X-Git-Url: http://git.ieval.ro/?a=blobdiff_plain;f=gson%2Fcom%2Fgoogle%2Fgson%2FInstanceCreator.java;fp=gson%2Fcom%2Fgoogle%2Fgson%2FInstanceCreator.java;h=d5096a07a3dd15334585f14960bfa1da5c3fdb03;hb=5c86ae2f45d293408d98a291e826948052d207bc;hp=0000000000000000000000000000000000000000;hpb=5cf4714f0675349ed599707e024cf0e70fe114b2;p=unical.git diff --git a/gson/com/google/gson/InstanceCreator.java b/gson/com/google/gson/InstanceCreator.java new file mode 100644 index 0000000..d5096a0 --- /dev/null +++ b/gson/com/google/gson/InstanceCreator.java @@ -0,0 +1,92 @@ +/* + * 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; + +import java.lang.reflect.Type; + +/** + * This interface is implemented to create instances of a class that does not define a no-args + * constructor. If you can modify the class, you should instead add a private, or public + * no-args constructor. However, that is not possible for library classes, such as JDK classes, or + * a third-party library that you do not have source-code of. In such cases, you should define an + * instance creator for the class. Implementations of this interface should be registered with + * {@link GsonBuilder#registerTypeAdapter(Type, Object)} method before Gson will be able to use + * them. + *
Let us look at an example where defining an InstanceCreator might be useful. The + * {@code Id} class defined below does not have a default no-args constructor.
+ * + *+ * public class Id<T> { + * private final Class<T> clazz; + * private final long value; + * public Id(Class<T> clazz, long value) { + * this.clazz = clazz; + * this.value = value; + * } + * } + *+ * + *
If Gson encounters an object of type {@code Id} during deserialization, it will throw an + * exception. The easiest way to solve this problem will be to add a (public or private) no-args + * constructor as follows:
+ * + *+ * private Id() { + * this(Object.class, 0L); + * } + *+ * + *
However, let us assume that the developer does not have access to the source-code of the + * {@code Id} class, or does not want to define a no-args constructor for it. The developer + * can solve this problem by defining an {@code InstanceCreator} for {@code Id}:
+ * + *+ * class IdInstanceCreator implements InstanceCreator<Id> { + * public Id createInstance(Type type) { + * return new Id(Object.class, 0L); + * } + * } + *+ * + *
Note that it does not matter what the fields of the created instance contain since Gson will + * overwrite them with the deserialized values specified in Json. You should also ensure that a + * new object is returned, not a common object since its fields will be overwritten. + * The developer will need to register {@code IdInstanceCreator} with Gson as follows:
+ * + *+ * Gson gson = new GsonBuilder().registerTypeAdapter(Id.class, new IdInstanceCreator()).create(); + *+ * + * @param