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Explore the source code of the class GsonBuilder.java

/*
 * 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 com.google.gson.stream.JsonReader;
import java.lang.reflect.Type;
import java.sql.Timestamp;
import java.text.DateFormat;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import com.google.gson.internal.$Gson$Preconditions;
import com.google.gson.internal.Excluder;
import com.google.gson.internal.bind.TreeTypeAdapter;
import com.google.gson.internal.bind.TypeAdapters;
import com.google.gson.reflect.TypeToken;

import static com.google.gson.Gson.DEFAULT_COMPLEX_MAP_KEYS;
import static com.google.gson.Gson.DEFAULT_ESCAPE_HTML;
import static com.google.gson.Gson.DEFAULT_JSON_NON_EXECUTABLE;
import static com.google.gson.Gson.DEFAULT_LENIENT;
import static com.google.gson.Gson.DEFAULT_PRETTY_PRINT;
import static com.google.gson.Gson.DEFAULT_SERIALIZE_NULLS;
import static com.google.gson.Gson.DEFAULT_SPECIALIZE_FLOAT_VALUES;

/**
 * 

Use this builder to construct a [email protected] Gson} instance when you need to set configuration * options other than the default. For [email protected] Gson} with default configuration, it is simpler to * use [email protected] new Gson()}. [email protected] GsonBuilder} is best used by creating it, and then invoking its * various configuration methods, and finally calling create.

* *

The following is an example shows how to use the [email protected] GsonBuilder} to construct a Gson * instance: * *

 * Gson gson = new GsonBuilder()
 *     .registerTypeAdapter(Id.class, new IdTypeAdapter())
 *     .enableComplexMapKeySerialization()
 *     .serializeNulls()
 *     .setDateFormat(DateFormat.LONG)
 *     .setFieldNamingPolicy(FieldNamingPolicy.UPPER_CAMEL_CASE)
 *     .setPrettyPrinting()
 *     .setVersion(1.0)
 *     .create();
 * 

* *

NOTES: *

    *
  • the order of invocation of configuration methods does not matter.
  • *
  • The default serialization of [email protected] Date} and its subclasses in Gson does * not contain time-zone information. So, if you are using date/time instances, * use [email protected] GsonBuilder} and its [email protected] setDateFormat} methods.
  • *
*

* * @author Inderjeet Singh * @author Joel Leitch * @author Jesse Wilson */ public final class GsonBuilder { private Excluder excluder = Excluder.DEFAULT; private LongSerializationPolicy longSerializationPolicy = LongSerializationPolicy.DEFAULT; private FieldNamingStrategy fieldNamingPolicy = FieldNamingPolicy.IDENTITY; private final Map> instanceCreators = new HashMap>(); private final List factories = new ArrayList(); /** tree-style hierarchy factories. These come after factories for backwards compatibility. */ private final List hierarchyFactories = new ArrayList(); private boolean serializeNulls = DEFAULT_SERIALIZE_NULLS; private String datePattern; private int dateStyle = DateFormat.DEFAULT; private int timeStyle = DateFormat.DEFAULT; private boolean complexMapKeySerialization = DEFAULT_COMPLEX_MAP_KEYS; private boolean serializeSpecialFloatingPointValues = DEFAULT_SPECIALIZE_FLOAT_VALUES; private boolean escapeHtmlChars = DEFAULT_ESCAPE_HTML; private boolean prettyPrinting = DEFAULT_PRETTY_PRINT; private boolean generateNonExecutableJson = DEFAULT_JSON_NON_EXECUTABLE; private boolean lenient = DEFAULT_LENIENT; /** * Creates a GsonBuilder instance that can be used to build Gson with various configuration * settings. GsonBuilder follows the builder pattern, and it is typically used by first * invoking various configuration methods to set desired options, and finally calling * [email protected] #create()}. */ public GsonBuilder() { } /** * Configures Gson to enable versioning support. * * @param ignoreVersionsAfter any field or type marked with a version higher than this value * are ignored during serialization or deserialization. * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern */ public GsonBuilder setVersion(double ignoreVersionsAfter) { excluder = excluder.withVersion(ignoreVersionsAfter); return this; } /** * Configures Gson to excludes all class fields that have the specified modifiers. By default, * Gson will exclude all fields marked transient or static. This method will override that * behavior. * * @param modifiers the field modifiers. You must use the modifiers specified in the * [email protected] java.lang.reflect.Modifier} class. For example, * [email protected] java.lang.reflect.Modifier#TRANSIENT}, * [email protected] java.lang.reflect.Modifier#STATIC}. * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern */ public GsonBuilder excludeFieldsWithModifiers(int... modifiers) { excluder = excluder.withModifiers(modifiers); return this; } /** * Makes the output JSON non-executable in Javascript by prefixing the generated JSON with some * special text. This prevents attacks from third-party sites through script sourcing. See * Gson Issue 42 * for details. * * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern * @since 1.3 */ public GsonBuilder generateNonExecutableJson() { this.generateNonExecutableJson = true; return this; } /** * Configures Gson to exclude all fields from consideration for serialization or deserialization * that do not have the [email protected] com.google.gson.annotations.Expose} annotation. * * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern */ public GsonBuilder excludeFieldsWithoutExposeAnnotation() { excluder = excluder.excludeFieldsWithoutExposeAnnotation(); return this; } /** * Configure Gson to serialize null fields. By default, Gson omits all fields that are null * during serialization. * * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern * @since 1.2 */ public GsonBuilder serializeNulls() { this.serializeNulls = true; return this; } /** * Enabling this feature will only change the serialized form if the map key is * a complex type (i.e. non-primitive) in its serialized JSON * form. The default implementation of map serialization uses [email protected] toString()} * on the key; however, when this is called then one of the following cases * apply: * *

