gson advanced list examples
This commit is contained in:
Ganesh Pagade
parent
00c115229b
commit
c2cb4d4bc0
|
|
@ -0,0 +1,5 @@
|
|||
package org.baeldung.gson.entities;
|
||||
|
||||
public abstract class Animal {
|
||||
public String type = "Animal";
|
||||
}
|
||||
|
|
@ -0,0 +1,19 @@
|
|||
package org.baeldung.gson.entities;
|
||||
|
||||
public class Cow extends Animal {
|
||||
private String breed;
|
||||
|
||||
public Cow() {
|
||||
breed = "Jersey";
|
||||
type = "Cow";
|
||||
}
|
||||
|
||||
public String getBreed() {
|
||||
return breed;
|
||||
}
|
||||
|
||||
public void setBreed(String breed) {
|
||||
this.breed = breed;
|
||||
}
|
||||
}
|
||||
|
||||
|
|
@ -0,0 +1,18 @@
|
|||
package org.baeldung.gson.entities;
|
||||
|
||||
public class Dog extends Animal {
|
||||
private String petName;
|
||||
|
||||
public Dog() {
|
||||
petName = "Milo";
|
||||
type = "Dog";
|
||||
}
|
||||
|
||||
public String getPetName() {
|
||||
return petName;
|
||||
}
|
||||
|
||||
public void setPetName(String petName) {
|
||||
this.petName = petName;
|
||||
}
|
||||
}
|
||||
|
|
@ -0,0 +1,37 @@
|
|||
package org.baeldung.gson.entities;
|
||||
|
||||
public class MyClass {
|
||||
private int id;
|
||||
private String[] strings;
|
||||
|
||||
public MyClass() {
|
||||
id = 1;
|
||||
strings = new String[] { "a", "b" };
|
||||
}
|
||||
|
||||
|
||||
// @Override
|
||||
// public String toString() {
|
||||
// return "{" +
|
||||
// "id=" + id +
|
||||
// ", name='" + name + '\'' +
|
||||
// ", strings=" + Arrays.toString(strings) +
|
||||
// '}';
|
||||
// }
|
||||
|
||||
public int getId() {
|
||||
return id;
|
||||
}
|
||||
|
||||
public void setId(int id) {
|
||||
this.id = id;
|
||||
}
|
||||
|
||||
public String[] getStrings() {
|
||||
return strings;
|
||||
}
|
||||
|
||||
public void setStrings(String[] strings) {
|
||||
this.strings = strings;
|
||||
}
|
||||
}
|
||||
|
|
@ -0,0 +1,35 @@
|
|||
package org.baeldung.gson.serialization;
|
||||
|
||||
import com.google.gson.Gson;
|
||||
import com.google.gson.JsonDeserializationContext;
|
||||
import com.google.gson.JsonDeserializer;
|
||||
import com.google.gson.JsonElement;
|
||||
import com.google.gson.JsonObject;
|
||||
import java.lang.reflect.Type;
|
||||
import java.util.HashMap;
|
||||
import java.util.Map;
|
||||
import org.baeldung.gson.entities.Animal;
|
||||
|
||||
public class AnimalDeserializer implements JsonDeserializer<Animal> {
|
||||
private String animalTypeElementName;
|
||||
private Gson gson;
|
||||
private Map<String, Class<? extends Animal>> animalTypeRegistry;
|
||||
|
||||
public AnimalDeserializer(String animalTypeElementName) {
|
||||
this.animalTypeElementName = animalTypeElementName;
|
||||
this.gson = new Gson();
|
||||
this.animalTypeRegistry = new HashMap<>();
|
||||
}
|
||||
|
||||
public void registerBarnType(String animalTypeName, Class<? extends Animal> animalType) {
|
||||
animalTypeRegistry.put(animalTypeName, animalType);
|
||||
}
|
||||
|
||||
public Animal deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) {
|
||||
JsonObject animalObject = json.getAsJsonObject();
|
||||
JsonElement animalTypeElement = animalObject.get(animalTypeElementName);
|
||||
|
||||
Class<? extends Animal> animalType = animalTypeRegistry.get(animalTypeElement.getAsString());
|
||||
return gson.fromJson(animalObject, animalType);
|
||||
}
|
||||
}
|
||||
|
|
@ -0,0 +1,110 @@
|
|||
package org.baeldung.gson.advance;
|
||||
|
||||
import static org.junit.Assert.assertEquals;
