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Groovy example source code file (JsonBuilder.groovy)

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

Java - Groovy tags/keywords

closure, closure, expected, jsonbuilder, jsonbuilder, jsonexception, map, map, object, string, string, writable, writer

The Groovy JsonBuilder.groovy source code

/*
 * Copyright 2003-2011 the original author or authors.
 *
 * 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 groovy.json

/**
 * A builder for creating JSON payloads.
 * <p>
 * This builder supports the usual builder syntax made of nested method calls and closures,
 * but also some specific aspects of JSON data structures, such as list of values, etc.
 * Please make sure to have a look at the various methods provided by this builder
 * to be able to learn about the various possibilities of usage.
 * <p>
 * Example:
 * <pre>
 *       def builder = new groovy.json.JsonBuilder()
 *       def root = builder.people {
 *           person {
 *               firstName 'Guillame'
 *               lastName 'Laforge'
 *               // Named arguments are valid values for objects too
 *               address(
 *                       city: 'Paris',
 *                       country: 'France',
 *                       zip: 12345,
 *               )
 *               married true
 *               // a list of values
 *               conferences 'JavaOne', 'Gr8conf'
 *           }
 *       }
 *
 *       // creates a data structure made of maps (Json object) and lists (Json array)
 *       assert root instanceof Map
 *
 *       assert builder.toString() == '{"people":{"person":{"firstName":"Guillame","lastName":"Laforge","address":{"city":"Paris","country":"France","zip":12345},"married":true,"conferences":["JavaOne","Gr8conf"]}}}'
 * </code>
* * @author Guillaume Laforge * @since 1.8.0 */ class JsonBuilder implements Writable { /** * Resulting data structure made of lists and maps, representing a JSON payload */ def content /** * Instanciates a JSON builder, possibly with some existing data structure. * * @param content a pre-existing data structure, default to null */ JsonBuilder(content = null) { this.content = content } /** * Named arguments can be passed to the JSON builder instance to create a root JSON object * <p> * Example: * <pre> * def json = new JsonBuilder() * json name: "Guillaume", age: 33 * * assert json.toString() == '{"name":"Guillaume","age":33}' * </code> * * @param m a map of key / value pairs * @return a map of key / value pairs */ def call(Map m) { this.content = m return content } /** * A list of elements as arguments to the JSON builder creates a root JSON array * <p> * Example: * <pre> * def json = new JsonBuilder() * def result = json([1, 2, 3]) * * assert result instanceof List * assert json.toString() == "[1,2,3]" * </code> * * @param l a list of values * @return a list of values */ def call(List l) { this.content = l return content } /** * Varargs elements as arguments to the JSON builder create a root JSON array * <p> * Example: * <pre> * def json = new JsonBuilder() * def result = json 1, 2, 3 * * assert result instanceof List * assert json.toString() == "[1,2,3]" * </code> * @param args an array of values * @return a list of values */ def call(Object... args) { this.content = args.toList() return this.content } /** * A closure passed to a JSON builder will create a root JSON object * <p> * Example: * <pre> * def json = new JsonBuilder() * def result = json { * name "Guillaume" * age 33 * } * * assert result instanceof Map * assert json.toString() == '{"name":"Guillaume","age":33}' * </code> * * @param c a closure whose method call statements represent key / values of a JSON object * @return a map of key / value pairs */ def call(Closure c) { this.content = JsonDelegate.cloneDelegateAndGetContent(c) return content } /** * A method call on the JSON builder instance will create a root object with only one key * whose name is the name of the method being called. * This method takes as arguments: * <ul> * <li>a closure * <li>a map (ie. named arguments) * <li>a map and a closure * <li>or no argument at all * </ul> * <p> * Example with a classicala builder-style: * <pre> * def json = new JsonBuilder() * def result = json.person { * name "Guillaume" * age 33 * } * * assert result instanceof Map * assert json.toString() == '{"person":{"name":"Guillaume","age":33}}' * </code> * * Or alternatively with a method call taking named arguments: * <pre> * def json = new JsonBuilder() * json.person name: "Guillaume", age: 33 * * assert json.toString() == '{"person":{"name":"Guillaume","age":33}}' * </code> * * If you use named arguments and a closure as last argument, * the key/value pairs of the map (as named arguments) * and the key/value pairs represented in the closure * will be merged together — * the closure properties overriding the map key/values * in case the same key is used. * <pre> * def json = new JsonBuilder() * json.person(name: "Guillaume", age: 33) { town "Paris" } * * assert json.toString() == '{"person":{"name":"Guillaume","age":33,"town":"Paris"}}' * </code> * * The empty args call will create a key whose value will be an empty JSON object: * <pre> * def json = new JsonBuilder() * json.person() * * assert json.toString() == '{"person":{}}' * </code> * * @param name the single key * @param args the value associated with the key * @return a map with a single key */ def invokeMethod(String name, Object args) { if (args?.size() == 0) { this.content = [(name): [:]] return content } else if (args?.size() == 1) { if (args[0] instanceof Closure) { this.content = [(name): JsonDelegate.cloneDelegateAndGetContent(args[0])] return content } else if (args[0] instanceof Map) { this.content = [(name): args[0]] return content } } else if (args?.size() == 2 && args[0] instanceof Map && args[1] instanceof Closure) { this.content = [(name): [*:args[0], *:JsonDelegate.cloneDelegateAndGetContent(args[1])]] return content } throw new JsonException("Expected no arguments, a single map, a single closure, or a map and closure as arguments.") } /** * Serializes the internal data structure built with the builder to a conformant JSON payload string * <p> * Example: * <pre> * def json = new JsonBuilder() * json { temperature 37 } * * assert json.toString() == '{"temperature":37}' * </code> * * @return a JSON output */ String toString() { JsonOutput.toJson(content) } /** * Pretty-prints and formats the JSON payload. * <p> * This method calls the JsonLexer to parser the output of the builder, * so this may not be an optimal method to call, * and should be used mainly for debugging purpose * for a human-readable output of the JSON content. * * @return a pretty printed JSON output */ String toPrettyString() { JsonOutput.prettyPrint(toString()) } /** * The JSON builder implements the <code>Writable interface, * so that you can have the builder serialize itself the JSON payload to a writer. * <p> * Example: * <pre> * def json = new JsonBuilder() * json { temperature 37 } * * def out = new StringWriter() * out << json * * assert out.toString() == '{"temperature":37}' * </code> * * @param out a writer on which to serialize the JSON payload * @return the writer */ Writer writeTo(Writer out) { out << toString() } }

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