Maps as JSON objects

* For this case, assume that a type adapter is registered to serialize and * deserialize some [email protected] Point} class, which contains an x and y coordinate, * to/from the JSON Primitive string value [email protected] "(x,y)"}. The Java map would * then be serialized as a [email protected] JsonObject}. * *

Below is an example: *

  [email protected]
   *   Gson gson = new GsonBuilder()
   *       .register(Point.class, new MyPointTypeAdapter())
   *       .enableComplexMapKeySerialization()
   *       .create();
   *
   *   Map original = new LinkedHashMap();
   *   original.put(new Point(5, 6), "a");
   *   original.put(new Point(8, 8), "b");
   *   System.out.println(gson.toJson(original, type));
   * }
* The above code prints this JSON object:
  [email protected]
   *   {
   *     "(5,6)": "a",
   *     "(8,8)": "b"
   *   }
   * }
* *

Maps as JSON arrays

* For this case, assume that a type adapter was NOT registered for some * [email protected] Point} class, but rather the default Gson serialization is applied. * In this case, some [email protected] new Point(2,3)} would serialize as [email protected] * {"x":2,"y":5}}. * *

Given the assumption above, a [email protected] Map} will be * serialize as an array of arrays (can be viewed as an entry set of pairs). * *

Below is an example of serializing complex types as JSON arrays: *

 [email protected]
   *   Gson gson = new GsonBuilder()
   *       .enableComplexMapKeySerialization()
   *       .create();
   *
   *   Map original = new LinkedHashMap();
   *   original.put(new Point(5, 6), "a");
   *   original.put(new Point(8, 8), "b");
   *   System.out.println(gson.toJson(original, type));
   * }
   *
   * The JSON output would look as follows:
   * 
   [email protected]
   *   [
   *     [
   *       {
   *         "x": 5,
   *         "y": 6
   *       },
   *       "a"
   *     ],
   *     [
   *       {
   *         "x": 8,
   *         "y": 8
   *       },
   *       "b"
   *     ]
   *   ]
   * }
* * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern * @since 1.7 */ public GsonBuilder enableComplexMapKeySerialization() { complexMapKeySerialization = true; return this; } /** * Configures Gson to exclude inner classes during serialization. * * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern * @since 1.3 */ public GsonBuilder disableInnerClassSerialization() { excluder = excluder.disableInnerClassSerialization(); return this; } /** * Configures Gson to apply a specific serialization policy for [email protected] Long} and [email protected] long} * objects. * * @param serializationPolicy the particular policy to use for serializing longs. * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern * @since 1.3 */ public GsonBuilder setLongSerializationPolicy(LongSerializationPolicy serializationPolicy) { this.longSerializationPolicy = serializationPolicy; return this; } /** * Configures Gson to apply a specific naming policy to an object's field during serialization * and deserialization. * * @param namingConvention the JSON field naming convention to use for serialization and * deserialization. * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern */ public GsonBuilder setFieldNamingPolicy(FieldNamingPolicy namingConvention) { this.fieldNamingPolicy = namingConvention; return this; } /** * Configures Gson to apply a specific naming policy strategy to an object's field during * serialization and deserialization. * * @param fieldNamingStrategy the actual naming strategy to apply to the fields * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern * @since 1.3 */ public GsonBuilder setFieldNamingStrategy(FieldNamingStrategy fieldNamingStrategy) { this.fieldNamingPolicy = fieldNamingStrategy; return this; } /** * Configures Gson