Issue #265: Prevent JVM crash when wrong datapath given

src/main/java/net/sourceforge/tess4j/ITesseract.java

@@ -136,6 +136,7 @@ default String doOCR(BufferedImage bi, String filename, List<Rectangle> rects) t
      * Sets tessdata path.
      *
      * @param datapath the tessdata path to set
+     * @throws IllegalArgumentException if the given datapath is not an existing directory
      */
     void setDatapath(String datapath);
 

src/main/java/net/sourceforge/tess4j/Tesseract.java

@@ -87,6 +87,10 @@ public Tesseract() {
                 datapath = "./";
             }
         }
+        File datapathFile = new File(datapath);
+        if (!datapathFile.exists() || !datapathFile.isDirectory()) {
+        	throw new IllegalArgumentException("Given datapath " + datapath + " is not an existing directory.");
+        }
     }
 
     /**
@@ -114,6 +118,10 @@ protected TessBaseAPI getHandle() {
      */
     @Override
     public void setDatapath(String datapath) {
+        File datapathFile = new File(datapath);
+        if (!datapathFile.exists() || !datapathFile.isDirectory()) {
+        	throw new IllegalArgumentException("Given datapath " + datapath + " is not an existing directory.");
+        }
         this.datapath = datapath;
     }
 

src/test/java/net/sourceforge/tess4j/TesseractTest.java

@@ -407,4 +407,11 @@ public void testGetOSD() {
         assertEquals("Latin", result.getScriptName());
         assertTrue(result.getScriptConf() > 0);
     }
+
+    @Test
+    public void testSetDatapath() {
+        logger.info("testSetDatapath");
+        IllegalArgumentException e = assertThrows(IllegalArgumentException.class, () ->  instance.setDatapath("non-existent-datapath"));
+        assertEquals("Given datapath non-existent-datapath is not an existing directory.", e.getMessage());
+    }
 }