1/**
2 * Copyright (C) 2008 Google Inc.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.google.inject.spi;
18
19import com.google.inject.Binder;
20
21/**
22 * A core component of a module or injector.
23 *
24 * <p>The elements of a module can be inspected, validated and rewritten. Use {@link
25 * Elements#getElements(com.google.inject.Module[]) Elements.getElements()} to read the elements
26 * from a module, and {@link Elements#getModule(Iterable) Elements.getModule()} to rewrite them.
27 * This can be used for static analysis and generation of Guice modules.
28 *
29 * <p>The elements of an injector can be inspected and exercised. Use {@link
30 * com.google.inject.Injector#getBindings Injector.getBindings()} to reflect on Guice injectors.
31 *
32 * @author jessewilson@google.com (Jesse Wilson)
33 * @author crazybob@google.com (Bob Lee)
34 * @since 2.0
35 */
36public interface Element {
37
38  /**
39   * Returns an arbitrary object containing information about the "place" where this element was
40   * configured. Used by Guice in the production of descriptive error messages.
41   *
42   * <p>Tools might specially handle types they know about; {@code StackTraceElement} is a good
43   * example. Tools should simply call {@code toString()} on the source object if the type is
44   * unfamiliar.
45   */
46  Object getSource();
47
48  /**
49   * Accepts an element visitor. Invokes the visitor method specific to this element's type.
50   *
51   * @param visitor to call back on
52   */
53  <T> T acceptVisitor(ElementVisitor<T> visitor);
54
55  /**
56   * Writes this module element to the given binder (optional operation).
57   *
58   * @param binder to apply configuration element to
59   * @throws UnsupportedOperationException if the {@code applyTo} method is not supported by this
60   *     element.
61   */
62  void applyTo(Binder binder);
63
64}
65