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- /*
- * Copyright (c) 2006-2015 DMDirc Developers
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
- * SOFTWARE.
- */
-
- package com.dmdirc.util;
-
- import java.lang.reflect.Constructor;
- import java.util.HashMap;
- import java.util.Map;
-
- /**
- * Facilitates simple injection of parameters into a constructor.
- * <p>
- * Injectors may be given a set of parent injectors, from which they will
- * inherit parameters. No checking is performed to prevent circular references
- * within parents.
- */
- public class SimpleInjector {
-
- /** The parent injectors, if any. */
- private final SimpleInjector[] parents;
-
- /** A mapping of known classes to the objects that should be injected. */
- private final Map<Class<?>, Object> parameters = new HashMap<>();
-
- /**
- * Creates a new injector which will inherit injection parameters from
- * the specified parent. Parent graphs must be acyclic.
- *
- * @param parents The injectors to inherit parameters from.
- */
- public SimpleInjector(final SimpleInjector ... parents) {
- this.parents = new SimpleInjector[parents.length];
- System.arraycopy(parents, 0, this.parents, 0, parents.length);
- }
-
- /**
- * Adds a new injectable object to this injector. If a constructor requires
- * an instance of the specified class, it will be given the specified
- * object. If an association has already been made for the specified class,
- * it will be replaced with the new object.
- *
- * @param clazz The type of parameter which should be injected
- * @param object The value to inject for the parameter
- */
- public void addParameter(final Class<?> clazz, final Object object) {
- parameters.put(clazz, object);
- }
-
- /**
- * Adds the specified object as an injectable parameter for all of its
- * known classes and interface. This is equivalent to calling
- * {@link #addParameter(Class, Object)} for the object's
- * class, all superclasses, and all interfaces.
- *
- * @param object The object to be injected
- */
- public void addParameter(final Object object) {
- // Iterate the object hierarchy up
- Class<?> target = object.getClass();
- do {
- addParameter(target, object);
-
- // Add all interfaces
- for (Class<?> iface : target.getInterfaces()) {
- addParameter(iface, object);
- }
-
- target = target.getSuperclass();
- } while (target != null);
- }
-
- /**
- * Retrieves a mapping of known injectable types to their corresponding
- * values. This mapping will also include mappings defined in all of this
- * injector's parents.
- *
- * @return A map of injectable parameters
- */
- public Map<Class<?>, Object> getParameters() {
- final Map<Class<?>, Object> localParams = new HashMap<>(parameters.size());
-
- for (SimpleInjector parent : parents) {
- localParams.putAll(parent.getParameters());
- }
-
- // Note: insert local parameters after so they override parent params.
- localParams.putAll(parameters);
-
- return localParams;
- }
-
- /**
- * Attempts to create a new instance of the specified class by injecting
- * parameters into the constructor(s). If no constructors are found which
- * can be satisfied by the known parameters, or if all satisfiable
- * constructors throw exceptions, an IllegalArgumentException will be
- * thrown.
- * <p>
- * If multiple constructors are available that are satisfiable using the
- * known arguments, no guarantee is given as to which will be used.
- *
- * @param <T> The type of object being instantiated
- * @param clazz The class to create an instance of
- * @return An instance of the specified class
- * @throws IllegalArgumentException If the class could not be instantiated
- */
- @SuppressWarnings("unchecked")
- public <T> T createInstance(final Class<T> clazz) {
- final Map<Class<?>, Object> params = getParameters();
- Throwable throwable = null;
-
- for (Constructor<?> rawCtor : clazz.getConstructors()) {
- final Constructor<T> ctor = (Constructor<T>) rawCtor;
- final Object[] args = new Object[ctor.getParameterTypes().length];
-
- int i = 0;
- for (Class<?> paramType : ctor.getParameterTypes()) {
- if (params.containsKey(paramType)) {
- args[i++] = params.get(paramType);
- } else {
- break;
- }
- }
-
- if (i == args.length) {
- try {
- return ctor.newInstance(args);
- } catch (ReflectiveOperationException ex) {
- throwable = ex;
- }
- }
- }
-
- if (throwable == null) {
- throw new IllegalArgumentException("No declared constructors "
- + "could be satisfied with known parameters");
- }
-
- throw new IllegalArgumentException("A satisfiable constructor was "
- + "found but threw an exception", throwable);
- }
-
- }
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