001 /*****************************************************************************
002 * Copyright (c) PicoContainer Organization. All rights reserved. *
003 * ------------------------------------------------------------------------- *
004 * The software in this package is published under the terms of the BSD *
005 * style license a copy of which has been included with this distribution in *
006 * the LICENSE.txt file. *
007 * *
008 * Idea by Rachel Davies, Original code by Jon Tirsen *
009 *****************************************************************************/
010
011 package org.picocontainer;
012
013 import org.picocontainer.parameters.ComponentParameter;
014 import org.picocontainer.parameters.DefaultConstructorParameter;
015
016 import java.lang.annotation.Annotation;
017 import java.lang.reflect.Type;
018
019 /**
020 * This class provides control over the arguments that will be passed to a constructor. It can be used for finer control over
021 * what arguments are passed to a particular constructor.
022 *
023 * @author Jon Tirsén
024 * @author Aslak Hellesøy
025 * @author Thomas Heller
026 * @see MutablePicoContainer#addComponent(Object,Object,Parameter[]) a method on the
027 * {@link MutablePicoContainer} interface which allows passing in of an array of {@linkplain Parameter Parameters}.
028 * @see org.picocontainer.parameters.ComponentParameter an implementation of this interface that allows you to specify the key
029 * used for resolving the parameter.
030 * @see org.picocontainer.parameters.ConstantParameter an implementation of this interface that allows you to specify a constant
031 * that will be used for resolving the parameter.
032 */
033 public interface Parameter {
034
035 /**
036 * Zero parameter is used when you wish a component to be instantiated with its default constructor. Ex:
037 * <div class="source">
038 * <pre>
039 * MutablePicoContainer mpc = new PicoBuilder().build();
040 * mpc.addComponent(Map.class, HashMap.class, Parameter.ZERO);
041 * mpc.addComponent(List.class, ArrayList.class, Parameter.ZERO);
042 * </pre>
043 * </div>
044 * <p>By specifying the default constructor in this example code, you allow PicoContainer to recognize
045 * that HashMap(Collection) should <em>not</em> be used and avoid a CircularDependencyException.</p>
046 */
047 Parameter[] ZERO = new Parameter[] {DefaultConstructorParameter.INSTANCE};
048
049 Parameter[] DEFAULT = new Parameter[]{ ComponentParameter.DEFAULT };
050
051
052 /**
053 * Check if the Parameter can satisfy the expected type using the container.
054 *
055 * @param container the container from which dependencies are resolved.
056 * @param forAdapter the {@link org.picocontainer.ComponentAdapter} that is asking for the instance
057 * @param injecteeAdapter
058 * @param expectedType the required type
059 * @param expectedNameBinding Expected parameter name
060 * @param useNames
061 * @param binding @return <code>true</code> if the component parameter can be resolved.
062 *
063 */
064 Resolver resolve(PicoContainer container, ComponentAdapter<?> forAdapter,
065 ComponentAdapter<?> injecteeAdapter, Type expectedType, NameBinding expectedNameBinding,
066 boolean useNames, Annotation binding);
067
068 /**
069 * Verify that the Parameter can satisfy the expected type using the container
070 *
071 * @param container the container from which dependencies are resolved.
072 * @param adapter the {@link ComponentAdapter} that is asking for the verification
073 * @param expectedType the required type
074 * @param expectedNameBinding Expected parameter name
075 *
076 * @param useNames
077 * @param binding
078 * @throws PicoCompositionException if parameter and its dependencies cannot be resolved
079 */
080 void verify(PicoContainer container, ComponentAdapter<?> adapter,
081 Type expectedType, NameBinding expectedNameBinding,
082 boolean useNames, Annotation binding);
083
084 /**
085 * Accepts a visitor for this Parameter. The method is normally called by visiting a {@link ComponentAdapter}, that
086 * cascades the {@linkplain PicoVisitor visitor} also down to all its {@linkplain Parameter Parameters}.
087 *
088 * @param visitor the visitor.
089 *
090 */
091 void accept(PicoVisitor visitor);
092
093 /**
094 * Resolver is used transitarily during resolving of Parameters.
095 * isResolvable() and resolveInstance() in series do not cause resolveAdapter() twice
096 */
097 public static interface Resolver {
098
099 /**
100 * @return can the parameter be resolved
101 */
102 public boolean isResolved();
103
104 /**
105 * @return the instance to be used to inject as a parameter
106 */
107 public Object resolveInstance();
108
109 /**
110 * @return the ComponentAdapter for the parameter in question
111 */
112 public ComponentAdapter<?> getComponentAdapter();
113
114 }
115
116 /**
117 * The Parameter cannot (ever) be resolved
118 */
119 public static class NotResolved implements Resolver {
120 public boolean isResolved() {
121 return false;
122 }
123
124 public Object resolveInstance() {
125 return null;
126 }
127
128 public ComponentAdapter<?> getComponentAdapter() {
129 return null;
130 }
131 }
132
133 /**
134 * Delegate to another reolver
135 */
136 public abstract static class DelegateResolver implements Resolver {
137 private final Resolver delegate;
138
139 public DelegateResolver(Resolver delegate) {
140 this.delegate = delegate;
141 }
142
143 public boolean isResolved() {
144 return delegate.isResolved();
145 }
146
147 public Object resolveInstance() {
148 return delegate.resolveInstance();
149 }
150
151 public ComponentAdapter<?> getComponentAdapter() {
152 return delegate.getComponentAdapter();
153 }
154 }
155
156 /**
157 * A fixed value wrapped as a Resolver
158 */
159 public static class ValueResolver implements Resolver {
160
161 private final boolean resolvable;
162 private final Object value;
163 private final ComponentAdapter<?> adapter;
164
165 public ValueResolver(boolean resolvable, Object value, ComponentAdapter<?> adapter) {
166 this.resolvable = resolvable;
167 this.value = value;
168 this.adapter = adapter;
169 }
170
171 public boolean isResolved() {
172 return resolvable;
173 }
174
175 public Object resolveInstance() {
176 return value;
177 }
178
179 public ComponentAdapter<?> getComponentAdapter() {
180 return adapter;
181 }
182 }
183
184 }