further gson testing work

Author: eugenp

gson/README.md

@@ -1,12 +1,6 @@
 =========
 
-## Jackson Cookbooks and Examples
+## GSON Cookbooks and Examples
 
 ### Relevant Articles: 
-- [Jackson Ignore Properties on Marshalling](http://www.baeldung.com/jackson-ignore-properties-on-serialization)
-- [Jackson – Unmarshall to Collection/Array](http://www.baeldung.com/jackson-collection-array)
-- [Jackson Unmarshalling json with Unknown Properties](http://www.baeldung.com/jackson-deserialize-json-unknown-properties)
-- [Jackson – Custom Serializer](http://www.baeldung.com/jackson-custom-serialization)
-- [Jackson – Custom Deserializer](http://www.baeldung.com/jackson-deserialization)
-
 

gson/pom.xml

@@ -41,7 +41,7 @@
 		<dependency>
 			<groupId>com.google.code.gson</groupId>
 			<artifactId>gson</artifactId>
-			<version>2.3</version>
+			<version>${gson.version}</version>
 		</dependency>
 
 		<!-- test scoped -->
@@ -76,7 +76,7 @@
 	</dependencies>
 
 	<build>
-		<finalName>jackson</finalName>
+		<finalName>gson</finalName>
 		<resources>
 			<resource>
 				<directory>src/main/resources</directory>
@@ -116,7 +116,7 @@
 		<mysql-connector-java.version>5.1.31</mysql-connector-java.version>
 
 		<!-- marshalling -->
-		<jackson.version>2.4.1</jackson.version>
+		<gson.version>2.3</gson.version>
 
 		<!-- logging -->
 		<org.slf4j.version>1.7.7</org.slf4j.version>

gson/src/test/java/org/baeldung/gson/deserialization/GenericSourceClass.java

@@ -0,0 +1,18 @@
+package org.baeldung.gson.deserialization;
+
+public class GenericTargetClass<INTEGER> {
+
+    public INTEGER intField;
+
+    GenericTargetClass(final INTEGER value) {
+        intField = value;
+    }
+
+    //
+
+    @Override
+    public String toString() {
+        return "GenericTargetClass{" + "intField=" + intField + '}';
+    }
+
+}

gson/src/test/java/org/baeldung/gson/deserialization/GenericTargetClass.java

@@ -0,0 +1,32 @@
+package org.baeldung.gson.deserialization;
+
+public class SourceClass {
+    int intValue;
+    String stringValue;
+
+    public SourceClass(int intValue, String stringValue) {
+        this.intValue = intValue;
+        this.stringValue = stringValue;
+    }
+
+    @Override
+    public String toString() {
+        return "SourceClass{" +
+                "intValue=" + intValue +
+                ", stringValue='" + stringValue + '\'' +
+                '}';
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (!(o instanceof SourceClass)) return false;
+
+        SourceClass that = (SourceClass) o;
+
+        if (intValue != that.intValue) return false;
+        if (!stringValue.equals(that.stringValue)) return false;
+
+        return true;
+    }
+}

gson/src/test/java/org/baeldung/gson/deserialization/SourceClass.java

@@ -0,0 +1,25 @@
+package org.baeldung.gson.deserialization;
+
+import com.google.gson.JsonArray;
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonParseException;
+
+import java.lang.reflect.Type;
+
+public class SourceClassDeserializer implements JsonDeserializer<SourceClass[]> {
+
+    @Override
+    public SourceClass[] deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
+        JsonArray jArray = json.getAsJsonArray();
+        SourceClass[] scArray = new SourceClass[jArray.size()];
+        int index = 0;
+        for (JsonElement jElement : jArray) {
+            int i = jElement.getAsJsonObject().get("intValue").getAsInt();
+            String s = jElement.getAsJsonObject().get("stringValue").getAsString();
+            scArray[index++] = new SourceClass(i, s);
+        }
+        return scArray;
+    }
+}

gson/src/test/java/org/baeldung/gson/deserialization/SourceClassDeserializer.java

@@ -0,0 +1,19 @@
+package org.baeldung.gson.deserialization;
+
+public class TargetClass {
+    public int intValue;
+    public String stringValue;
+
+    public TargetClass(final int intValue, final String stringValue) {
+        this.intValue = intValue;
+        this.stringValue = stringValue;
+    }
+
+    // API
+
+    @Override
+    public String toString() {
+        return "TargetClass{" + "intValue= " + intValue + ", stringValue= " + stringValue + '}';
+    }
+
+}

gson/src/test/java/org/baeldung/gson/deserialization/TargetClass.java

@@ -0,0 +1,21 @@
+package org.baeldung.gson.deserialization;
+
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParseException;
+
+import java.lang.reflect.Type;
+
+
+public class TargetClassDeserializer implements JsonDeserializer<TargetClass> {
+
+    @Override
+    public TargetClass deserialize(JsonElement jElement, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
+        JsonObject jObject = jElement.getAsJsonObject();
+        int intValue = jObject.get("valueInt").getAsInt();
+        String stringValue = jObject.get("valueString").getAsString();
+        return new TargetClass(intValue, stringValue);
+    }
+}

gson/src/test/java/org/baeldung/gson/deserialization/TargetClassDeserializer.java

