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Java example source code file (NullObjectAndFieldTest.java)

This example Java source code file (NullObjectAndFieldTest.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

classwithinitializedmembers, classwithmembers, classwithnullwrappedprimitive, classwithobjects, classwithobjectsserializer, exception, gson, gsonbuilder, jvm, my_boolean_default, objectwithfield, override, reflection, string, type, util

The NullObjectAndFieldTest.java Java example source code

/*
 * Copyright (C) 2008 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.gson.functional;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonElement;
import com.google.gson.JsonNull;
import com.google.gson.JsonObject;
import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonSerializationContext;
import com.google.gson.JsonSerializer;
import com.google.gson.common.TestTypes.BagOfPrimitives;
import com.google.gson.common.TestTypes.ClassWithObjects;

import junit.framework.TestCase;

import java.lang.reflect.Type;
import java.util.Collection;

/**
 * Functional tests for the different cases for serializing (or ignoring) null fields and object.
 *
 * @author Inderjeet Singh
 * @author Joel Leitch
 */
public class NullObjectAndFieldTest extends TestCase {
  private GsonBuilder gsonBuilder;

  @Override
  protected void setUp() throws Exception {
    super.setUp();
    gsonBuilder = new GsonBuilder().serializeNulls();
  }

  public void testTopLevelNullObjectSerialization() {
    Gson gson = gsonBuilder.create();
    String actual = gson.toJson(null);
    assertEquals("null", actual);

    actual = gson.toJson(null, String.class);
    assertEquals("null", actual);
  }

  public void testTopLevelNullObjectDeserialization() throws Exception {
    Gson gson = gsonBuilder.create();
    String actual = gson.fromJson("null", String.class);
    assertNull(actual);
  }

  public void testExplicitSerializationOfNulls() {
    Gson gson = gsonBuilder.create();
    ClassWithObjects target = new ClassWithObjects(null);
    String actual = gson.toJson(target);
    String expected = "{\"bag\":null}";
    assertEquals(expected, actual);
  }

  public void testExplicitDeserializationOfNulls() throws Exception {
    Gson gson = gsonBuilder.create();
    ClassWithObjects target = gson.fromJson("{\"bag\":null}", ClassWithObjects.class);
    assertNull(target.bag);
  }
  
  public void testExplicitSerializationOfNullArrayMembers() {
    Gson gson = gsonBuilder.create();
    ClassWithMembers target = new ClassWithMembers();
    String json = gson.toJson(target);
    assertTrue(json.contains("\"array\":null"));
  }
  
  /** 
   * Added to verify http://code.google.com/p/google-gson/issues/detail?id=68
   */
  public void testNullWrappedPrimitiveMemberSerialization() {
    Gson gson = gsonBuilder.serializeNulls().create();
    ClassWithNullWrappedPrimitive target = new ClassWithNullWrappedPrimitive();
    String json = gson.toJson(target);
    assertTrue(json.contains("\"value\":null"));
  }
  
  /** 
   * Added to verify http://code.google.com/p/google-gson/issues/detail?id=68
   */
  public void testNullWrappedPrimitiveMemberDeserialization() {
    Gson gson = gsonBuilder.create();
    String json = "{'value':null}";
    ClassWithNullWrappedPrimitive target = gson.fromJson(json, ClassWithNullWrappedPrimitive.class);
    assertNull(target.value);
  }
  
  public void testExplicitSerializationOfNullCollectionMembers() {
    Gson gson = gsonBuilder.create();
    ClassWithMembers target = new ClassWithMembers();
    String json = gson.toJson(target);
    assertTrue(json.contains("\"col\":null"));
  }
  
  public void testExplicitSerializationOfNullStringMembers() {
    Gson gson = gsonBuilder.create();
    ClassWithMembers target = new ClassWithMembers();
    String json = gson.toJson(target);
    assertTrue(json.contains("\"str\":null"));
  }

  public void testCustomSerializationOfNulls() {
    gsonBuilder.registerTypeAdapter(ClassWithObjects.class, new ClassWithObjectsSerializer());
    Gson gson = gsonBuilder.create();
    ClassWithObjects target = new ClassWithObjects(new BagOfPrimitives());
    String actual = gson.toJson(target);
    String expected = "{\"bag\":null}";
    assertEquals(expected, actual);
  }
  
