Gson Type Adaptateur vs Personnalisé Deseralizer

Ok, véritable exemple de travail (je suis sûr que cette fois).

Le Club

package gson.test;
import java.util.ArrayList;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
public class Club {
public static void main(String[] args) {
//Setup a Club with 2 members
Club myClub = new Club();
myClub.addMember(new Silver("Jack"));
myClub.addMember(new Gold("Jill"));
myClub.addMember(new Silver("Mike"));
//Get the GSON Object and register Type Adapter
GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(Member.class, new MemberDeserializer());
builder.registerTypeAdapter(Member.class, new MemberSerializer());
builder.setPrettyPrinting();
Gson gson = builder.create();
//Serialize Club to JSON
String myJsonClub = gson.toJson(myClub); 
//De-Serialize to Club
Club myNewClub = gson.fromJson(myJsonClub, Club.class);
System.out.println(myClub.equals(myNewClub) ? "Cloned!" : "Failed");
System.out.println(gson.toJson(myNewClub));
}
private String title = "MyClub";
private ArrayList<Member> members = new ArrayList<Member>();
public boolean equals(Object club) {
Club that = (Club) club;
if (!this.title.equals(that.title)) return false;
for (int i=0; i<this.members.size(); i++) {
Member member1 = this.getMember(i);
Member member2 = that.getMember(i);
if (! member1.equals(member2)) return false;
}
return true;
}
public void addMember(Member newMember) { members.add(newMember); }
public Member getMember(int i) { return members.get(i); }
}

Le Membre De La Classe Abstraite

package gson.test;
public abstract class Member {
private String clsname = this.getClass().getName() ;
private int type;
private String name = "unknown";
public Member() { }
public Member(String theName) {this.name = theName;}
public int getType() { return type; }
public void setType(int type) { this.type = type; }
public boolean equals(Object member) {
Member that = (Member) member;
return this.name.equals(that.name);
}
}

Le Béton des Sous-Classes d'Argent et d'Or

package gson.test;
public class Silver extends Member {
private String silverData = "SomeSilverData";
public Silver() { 
super(); 
this.setType(1); 
}
public Silver(String theName) {
super(theName); 
this.setType(1); 
}
public boolean equals(Object that) {
Silver silver = (Silver)that;
return (super.equals(that) && this.silverData.equals(silver.silverData)); 
}
}
package gson.test;
public class Gold extends Member {
private String goldData = "SomeGoldData";
private String extraData = "Extra Gold Data";
public Gold() {
super(); 
this.setType(2);
}
public Gold(String theName) { 
super(theName); 
this.setType(2); 
}
public boolean equals(Gold that) {
Gold gold = (Gold) that;
return (super.equals(that) && this.goldData.equals(gold.goldData)); 
}
}

Le Membre Personnalisé Serailizer

package gson.test;
import java.lang.reflect.Type;
import com.google.gson.JsonElement;
import com.google.gson.JsonSerializationContext;
import com.google.gson.JsonSerializer;
public class MemberSerializer implements JsonSerializer<Member> {
public JsonElement serialize(Member src, Type member, JsonSerializationContext context) {
switch (src.getType()) {
case 1: return context.serialize((Silver)src);
case 2: return context.serialize((Gold)src);
default: return null;
}
}
}

La coutume Deserializer

package gson.test;
import java.lang.reflect.Type;
import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
public class MemberDeserializer implements JsonDeserializer<Member> {
@Override
public Member deserialize(JsonElement json, Type member, JsonDeserializationContext context) {
int myType = json.getAsJsonObject().get("type").getAsInt();
switch (myType) {
case 1: return context.deserialize(json, Silver.class);
case 2: return context.deserialize(json, Gold.class);
default: return null;
}
}
}

Et... la sortie

Cloned!
{
"title": "MyClub",
"members": [
{
"silverData": "SomeSilverData",
"clsname": "gson.test.Silver",
"type": 1,
"name": "Jack"
},
{
"goldData": "SomeGoldData",
"extraData": "Extra Gold Data",
"clsname": "gson.test.Gold",
"type": 2,
"name": "Jill"
},
{
"silverData": "SomeSilverData",
"clsname": "gson.test.Silver",
"type": 1,
"name": "Mike"
}
]
}

Je note que mon réel de cas d'utilisation est celui où la performance ne devrait pas être un problème, je suis le chargement d'un cache d'objets à partir de jSon fichiers de texte de sorte que la fréquence de ce code est exécuté rend performances beaucoup moins important que la facilité de maintenance.

OriginalL'auteur Mike Storey