to apply a set of exclusion strategies during both serialization and * deserialization. Each of the [email protected] strategies} will be applied as a disjunction rule. * This means that if one of the [email protected] strategies} suggests that a field (or class) should be * skipped then that field (or object) is skipped during serialization/deserialization. * * @param strategies the set of strategy object to apply during object (de)serialization. * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern * @since 1.4 */ public GsonBuilder setExclusionStrategies(ExclusionStrategy... strategies) { for (ExclusionStrategy strategy : strategies) { excluder = excluder.withExclusionStrategy(strategy, true, true); } return this; } /** * Configures Gson to apply the passed in exclusion strategy during serialization. * If this method is invoked numerous times with different exclusion strategy objects * then the exclusion strategies that were added will be applied as a disjunction rule. * This means that if one of the added exclusion strategies suggests that a field (or * class) should be skipped then that field (or object) is skipped during its * serialization. * * @param strategy an exclusion strategy to apply during serialization. * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern * @since 1.7 */ public GsonBuilder addSerializationExclusionStrategy(ExclusionStrategy strategy) { excluder = excluder.withExclusionStrategy(strategy, true, false); return this; } /** * Configures Gson to apply the passed in exclusion strategy during deserialization. * If this method is invoked numerous times with different exclusion strategy objects * then the exclusion strategies that were added will be applied as a disjunction rule. * This means that if one of the added exclusion strategies suggests that a field (or * class) should be skipped then that field (or object) is skipped during its * deserialization. * * @param strategy an exclusion strategy to apply during deserialization. * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern * @since 1.7 */ public GsonBuilder addDeserializationExclusionStrategy(ExclusionStrategy strategy) { excluder = excluder.withExclusionStrategy(strategy, false, true); return this; } /** * Configures Gson to output Json that fits in a page for pretty printing. This option only * affects Json serialization. * * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern */ public GsonBuilder setPrettyPrinting() { prettyPrinting = true; return this; } /** * By default, Gson is strict and only accepts JSON as specified by * RFC 4627. This option makes the parser * liberal in what it accepts. * * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern * @see JsonReader#setLenient(boolean) */ public GsonBuilder setLenient() { lenient = true; return this; } /** * By default, Gson escapes HTML characters such as < > etc. Use this option to configure * Gson to pass-through HTML characters as is. * * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern * @since 1.3 */ public GsonBuilder disableHtmlEscaping() { this.escapeHtmlChars = false; return this; } /** * Configures Gson to serialize [email protected] Date} objects according to the pattern provided. You can * call this method or [email protected] #setDateFormat(int)} multiple times, but only the last invocation * will be used to decide the serialization format. * *

The date format will be used to serialize and deserialize [email protected] java.util.Date}, [email protected] * java.sql.Timestamp} and [email protected] java.sql.Date}. * *

Note that this pattern must abide by the convention provided by [email protected] SimpleDateFormat} * class. See the documentation in [email protected] java.text.SimpleDateFormat} for more information on * valid date and time patterns.

