Java Gson序列化多态对象列表
我正在尝试使用Gson将一个涉及多态性的对象序列化/反序列化为JSON 这是我的序列化代码:Java Gson序列化多态对象列表,java,json,serialization,gson,Java,Json,Serialization,Gson,我正在尝试使用Gson将一个涉及多态性的对象序列化/反序列化为JSON 这是我的序列化代码: ObixBaseObj lobbyObj = new ObixBaseObj(); lobbyObj.setIs("obix:Lobby"); ObixOp batchOp = new ObixOp(); batchOp.setName("batch"); batchOp.setIn("obix:BatchIn"); batchOp.setOut("obix:BatchOut"); lobbyObj
ObixBaseObj lobbyObj = new ObixBaseObj();
lobbyObj.setIs("obix:Lobby");
ObixOp batchOp = new ObixOp();
batchOp.setName("batch");
batchOp.setIn("obix:BatchIn");
batchOp.setOut("obix:BatchOut");
lobbyObj.addChild(batchOp);
Gson gson = new Gson();
System.out.println(gson.toJson(lobbyObj));
结果如下:
{"obix":"obj","is":"obix:Lobby","children":[{"obix":"op","name":"batch"}]}
除了缺少继承成员的内容(尤其是缺少obix:BatchIn
和obixBatchout
字符串)之外,序列化基本上是有效的。
这是我的基本类:
public class ObixBaseObj {
protected String obix;
private String display;
private String displayName;
private ArrayList<ObixBaseObj> children;
public ObixBaseObj()
{
obix = "obj";
}
public void setName(String name) {
this.name = name;
}
...
}
我意识到我可以为此使用适配器,但问题是我正在序列化基类类型的集合
ObixBaseObj
。大约有25个类继承自此。我怎样才能使它优雅地工作呢?我认为定制序列化器/反序列化器是唯一可以继续工作的方法,我试图向您推荐我发现的实现它的最简洁的方法。我很抱歉没有使用您的类,但是想法是一样的(我只想要至少一个基类和两个扩展类)
BaseClass.java
public class BaseClass{
@Override
public String toString() {
return "BaseClass [list=" + list + ", isA=" + isA + ", x=" + x + "]";
}
public ArrayList<BaseClass> list = new ArrayList<BaseClass>();
protected String isA="BaseClass";
public int x;
}
public class ExtendedClass1 extends BaseClass{
@Override
public String toString() {
return "ExtendedClass1 [total=" + total + ", number=" + number
+ ", list=" + list + ", isA=" + isA + ", x=" + x + "]";
}
public ExtendedClass1(){
isA = "ExtendedClass1";
}
public Long total;
public Long number;
}
public class ExtendedClass2 extends BaseClass{
@Override
public String toString() {
return "ExtendedClass2 [total=" + total + ", list=" + list + ", isA="
+ isA + ", x=" + x + "]";
}
public ExtendedClass2(){
isA = "ExtendedClass2";
}
public Long total;
}
public class CustomDeserializer implements JsonDeserializer<List<BaseClass>> {
private static Map<String, Class> map = new TreeMap<String, Class>();
static {
map.put("BaseClass", BaseClass.class);
map.put("ExtendedClass1", ExtendedClass1.class);
map.put("ExtendedClass2", ExtendedClass2.class);
}
public List<BaseClass> deserialize(JsonElement json, Type typeOfT,
JsonDeserializationContext context) throws JsonParseException {
List list = new ArrayList<BaseClass>();
JsonArray ja = json.getAsJsonArray();
for (JsonElement je : ja) {
String type = je.getAsJsonObject().get("isA").getAsString();
Class c = map.get(type);
if (c == null)
throw new RuntimeException("Unknow class: " + type);
list.add(context.deserialize(je, c));
}
return list;
}
}
public class CustomSerializer implements JsonSerializer<ArrayList<BaseClass>> {
private static Map<String, Class> map = new TreeMap<String, Class>();
static {
map.put("BaseClass", BaseClass.class);
map.put("ExtendedClass1", ExtendedClass1.class);
map.put("ExtendedClass2", ExtendedClass2.class);
}
@Override
public JsonElement serialize(ArrayList<BaseClass> src, Type typeOfSrc,
JsonSerializationContext context) {
if (src == null)
return null;
else {
JsonArray ja = new JsonArray();
for (BaseClass bc : src) {
Class c = map.get(bc.isA);
if (c == null)
throw new RuntimeException("Unknow class: " + bc.isA);
ja.add(context.serialize(bc, c));
}
return ja;
}
}
}
ExtendedClass2.java
public class BaseClass{
@Override
public String toString() {
