Merge pull request #478 from BenFradet/issue/438

Do not map non-existing values, fixes #438

json-path/src/main/java/com/jayway/jsonpath/internal/PathRef.java

@@ -298,9 +298,11 @@ public abstract class PathRef implements Comparable<PathRef>  {
         public void convert(MapFunction mapFunction, Configuration configuration) {
             for (String property : properties) {
                 Object currentValue = configuration.jsonProvider().getMapValue(parent, property);
+                if (currentValue != JsonProvider.UNDEFINED) {
                     configuration.jsonProvider().setProperty(parent, property, mapFunction.map(currentValue, configuration));
                 }
             }
+        }
 
         public void delete(Configuration configuration){
             for (String property : properties) {

json-path/src/test/java/com/jayway/jsonpath/JacksonJsonNodeJsonProviderTest.java

@@ -3,9 +3,13 @@ package com.jayway.jsonpath;
 import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
 import com.fasterxml.jackson.databind.node.ArrayNode;
 import com.fasterxml.jackson.databind.node.JsonNodeFactory;
 import com.fasterxml.jackson.databind.node.ObjectNode;
+import com.jayway.jsonpath.spi.json.JacksonJsonNodeJsonProvider;
+import com.jayway.jsonpath.spi.mapper.JacksonMappingProvider;
 import com.jayway.jsonpath.spi.mapper.MappingException;
 import org.junit.Test;
 
@@ -113,6 +117,31 @@ public class JacksonJsonNodeJsonProviderTest extends BaseTest {
         using(JACKSON_JSON_NODE_CONFIGURATION).parse(JSON).read("$", typeRef);
     }
 
+    @Test
+    public void mapPropertyWithPOJO() {
+        String someJson = "" +
+                "{\n" +
+                "  \"a\": \"a\",\n" +
+                "  \"b\": \"b\"\n" +
+                "}";
+        ObjectMapper om = new ObjectMapper();
+        om.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
+        Configuration c = Configuration
+                .builder()
+                .mappingProvider(new JacksonMappingProvider())
+                .jsonProvider(new JacksonJsonNodeJsonProvider(om))
+                .build();
+        DocumentContext context = JsonPath.using(c).parse(someJson);
+        String someJsonStr = context.jsonString();
+        DocumentContext altered = context.map("$['a', 'b', 'c']", new MapFunction() {
+            @Override
+            public Object map(Object currentValue, Configuration configuration) {
+                return currentValue;
+            }
+        });
+        assertThat(altered.jsonString()).isEqualTo(someJsonStr);
+    }
+
     @Test
     // https://github.com/json-path/JsonPath/issues/364
     public void setPropertyWithPOJO() {