* * @param pattern the pattern that dates will be serialized/deserialized to/from * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern * @since 1.2 */ public GsonBuilder setDateFormat(String pattern) { // TODO(Joel): Make this fail fast if it is an invalid date format this.datePattern = pattern; return this; } /** * Configures Gson to to serialize [email protected] Date} objects according to the style value provided. * You can call this method or [email protected] #setDateFormat(String)} multiple times, but only the last * invocation will be used to decide the serialization format. * *

Note that this style value should be one of the predefined constants in the * [email protected] DateFormat} class. See the documentation in [email protected] java.text.DateFormat} for more * information on the valid style constants.

* * @param style the predefined date style that date objects will be serialized/deserialized * to/from * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern * @since 1.2 */ public GsonBuilder setDateFormat(int style) { this.dateStyle = style; this.datePattern = null; return this; } /** * Configures Gson to to serialize [email protected] Date} objects according to the style value provided. * You can call this method or [email protected] #setDateFormat(String)} multiple times, but only the last * invocation will be used to decide the serialization format. * *

Note that this style value should be one of the predefined constants in the * [email protected] DateFormat} class. See the documentation in [email protected] java.text.DateFormat} for more * information on the valid style constants.

* * @param dateStyle the predefined date style that date objects will be serialized/deserialized * to/from * @param timeStyle the predefined style for the time portion of the date objects * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern * @since 1.2 */ public GsonBuilder setDateFormat(int dateStyle, int timeStyle) { this.dateStyle = dateStyle; this.timeStyle = timeStyle; this.datePattern = null; return this; } /** * Configures Gson for custom serialization or deserialization. This method combines the * registration of an [email protected] TypeAdapter}, [email protected] InstanceCreator}, [email protected] JsonSerializer}, and a * [email protected] JsonDeserializer}. It is best used when a single object [email protected] typeAdapter} implements * all the required interfaces for custom serialization with Gson. If a type adapter was * previously registered for the specified [email protected] type}, it is overwritten. * *

This registers the type specified and no other types: you must manually register related * types! For example, applications registering [email protected] boolean.class} should also register [email protected] * Boolean.class}. * * @param type the type definition for the type adapter being registered * @param typeAdapter This object must implement at least one of the [email protected] TypeAdapter}, * [email protected] InstanceCreator}, [email protected] JsonSerializer}, and a [email protected] JsonDeserializer} interfaces. * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern */ @SuppressWarnings({"unchecked", "rawtypes"}) public GsonBuilder registerTypeAdapter(Type type, Object typeAdapter) { $Gson$Preconditions.checkArgument(typeAdapter instanceof JsonSerializer || typeAdapter instanceof JsonDeserializer || typeAdapter instanceof InstanceCreator || typeAdapter instanceof TypeAdapter); if (typeAdapter instanceof InstanceCreator) { instanceCreators.put(type, (InstanceCreator) typeAdapter); } if (typeAdapter instanceof JsonSerializer || typeAdapter instanceof JsonDeserializer) { TypeToken typeToken = TypeToken.get(type); factories.add(TreeTypeAdapter.newFactoryWithMatchRawType(typeToken, typeAdapter)); } if (typeAdapter instanceof TypeAdapter) { factories.add(TypeAdapters.newFactory(TypeToken.get(type), (TypeAdapter)typeAdapter)); } return this; } /** * Register a factory for type adapters. Registering a factory is useful when the type * adapter needs to be configured based on the type of the field being processed. Gson * is designed to handle a large number of factories, so you should consider registering * them to be at par with registering an individual type adapter. * * @since 2.1 */ public GsonBuilder registerTypeAdapterFactory(TypeAdapterFactory factory) { factories.add(factory); return this; } /** * Configures Gson for custom serialization or deserialization for an inheritance type hierarchy. * This method combines the registration of a [email protected] TypeAdapter}, [email protected] JsonSerializer} and * a [email protected] JsonDeserializer}. If a type adapter was previously registered for the specified * type hierarchy, it is overridden. If a type adapter is registered for a specific type in * the type hierarchy, it will be invoked instead of the one registered for the type hierarchy. * * @param baseType the class definition for the type adapter being registered for the base class * or interface * @param typeAdapter This object must implement at least one of [email protected] TypeAdapter}, * [email protected] JsonSerializer} or [email protected] JsonDeserializer} interfaces. * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern * @since 1.7 */ @SuppressWarnings({"unchecked", "rawtypes"}) public GsonBuilder registerTypeHierarchyAdapter(Class baseType, Object typeAdapter) { $Gson$Preconditions.checkArgument(typeAdapter instanceof JsonSerializer || typeAdapter instanceof JsonDeserializer || typeAdapter instanceof TypeAdapter); if (typeAdapter instanceof JsonDeserializer || typeAdapter instanceof JsonSerializer) { hierarchyFactories.add(0, TreeTypeAdapter.newTypeHierarchyFactory(baseType, typeAdapter)); } if (typeAdapter instanceof TypeAdapter) { factories.add(TypeAdapters.newTypeHierarchyFactory(baseType, (TypeAdapter)typeAdapter)); } return this; } /** * Section 2.4 of JSON specification disallows * special double values (NaN, Infinity, -Infinity). However, * Javascript * specification (see section 4.3.20, 4.3.22, 4.3.23) allows these values as valid Javascript * values. Moreover, most JavaScript engines will accept these special values in JSON without * problem. So, at a practical level, it makes sense to accept these values as valid JSON even * though JSON specification disallows them. * *

