multi gson

src/main/java/me/cortex/voxy/common/util/MultiGson.java

@@ -0,0 +1,72 @@
+package me.cortex.voxy.common.util;
+
+import com.google.gson.*;
+
+import java.lang.reflect.Modifier;
+import java.util.*;
+
+public class MultiGson {
+    private final List<Class<?>> classes;
+    private final Gson GSON = new GsonBuilder()
+            .setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES)
+            .setPrettyPrinting()
+            .excludeFieldsWithModifiers(Modifier.PRIVATE)
+            .create();
+
+    private MultiGson(List<Class<?>> classes) {
+        this.classes = classes;
+    }
+
+    public String toJson(Object... objects) {
+        Object[] map = new Object[this.classes.size()];
+        if (map.length != objects.length) {
+            throw new IllegalArgumentException("Incorrect number of input args");
+        }
+        for (var obj : objects) {
+            if (obj == null) {
+                throw new IllegalArgumentException();
+            }
+            int i = this.classes.indexOf(obj.getClass());
+            if (i == -1) {
+                throw new IllegalArgumentException("Unknown object class: " + obj.getClass());
+            }
+            if (map[i] != null) {
+                throw new IllegalArgumentException("Duplicate entry classes");
+            }
+        }
+
+        var json = new JsonObject();
+        for (Object entry : map) {
+            GSON.toJsonTree(entry).getAsJsonObject().asMap().forEach((i,j) -> {
+                if (json.has(i)) {
+                    throw new IllegalArgumentException("Duplicate name inside unified json: " + i);
+                }
+                json.add(i, j);
+            });
+        }
+        return GSON.toJson(json);
+    }
+
+    public Map<Class<?>, Object> fromJson(String json) {
+        var obj = GSON.fromJson(json, JsonObject.class);
+        LinkedHashMap<Class<?>, Object> objects = new LinkedHashMap<>();
+        for (var cls : this.classes) {
+            objects.put(cls, GSON.fromJson(obj, cls));
+        }
+        return objects;
+    }
+
+    public static class Builder {
+        private final LinkedHashSet<Class<?>> classes = new LinkedHashSet<>();
+        public Builder add(Class<?> clz) {
+            if (!this.classes.add(clz)) {
+                throw new IllegalArgumentException("Class has already been added");
+            }
+            return this;
+        }
+
+        public MultiGson build() {
+            return new MultiGson(new ArrayList<>(this.classes));
+        }
+    }
+}