nc2.ft.point.writer.CFPointW
 
 ## GribCdmIndex
 
-Write GRIB Collection Indexes from an XML file containing a [GRIB `<featureCollection>`](/grib_feature_collections_ref.html) XML element.
+Write GRIB Collection Indexes from an XML file containing a [GRIB `<featureCollection>`](grib_feature_collections_ref.html) XML element.
 
 ~~~bash
 java -Xmx1g -classpath netcdfAll-<version>.jar ucar.nc2.grib.collection.GribCdmIndex [options]
@@ -173,7 +173,7 @@ Example:
 java -Xmx1g -classpath netcdfAll-<version>.jar ucar.nc2.grib.collection.GribCdmIndex -fc /data/fc/gfs_example.xml
 ~~~
 
-Note that the output file is placed in the root directory of the collection, as specified by the [Collection Specification](/collection_spec_string_ref.html) of the GRIB [`<featureCollection>`](feature_collections_ref.html).
+Note that the output file is placed in the root directory of the collection, as specified by the [Collection Specification string](https://docs.unidata.ucar.edu/tds/current/userguide/collection_spec_string_ref.html){:target="_blank"} of the GRIB [`<featureCollection>`](grib_feature_collections_ref.html).
 
 ## FeatureScan
 

@@ -212,11 +212,11 @@ In the following example, the <b>_type_</b> may be byte, short, int or long:
 ### Reading
 #### Q: What files can the library read?
 
-See [File Types])/common_data_model_overview.html).
+See [File Types](common_data_model_overview.html).
 
 #### Q: How do I read a file of type X?
 
-In general, you [open any CDM file](common_data_model_overview.html) in the same way, and access it through the [extended netCDF data model(/common_data_model_overview.html#data-access-layer-object-model). The whole point of the CDM is to hide the details of the file format. However, some file type may require special handling:
+In general, you [open any CDM file](common_data_model_overview.html) in the same way, and access it through the [extended netCDF data model](common_data_model_overview.html#data-access-layer-object-model). The whole point of the CDM is to hide the details of the file format. However, some file type may require special handling:
 
 GRIB and BUFR files may require special tables that the CDM doesn't have. Open the file as above and see 1) if you get any error messages, 2) if any of the variables have "Unknown" in their name, and 3) if the data looks wrong. If any of those happen, prepare to enter [GRIB table hell realm](grib_tables.html). (BUFR is arguably worse, but there's nothing yet that you can do about it).
 

@@ -10,7 +10,7 @@ toc: false
 
 The netCDF-Java source code is hosted on GitHub, and — as of v4.6.1 — we use Gradle to build it.
 Ant and Maven builds are no longer supported.
-To build, you need Git and, as of v5.9.2, Java 17 or higher (required for Gradle 9.0.0 or higher).
+To build, you need Git and, as of v5.10.0, Java 17 or higher (required for Gradle 9.0.0 or higher).
 Note that the bytecode produced by the Gradle build will be compatible with Java 8, and the test task will run using JDK 8 (thanks to the Gradle Toolchain feature).
 If the build cannot find a suitable JDK for testing, you will need to specify one in your `gradle.properties` file (see the [Gradle toolchain documentation](https://docs.gradle.org/current/userguide/toolchains.html#sec:custom_loc){:target="_blank"} for more details).
 The tests can be run using other JDK versions using `testX`, where `X` is the version number of one of the LTS releases of Java (currently `11`, `17`, `21`, or `25`).

@@ -35,7 +35,7 @@ For maximum compatibility, please include the Unidata repository after any other
 
