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Support arbitrary Number implementation for Object and Number deseria…
…lization (#1290) * Object and Number type adapters number deserialization can be configured * Change wording of ToNumberStrategy documentation * Use inline links in doc sparingly If the element has already been linked before, don't create a link for every subsequent occurrence. See also (slightly dated) https://www.oracle.com/technical-resources/articles/java/javadoc-tool.html#inlinelinks * Link to default to-number policies in ToNumberStrategy doc * Reduce code duplication for deserializing Number * Hide default factory constants of NumberTypeAdapter and ObjectTypeAdapter This encapsulates the logic a little bit better. Additionally refactored factory created by NumberTypeAdapter to only create TypeAdapter once and then have factory reuse that adapter for better performance. Co-authored-by: Marcono1234 <[email protected]>
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| Original file line number | Diff line number | Diff line change |
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| /* | ||
| * Copyright (C) 2021 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. | ||
| */ | ||
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| package com.google.gson; | ||
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| import java.io.IOException; | ||
| import java.math.BigDecimal; | ||
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| import com.google.gson.internal.LazilyParsedNumber; | ||
| import com.google.gson.stream.JsonReader; | ||
| import com.google.gson.stream.MalformedJsonException; | ||
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| /** | ||
| * An enumeration that defines two standard number reading strategies and a couple of | ||
| * strategies to overcome some historical Gson limitations while deserializing numbers as | ||
| * {@link Object} and {@link Number}. | ||
| * | ||
| * @see ToNumberStrategy | ||
| */ | ||
| public enum ToNumberPolicy implements ToNumberStrategy { | ||
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| /** | ||
| * Using this policy will ensure that numbers will be read as {@link Double} values. | ||
| * This is the default strategy used during deserialization of numbers as {@link Object}. | ||
| */ | ||
| DOUBLE { | ||
| @Override public Double readNumber(JsonReader in) throws IOException { | ||
| return in.nextDouble(); | ||
| } | ||
| }, | ||
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| /** | ||
| * Using this policy will ensure that numbers will be read as a lazily parsed number backed | ||
| * by a string. This is the default strategy used during deserialization of numbers as | ||
| * {@link Number}. | ||
| */ | ||
| LAZILY_PARSED_NUMBER { | ||
| @Override public Number readNumber(JsonReader in) throws IOException { | ||
| return new LazilyParsedNumber(in.nextString()); | ||
| } | ||
| }, | ||
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| /** | ||
| * Using this policy will ensure that numbers will be read as {@link Long} or {@link Double} | ||
| * values depending on how JSON numbers are represented: {@code Long} if the JSON number can | ||
| * be parsed as a {@code Long} value, or otherwise {@code Double} if it can be parsed as a | ||
| * {@code Double} value. If the parsed double-precision number results in a positive or negative | ||
| * infinity ({@link Double#isInfinite()}) or a NaN ({@link Double#isNaN()}) value and the | ||
| * {@code JsonReader} is not {@link JsonReader#isLenient() lenient}, a {@link MalformedJsonException} | ||
| * is thrown. | ||
| */ | ||
| LONG_OR_DOUBLE { | ||
| @Override public Number readNumber(JsonReader in) throws IOException, JsonParseException { | ||
| String value = in.nextString(); | ||
| try { | ||
| return Long.parseLong(value); | ||
| } catch (NumberFormatException longE) { | ||
| try { | ||
| Double d = Double.valueOf(value); | ||
| if ((d.isInfinite() || d.isNaN()) && !in.isLenient()) { | ||
| throw new MalformedJsonException("JSON forbids NaN and infinities: " d in); | ||
| } | ||
| return d; | ||
| } catch (NumberFormatException doubleE) { | ||
| throw new JsonParseException("Cannot parse " value, doubleE); | ||
| } | ||
| } | ||
| } | ||
| }, | ||
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| /** | ||
| * Using this policy will ensure that numbers will be read as numbers of arbitrary length | ||
| * using {@link BigDecimal}. | ||
| */ | ||
| BIG_DECIMAL { | ||
| @Override public BigDecimal readNumber(JsonReader in) throws IOException { | ||
| String value = in.nextString(); | ||
| try { | ||
| return new BigDecimal(value); | ||
| } catch (NumberFormatException e) { | ||
| throw new JsonParseException("Cannot parse " value, e); | ||
| } | ||
| } | ||
| } | ||
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|
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| } |
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| /* | ||
| * Copyright (C) 2021 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. | ||
| */ | ||
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| package com.google.gson; | ||
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| import java.io.IOException; | ||
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| import com.google.gson.stream.JsonReader; | ||
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| /** | ||
| * A strategy that is used to control how numbers should be deserialized for {@link Object} and {@link Number} | ||
| * when a concrete type of the deserialized number is unknown in advance. By default, Gson uses the following | ||
