Spring学习之IOC容器1

　　在Spring IOC容器的设计中，有两个主要的容器系列，一个是实现BeanFactory接口的简单容器系列，这系列容器只实现了容器的最基本功能；另一个是ApplicationContext应用上下文，它作为容器的高级形态而存在。应用上下文在简单容器的基础上，增加了许多面向框架的特性，同时对应用环境做了许多适配。

　　用户在使用容器时，可以使用转义符“&”来得到FactoryBean本身，用来区分通过容器来获得FactoryBean产生的对象和获取FactoryBean本身。例如，如果MyBean是一个FactoryBean，那么使用&MyBean得到的是FactoryBean，而不是MyBean这个FactoryBean产生出来的对象。

　　BeanFactory接口设计了getBean()方法，通过这个方法可以得到IOC容器中管理的bean，bean的去的是通过指定名字来索引的。

　　用户可以执行以下操作：

　　1.通过接口方法constainsBean让用户能够判断容器事都含有指定名字的Bean。

　　2.通过接口方法isSingleton来查询指定名字的Bean是否是Singleton类型的Bean。对于Singleton属性，用户可以在BeanDefinition中指定。

　　3.通过接口方法isPrototype来查询指定名字的Bean是否是prototype类型的。与Singleton属性是一样的，这个属性也可以由用户在BeanDefinition中指定。

