resolver: attempt to get a known System ID when the supplied System ID is unknown but the Public ID is known

Author: carlosame

junit/io/sf/carte/doc/xml/dtd/DefaultEntityResolverTest.java

@@ -161,6 +161,19 @@ public void resolveEntityStringStringSVG10() throws SAXException, IOException {
 		re.close();
 	}
 
+	@Test
+	public void resolveEntityStringStringSVG10_WrongSystemID() throws SAXException, IOException {
+		InputSource isrc = resolver.resolveEntity("-//W3C//DTD SVG 1.0//EN",
+				"http://www.w3.org/TR/SVG/DTD/svg10.dtd");
+		assertNotNull(isrc);
+		assertEquals("-//W3C//DTD SVG 1.0//EN", isrc.getPublicId());
+		assertEquals("http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd",
+				isrc.getSystemId());
+		Reader re = isrc.getCharacterStream();
+		assertNotNull(re);
+		re.close();
+	}
+
 	@Test
 	public void resolveEntityStringStringRemoteDisallow() throws SAXException, IOException {
 		assertThrows(SAXException.class,
@@ -171,7 +184,7 @@ public void resolveEntityStringStringRemoteDisallow() throws SAXException, IOExc
 	@Test
 	public void resolveEntityStringStringRemoteDisallowConstructor1Arg()
 		throws SAXException, IOException {
-		assertThrows(SAXException.class, () -> resolver.resolveEntity("-//W3C//DTD SVG 1.1//EN",
+		assertThrows(SAXException.class, () -> resolver.resolveEntity("-//W3C//DTD SVG 0.9//EN",
 			"https://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd"));
 	}
 

src/io/sf/carte/doc/xml/dtd/DefaultEntityResolver.java

@@ -492,6 +492,15 @@ public InputSource resolveEntity(String name, String publicId, String baseURI, S
 		}
 		String fname = systemIdToFilename.get(systemId);
 
+		if (fname == null && publicId != null) {
+			// Attempt to get a known DTD by Public ID
+			String knownSystemId = getSystemIdFromPublicId(publicId);
+			if (knownSystemId != null) {
+				fname = systemIdToFilename.get(knownSystemId);
+				systemId = knownSystemId;
+			}
+		}
+
 		InputSource isrc = null;
 		if (fname != null) {
 			Reader re = dtdLoader.loadDTDfromClasspath(loader, fname);