|
||||
import static org.junit.Assert.assertTrue;
|
||||
|
||||
import com.google.gson.Gson;
|
||||
import com.google.gson.GsonBuilder;
|
||||
import com.google.gson.reflect.TypeToken;
|
||||
import java.lang.reflect.Type;
|
||||
import java.util.ArrayList;
|
||||
import java.util.List;
|
||||
import org.baeldung.gson.entities.Animal;
|
||||
import org.baeldung.gson.entities.Cow;
|
||||
import org.baeldung.gson.entities.Dog;
|
||||
import org.baeldung.gson.entities.MyClass;
|
||||
import org.baeldung.gson.serialization.AnimalDeserializer;
|
||||
import org.junit.Test;
|
||||
|
||||
public class GsonAdvanceUnitTest {
|
||||
|
||||
@Test public void givenListOfMyClass_whenSerializing_thenCorrect() {
|
||||
List<MyClass> list = new ArrayList<>();
|
||||
list.add(new MyClass());
|
||||
list.add(new MyClass());
|
||||
|
||||
Gson gson = new Gson();
|
||||
String jsonString = gson.toJson(list);
|
||||
String expectedString = "[{\"id\":1,\"strings\":[\"a\",\"b\"]},{\"id\":1,\"strings\":[\"a\",\"b\"]}]";
|
||||
|
||||
assertEquals(expectedString, jsonString);
|
||||
}
|
||||
|
||||
@Test(expected = ClassCastException.class)
|
||||
public void givenJsonString_whenIncorrectDeserializing_thenThrowClassCastException() {
|
||||
String inputString = "[{\"id\":1,\"strings\":[\"a\",\"b\"]},{\"id\":1,\"strings\":[\"a\",\"b\"]}]";
|
||||
|
||||
Gson gson = new Gson();
|
||||
List<MyClass> list = gson.fromJson(inputString, ArrayList.class);
|
||||
|
||||
assertEquals(2, list.size());
|
||||
int id = list.get(0).getId();
|
||||
}
|
||||
|
||||
@Test public void givenJsonString_whenDeserializing_thenReturnListOfMyClass() {
|
||||
String inputString = "[{\"id\":1,\"strings\":[\"a\",\"b\"]},{\"id\":1,\"strings\":[\"a\",\"b\"]}]";
|
||||
Type listOfMyClassObject = new TypeToken<ArrayList<MyClass>>() {}.getType();
|
||||
|
||||
Gson gson = new Gson();
|
||||
List<MyClass> list = gson.fromJson(inputString, listOfMyClassObject);
|
||||
|
||||
assertEquals(2, list.size());
|
||||
assertEquals(1, list.get(0).getId());
|
||||
}
|
||||
|
||||
@Test public void givenPolymorphicList_whenSerializeWithTypeAdapter_thenCorrect() {
|
||||
String expectedString = "[{\"petName\":\"Milo\",\"type\":\"Dog\"},{\"breed\":\"Jersey\",\"type\":\"Cow\"}]";
|
||||
|
||||
List<Animal> inList = new ArrayList<>();
|
||||
inList.add(new Dog());
|
||||
inList.add(new Cow());
|
||||
|
||||
String jsonString = new Gson().toJson(inList);
|
||||
|
||||
assertEquals(expectedString, jsonString);
|
||||
}
|
||||
|
||||
@Test public void givenPolymorphicList_whenDeserializeWithTypeAdapter_thenCorrect() {
|
||||
String inputString = "[{\"petName\":\"Milo\",\"type\":\"Dog\"},{\"breed\":\"Jersey\",\"type\":\"Cow\"}]";
|
||||
|
||||
AnimalDeserializer deserializer = new AnimalDeserializer("type");
|
||||
deserializer.registerBarnType("Dog", Dog.class);
|
||||
deserializer.registerBarnType("Cow", Cow.class);
|
||||
Gson gson = new GsonBuilder()
|
||||
.registerTypeAdapter(Animal.class, deserializer)
|
||||
.create();
|
||||
|
||||
List<Animal> outList = gson.fromJson(inputString, new TypeToken<List<Animal>>(){}.getType());
|
||||
|
||||
assertEquals(2, outList.size());
|
||||
assertTrue(outList.get(0) instanceof Dog);
|
||||
}
|
||||
|
||||
@Test public void givenPolymorphicList_whenSerializeWithRuntimeTypeAdapter_thenCorrect() {
|
||||
String expectedString = "[{\"petName\":\"Milo\",\"type\":\"Dog\"},{\"breed\":\"Jersey\",\"type\":\"Cow\"}]";
|
||||
|
||||