| * deserialization strategies: | ||
| * | ||
| * <ul> | ||
| * <li>{@link Double} values are returned for JSON numbers if the deserialization type is declared as | ||
| * {@code Object}, see {@link ToNumberPolicy#DOUBLE};</li> | ||
| * <li>Lazily parsed number values are returned if the deserialization type is declared as {@code Number}, | ||
| * see {@link ToNumberPolicy#LAZILY_PARSED_NUMBER}.</li> | ||
| * </ul> | ||
| * | ||
| * <p>For historical reasons, Gson does not support deserialization of arbitrary-length numbers for | ||
| * {@code Object} and {@code Number} by default, potentially causing precision loss. However, | ||
| * <a href="https://tools.ietf.org/html/rfc8259#section-6">RFC 8259</a> permits this: | ||
| * | ||
| * <pre> | ||
| * This specification allows implementations to set limits on the range | ||
| * and precision of numbers accepted. Since software that implements | ||
| * IEEE 754 binary64 (double precision) numbers [IEEE754] is generally | ||
| * available and widely used, good interoperability can be achieved by | ||
| * implementations that expect no more precision or range than these | ||
| * provide, in the sense that implementations will approximate JSON | ||
| * numbers within the expected precision. A JSON number such as 1E400 | ||
| * or 3.141592653589793238462643383279 may indicate potential | ||
| * interoperability problems, since it suggests that the software that | ||
| * created it expects receiving software to have greater capabilities | ||
| * for numeric magnitude and precision than is widely available. | ||
| * </pre> | ||
| * | ||
| * <p>To overcome the precision loss, use for example {@link ToNumberPolicy#LONG_OR_DOUBLE} or | ||
| * {@link ToNumberPolicy#BIG_DECIMAL}.</p> | ||
| * | ||
| * @see ToNumberPolicy | ||
| * @see GsonBuilder#setObjectToNumberStrategy(ToNumberStrategy) | ||
| * @see GsonBuilder#setNumberToNumberStrategy(ToNumberStrategy) | ||
| */ | ||
| public interface ToNumberStrategy { | ||
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| /** | ||
| * Reads a number from the given JSON reader. A strategy is supposed to read a single value from the | ||
| * reader, and the read value is guaranteed never to be {@code null}. | ||
| * | ||
| * @param in JSON reader to read a number from | ||
| * @return number read from the JSON reader. | ||
| * @throws IOException | ||
| */ | ||
| public Number readNumber(JsonReader in) throws IOException; | ||
| } |
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gson/src/main/java/com/google/gson/internal/bind/NumberTypeAdapter.java
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| /* | ||
| * Copyright (C) 2020 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. | ||
| */ | ||
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| package com.google.gson.internal.bind; | ||
|
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| import com.google.gson.Gson; | ||
| import com.google.gson.JsonSyntaxException; | ||
| import com.google.gson.ToNumberStrategy; | ||
| import com.google.gson.ToNumberPolicy; | ||
| import com.google.gson.TypeAdapter; | ||
| import com.google.gson.TypeAdapterFactory; | ||
| import com.google.gson.reflect.TypeToken; | ||
| import com.google.gson.stream.JsonReader; | ||
| import com.google.gson.stream.JsonToken; | ||
| import com.google.gson.stream.JsonWriter; | ||
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| import java.io.IOException; | ||
|
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| /** | ||
| * Type adapter for {@link Number}. | ||
| */ | ||
| public final class NumberTypeAdapter extends TypeAdapter<Number> { | ||
| /** | ||
| * Gson default factory using {@link ToNumberPolicy#LAZILY_PARSED_NUMBER}. | ||
| */ | ||
| private static final TypeAdapterFactory LAZILY_PARSED_NUMBER_FACTORY = newFactory(ToNumberPolicy.LAZILY_PARSED_NUMBER); | ||
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| private final ToNumberStrategy toNumberStrategy; | ||
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| private NumberTypeAdapter(ToNumberStrategy toNumberStrategy) { | ||
| this.toNumberStrategy = toNumberStrategy; | ||
| } | ||
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| private static TypeAdapterFactory newFactory(ToNumberStrategy toNumberStrategy) { | ||
| final NumberTypeAdapter adapter = new NumberTypeAdapter(toNumberStrategy); | ||
| return new TypeAdapterFactory() { | ||
| @SuppressWarnings("unchecked") | ||
| @Override public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) { | ||
| return type.getRawType() == Number.class ? (TypeAdapter<T>) adapter : null; | ||
| } | ||
| }; | ||
| } | ||
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| public static TypeAdapterFactory getFactory(ToNumberStrategy toNumberStrategy) { | ||
| if (toNumberStrategy == ToNumberPolicy.LAZILY_PARSED_NUMBER) { | ||
| return LAZILY_PARSED_NUMBER_FACTORY; | ||
| } else { | ||
| return newFactory(toNumberStrategy); | ||
| } | ||
| } | ||
|
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| @Override public Number read(JsonReader in) throws IOException { | ||
| JsonToken jsonToken = in.peek(); | ||
| switch (jsonToken) { | ||
| case NULL: | ||
| in.nextNull(); | ||
| return null; | ||
| case NUMBER: | ||
| case STRING: | ||
| return toNumberStrategy.readNumber(in); | ||
| default: | ||
| throw new JsonSyntaxException("Expecting number, got: " jsonToken); | ||
| } | ||
| } | ||
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| @Override public void write(JsonWriter out, Number value) throws IOException { | ||
| out.value(value); | ||
| } | ||
| } |
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