NIFI-6682 SplitJson does not work if the input is null

This closes #3772

Signed-off-by: Mike Thomsen <mthomsen@apache.org>

nifi-nar-bundles/nifi-standard-bundle/nifi-standard-processors/src/main/java/org/apache/nifi/processors/standard/AbstractJsonPathProcessor.java

@@ -18,6 +18,7 @@ package org.apache.nifi.processors.standard;
 
 import com.jayway.jsonpath.Configuration;
 import com.jayway.jsonpath.DocumentContext;
+import com.jayway.jsonpath.InvalidJsonException;
 import com.jayway.jsonpath.JsonPath;
 import com.jayway.jsonpath.spi.json.JacksonJsonProvider;
 import com.jayway.jsonpath.spi.json.JsonProvider;
@@ -79,6 +80,16 @@ public abstract class AbstractJsonPathProcessor extends AbstractProcessor {
                 try (BufferedInputStream bufferedInputStream = new BufferedInputStream(in)) {
                     DocumentContext ctx = JsonPath.using(STRICT_PROVIDER_CONFIGURATION).parse(bufferedInputStream);
                     contextHolder.set(ctx);
+                } catch (IllegalArgumentException iae) {
+                    // The JsonPath.parse() above first parses the json, then creates a context object from the parsed
+                    // json.  It is possible for the json parsing to complete without error, but produce a null object.
+                    // In this case the context creation will fail and throw an IllegalArgumentException.  This is in
+                    // my opinion a bug in the JsonPath library, as it doesn't really throw the correct exception
+                    // contextually.
+                    // The general handling in derived classes handles InvalidJsonException.
+                    // The best thing to do here, is to re-throw with the proper exception, such that the calling logic
+                    // can route.
+                    throw new InvalidJsonException(iae);
                 }
             }
         });

nifi-nar-bundles/nifi-standard-bundle/nifi-standard-processors/src/test/java/org/apache/nifi/processors/standard/TestSplitJson.java

@@ -235,4 +235,23 @@ public class TestSplitJson {
             testRunner.getFlowFilesForRelationship(SplitJson.REL_SPLIT).get(i).assertContentEquals("null");
         }
     }
+
+    @Test
+    public void testSplit_pathToInputStringNullValue() throws Exception {
+        final TestRunner testRunner = TestRunners.newTestRunner(new SplitJson());
+        testRunner.setProperty(SplitJson.ARRAY_JSON_PATH_EXPRESSION, "$.*");
+        ProcessSession session = testRunner.getProcessSessionFactory().createSession();
+        FlowFile ff = session.create();
+        ff = session.write(ff, new OutputStreamCallback() {
+            @Override
+            public void process(OutputStream out) throws IOException {
+                try (OutputStream outputStream = new BufferedOutputStream(out)) {
+                    outputStream.write("null".getBytes(StandardCharsets.UTF_8));
+                }
+            }
+        });
+        testRunner.enqueue(ff);
+        testRunner.run();
+        testRunner.assertTransferCount(SplitJson.REL_FAILURE, 1);
+    }
 }