111 lines
4.0 KiB
Java
111 lines
4.0 KiB
Java
/*
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* Copyright (C) 2008 Google Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.gson;
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/**
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* A strategy (or policy) definition that is used to decide whether or not a field or
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* class should be serialized or deserialized as part of the JSON output/input.
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*
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* <p>The following are a few examples that shows how you can use this exclusion mechanism.
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*
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* <p><strong>Exclude fields and objects based on a particular class type:</strong>
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* <pre class="code">
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* private static class SpecificClassExclusionStrategy implements ExclusionStrategy {
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* private final Class<?> excludedThisClass;
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*
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* public SpecificClassExclusionStrategy(Class<?> excludedThisClass) {
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* this.excludedThisClass = excludedThisClass;
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* }
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*
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* public boolean shouldSkipClass(Class<?> clazz) {
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* return excludedThisClass.equals(clazz);
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* }
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*
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* public boolean shouldSkipField(FieldAttributes f) {
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* return excludedThisClass.equals(f.getDeclaredClass());
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* }
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* }
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* </pre>
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*
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* <p><strong>Excludes fields and objects based on a particular annotation:</strong>
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* <pre class="code">
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* public @interface FooAnnotation {
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* // some implementation here
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* }
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*
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* // Excludes any field (or class) that is tagged with an "@FooAnnotation"
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* private static class FooAnnotationExclusionStrategy implements ExclusionStrategy {
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* public boolean shouldSkipClass(Class<?> clazz) {
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* return clazz.getAnnotation(FooAnnotation.class) != null;
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* }
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*
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* public boolean shouldSkipField(FieldAttributes f) {
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* return f.getAnnotation(FooAnnotation.class) != null;
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* }
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* }
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* </pre>
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*
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* <p>Now if you want to configure {@code Gson} to use a user defined exclusion strategy, then
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* the {@code GsonBuilder} is required. The following is an example of how you can use the
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* {@code GsonBuilder} to configure Gson to use one of the above samples:
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* <pre class="code">
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* ExclusionStrategy excludeStrings = new UserDefinedExclusionStrategy(String.class);
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* Gson gson = new GsonBuilder()
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* .setExclusionStrategies(excludeStrings)
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* .create();
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* </pre>
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*
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* <p>For certain model classes, you may only want to serialize a field, but exclude it for
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* deserialization. To do that, you can write an {@code ExclusionStrategy} as per normal;
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* however, you would register it with the
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* {@link GsonBuilder#addDeserializationExclusionStrategy(ExclusionStrategy)} method.
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* For example:
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* <pre class="code">
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* ExclusionStrategy excludeStrings = new UserDefinedExclusionStrategy(String.class);
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* Gson gson = new GsonBuilder()
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* .addDeserializationExclusionStrategy(excludeStrings)
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* .create();
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* </pre>
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*
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* @author Inderjeet Singh
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* @author Joel Leitch
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*
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* @see GsonBuilder#setExclusionStrategies(ExclusionStrategy...)
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* @see GsonBuilder#addDeserializationExclusionStrategy(ExclusionStrategy)
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* @see GsonBuilder#addSerializationExclusionStrategy(ExclusionStrategy)
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*
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* @since 1.4
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*/
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public interface ExclusionStrategy {
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/**
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* Decides if a field should be skipped during serialization or deserialization.
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*
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* @param f the field object that is under test
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* @return true if the field should be ignored; otherwise false
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*/
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public boolean shouldSkipField(FieldAttributes f);
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/**
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* Decides if a class should be serialized or deserialized
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*
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* @param clazz the class object that is under test
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* @return true if the class should be ignored; otherwise false
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*/
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public boolean shouldSkipClass(Class<?> clazz);
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}
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