List<Animal> inList = new ArrayList<>();
|
||||
inList.add(new Dog());
|
||||
inList.add(new Cow());
|
||||
String jsonString = new Gson().toJson(inList);
|
||||
|
||||
assertEquals(expectedString, jsonString);
|
||||
}
|
||||
|
||||
@Test public void givenPolymorphicList_whenDeserializeWithRuntimeTypeAdapter_thenCorrect() {
|
||||
String inputString = "[{\"petName\":\"Milo\",\"type\":\"Dog\"},{\"breed\":\"Jersey\",\"type\":\"Cow\"}]";
|
||||
|
||||
Type listOfAnimals = new TypeToken<ArrayList<Animal>>() {}.getType();
|
||||
|
||||
RuntimeTypeAdapterFactory<Animal> adapter = RuntimeTypeAdapterFactory.of(Animal.class)
|
||||
.registerSubtype(Dog.class)
|
||||
.registerSubtype(Cow.class);
|
||||
|
||||
Gson gson = new GsonBuilder().registerTypeAdapterFactory(adapter).create();
|
||||
|
||||
List<Animal> outList = gson.fromJson(inputString, listOfAnimals);
|
||||
|
||||
assertEquals(2, outList.size());
|
||||
assertTrue(outList.get(0) instanceof Dog);
|
||||
}
|
||||
}
|
||||
|
|
@ -0,0 +1,265 @@
|
|||
package org.baeldung.gson.advance;
|
||||
|
||||
/*
|
||||
* Copyright (C) 2011 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.
|
||||
*/
|
||||
|
||||
import java.io.IOException;
|
||||
import java.util.LinkedHashMap;
|
||||
import java.util.Map;
|
||||
|
||||
import com.google.gson.Gson;
|
||||
import com.google.gson.JsonElement;
|
||||
import com.google.gson.JsonObject;
|
||||
import com.google.gson.JsonParseException;
|
||||
import com.google.gson.JsonPrimitive;
|
||||
import com.google.gson.TypeAdapter;
|
||||
import com.google.gson.TypeAdapterFactory;
|
||||
import com.google.gson.internal.Streams;
|
||||
import com.google.gson.reflect.TypeToken;
|
||||
import com.google.gson.stream.JsonReader;
|
||||
import com.google.gson.stream.JsonWriter;
|
||||
|
||||
/**
|
||||
* Adapts values whose runtime type may differ from their declaration type. This
|
||||
* is necessary when a field's type is not the same type that GSON should create
|
||||
* when deserializing that field. For example, consider these types:
|
||||
* <pre> {@code
|
||||
* abstract class Shape {
|
||||
* int x;
|
||||
* int y;
|
||||
* }
|
||||
* class Circle extends Shape {
|
||||
* int radius;
|
||||
* }
|
||||
* class Rectangle extends Shape {
|
||||
* int width;
|
||||
* int height;
|
||||
* }
|
||||
* class Diamond extends Shape {
|
||||
* int width;
|
||||
* int height;
|
||||
* }
|
||||
* class Drawing {
|
||||
* Shape bottomShape;
|
||||
* Shape topShape;
|
||||
* }
|
||||
* }</pre>
|
||||
* <p>Without additional type information, the serialized JSON is ambiguous. Is
|
||||
* the bottom shape in this drawing a rectangle or a diamond? <pre> {@code
|
||||
* {
|
||||
* "bottomShape": {
|
||||
* "width": 10,
|
||||
* "height": 5,
|
||||
* "x": 0,
|
||||
* "y": 0
|
||||
* },
|
||||
* "topShape": {
|
||||
* "radius": 2,
|
||||
* "x": 4,
|
||||
* "y": 1
|
||||
* }
|
||||
* }}</pre>
|
||||
* This class addresses this problem by adding type information to the
|
||||
* serialized JSON and honoring that type information when the JSON is
|
||||
* deserialized: <pre> {@code
|
||||
* {
|
||||
* "bottomShape": {
|
||||
* "type": "Diamond",
|
||||
* "width": 10,
|
||||
* "height": 5,
|
||||
* "x": 0,
|
||||
* "y": 0
|
||||
* },
|
||||
* "topShape": {
|
||||
* "type": "Circle",
|
||||
* "radius": 2,
|
||||
* "x": 4,
|
||||
* "y": 1
|
||||
* }
|
||||
* }}</pre>
|
||||
* Both the type field name ({@code "type"}) and the type labels ({@code
|
||||
* "Rectangle"}) are configurable.