  public void testPrintPrintingObjectWithNulls() throws Exception {
    gsonBuilder = new GsonBuilder();
    Gson gson = gsonBuilder.create();
    String result = gson.toJson(new ClassWithMembers());
    assertEquals("{}", result);

    gson = gsonBuilder.serializeNulls().create();
    result = gson.toJson(new ClassWithMembers());
    assertTrue(result.contains("\"str\":null"));
  }
  
  public void testPrintPrintingArraysWithNulls() throws Exception {
    gsonBuilder = new GsonBuilder();
    Gson gson = gsonBuilder.create();
    String result = gson.toJson(new String[] { "1", null, "3" });
    assertEquals("[\"1\",null,\"3\"]", result);

    gson = gsonBuilder.serializeNulls().create();
    result = gson.toJson(new String[] { "1", null, "3" });
    assertEquals("[\"1\",null,\"3\"]", result);
  }

  // test for issue 389
  public void testAbsentJsonElementsAreSetToNull() {
    Gson gson = new Gson();
    ClassWithInitializedMembers target =
        gson.fromJson("{array:[1,2,3]}", ClassWithInitializedMembers.class);
    assertTrue(target.array.length == 3 && target.array[1] == 2);
    assertEquals(ClassWithInitializedMembers.MY_STRING_DEFAULT, target.str1);
    assertNull(target.str2);
    assertEquals(ClassWithInitializedMembers.MY_INT_DEFAULT, target.int1);
    assertEquals(0, target.int2); // test the default value of a primitive int field per JVM spec
    assertEquals(ClassWithInitializedMembers.MY_BOOLEAN_DEFAULT, target.bool1);
    assertFalse(target.bool2); // test the default value of a primitive boolean field per JVM spec
  }

  public static class ClassWithInitializedMembers  {
    // Using a mix of no-args constructor and field initializers
    // Also, some fields are intialized and some are not (so initialized per JVM spec)
    public static final String MY_STRING_DEFAULT = "string";
    private static final int MY_INT_DEFAULT = 2;
    private static final boolean MY_BOOLEAN_DEFAULT = true;
    int[] array;
    String str1, str2;
    int int1 = MY_INT_DEFAULT;
    int int2;
    boolean bool1 = MY_BOOLEAN_DEFAULT;
    boolean bool2;
    public ClassWithInitializedMembers() {
      str1 = MY_STRING_DEFAULT;
    }
  }

  private static class ClassWithNullWrappedPrimitive {
    private Long value;
  }

  @SuppressWarnings("unused")
  private static class ClassWithMembers {
    String str;
    int[] array;
    Collection<String> col;
  }
  
  private static class ClassWithObjectsSerializer implements JsonSerializer<ClassWithObjects> {
    @Override public JsonElement serialize(ClassWithObjects src, Type typeOfSrc,
        JsonSerializationContext context) {
      JsonObject obj = new JsonObject();
      obj.add("bag", JsonNull.INSTANCE);
      return obj;
    }
  }

  public void testExplicitNullSetsFieldToNullDuringDeserialization() {
    Gson gson = new Gson();
    String json = "{value:null}";
    ObjectWithField obj = gson.fromJson(json, ObjectWithField.class);
    assertNull(obj.value);    
  }

  public void testCustomTypeAdapterPassesNullSerialization() {
    Gson gson = new GsonBuilder()
        .registerTypeAdapter(ObjectWithField.class, new JsonSerializer<ObjectWithField>() {
          @Override public JsonElement serialize(ObjectWithField src, Type typeOfSrc,
              JsonSerializationContext context) {
            return context.serialize(null);
          }
        }).create();
    ObjectWithField target = new ObjectWithField();
    target.value = "value1";
    String json = gson.toJson(target);
    assertFalse(json.contains("value1"));
  }

  public void testCustomTypeAdapterPassesNullDesrialization() {
    Gson gson = new GsonBuilder()
        .registerTypeAdapter(ObjectWithField.class, new JsonDeserializer<ObjectWithField>() {
          @Override public ObjectWithField deserialize(JsonElement json, Type type,
              JsonDeserializationContext context) {
            return context.deserialize(null, type);
          }
        }).create();
    String json = "{value:'value1'}";
    ObjectWithField target = gson.fromJson(json, ObjectWithField.class);
    assertNull(target);
  }

  private static class ObjectWithField {
    String value = "";
  }
}

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