 Next, select modules based on the functionality you need.
 In the minimal case, you’ll just want `cdm-core` and a logger.
-`cdm` implements the CDM data model and allows you to read NetCD-3 files (and a number of other file types).
+`cdm-core` implements the [Common Data Model (CDM)](common_data_model_overview.html) and allows you to read NetCD-3 files (and a number of other file types).
 An example using JDK14 logging:
 
 ~~~xml
@@ -128,8 +128,10 @@ dependencies {
 
 ## Native compression code
 
+### libaec
+
 netCDF-Java `>=v5.8.0` supports libaec compression for GRIB2 messages using JNA to call the libaec C library.
-To ease the use of this feature, we now distribute a jar file containing the native libraries for the following platforms/architectures:
+To ease the use of this feature, we distribute a jar file containing the native libraries for the following platforms/architectures:
 
 |---
 | platform | x86-64 | aarch64
@@ -138,14 +140,29 @@ To ease the use of this feature, we now distribute a jar file containing the nat
 | MacOS | <span class="glyphicon glyphicon-ok" style="color: green;"> | <span class="glyphicon glyphicon-ok" style="color: green;">
 | Windows | <span class="glyphicon glyphicon-ok" style="color: green;"> | <span class="glyphicon glyphicon-ok" style="color: green;">
 
-If you are using on the of the supported platform/architecture combinations above, you may include the `edu.ucar:libaec-native:${netcdfJavaVersion}` artifact in your project to bypass the need to install libaec on your system.
+If you are using on the of the supported platform/architecture combinations above, you may include the `edu.ucar.unidata:libaec-native:{{ site.libaec_version }}` artifact in your project to bypass the need to install libaec on your system.
 Otherwise, libaec will need to be installed and reachable in your system library path in order to read data compressed using libaec.
 
+### C-Blosc2
+
+netCDF-Java `>=v5.10.0` supports blosc compression using JNA to call the C-Blosc2 library.
+To ease the use of this feature, we distribute a jar file containing the native libraries for the following platforms/architectures:
+
+|---
+| platform | x86-64 | aarch64
+|:-|:-:|:-:
+| Linux | <span class="glyphicon glyphicon-ok" style="color: green;"></span> | <span class="glyphicon glyphicon-ok" style="color: green;">
+| MacOS | <span class="glyphicon glyphicon-ok" style="color: green;"> | <span class="glyphicon glyphicon-ok" style="color: green;">
+| Windows | <span class="glyphicon glyphicon-ok" style="color: green;"> | <span class="glyphicon glyphicon-ok" style="color: green;">
+
+If you are using on the of the supported platform/architecture combinations above, you may include the `edu.ucar.unidata:libblosc2-native:{{ site.cblosc2_version }}` artifact in your project to bypass the need to install C-Blosc2 on your system.
+Otherwise, C-Blosc2 will need to be installed and reachable in your system library path in order to read data compressed using blosc.
+
 ## Building with netcdfAll
 
 This is the appropriate option if you’re not using a dependency management tool like Maven or Gradle and you don’t care about jar size or compatibility with other libraries. Simply include netcdfAll-${netcdfJavaVersion}.jar on the classpath when you run your program.
 You’ll also need a logger.
-Currently, the netcdfAll jar does not include `cdm-s3` due to the size of the AWS S3 SDK dependency, and does not include the `libaec-native` (native library binaries for libaec).
+Currently, the netcdfAll jar does not include `cdm-s3` due to the size of the AWS S3 SDK dependency, and does not include any `edu.ucar.unidata:*-native` jars (native library binaries for compression).
 The netcdfAll jar can be found at https://downloads.unidata.ucar.edu, or (starting with `5.9.0`) on the [GitHub release page](https://github.com/Unidata/netcdf-java/releases).
 
 ## Logging

@@ -0,0 +1,10 @@
+# Publishing Native Jars
+
+The native jars are versioned based on the native library version (plus a build number).
+These jars are also published separate to the rest of the project jars.
+To publish a native jar, you must set the `` system property when running the gradle publish command.
+For example, to publish the libblosc2-native jar, run:
+
+```
+./gradlew -D"unidata.native.publish=true" :libblosc2-native:publish
+```
@@ -7,14 +7,24 @@ import java.net.URL
 import java.security.DigestInputStream
 import java.security.MessageDigest
 
-plugins { id("java-library-conventions") }
+plugins {
+  id("java-base-conventions")
+  id("artifact-publishing-conventions")
+}
+
+group = "edu.ucar.unidata"
+
+var aecVersion = "1.1.3"
+var build = "0"
+
+version = "${aecVersion}.${build}"
 
 description = "Jar distribution of native libraries for libaec compression."
 
 project.extra["project.title"] = "Native libraries for libaec."
 
 // zip file produced by GitHub workflow
-val libaecNative = "libaec-native-1.1.3-fec016ecd4b8ff1918877e582898d4257c405168.zip"
+val libaecNative = "libaec-native-${aecVersion}-fec016ecd4b8ff1918877e582898d4257c405168.zip"
 
 // sha256 checksum from GitHub workflow output
 val expectedChecksum = "3db1ba7bc95b48eff74501382b90b0c7d0770a98f369d8c376c8ca4b6003487e"
@@ -58,3 +68,21 @@ val processNativeResources =
   }
 
 tasks.processResources { dependsOn(processNativeResources) }
+
+var publishTaskName = "nativeLibs"
+
+publishing {
+  publications {
+    create<MavenPublication>(publishTaskName) {
+      from(components["java"])
+      versionMapping {
+        usage("java-api") { fromResolutionOf("runtimeClasspath") }
+        usage("java-runtime") { fromResolutionResult() }
+      }
+    }
+  }
+}
+
+tasks
+  .matching { it.group == "publishing" }
+  .forEach { it.enabled = System.getProperty("unidata.native.publish")?.toBoolean() ?: false }