feat: Do not depend anymore on providing env variable PROJ_DATA. Instead, generate temp path and use LibC to set it as env variable

Author: REASY

README.md

@@ -2,20 +2,18 @@ gdal-jni-with-native
 ======
 [<img src="https://jitpack.io/v/REASY/gdal-jni-with-native.svg">](https://jitpack.io/#REASY/gdal-jni-with-native)
 
-This project builds GDAL, extract native libraries and makes it available as Java library. At the moment it only supports GDAL on Ubuntu x64  (Linux)
+This project builds GDAL, extracts native libraries and makes them available as Java library. At the moment it only supports GDAL on Ubuntu x64  (Linux)
 
 ### Build
 In order to build the project the following should happen:
 1. Build GDAL docker image, [build_gdal.sh](scripts.build_gdal.sh) is responsible for that
 2. Build [lddtopo-rs](https://github.com/REASY/lddtopo-rs), [build_lddtopo.sh](scripts/build_lddtopo.sh) is responsible for that
 3. Analyze the dependencies of /usr/share/java/libgdalalljni.so by building DAG and running topological sort on it
-4. Copy all required native modules to src/main/resources/native
-5. Generate src/main/resources/native/modules.txt that contains new line separated list of modules to be loaded. The order comes from topological sort!
+4. Copy all required native modules to `src/main/resources/native/%os%-%arch%`
+5. Copy proj DB to [src/main/resources/proj/proj.db](src/main/resources/proj/proj.db)
+7. Generate `src/main/resources/native/%os%-%arch%.txt` that contains new line separated list of modules to be loaded. The order comes from topological sort!
 
 All of this is done in a script [generate_native_modules.sh](scripts/generate_native_modules.sh), just run it from root folder of the repo to get the final JAR
 ```bash
 ./scripts/generate_native_modules.sh
 ```
-
-### Note on the usage
-Please, make sure that you set an environment variable PROJ_DATA to writable (preferably temporary) folder, for example `/tmp/gdal-jni-with-native/proj/`. That env variable is expected by PROJ, so it cannot be set on runtime by the same process.

build.gradle

@@ -1,5 +1,5 @@
 group = 'gdal-jni-with-native'
-version = '3.5.3.2'
+version = '3.5.3.3'
 
 buildscript {
     repositories {

scripts/generate_native_modules.sh

@@ -36,5 +36,5 @@ docker run -u $(id -u):$(id -g) \
 lib_name=$(./gradlew properties | grep ^name | sed 's/name: //g')
 lib_version=$(./gradlew properties | grep ^version | sed 's/version: //g')
 lib_full_name="$lib_name-$lib_version.jar"
-./gradlew clean build && PROJ_DATA=/tmp/gdal-jni-with-native/proj/ java -cp "build/libs/$lib_full_name" com.github.reasy.gdal.GdalExample
+./gradlew clean build && java -cp "build/libs/$lib_full_name" com.github.reasy.gdal.GdalExample
 

src/main/java/com/github/reasy/gdal/GdalExample.java

@@ -49,7 +49,10 @@ private static void writeCogGeoTiff() throws IOException {
         Dataset memDs = drv.Create("", xSize, ySize, 1, type);
         System.out.printf("Created %d x %d dataset with 1 band and type %d\n", xSize, ySize, type);
 
-        memDs.SetProjection("EPSG:32611");
+        int err = memDs.SetProjection("EPSG:32611");
+        if (err != gdalconstConstants.CE_None) {
+            throw new IllegalStateException(String.format("Could not set projection, error: %d", err));
+        }
         memDs.GetRasterBand(1).WriteRaster(0, 0, xSize, ySize, data);
         memDs.BuildOverviews("NEAREST", new int[]{2, 4, 8, 16, 32});
 
@@ -87,7 +90,6 @@ public static void main(String[] args) throws Exception {
 
         // Force to load GDAL JNI and all dependencies
         JNIGdalLoader.load();
-
         gdal.AllRegister();
 
         runExamples();

src/main/java/com/github/reasy/gdal/JNIGdalLoader.java

@@ -1,14 +1,11 @@
 package com.github.reasy.gdal;
 
+import com.sun.jna.Native;
 import com.sun.jna.Platform;
 