@@ -0,0 +1,98 @@
+package org.baeldung.gson.deserialization.test;
+
+import static org.hamcrest.Matchers.instanceOf;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThat;
+
+import java.lang.reflect.Type;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.List;
+
+import org.baeldung.gson.deserialization.GenericTargetClass;
+import org.baeldung.gson.deserialization.SourceClass;
+import org.baeldung.gson.deserialization.SourceClassDeserializer;
+import org.baeldung.gson.deserialization.TargetClass;
+import org.baeldung.gson.deserialization.TargetClassDeserializer;
+import org.junit.Test;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+import com.google.gson.reflect.TypeToken;
+
+public class GsonDeserializationTest {
+
+    @Test
+    public void givenJsonHasDissimilarFieldNamesButGsonMapsRight_whenUsingCustomDeserializer_thenCorrect() {
+        final String jsonSourceObject = "{\"valueInt\":7,\"valueString\":\"seven\"}";
+        final GsonBuilder gsonBldr = new GsonBuilder();
+        gsonBldr.registerTypeAdapter(TargetClass.class, new TargetClassDeserializer());
+        final Gson gson = gsonBldr.create();
+        final TargetClass targetObject = gson.fromJson(jsonSourceObject, TargetClass.class);
+
+        assertEquals(targetObject.intValue, 7);
+        assertEquals(targetObject.stringValue, "seven");
+    }
+
+    @Test
+    public void givenJsonWithArray_whenUsingGsonCustomDeserializer_thenMapsToArrayList() {
+        // It is necessary to override the equals() method in SourceClass
+        final String jsonSourceObject = "[{\"intValue\":1,\"stringValue\":\"one\"},{\"intValue\":2,\"stringValue\":\"two\"}]";
+        final GsonBuilder gsonBldr = new GsonBuilder();
+        gsonBldr.registerTypeHierarchyAdapter(SourceClass[].class, new SourceClassDeserializer());
+        final Gson gson = gsonBldr.create();
+
+        final List<SourceClass> targetList = Arrays.asList(gson.fromJson(jsonSourceObject, SourceClass[].class));
+
+        assertEquals(new SourceClass(1, "one"), targetList.get(0));
+    }
+
+    @Test
+    public void givenJsonHasDissimilarFieldNamesButGsonMapsRight_whenDeserializingManualy_thenCorrect() {
+        final String jsonSourceObject = "{\"valueInt\":7,\"valueString\":\"seven\"}";
+        final JsonParser jParser = new JsonParser();
+        final JsonElement jElement = jParser.parse(jsonSourceObject);
+        final JsonObject jObject = jElement.getAsJsonObject();
+        final int intValue = jObject.get("valueInt").getAsInt();
+        final String stringValue = jObject.get("valueString").getAsString();
+
+        final TargetClass targetObject = new TargetClass(intValue, stringValue);
+
+        assertEquals(targetObject.intValue, 7);
+        assertEquals(targetObject.stringValue, "seven");
+    }
+
+    @Test
+    public void givenJsonHasExtraValuesButGsonIsIgnoringExtras_whenDeserializing_thenCorrect() {
+        final String serializedSourceObject = "{\"intValue\":1,\"stringValue\":\"one\",\"extraString\":\"two\",\"extraFloat\":2.2}";
+        final TargetClass targetObject = new Gson().fromJson(serializedSourceObject, TargetClass.class);
+
+        assertEquals(targetObject.intValue, 1);
+        assertEquals(targetObject.stringValue, "one");
+    }
+
+    @Test
+    public void givenUsingGson_whenDeserializingGeneric_thenCorrect() {
+        final Type genericTargetClassType = new TypeToken<GenericTargetClass<Integer>>() {
+        }.getType();
+        final String serializedSourceObject = "{\"intField\":1}";
+
+        final GenericTargetClass<Integer> targetObject = new Gson().fromJson(serializedSourceObject, genericTargetClassType);
+
+        assertEquals(targetObject.intField, new Integer(1));
+    }
+
+    @Test
+    public void givenUsingGson_whenDeserializingCollection_thenCorrect() {
+        final String serializedSourceCollection = "[{\"intValue\":1,\"stringValue\":\"one\"},{\"intValue\":2,\"stringValue\":\"two\"}]";
+        final Type targetClassType = new TypeToken<ArrayList<TargetClass>>() {
+        }.getType();
+
+        final Collection<TargetClass> targetCollection = new Gson().fromJson(serializedSourceCollection, targetClassType);
+        assertThat(targetCollection, instanceOf(ArrayList.class));
+    }
+}