1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.configuration2.beanutils;
18
19 import java.util.Collection;
20 import java.util.Map;
21
22 /**
23 * <p>
24 * Definition of an interface for declaring a bean in a configuration file.
25 * </p>
26 * <p>
27 * Commons Configurations allows to define beans (i.e. simple Java objects) in configuration files, which can be created
28 * at runtime. This is especially useful if you program against interfaces and want to define the concrete
29 * implementation class is a configuration file.
30 * </p>
31 * <p>
32 * This interface defines methods for retrieving all information about a bean that should be created from a
33 * configuration file, e.g. the bean's properties or the factory to use for creating the instance. With different
34 * implementations different "layouts" of bean declarations can be supported. For instance if an XML
35 * configuration file is used, all features of XML (e.g. attributes, nested elements) can be used to define the bean. In
36 * a properties file the declaration format is more limited. The purpose of this interface is to abstract from the
37 * concrete declaration format.
38 * </p>
39 *
40 * @since 1.3
41 */
42 public interface BeanDeclaration {
43
44 /**
45 * Gets the name of the bean class, from which an instance is to be created. This value must be defined unless a
46 * default class is provided for the bean creation operation.
47 *
48 * @return the name of the bean class
49 */
50 String getBeanClassName();
51
52 /**
53 * Gets the name of the {@code BeanFactory} that should be used for creating the bean instance. This can be
54 * <b>null</b>, then a default factory will be used.
55 *
56 * @return the name of the bean factory
57 */
58 String getBeanFactoryName();
59
60 /**
61 * Gets an arbitrary object that will be passed to the bean factory. Its meaning is not further
62 * specified. The purpose of this additional parameter is to support a further configuration of the bean factory that
63 * can be placed directly at the bean declaration.
64 *
65 * @return a parameter for the bean factory
66 */
67 Object getBeanFactoryParameter();
68
69 /**
70 * Gets a map with properties that should be initialized on the newly created bean. The map's keys are the names of
71 * the properties; the corresponding values are the properties' values. The return value can be <b>null</b> if no
72 * properties should be set.
73 *
74 * @return a map with properties to be initialized
75 */
76 Map<String, Object> getBeanProperties();
77
78 /**
79 * Gets a collection with constructor arguments. This data is used to determine the constructor of the bean class to
80 * be invoked. The values of the arguments are passed to the constructor. An implementation can return <b>null</b> or an
81 * empty collection; then the standard constructor of the bean class is called.
82 *
83 * @return a collection with the arguments to be passed to the bean class's constructor
84 */
85 Collection<ConstructorArg> getConstructorArgs();
86
87 /**
88 * Gets a map with declarations for beans that should be set as properties of the newly created bean. This allows for
89 * complex initialization scenarios: a bean for a bean that contains complex properties (e.g. other beans) can have
90 * nested declarations for defining these complex properties. The returned map's key are the names of the properties to
91 * initialize. The values are either {@code BeanDeclaration} implementations or collections thereof. They will be
92 * treated like this declaration (in a recursive manner), and the resulting beans are assigned to the corresponding
93 * properties.
94 *
95 * @return a map with nested bean declarations
96 */
97 Map<String, Object> getNestedBeanDeclarations();
98 }