-import java.io.BufferedReader;
-import java.io.IOException;
-import java.io.InputStream;
-import java.io.InputStreamReader;
+import java.io.*;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
-import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.nio.file.StandardCopyOption;
 import java.util.ArrayList;
@@ -20,25 +17,41 @@ public class JNIGdalLoader {
     public static final boolean IS_LOADED;
     public static final String PATH_TO_MODULES = String.format("native/%s.txt", Platform.RESOURCE_PREFIX);
     public static final String PROJ_DB_PATH = "proj/proj.db";
-    public static final String TEMP_PATH_FOR_PROJ_DATA;
+    public static final File TEMP_PATH_FOR_PROJ_DATA;
+
+    public static final LibC libc;
+
 
     static {
-        if (System.getenv("PROJ_DATA") == null) {
-            throw new IllegalStateException("There must be an env variable `PROJ_DATA` set to writable (preferably temporary) folder, for example `/tmp/gdal-jni-with-native/proj/`");
-        }
-        TEMP_PATH_FOR_PROJ_DATA = System.getenv("PROJ_DATA");
+        // TODO: Add support of Windows (need to load msvcrt and use `_putenv` instead
+        // https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/putenv-wputenv?view=msvc-170
+        libc = Native.load("c", LibC.class);
 
         try {
+            TEMP_PATH_FOR_PROJ_DATA = Files.createTempDirectory("JNIGdalLoader").toFile();
+            cleanUpOnShutdown();
+            System.out.println("TEMP_PATH_FOR_PROJ_DATA: " + TEMP_PATH_FOR_PROJ_DATA);
+
+            copyProjDb(TEMP_PATH_FOR_PROJ_DATA + "/proj.db");
+
+            // Make PROJ used by GDAL aware of a path to proj.db via setting PROJ_DATA
+            // https://proj.org/usage/environmentvars.html#envvar-PROJ_DATA
+            final int err = libc.setenv("PROJ_DATA", TEMP_PATH_FOR_PROJ_DATA.getAbsolutePath(), 1);
+            if (err != 0) {
+                throw new IllegalStateException(String.format("Could not set env variable `PROJ_DATA` to %s", TEMP_PATH_FOR_PROJ_DATA));
+            }
+
+            // Get the list of modules to load
             MODULES_TO_LOAD = getModules();
             System.out.printf("JNIGdalLoader: loading %d shared library...\n", MODULES_TO_LOAD.length);
 
+            // Load modules
             NativeLibraryLoader loader = new NativeLibraryLoader("/native");
             for (String module : MODULES_TO_LOAD) {
                 loader.load(module);
             }
             System.out.println("JNIGdalLoader: loaded all shared libraries");
 
-            copyProjDb();
 
             IS_LOADED = true;
         } catch (Exception ex) {
@@ -49,7 +62,6 @@ public class JNIGdalLoader {
         }
     }
 
-
     public static void load() {
         // Just make sure it that it is loaded.
         // If we reach here, it must always be true (because otherwise the RuntimeException should have been thrown before in static ctor)
@@ -71,14 +83,28 @@ private static String[] getModules() throws IOException {
         return modules.toArray(new String[0]);
     }
 
-    private static void copyProjDb() throws IOException {
+    private static void copyProjDb(String destPath) throws IOException {
         try (InputStream in = NativeLibraryLoader.class.getResourceAsStream("/" + PROJ_DB_PATH)) {
             Objects.requireNonNull(in, String.format("Resource as stream for '%s' is null", PROJ_DB_PATH));
-            Files.createDirectories(Paths.get(TEMP_PATH_FOR_PROJ_DATA));
-            String destPath = TEMP_PATH_FOR_PROJ_DATA + "/proj.db";
             Files.copy(in, Paths.get(destPath), StandardCopyOption.REPLACE_EXISTING);
             System.out.printf("JNIGdalLoader java: Copied resource at %s to %s\n", PROJ_DB_PATH, destPath);
         }
     }
 
+    private static void cleanUpOnShutdown() {
+        Runtime.getRuntime().addShutdownHook(new Thread(() -> {
+            try {
+                cleanUp();
+            } catch (IOException ex) {
+                System.err.printf("Could not clean-up TEMP_PATH_FOR_PROJ_DATA '%s'. Error: %s [%s]%n", TEMP_PATH_FOR_PROJ_DATA, ex.getClass(), ex.getMessage());
+                ex.printStackTrace();
+            }
+        }));
+    }
+
+    private static void cleanUp() throws IOException {
+        Files.delete(Paths.get(TEMP_PATH_FOR_PROJ_DATA + "/proj.db"));
+        TEMP_PATH_FOR_PROJ_DATA.delete();
+    }
+
 }

src/main/java/com/github/reasy/gdal/LibC.java

@@ -0,0 +1,7 @@
+package com.github.reasy.gdal;
+
+import com.sun.jna.Library;
+
+public interface LibC extends Library {
+    int setenv(String name, String value, int overwrite);
+}