com.google.gson.ExclusionStrategy Maven / Gradle / Ivy
/*
* 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;
/**
* A strategy (or policy) definition that is used to decide whether or not a field or top-level
* class should be serialized or deserialized as part of the JSON output/input. For serialization,
* if the {@link #shouldSkipClass(Class)} method returns true then that class or field type
* will not be part of the JSON output. For deserialization, if {@link #shouldSkipClass(Class)}
* returns true, then it will not be set as part of the Java object structure.
*
* The following are a few examples that shows how you can use this exclusion mechanism.
*
*
Exclude fields and objects based on a particular class type:
*
* private static class SpecificClassExclusionStrategy implements ExclusionStrategy {
* private final Class<?> excludedThisClass;
*
* public SpecificClassExclusionStrategy(Class<?> excludedThisClass) {
* this.excludedThisClass = excludedThisClass;
* }
*
* public boolean shouldSkipClass(Class<?> clazz) {
* return excludedThisClass.equals(clazz);
* }
*
* public boolean shouldSkipField(FieldAttributes f) {
* return excludedThisClass.equals(f.getDeclaredClass());
* }
* }
*
*
* Excludes fields and objects based on a particular annotation:
*
* public @interface FooAnnotation {
* // some implementation here
* }
*
* // Excludes any field (or class) that is tagged with an "@FooAnnotation"
* private static class FooAnnotationExclusionStrategy implements ExclusionStrategy {
* public boolean shouldSkipClass(Class<?> clazz) {
* return clazz.getAnnotation(FooAnnotation.class) != null;
* }
*
* public boolean shouldSkipField(FieldAttributes f) {
* return f.getAnnotation(FooAnnotation.class) != null;
* }
* }
*
*
* Now if you want to configure {@code Gson} to use a user defined exclusion strategy, then
* the {@code GsonBuilder} is required. The following is an example of how you can use the
* {@code GsonBuilder} to configure Gson to use one of the above sample:
*
* ExclusionStrategy excludeStrings = new UserDefinedExclusionStrategy(String.class);
* Gson gson = new GsonBuilder()
* .setExclusionStrategies(excludeStrings)
* .create();
*
*
* For certain model classes, you may only want to serialize a field, but exclude it for
* deserialization. To do that, you can write an {@code ExclusionStrategy} as per normal;
* however, you would register it with the
* {@link GsonBuilder#addDeserializationExclusionStrategy(ExclusionStrategy)} method.
* For example:
*
* ExclusionStrategy excludeStrings = new UserDefinedExclusionStrategy(String.class);
* Gson gson = new GsonBuilder()
* .addDeserializationExclusionStrategy(excludeStrings)
* .create();
*
*
* @author Inderjeet Singh
* @author Joel Leitch
*
* @see GsonBuilder#setExclusionStrategies(ExclusionStrategy...)
* @see GsonBuilder#addDeserializationExclusionStrategy(ExclusionStrategy)
* @see GsonBuilder#addSerializationExclusionStrategy(ExclusionStrategy)
*
* @since 1.4
*/
public interface ExclusionStrategy {
/**
* @param f the field object that is under test
* @return true if the field should be ignored; otherwise false
*/
public boolean shouldSkipField(FieldAttributes f);
/**
* @param clazz the class object that is under test
* @return true if the class should be ignored; otherwise false
*/
public boolean shouldSkipClass(Class clazz);
}