handle indefinite results in JsonPath transformations

...as JsonPath may return a List if multiple elements matched, even if they were correctly filtered down to a single element. fixes eclipse-archived#4862 Signed-off-by: Simon Kaufmann <simon.kfm@googlemail.com>
sjsf · Jan 19, 2018 · 4d520d7 · 4d520d7
1 parent 0cc5fb1
commit 4d520d7
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diff --git a/.../org/eclipse/smarthome/transform/jsonpath/internal/JSonPathTransformationServiceTest.java b/.../org/eclipse/smarthome/transform/jsonpath/internal/JSonPathTransformationServiceTest.java
@@ -80,4 +80,22 @@ public void testNullValue() throws TransformationException {
         assertEquals("NULL", transformedResponse);
     }
 
+    @Test
+    public void testIndefinite_filteredToSingle() throws TransformationException {
+        String transformedResponse = processor.transform("$.*[?(@.name=='bob')].id", jsonArray);
+        assertEquals("1", transformedResponse);
+    }
+
+    @Test
+    public void testIndefinite_notFiltered() throws TransformationException {
+        String transformedResponse = processor.transform("$.*.id", jsonArray);
+        assertEquals("NULL", transformedResponse);
+    }
+
+    @Test
+    public void testIndefinite_noMatch() throws TransformationException {
+        String transformedResponse = processor.transform("$.*[?(@.name=='unknown')].id", jsonArray);
+        assertEquals("NULL", transformedResponse);
+    }
+
 }
diff --git a/...java/org/eclipse/smarthome/transform/jsonpath/internal/JSonPathTransformationService.java b/...java/org/eclipse/smarthome/transform/jsonpath/internal/JSonPathTransformationService.java
@@ -12,6 +12,8 @@
  */
 package org.eclipse.smarthome.transform.jsonpath.internal;
 
+import java.util.List;
+
 import org.eclipse.smarthome.core.transform.TransformationException;
 import org.eclipse.smarthome.core.transform.TransformationService;
 import org.eclipse.smarthome.core.types.UnDefType;
@@ -55,7 +57,13 @@ public String transform(String jsonPathExpression, String source) throws Transfo
         try {
             Object transformationResult = JsonPath.read(source, jsonPathExpression);
             logger.debug("transformation resulted in '{}'", transformationResult);
-            return (transformationResult != null) ? transformationResult.toString() : UnDefType.NULL.toFullString();
+            if (transformationResult == null) {
+                return UnDefType.NULL.toFullString();
+            } else if (transformationResult instanceof List) {
+                return flattenList((List<?>) transformationResult);
+            } else {
+                return transformationResult.toString();
+            }
         } catch (PathNotFoundException e) {
             throw new TransformationException("Invalid path '" + jsonPathExpression + "' in '" + source + "'");
         } catch (InvalidPathException | InvalidJsonException e) {
@@ -64,4 +72,14 @@ public String transform(String jsonPathExpression, String source) throws Transfo
 
     }
 
+    private String flattenList(List<?> list) {
+        if (list.size() == 1) {
+            return list.get(0).toString();
+        }
+        if (list.size() > 1) {
+            logger.warn("The JsonPath expression yielded more than one result: {}", list);
+        }
+        return UnDefType.NULL.toFullString();
+    }
+
 }