Add parser for Optional types to avoid the null madness

src/main/java/com/suse/saltstack/netapi/parser/JsonParser.java

@@ -8,6 +8,7 @@
 import com.google.gson.JsonObject;
 import com.google.gson.JsonParseException;
 import com.google.gson.TypeAdapter;
+import com.google.gson.TypeAdapterFactory;
 import com.google.gson.reflect.TypeToken;
 import com.google.gson.stream.JsonReader;
 import com.google.gson.stream.JsonToken;
@@ -31,9 +32,11 @@
 import java.io.InputStreamReader;
 import java.io.Reader;
 import java.lang.reflect.Type;
+import java.lang.reflect.ParameterizedType;
 import java.util.Date;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 
 /**
  * Parser for Saltstack responses.
@@ -79,6 +82,7 @@ public JsonParser(TypeToken<T> type) {
                 .registerTypeAdapter(StartTime.class, new StartTimeAdapter().nullSafe())
                 .registerTypeAdapter(Stats.class, new StatsDeserializer())
                 .registerTypeAdapter(Arguments.class, new ArgumentsDeserializer())
+                .registerTypeAdapterFactory(new OptionalTypeAdapterFactory())
                 .create();
     }
 
@@ -126,6 +130,47 @@ public Date read(JsonReader jsonReader) throws IOException {
         }
     }
 
+    /**
+     * TypeAdaptorFactory creating TypeAdapters for Optional
+     */
+    private class OptionalTypeAdapterFactory implements TypeAdapterFactory {
+
+        @Override
+        @SuppressWarnings("unchecked")
+        public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
+            Type type = typeToken.getType();
+            boolean isOptional = typeToken.getRawType() == Optional.class;
+            boolean isParameterized = type instanceof ParameterizedType;
+            if (isOptional && isParameterized) {
+                Type elementType = ((ParameterizedType) type).getActualTypeArguments()[0];
+                TypeAdapter<?> elementAdapter = gson.getAdapter(TypeToken.get(elementType));
+                return (TypeAdapter<T>) optionalAdapter(elementAdapter);
+            } else {
+                return null;
+            }
+        }
+
+        private <A> TypeAdapter<Optional<A>> optionalAdapter(TypeAdapter<A> innerAdapter) {
+            return new TypeAdapter<Optional<A>>() {
+                @Override
+                public Optional<A> read(JsonReader in) throws IOException {
+                    if (in.peek() == JsonToken.NULL) {
+                        in.nextNull();
+                        return Optional.empty();
+                    } else {
+                        A value = innerAdapter.read(in);
+                        return Optional.of(value);
+                    }
+                }
+
+                @Override
+                public void write(JsonWriter out, Optional<A> optional) throws IOException {
+                    innerAdapter.write(out, optional.orElse(null));
+                }
+            };
+        }
+    }
+
     /**
      * Deserializer for the Stats object received from the API.
      */

src/test/java/com/suse/saltstack/netapi/parser/JsonParserTest.java

@@ -2,6 +2,7 @@
 
 import com.google.gson.JsonParseException;
 import com.suse.saltstack.netapi.calls.wheel.Key;
+import com.google.gson.reflect.TypeToken;
 import com.suse.saltstack.netapi.datatypes.Arguments;
 import com.suse.saltstack.netapi.datatypes.Job;
 import com.suse.saltstack.netapi.datatypes.ScheduledJob;
@@ -14,7 +15,9 @@
 import com.suse.saltstack.netapi.datatypes.Token;
 import java.util.Date;
 import java.util.Arrays;
+import java.util.Optional;
 import java.util.LinkedHashMap;
+import java.util.LinkedList;
 import java.util.Map;
 import org.junit.Test;
 
@@ -24,6 +27,7 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertFalse;
 
 /**
  * Json parser unit tests.
@@ -202,6 +206,39 @@ public void testSaltStackJobsWithKwargsParser() throws Exception {
         assertEquals("lucid", job.getUser());
     }
 
+    @Test
+    public void testOptionalParser() {
+        InputStream is = this.getClass()
+                .getResourceAsStream("/optional_parser_test.json");
+        JsonParser<OptionalTest> parser = new JsonParser<>(new TypeToken<OptionalTest>(){});
+        OptionalTest result = parser.parse(is);
+        assertFalse(result.nullString.isPresent());
+        assertFalse(result.absentString.isPresent());
+        result.valueString.ifPresent((value) ->
+                assertEquals("string with value", value)
+        );
+        List<Optional<Integer>> expected = new LinkedList<>();
+        expected.add(Optional.of(1));
+        expected.add(Optional.of(2));
+        expected.add(Optional.of(3));
+        expected.add(Optional.empty());
+        expected.add(Optional.of(5));
+        assertEquals(expected, result.maybeInts);
+    }
+
+    @Test
+    public void testOptionalSingleValue() {
+        JsonParser<Optional<Integer>> parser =
+                new JsonParser<>(new TypeToken<Optional<Integer>>(){});
+        InputStream nullValue = this.getClass()
+                .getResourceAsStream("/single_null_value.json");
+        assertFalse(parser.parse(nullValue).isPresent());
+
+        InputStream intValue = this.getClass()
+                .getResourceAsStream("/single_int_value.json");
+        assertEquals(new Integer(123), parser.parse(intValue).get());
+    }
+
     @Test
     public void testSaltStackJobsWithArgsAsKwargsParser() throws Exception {
         InputStream is = this.getClass()

src/test/java/com/suse/saltstack/netapi/parser/OptionalTest.java

@@ -0,0 +1,15 @@
+package com.suse.saltstack.netapi.parser;
+
+import java.util.Optional;
+import java.util.List;
+
+/**
+ * Helper Type to test the Optional Parser
+ */
+public class OptionalTest {
+
+    public Optional<String> nullString = Optional.empty();
+    public Optional<String> valueString = Optional.empty();
+    public Optional<String> absentString = Optional.empty();
+    public List<Optional<Integer>> maybeInts;
+}

src/test/resources/optional_parser_test.json

@@ -0,0 +1,5 @@
+{
+  "nullString": null,
+  "valueString": "string with value",
+  "maybeInts": [1, 2, 3, null, 5]
+}

src/test/resources/single_int_value.json

@@ -0,0 +1 @@
+123

src/test/resources/single_null_value.json

@@ -0,0 +1 @@
+null