|
||||
*
|
||||
* <h3>Registering Types</h3>
|
||||
* Create a {@code RuntimeTypeAdapterFactory} by passing the base type and type field
|
||||
* name to the {@link #of} factory method. If you don't supply an explicit type
|
||||
* field name, {@code "type"} will be used. <pre> {@code
|
||||
* RuntimeTypeAdapterFactory<Shape> shapeAdapterFactory
|
||||
* = RuntimeTypeAdapterFactory.of(Shape.class, "type");
|
||||
* }</pre>
|
||||
* Next register all of your subtypes. Every subtype must be explicitly
|
||||
* registered. This protects your application from injection attacks. If you
|
||||
* don't supply an explicit type label, the type's simple name will be used.
|
||||
* <pre> {@code
|
||||
* shapeAdapterFactory.registerSubtype(Rectangle.class, "Rectangle");
|
||||
* shapeAdapterFactory.registerSubtype(Circle.class, "Circle");
|
||||
* shapeAdapterFactory.registerSubtype(Diamond.class, "Diamond");
|
||||
* }</pre>
|
||||
* Finally, register the type adapter factory in your application's GSON builder:
|
||||
* <pre> {@code
|
||||
* Gson gson = new GsonBuilder()
|
||||
* .registerTypeAdapterFactory(shapeAdapterFactory)
|
||||
* .create();
|
||||
* }</pre>
|
||||
* Like {@code GsonBuilder}, this API supports chaining: <pre> {@code
|
||||
* RuntimeTypeAdapterFactory<Shape> shapeAdapterFactory = RuntimeTypeAdapterFactory.of(Shape.class)
|
||||
* .registerSubtype(Rectangle.class)
|
||||
* .registerSubtype(Circle.class)
|
||||
* .registerSubtype(Diamond.class);
|
||||
* }</pre>
|
||||
*/
|
||||
public final class RuntimeTypeAdapterFactory<T> implements TypeAdapterFactory {
|
||||
private final Class<?> baseType;
|
||||
private final String typeFieldName;
|
||||
private final Map<String, Class<?>> labelToSubtype = new LinkedHashMap<String, Class<?>>();
|
||||
private final Map<Class<?>, String> subtypeToLabel = new LinkedHashMap<Class<?>, String>();
|
||||
private final boolean maintainType;
|
||||
|
||||
private RuntimeTypeAdapterFactory(Class<?> baseType, String typeFieldName, boolean maintainType) {
|
||||
if (typeFieldName == null || baseType == null) {
|
||||
throw new NullPointerException();
|
||||
}
|
||||
this.baseType = baseType;
|
||||
this.typeFieldName = typeFieldName;
|
||||
this.maintainType = maintainType;
|
||||
}
|
||||
|
||||
/**
|
||||
* Creates a new runtime type adapter using for {@code baseType} using {@code
|
||||
* typeFieldName} as the type field name. Type field names are case sensitive.
|
||||
* {@code maintainType} flag decide if the type will be stored in pojo or not.
|
||||
*/
|
||||
public static <T> RuntimeTypeAdapterFactory<T> of(Class<T> baseType, String typeFieldName, boolean maintainType) {
|
||||
return new RuntimeTypeAdapterFactory<T>(baseType, typeFieldName, maintainType);
|
||||
}
|
||||
|
||||
/**
|
||||
* Creates a new runtime type adapter using for {@code baseType} using {@code
|
||||
* typeFieldName} as the type field name. Type field names are case sensitive.
|
||||
*/
|
||||
public static <T> RuntimeTypeAdapterFactory<T> of(Class<T> baseType, String typeFieldName) {
|
||||
return new RuntimeTypeAdapterFactory<T>(baseType, typeFieldName, false);
|
||||
}
|
||||
|
||||
/**
|
||||
* Creates a new runtime type adapter for {@code baseType} using {@code "type"} as
|
||||
* the type field name.
|
||||
*/
|
||||
public static <T> RuntimeTypeAdapterFactory<T> of(Class<T> baseType) {
|
||||
return new RuntimeTypeAdapterFactory<T>(baseType, "type", false);
|
||||
}
|
||||
|
||||
/**
|
||||
* Registers {@code type} identified by {@code label}. Labels are case
|
||||
* sensitive.
|
||||
*
|
||||
* @throws IllegalArgumentException if either {@code type} or {@code label}
|
||||
* have already been registered on this type adapter.