Gson always accepts these special values during deserialization. However, it outputs * strictly compliant JSON. Hence, if it encounters a float value [email protected] Float#NaN}, * [email protected] Float#POSITIVE_INFINITY}, [email protected] Float#NEGATIVE_INFINITY}, or a double value * [email protected] Double#NaN}, [email protected] Double#POSITIVE_INFINITY}, [email protected] Double#NEGATIVE_INFINITY}, it * will throw an [email protected] IllegalArgumentException}. This method provides a way to override the * default behavior when you know that the JSON receiver will be able to handle these special * values. * * @return a reference to this [email protected] GsonBuilder} object to fulfill the "Builder" pattern * @since 1.3 */ public GsonBuilder serializeSpecialFloatingPointValues() { this.serializeSpecialFloatingPointValues = true; return this; } /** * Creates a [email protected] Gson} instance based on the current configuration. This method is free of * side-effects to this [email protected] GsonBuilder} instance and hence can be called multiple times. * * @return an instance of Gson configured with the options currently set in this builder */ public Gson create() { List factories = new ArrayList(); factories.addAll(this.factories); Collections.reverse(factories); factories.addAll(this.hierarchyFactories); addTypeAdaptersForDate(datePattern, dateStyle, timeStyle, factories); return new Gson(excluder, fieldNamingPolicy, instanceCreators, serializeNulls, complexMapKeySerialization, generateNonExecutableJson, escapeHtmlChars, prettyPrinting, lenient, serializeSpecialFloatingPointValues, longSerializationPolicy, factories); } private void addTypeAdaptersForDate(String datePattern, int dateStyle, int timeStyle, List factories) { DefaultDateTypeAdapter dateTypeAdapter; if (datePattern != null && !"".equals(datePattern.trim())) { dateTypeAdapter = new DefaultDateTypeAdapter(datePattern); } else if (dateStyle != DateFormat.DEFAULT && timeStyle != DateFormat.DEFAULT) { dateTypeAdapter = new DefaultDateTypeAdapter(dateStyle, timeStyle); } else { return; } factories.add(TreeTypeAdapter.newFactory(TypeToken.get(Date.class), dateTypeAdapter)); factories.add(TreeTypeAdapter.newFactory(TypeToken.get(Timestamp.class), dateTypeAdapter)); factories.add(TreeTypeAdapter.newFactory(TypeToken.get(java.sql.Date.class), dateTypeAdapter)); } }