UseJava: Add RESOURCES with NAMESPACE to add_jar()

add_jar() currently requires (undocumented) that resources be supplied
as relative paths.  The resources *may* then end up in a path which does
not reflect the original path particularly when performing out-of-source
builds.  This change adds a RESOURCE (and NAMESPACE) parameter and a
function to add the names resources into the named namespace within the
jar- and thus address both of these problems.

Fixes: #22101

3 files changed, 56 insertions, 0 deletions

diff --git a/Tests/Java/CMakeLists.txt b/Tests/Java/CMakeLists.txt
index e4f28211c6..1d8d7ac67b 100644
--- a/Tests/Java/CMakeLists.txt
+++ b/Tests/Java/CMakeLists.txt
@@ -17,9 +17,16 @@ add_jar(hello2 @${CMAKE_CURRENT_BINARY_DIR}/java_fileslist)
 # use listing file to specify sources and specify output directory (issue #17316)
 add_jar(hello3 @${CMAKE_CURRENT_BINARY_DIR}/java_fileslist OUTPUT_DIR "${CMAKE_CURRENT_BINARY_DIR}/hello3")
 
+add_jar(ResourceNS
+        SOURCES ResourceNS.java
+        RESOURCES NAMESPACE ns/ns1 HelloWorld.txt
+                  NAMESPACE ns/ns2 HelloWorld.txt) # add a second namespace
+
 add_test (NAME Java.Jar
           COMMAND "${Java_JAVA_EXECUTABLE}" -classpath hello.jar HelloWorld)
 add_test (NAME Java.JarSourceList
           COMMAND "${Java_JAVA_EXECUTABLE}" -classpath hello2.jar HelloWorld)
 add_test (NAME Java.JarSourceListAndOutput
           COMMAND "${Java_JAVA_EXECUTABLE}" -classpath "${CMAKE_CURRENT_BINARY_DIR}/hello3/hello3.jar" HelloWorld)
+add_test (NAME Java.JarResourceNS
+          COMMAND "${Java_JAVA_EXECUTABLE}" -classpath ResourceNS.jar ResourceNS)
diff --git a/Tests/Java/HelloWorld.txt b/Tests/Java/HelloWorld.txt
new file mode 100644
index 0000000000..d7407a1fcb
--- /dev/null
+++ b/Tests/Java/HelloWorld.txt
@@ -0,0 +1 @@
+Hello World !
diff --git a/Tests/Java/ResourceNS.java b/Tests/Java/ResourceNS.java
new file mode 100644
index 0000000000..7289e6ea35
--- /dev/null
+++ b/Tests/Java/ResourceNS.java
@@ -0,0 +1,48 @@
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.BufferedReader;
+import java.io.IOException;
+
+class ResourceNS
+{
+    public static void main(String args[])
+    {
+        ResourceNS res = new ResourceNS();
+        res.displayResourceText();
+    }
+
+    public void displayResourceText()
+    {
+        /*
+         * Since Java SE 9, invoking getResourceXXX on a class in a named
+         * module will only locate the resource in that module, it will
+         * not search the class path as it did in previous release. So when
+         * you use Class.getClassLoader().getResource() it will attempt to
+         * locate the resource in the module containing the ClassLoader,
+         * possibly something like:
+         *      jdk.internal.loader.ClassLoaders.AppClassLoader
+         * which is probably not the module that your resource is in, so it
+         * returns null.
+         *
+         * You have to make java 9+ search for the file in your module.
+         * Do that by changing Class to any class defined in your module in
+         * order to make java use the proper class loader.
+        */
+
+        // Namespaces are relative, use leading '/' for full namespace
+        InputStream is =
+            ResourceNS.class.getResourceAsStream("/ns/ns1/HelloWorld.txt");
+        // C++:    cout << is.readline();    // oh, well !
+        InputStreamReader isr = new InputStreamReader(is);
+        BufferedReader reader = new BufferedReader(isr);
+        String out = "";
+        try{
+            out = reader.readLine();
+        } catch(IOException e) {
+            e.printStackTrace();
+            System.out.println(e);
+        }
+
+        System.out.println(out);
+    }
+}