|
||||
*/
|
||||
public RuntimeTypeAdapterFactory<T> registerSubtype(Class<? extends T> type, String label) {
|
||||
if (type == null || label == null) {
|
||||
throw new NullPointerException();
|
||||
}
|
||||
if (subtypeToLabel.containsKey(type) || labelToSubtype.containsKey(label)) {
|
||||
throw new IllegalArgumentException("types and labels must be unique");
|
||||
}
|
||||
labelToSubtype.put(label, type);
|
||||
subtypeToLabel.put(type, label);
|
||||
return this;
|
||||
}
|
||||
|
||||
/**
|
||||
* Registers {@code type} identified by its {@link Class#getSimpleName simple
|
||||
* name}. Labels are case sensitive.
|
||||
*
|
||||
* @throws IllegalArgumentException if either {@code type} or its simple name
|
||||
* have already been registered on this type adapter.
|
||||
*/
|
||||
public RuntimeTypeAdapterFactory<T> registerSubtype(Class<? extends T> type) {
|
||||
return registerSubtype(type, type.getSimpleName());
|
||||
}
|
||||
|
||||
public <R> TypeAdapter<R> create(Gson gson, TypeToken<R> type) {
|
||||
if (type.getRawType() != baseType) {
|
||||
return null;
|
||||
}
|
||||
|
||||
final Map<String, TypeAdapter<?>> labelToDelegate
|
||||
= new LinkedHashMap<String, TypeAdapter<?>>();
|
||||
final Map<Class<?>, TypeAdapter<?>> subtypeToDelegate
|
||||
= new LinkedHashMap<Class<?>, TypeAdapter<?>>();
|
||||
for (Map.Entry<String, Class<?>> entry : labelToSubtype.entrySet()) {
|
||||
TypeAdapter<?> delegate = gson.getDelegateAdapter(this, TypeToken.get(entry.getValue()));
|
||||
labelToDelegate.put(entry.getKey(), delegate);
|
||||
subtypeToDelegate.put(entry.getValue(), delegate);
|
||||
}
|
||||
|
||||
return new TypeAdapter<R>() {
|
||||
@Override public R read(JsonReader in) throws IOException {
|
||||
JsonElement jsonElement = Streams.parse(in);
|
||||
JsonElement labelJsonElement;
|
||||
if (maintainType) {
|
||||
labelJsonElement = jsonElement.getAsJsonObject().get(typeFieldName);
|
||||
} else {
|
||||
labelJsonElement = jsonElement.getAsJsonObject().remove(typeFieldName);
|
||||
}
|
||||
|
||||
if (labelJsonElement == null) {
|
||||
throw new JsonParseException("cannot deserialize " + baseType
|
||||
+ " because it does not define a field named " + typeFieldName);
|
||||
}
|
||||
String label = labelJsonElement.getAsString();
|
||||
@SuppressWarnings("unchecked") // registration requires that subtype extends T
|
||||
TypeAdapter<R> delegate = (TypeAdapter<R>) labelToDelegate.get(label);
|
||||
if (delegate == null) {
|
||||
throw new JsonParseException("cannot deserialize " + baseType + " subtype named "
|
||||
+ label + "; did you forget to register a subtype?");
|
||||
}
|
||||
return delegate.fromJsonTree(jsonElement);
|
||||
}
|
||||
|
||||
@Override public void write(JsonWriter out, R value) throws IOException {
|
||||
Class<?> srcType = value.getClass();
|
||||
String label = subtypeToLabel.get(srcType);
|
||||
@SuppressWarnings("unchecked") // registration requires that subtype extends T
|
||||
TypeAdapter<R> delegate = (TypeAdapter<R>) subtypeToDelegate.get(srcType);
|
||||
if (delegate == null) {
|
||||
throw new JsonParseException("cannot serialize " + srcType.getName()
|
||||
+ "; did you forget to register a subtype?");
|
||||
}
|
||||
JsonObject jsonObject = delegate.toJsonTree(value).getAsJsonObject();
|
||||
|
||||
if (maintainType) {
|
||||
Streams.write(jsonObject, out);
|
||||
return;
|
||||
}
|
||||
|
||||
JsonObject clone = new JsonObject();
|
||||
|
||||
if (jsonObject.has(typeFieldName)) {
|
||||
throw new JsonParseException("cannot serialize " + srcType.getName()
|
||||
+ " because it already defines a field named " + typeFieldName);
|
||||
}
|
||||
clone.add(typeFieldName, new JsonPrimitive(label));
|
||||
|
||||
for (Map.Entry<String, JsonElement> e : jsonObject.entrySet()) {
|
||||
clone.add(e.getKey(), e.getValue());
|
||||
}
|
||||
Streams.write(clone, out);
|
||||
}
|
||||
}.nullSafe();
|
||||
}
|
||||
}
|
||||
Loading…
Reference in New Issue