return "BaseClass [list=" + list + ", isA=" + isA + ", x=" + x + "]";
}
public ArrayList<BaseClass> list = new ArrayList<BaseClass>();
protected String isA="BaseClass";
public int x;
}
public class ExtendedClass1 extends BaseClass{
@Override
public String toString() {
return "ExtendedClass1 [total=" + total + ", number=" + number
+ ", list=" + list + ", isA=" + isA + ", x=" + x + "]";
}
public ExtendedClass1(){
isA = "ExtendedClass1";
}
public Long total;
public Long number;
}
public class ExtendedClass2 extends BaseClass{
@Override
public String toString() {
return "ExtendedClass2 [total=" + total + ", list=" + list + ", isA="
+ isA + ", x=" + x + "]";
}
public ExtendedClass2(){
isA = "ExtendedClass2";
}
public Long total;
}
public class CustomDeserializer implements JsonDeserializer<List<BaseClass>> {
private static Map<String, Class> map = new TreeMap<String, Class>();
static {
map.put("BaseClass", BaseClass.class);
map.put("ExtendedClass1", ExtendedClass1.class);
map.put("ExtendedClass2", ExtendedClass2.class);
}
public List<BaseClass> deserialize(JsonElement json, Type typeOfT,
JsonDeserializationContext context) throws JsonParseException {
List list = new ArrayList<BaseClass>();
JsonArray ja = json.getAsJsonArray();
for (JsonElement je : ja) {
String type = je.getAsJsonObject().get("isA").getAsString();
Class c = map.get(type);
if (c == null)
throw new RuntimeException("Unknow class: " + type);
list.add(context.deserialize(je, c));
}
return list;
}
}
public class CustomSerializer implements JsonSerializer<ArrayList<BaseClass>> {
private static Map<String, Class> map = new TreeMap<String, Class>();
static {
map.put("BaseClass", BaseClass.class);
map.put("ExtendedClass1", ExtendedClass1.class);
map.put("ExtendedClass2", ExtendedClass2.class);
}
@Override
public JsonElement serialize(ArrayList<BaseClass> src, Type typeOfSrc,
JsonSerializationContext context) {
if (src == null)
return null;
else {
JsonArray ja = new JsonArray();
for (BaseClass bc : src) {
Class c = map.get(bc.isA);
if (c == null)
throw new RuntimeException("Unknow class: " + bc.isA);
ja.add(context.serialize(bc, c));
}
return ja;
}
}
}
CustomDeserializer.java
public class BaseClass{
@Override
public String toString() {
return "BaseClass [list=" + list + ", isA=" + isA + ", x=" + x + "]";
}
public ArrayList<BaseClass> list = new ArrayList<BaseClass>();
protected String isA="BaseClass";
public int x;
}
public class ExtendedClass1 extends BaseClass{
@Override
public String toString() {
return "ExtendedClass1 [total=" + total + ", number=" + number
+ ", list=" + list + ", isA=" + isA + ", x=" + x + "]";
}
public ExtendedClass1(){
isA = "ExtendedClass1";
}
public Long total;
public Long number;
}
public class ExtendedClass2 extends BaseClass{
@Override
public String toString() {
return "ExtendedClass2 [total=" + total + ", list=" + list + ", isA="
+ isA + ", x=" + x + "]";
}
public ExtendedClass2(){
isA = "ExtendedClass2";
}
public Long total;
}
public class CustomDeserializer implements JsonDeserializer<List<BaseClass>> {
private static Map<String, Class> map = new TreeMap<String, Class>();
static {
map.put("BaseClass", BaseClass.class);
map.put("ExtendedClass1", ExtendedClass1.class);
map.put("ExtendedClass2", ExtendedClass2.class);
}
public List<BaseClass> deserialize(JsonElement json, Type typeOfT,
JsonDeserializationContext context) throws JsonParseException {
List list = new ArrayList<BaseClass>();
JsonArray ja = json.getAsJsonArray();
for (JsonElement je : ja) {
