001// ***************************************************************************************************************************
002// * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.  See the NOTICE file *
003// * distributed with this work for additional information regarding copyright ownership.  The ASF licenses this file        *
004// * to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance            *
005// * with the License.  You may obtain a copy of the License at                                                              *
006// *                                                                                                                         *
007// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
008// *                                                                                                                         *
009// * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an  *
010// * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the License for the        *
011// * specific language governing permissions and limitations under the License.                                              *
012// ***************************************************************************************************************************
013package org.apache.juneau.annotation;
014
015import static java.lang.annotation.ElementType.*;
016import static java.lang.annotation.RetentionPolicy.*;
017
018import java.lang.annotation.*;
019
020import org.apache.juneau.*;
021
022/**
023 * Maps constructor arguments to property names on beans with read-only properties.
024 *
025 * <p>
026 * This annotation can be used in the case of beans with properties whose values can only be set by passing them in
027 * through a constructor on the class.
028 * <br>Since method parameter names are lost during compilation, this annotation essentially redefines them so that they
029 * are available at runtime.
030 *
031 * <p>
032 * This annotation can only be applied to constructors and can only be applied to one constructor per class.
033 *
034 * <p>
035 * When present, bean instantiation is delayed until the call to {@link BeanMap#getBean()}.
036 * Until then, bean property values are stored in a local cache until <c>getBean()</c> is called.
037 * Because of this additional caching step, parsing into read-only beans tends to be slower and use more memory than
038 * parsing into beans with writable properties.
039 *
040 * <p>
041 * Attempting to call {@link BeanMap#put(String,Object)} on a read-only property after calling {@link BeanMap#getBean()}
042 * will result in a {@link BeanRuntimeException} being thrown.
043 * Multiple calls to {@link BeanMap#getBean()} will return the same bean instance.
044 *
045 * <ul class='seealso'>
046 *    <li class='link'>{@doc juneau-marshall.Transforms.BeancAnnotation}
047 * </ul>
048 *
049 * <div class='warn'>
050 *    <b>Deprecated</b> - {@link Beanc}.
051 * </div>
052 */
053@Documented
054@Target(CONSTRUCTOR)
055@Retention(RUNTIME)
056@Inherited
057@Deprecated
058public @interface BeanConstructor {
059
060   /**
061    * The names of the properties of the constructor arguments.
062    * <p>
063    * The {@link org.apache.juneau.annotation.BeanConstructor @BeanConstructor} annotation is used to
064    * map constructor arguments to property names on bean with read-only properties.
065    *    <br>Since method parameter names are lost during compilation, this annotation essentially redefines
066    * them so that they are available at runtime.
067    * </p>
068    *    <p>
069    * The definition of a read-only bean is a bean with properties with only getters, like shown below:
070    * </p>
071    * <p class='bpcode w800'>
072    *    <jc>// Our read-only bean.</jc>
073    *    <jk>public class</jk> Person {
074    *       <jk>private final</jk> String <jf>name</jf>;
075    *       <jk>private final int</jk> <jf>age</jf>;
076    *
077    *       <ja>@BeanConstructor</ja>(properties=<js>"name,age"</js>)
078    *       <jk>public</jk> Person(String name, <jk>int</jk> age) {
079    *          <jk>this</jk>.<jf>name</jf> = name;
080    *          <jk>this</jk>.<jf>age</jf> = age;
081    *       }
082    *
083    *       <jc>// Read only properties.</jc>
084    *       <jc>// Getters, but no setters.</jc>
085    *
086    *       <jk>public</jk> String getName() {
087    *          <jk>return</jk> <jf>name</jf>;
088    *       }
089    *
090    *       <jk>public int</jk> getAge() {
091    *          <jk>return</jk> <jf>age</jf>;
092    *       }
093    *    }
094    * </p>
095    * <p class='bpcode w800'>
096    *    <jc>// Parsing into a read-only bean.</jc>
097    *    String json = <js>"{name:'John Smith',age:45}"</js>;
098    *    Person p = JsonParser.<jsf>DEFAULT</jsf>.parse(json);
099    *    String name = p.getName();  <jc>// "John Smith"</jc>
100    *    <jk>int</jk> age = p.getAge();   <jc>// 45</jc>
101    * </p>
102    * <p>
103    *    Note that the {@link Name @Name} annotation can also be used to identify bean property names on constructor
104    *    arguments.  If neither this annotation or {@link Name @Name} is used, then we try to get the property names
105    *    from the parameter names if they are available in the bytecode.
106    * </p>
107    */
108   String properties() default "";
109}