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Java example source code file (Excluder.java)

This example Java source code file (Excluder.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

arraylist, assertionerror, cloneable, excluder, exclusionstrategy, fieldattributes, gson, ignore_versions, ioexception, list, override, reflection, typeadapter, typeadapterfactory, util

The Excluder.java Java example source code

/*
 * 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.internal;

import com.google.gson.ExclusionStrategy;
import com.google.gson.FieldAttributes;
import com.google.gson.Gson;
import com.google.gson.TypeAdapter;
import com.google.gson.TypeAdapterFactory;
import com.google.gson.annotations.Expose;
import com.google.gson.annotations.Since;
import com.google.gson.annotations.Until;
import com.google.gson.reflect.TypeToken;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonWriter;
import java.io.IOException;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * This class selects which fields and types to omit. It is configurable,
 * supporting version attributes {@link Since} and {@link Until}, modifiers,
 * synthetic fields, anonymous and local classes, inner classes, and fields with
 * the {@link Expose} annotation.
 *
 * <p>This class is a type adapter factory; types that are excluded will be
 * adapted to null. It may delegate to another type adapter if only one
 * direction is excluded.
 *
 * @author Joel Leitch
 * @author Jesse Wilson
 */
public final class Excluder implements TypeAdapterFactory, Cloneable {
  private static final double IGNORE_VERSIONS = -1.0d;
  public static final Excluder DEFAULT = new Excluder();

  private double version = IGNORE_VERSIONS;
  private int modifiers = Modifier.TRANSIENT | Modifier.STATIC;
  private boolean serializeInnerClasses = true;
  private boolean requireExpose;
  private List<ExclusionStrategy> serializationStrategies = Collections.emptyList();
  private List<ExclusionStrategy> deserializationStrategies = Collections.emptyList();

  @Override protected Excluder clone() {
    try {
      return (Excluder) super.clone();
    } catch (CloneNotSupportedException e) {
      throw new AssertionError(e);
    }
  }

  public Excluder withVersion(double ignoreVersionsAfter) {
    Excluder result = clone();
    result.version = ignoreVersionsAfter;
    return result;
  }

  public Excluder withModifiers(int... modifiers) {
    Excluder result = clone();
    result.modifiers = 0;
    for (int modifier : modifiers) {
      result.modifiers |= modifier;
    }
    return result;
  }

  public Excluder disableInnerClassSerialization() {
    Excluder result = clone();
    result.serializeInnerClasses = false;
    return result;
  }

  public Excluder excludeFieldsWithoutExposeAnnotation() {
    Excluder result = clone();
    result.requireExpose = true;
    return result;
  }

  public Excluder withExclusionStrategy(ExclusionStrategy exclusionStrategy,
      boolean serialization, boolean deserialization) {
    Excluder result = clone();
    if (serialization) {
      result.serializationStrategies = new ArrayList<ExclusionStrategy>(serializationStrategies);
      result.serializationStrategies.add(exclusionStrategy);
    }
    if (deserialization) {
      result.deserializationStrategies
          = new ArrayList<ExclusionStrategy>(deserializationStrategies);
      result.deserializationStrategies.add(exclusionStrategy);
    }
    return result;
  }

  public <T> TypeAdapter create(final Gson gson, final TypeToken type) {
    Class<?> rawType = type.getRawType();
    final boolean skipSerialize = excludeClass(rawType, true);
    final boolean skipDeserialize = excludeClass(rawType, false);

    if (!skipSerialize && !skipDeserialize) {
      return null;
    }

    return new TypeAdapter<T>() {
      /** The delegate is lazily created because it may not be needed, and creating it may fail. */
      private TypeAdapter<T> delegate;

      @Override public T read(JsonReader in) throws IOException {
        if (skipDeserialize) {
          in.skipValue();
          return null;
        }
        return delegate().read(in);
      }

      @Override public void write(JsonWriter out, T value) throws IOException {
        if (skipSerialize) {
          out.nullValue();
          return;
        }
        delegate().write(out, value);
      }

      private TypeAdapter<T> delegate() {
        TypeAdapter<T> d = delegate;
        return d != null
            ? d
            : (delegate = gson.getDelegateAdapter(Excluder.this, type));
      }
    };
  }

  public boolean excludeField(Field field, boolean serialize) {
    if ((modifiers & field.getModifiers()) != 0) {
      return true;
    }

    if (version != Excluder.IGNORE_VERSIONS
        && !isValidVersion(field.getAnnotation(Since.class), field.getAnnotation(Until.class))) {
      return true;
    }

    if (field.isSynthetic()) {
      return true;
    }

    if (requireExpose) {
      Expose annotation = field.getAnnotation(Expose.class);
      if (annotation == null || (serialize ? !annotation.serialize() : !annotation.deserialize())) {
        return true;
      }
    }

    if (!serializeInnerClasses && isInnerClass(field.getType())) {
      return true;
    }

    if (isAnonymousOrLocal(field.getType())) {
      return true;
    }

    List<ExclusionStrategy> list = serialize ? serializationStrategies : deserializationStrategies;
    if (!list.isEmpty()) {
      FieldAttributes fieldAttributes = new FieldAttributes(field);
      for (ExclusionStrategy exclusionStrategy : list) {
        if (exclusionStrategy.shouldSkipField(fieldAttributes)) {
          return true;
        }
      }
    }

    return false;
  }

  public boolean excludeClass(Class<?> clazz, boolean serialize) {
    if (version != Excluder.IGNORE_VERSIONS
        && !isValidVersion(clazz.getAnnotation(Since.class), clazz.getAnnotation(Until.class))) {
      return true;
    }

    if (!serializeInnerClasses && isInnerClass(clazz)) {
      return true;
    }

    if (isAnonymousOrLocal(clazz)) {
      return true;
    }

    List<ExclusionStrategy> list = serialize ? serializationStrategies : deserializationStrategies;
    for (ExclusionStrategy exclusionStrategy : list) {
      if (exclusionStrategy.shouldSkipClass(clazz)) {
        return true;
      }
    }

    return false;
  }

  private boolean isAnonymousOrLocal(Class<?> clazz) {
    return !Enum.class.isAssignableFrom(clazz)
        && (clazz.isAnonymousClass() || clazz.isLocalClass());
  }

  private boolean isInnerClass(Class<?> clazz) {
    return clazz.isMemberClass() && !isStatic(clazz);
  }

  private boolean isStatic(Class<?> clazz) {
    return (clazz.getModifiers() & Modifier.STATIC) != 0;
  }

  private boolean isValidVersion(Since since, Until until) {
    return isValidSince(since) && isValidUntil(until);
  }

  private boolean isValidSince(Since annotation) {
    if (annotation != null) {
      double annotationVersion = annotation.value();
      if (annotationVersion > version) {
        return false;
      }
    }
    return true;
  }

  private boolean isValidUntil(Until annotation) {
    if (annotation != null) {
      double annotationVersion = annotation.value();
      if (annotationVersion <= version) {
        return false;
      }
    }
    return true;
  }
}

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