String type = je.getAsJsonObject().get("isA").getAsString();
Class c = map.get(type);
if (c == null)
throw new RuntimeException("Unknow class: " + type);
list.add(context.deserialize(je, c));
}
return list;
}
}
public class CustomSerializer implements JsonSerializer<ArrayList<BaseClass>> {
private static Map<String, Class> map = new TreeMap<String, Class>();
static {
map.put("BaseClass", BaseClass.class);
map.put("ExtendedClass1", ExtendedClass1.class);
map.put("ExtendedClass2", ExtendedClass2.class);
}
@Override
public JsonElement serialize(ArrayList<BaseClass> src, Type typeOfSrc,
JsonSerializationContext context) {
if (src == null)
return null;
else {
JsonArray ja = new JsonArray();
for (BaseClass bc : src) {
Class c = map.get(bc.isA);
if (c == null)
throw new RuntimeException("Unknow class: " + bc.isA);
ja.add(context.serialize(bc, c));
}
return ja;
}
}
}
一些解释:这个技巧是由序列化器/反序列化器中的另一个Gson完成的。我使用justisA
字段来确定正确的类。为了更快,我使用映射将isA
字符串与相应的类相关联。然后,我使用第二个Gson对象执行适当的序列化/反序列化。我将其声明为静态,这样您就不会因为多次分配Gson而减慢序列化/反序列化的速度
Pro
实际上,您编写的代码并不比这多,而是让Gson完成所有工作。您只需记住在映射中放入一个新的子类(异常提醒您这一点)
缺点
你有两张地图。我认为我的实现可以进行一些改进,以避免地图重复,但我把它们留给了您(或者未来的编辑器,如果有的话)
也许您想将序列化和反序列化统一到一个唯一的对象中,您应该检查
TypeAdapter
类或使用实现这两个接口的对象进行实验。有一个简单的解决方案:(来自com.google.code.gson:gson extras:$gsonVersion
)。您不必编写任何序列化程序,这个类为您完成所有工作。使用您的代码尝试以下操作:
ObixBaseObj lobbyObj = new ObixBaseObj();
lobbyObj.setIs("obix:Lobby");
ObixOp batchOp = new ObixOp();
batchOp.setName("batch");
batchOp.setIn("obix:BatchIn");
batchOp.setOut("obix:BatchOut");
lobbyObj.addChild(batchOp);
RuntimeTypeAdapterFactory<ObixBaseObj> adapter =
RuntimeTypeAdapterFactory
.of(ObixBaseObj.class)
.registerSubtype(ObixBaseObj.class)
.registerSubtype(ObixOp.class);
Gson gson2=new GsonBuilder().setPrettyPrinting().registerTypeAdapterFactory(adapter).create();
Gson gson = new Gson();
System.out.println(gson.toJson(lobbyObj));
System.out.println("---------------------");
System.out.println(gson2.toJson(lobbyObj));
}
编辑:更好的工作示例
您说过大约有25个类继承自ObixBaseObj
我们开始编写一个新类,GsonUtils
public class GsonUtils {
private static final GsonBuilder gsonBuilder = new GsonBuilder()
.setPrettyPrinting();
public static void registerType(
RuntimeTypeAdapterFactory<?> adapter) {
gsonBuilder.registerTypeAdapterFactory(adapter);
}
public static Gson getGson() {
return gsonBuilder.create();
}
我们将此代码添加到ObixBaseObj中:
public class ObixBaseObj {
protected String obix;
private String display;
private String displayName;
private String name;
private String is;
private ArrayList<ObixBaseObj> children = new ArrayList<ObixBaseObj>();
// new code
private static final RuntimeTypeAdapterFactory<ObixBaseObj> adapter =
RuntimeTypeAdapterFactory.of(ObixBaseObj.class);
private static final HashSet<Class<?>> registeredClasses= new HashSet<Class<?>>();
static {
GsonUtils.registerType(adapter);
}
private synchronized void registerClass() {
if (!registeredClasses.contains(this.getClass())) {
registeredClasses.add(this.getClass());
adapter.registerSubtype(this.getClass());
}
}
public ObixBaseObj() {
registerClass();
obix = "obj";
}
工作示例:
{"obix":"obj","is":"obix:Lobby","children":[{"obix":"op","name":"batch","children":[]}]}
---------------------
{
"type": "ObixBaseObj",
"obix": "obj",
"is": "obix:Lobby",
"children": [
{
"type": "ObixOp",
"in": "obix:BatchIn",
"out": "obix:BatchOut",
"obix": "op",
"name": "batch",
"children": []
}
]
}
public static void main(String[] args) {
ObixBaseObj lobbyObj = new ObixBaseObj();
lobbyObj.setIs("obix:Lobby");
ObixOp batchOp = new ObixOp();
batchOp.setName("batch");
batchOp.setIn("obix:BatchIn");
