Merge pull request #377 from Cofinity-X/feature/CXCS-422-create-only-one-font-tmp-file

Write temporary font file when generating diagrams. Fixes #371 .

Author: atextor

core/esmf-aspect-model-document-generators/src/main/java/org/eclipse/esmf/aspectmodel/generator/diagram/AspectModelDiagramGenerator.java

@@ -17,11 +17,14 @@
 import java.awt.FontFormatException;
 import java.awt.GraphicsEnvironment;
 import java.io.ByteArrayOutputStream;
+import java.io.File;
+import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.io.UncheckedIOException;
 import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
 import java.util.Base64;
 import java.util.EnumMap;
 import java.util.List;
@@ -168,8 +171,9 @@ String getInputStreamAsString( final String resource ) {
    private void generatePng( final String dotInput, final OutputStream output ) throws IOException {
       // To make the font available during PNG generation, it needs to be registered
       // in Java Runtime's graphics environment
-      try ( final InputStream fontStream = getInputStream( FONT_FILE ) ) {
-         final Font f = Font.createFont( Font.TRUETYPE_FONT, fontStream );
+      try{
+         final File tmpFontFile = generateTmpFontFile();
+         final Font f = Font.createFont( Font.TRUETYPE_FONT, tmpFontFile );
          final GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
          ge.registerFont( f );
       } catch ( final FontFormatException e ) {
@@ -180,7 +184,17 @@ private void generatePng( final String dotInput, final OutputStream output ) thr
       final Graphviz graphviz = Graphviz.fromGraph( g );
       graphviz.render( guru.nidi.graphviz.engine.Format.PNG ).toOutputStream( output );
    }
-
+   private File generateTmpFontFile() throws IOException {
+      File tempFontFile = new File( System.getProperty( "java.io.tmpdir" ) + File.separator + "aspect-model-diagram.tmp" );
+      if ( !tempFontFile.exists() ){
+         try ( final InputStream fontStream = getInputStream( FONT_FILE );
+              final OutputStream output = new FileOutputStream( tempFontFile, false ) ){
+               fontStream.transferTo( output );
+            }
+      }
+      tempFontFile.deleteOnExit();
+      return  tempFontFile;
+   }
    private String base64EncodeInputStream( final InputStream in ) throws IOException {
       try ( final ByteArrayOutputStream os = new ByteArrayOutputStream() ) {
          final byte[] buffer = new byte[1024];