batchOp.setOut("obix:BatchOut");
lobbyObj.addChild(batchOp);
Gson gson = GsonUtils.getGson();
System.out.println(gson.toJson(lobbyObj));
}
{
"type": "ObixBaseObj",
"obix": "obj",
"is": "obix:Lobby",
"children": [
{
"type": "ObixOp",
"in": "obix:BatchIn",
"out": "obix:BatchOut",
"obix": "op",
"name": "batch",
"children": []
}
]
}
输出:
{"obix":"obj","is":"obix:Lobby","children":[{"obix":"op","name":"batch","children":[]}]}
---------------------
{
"type": "ObixBaseObj",
"obix": "obj",
"is": "obix:Lobby",
"children": [
{
"type": "ObixOp",
"in": "obix:BatchIn",
"out": "obix:BatchOut",
"obix": "op",
"name": "batch",
"children": []
}
]
}
public static void main(String[] args) {
ObixBaseObj lobbyObj = new ObixBaseObj();
lobbyObj.setIs("obix:Lobby");
ObixOp batchOp = new ObixOp();
batchOp.setName("batch");
batchOp.setIn("obix:BatchIn");
batchOp.setOut("obix:BatchOut");
lobbyObj.addChild(batchOp);
Gson gson = GsonUtils.getGson();
System.out.println(gson.toJson(lobbyObj));
}
{
"type": "ObixBaseObj",
"obix": "obj",
"is": "obix:Lobby",
"children": [
{
"type": "ObixOp",
"in": "obix:BatchIn",
"out": "obix:BatchOut",
"obix": "op",
"name": "batch",
"children": []
}
]
}
我希望这能有所帮助。我很感激这里的其他答案,这些答案引导我走上了解决这个问题的道路。我使用了
RuntimeTypeAdapterFactory
与的组合
我还创建了一个helper类,以确保使用了正确配置的Gson
在GsonHelper类内的静态块中,我有以下代码遍历我的项目以查找和注册所有适当的类型。我所有将通过JSON转换的对象都是Jsonable的子类型。
您将要更改以下内容:
Reflections
中的my.project应该是您的包名Jsonable.class
是我的基类。代替你的RuntimeAdapterFactory
中的className
也是如此;我的数据项已经在使用类型
字段
private static final GsonBuilder gsonBuilder = new GsonBuilder()
.setDateFormat("yyyy-MM-dd'T'HH:mm:ssZ")
.excludeFieldsWithoutExposeAnnotation()
.setPrettyPrinting();
static {
Reflections reflections = new Reflections("my.project");
Set<Class<? extends Jsonable>> allTypes = reflections.getSubTypesOf(Jsonable.class);
for (Class< ? extends Jsonable> serClass : allTypes){
Set<?> subTypes = reflections.getSubTypesOf(serClass);
if (subTypes.size() > 0){
RuntimeTypeAdapterFactory<?> adapterFactory = RuntimeTypeAdapterFactory.of(serClass, "className");
for (Object o : subTypes ){
Class c = (Class)o;
adapterFactory.registerSubtype(c, c.getCanonicalName());
}
gsonBuilder.registerTypeAdapterFactory(adapterFactory);
}
}
}
public static Gson getGson() {
return gsonBuilder.create();
}
private static final GsonBuilder GsonBuilder=new GsonBuilder()
.setDateFormat(“yyyy-MM-dd'T'HH:MM:ssZ”)
.excludeFieldsWithoutExposeAnnotation()
.setPrettyPrinting();
静止的{
反思=新的反思(“我的项目”);
Set subtype=reflections.getsubscriptsof(serClass);
如果(子类型.size()>0){
RuntimeTypeAdapterFactoryAdapterFactory=RuntimeTypeAdapterFactory.of(serClass,“className”);
用于(对象o:子类型){
c类=(o类);
registerSubtype(c,c.getCanonicalName());
}
gsonBuilder.registerTypeAdapterFactory(adapterFactory);
}
}
}
公共静态Gson getGson(){
返回gsonBuilder.create();
}
我创建了一个类型适配器工厂,它使用注释和发现子类,并支持多种序列化样式(类型属性、属性、数组)。有关源代码和maven坐标,请参阅。我还没有检查反序列化,但对于序列化,存在一个问题。如果您检查我的ObixBaseObj类,我有一个基类型的arraylist,它被添加为其子类的一部分。在您的示例中,您直接序列化了基类的arraylist,但在我的示例中,我序列化了一个包含多态对象数组列表的基类对象。在这种情况下,序列化无法正常工作。更具体地说,如果我将私有ArrayList baseList成员添加到基类中,将从基类继承的对象添加到该列表(ExtendedClass1,2),然后尝试序列化基类的单个实例,则无法正确序列化包含的ArrayList。实际上,反序列化也有类似的问题。所有内容都被反序列化为基类。我将我的示例更改为类似于您的示例。我想现在您的问题已经解决了,请参见上面我编辑的答案。al.getClass()返回一个通用的java.util.ArrayList类型,但它并不总是正确的。使用类型listType=newTypeToken(){}.getType();获取java.util.ArrayList。取而代之的是从wiki页面获取或创建wiki页面。RuntimeTypeAdapterFactory现在可用吗?RuntimeTypeAdapterFactory对根对象的工作不正确,我注册了一个问题:@mavixce有任何线索说明为什么这个类没有随gson工件一起提供吗?Thanks@Shyri,RuntimeTypeAdapterFactory位于gson库的extras包中。我不是谷歌员工,也不是gson图书馆的贡献者