　　4.通过接口方法isTypeMatch来查询指定了名字的Bean的Class类型是否是特定的Class类型。这个Class类型可以由用户来指定。

　　5.通过接口方法getType来查询指定名字的Bean的Class类型。

　　6.通过接口方法getAliases来查询指定了名字的Bean的所有别名，这些别名都是由用户在Beandefinition中定义的。

  1 /*
  2  * Copyright 2002-2013 the original author or authors.
  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
 17 package org.springframework.beans.factory;
 18
 19 import org.springframework.beans.BeansException;
 20
 21 /**
 22  * The root interface for accessing a Spring bean container.
 23  * This is the basic client view of a bean container;
 24  * further interfaces such as {@link ListableBeanFactory} and
 25  * {@link org.springframework.beans.factory.config.ConfigurableBeanFactory}
 26  * are available for specific purposes.
 27  *
 28  * <p>This interface is implemented by objects that hold a number of bean definitions,
 29  * each uniquely identified by a String name. Depending on the bean definition,
 30  * the factory will return either an independent instance of a contained object
 31  * (the Prototype design pattern), or a single shared instance (a superior
 32  * alternative to the Singleton design pattern, in which the instance is a
 33  * singleton in the scope of the factory). Which type of instance will be returned
 34  * depends on the bean factory configuration: the API is the same. Since Spring
 35  * 2.0, further scopes are available depending on the concrete application
 36  * context (e.g. "request" and "session" scopes in a web environment).
 37  *
 38  * <p>The point of this approach is that the BeanFactory is a central registry
 39  * of application components, and centralizes configuration of application
 40  * components (no more do individual objects need to read properties files,
 41  * for example). See chapters 4 and 11 of "Expert One-on-One J2EE Design and
 42  * Development" for a discussion of the benefits of this approach.
 43  *
 44  * <p>Note that it is generally better to rely on Dependency Injection
 45  * ("push" configuration) to configure application objects through setters
 46  * or constructors, rather than use any form of "pull" configuration like a
 47  * BeanFactory lookup. Spring‘s Dependency Injection functionality is
 48  * implemented using this BeanFactory interface and its subinterfaces.
 49  *
 50  * <p>Normally a BeanFactory will load bean definitions stored in a configuration
 51  * source (such as an XML document), and use the {@code org.springframework.beans}
 52  * package to configure the beans. However, an implementation could simply return
 53  * Java objects it creates as necessary directly in Java code. There are no
 54  * constraints on how the definitions could be stored: LDAP, RDBMS, XML,
 55  * properties file, etc. Implementations are encouraged to support references
 56  * amongst beans (Dependency Injection).
 57  *
 58  * <p>In contrast to the methods in {@link ListableBeanFactory}, all of the
 59  * operations in this interface will also check parent factories if this is a
 60  * {@link HierarchicalBeanFactory}. If a bean is not found in this factory instance,
 61  * the immediate parent factory will be asked. Beans in this factory instance
 62  * are supposed to override beans of the same name in any parent factory.
 63  *
 64  * <p>Bean factory implementations should support the standard bean lifecycle interfaces
 65  * as far as possible. The full set of initialization methods and their standard order is:<br>
 66  * 1. BeanNameAware‘s {@code setBeanName}<br>
 67  * 2. BeanClassLoaderAware‘s {@code setBeanClassLoader}<br>
 68  * 3. BeanFactoryAware‘s {@code setBeanFactory}<br>
 69  * 4. ResourceLoaderAware‘s {@code setResourceLoader}
 70  * (only applicable when running in an application context)<br>
 71  * 5. ApplicationEventPublisherAware‘s {@code setApplicationEventPublisher}
 72  * (only applicable when running in an application context)<br>
 73  * 6. MessageSourceAware‘s {@code setMessageSource}
 74  * (only applicable when running in an application context)<br>
 75  * 7. ApplicationContextAware‘s {@code setApplicationContext}
 76  * (only applicable when running in an application context)<br>
 77  * 8. ServletContextAware‘s {@code setServletContext}
 78  * (only applicable when running in a web application context)<br>
 79  * 9. {@code postProcessBeforeInitialization} methods of BeanPostProcessors<br>
 80  * 10. InitializingBean‘s {@code afterPropertiesSet}<br>
 81  * 11. a custom init-method definition<br>
 82  * 12. {@code postProcessAfterInitialization} methods of BeanPostProcessors
 83  *
 84  * <p>On shutdown of a bean factory, the following lifecycle methods apply:<br>
 85  * 1. DisposableBean‘s {@code destroy}<br>
 86  * 2. a custom destroy-method definition
 87  *
 88  * @author Rod Johnson
 89  * @author Juergen Hoeller
 90  * @author Chris Beams
 91  * @since 13 April 2001
 92  * @see BeanNameAware#setBeanName
 93  * @see BeanClassLoaderAware#setBeanClassLoader
 94  * @see BeanFactoryAware#setBeanFactory
 95  * @see org.springframework.context.ResourceLoaderAware#setResourceLoader
 96  * @see org.springframework.context.ApplicationEventPublisherAware#setApplicationEventPublisher
 97  * @see org.springframework.context.MessageSourceAware#setMessageSource
 98  * @see org.springframework.context.ApplicationContextAware#setApplicationContext
 99  * @see org.springframework.web.context.ServletContextAware#setServletContext
100  * @see org.springframework.beans.factory.config.BeanPostProcessor#postProcessBeforeInitialization
101  * @see InitializingBean#afterPropertiesSet
102  * @see org.springframework.beans.factory.support.RootBeanDefinition#getInitMethodName
103  * @see org.springframework.beans.factory.config.BeanPostProcessor#postProcessAfterInitialization
104  * @see DisposableBean#destroy
105  * @see org.springframework.beans.factory.support.RootBeanDefinition#getDestroyMethodName
106  */
107 public interface BeanFactory {
108
109     /**
110      * Used to dereference a {@link FactoryBean} instance and distinguish it from
111      * beans <i>created</i> by the FactoryBean. For example, if the bean named
112      * {@code myJndiObject} is a FactoryBean, getting {@code &myJndiObject}
113      * will return the factory, not the instance returned by the factory.
114      */
115     String FACTORY_BEAN_PREFIX = "&";
116
117     /**
118      * Return an instance, which may be shared or independent, of the specified bean.
119      * <p>This method allows a Spring BeanFactory to be used as a replacement for the
120      * Singleton or Prototype design pattern. Callers may retain references to
121      * returned objects in the case of Singleton beans.
122      * <p>Translates aliases back to the corresponding canonical bean name.
123      * Will ask the parent factory if the bean cannot be found in this factory instance.
124      * @param name the name of the bean to retrieve
125      * @return an instance of the bean
126      * @throws NoSuchBeanDefinitionException if there is no bean definition
127      * with the specified name
128      * @throws BeansException if the bean could not be obtained
129      */
130     Object getBean(String name) throws BeansException;
131
132     /**
133      * Return an instance, which may be shared or independent, of the specified bean.
134      * <p>Behaves the same as {@link #getBean(String)}, but provides a measure of type
135      * safety by throwing a BeanNotOfRequiredTypeException if the bean is not of the
136      * required type. This means that ClassCastException can‘t be thrown on casting
137      * the result correctly, as can happen with {@link #getBean(String)}.
138      * <p>Translates aliases back to the corresponding canonical bean name.
139      * Will ask the parent factory if the bean cannot be found in this factory instance.
140      * @param name the name of the bean to retrieve
141      * @param requiredType type the bean must match. Can be an interface or superclass
142      * of the actual class, or {@code null} for any match. For example, if the value
143      * is {@code Object.class}, this method will succeed whatever the class of the
144      * returned instance.
145      * @return an instance of the bean
146      * @throws NoSuchBeanDefinitionException if there is no such bean definition
147      * @throws BeanNotOfRequiredTypeException if the bean is not of the required type
148      * @throws BeansException if the bean could not be created
149      */
150     <T> T getBean(String name, Class<T> requiredType) throws BeansException;
151
152     /**
153      * Return the bean instance that uniquely matches the given object type, if any.
154      * @param requiredType type the bean must match; can be an interface or superclass.
155      * {@code null} is disallowed.
156      * <p>This method goes into {@link ListableBeanFactory} by-type lookup territory
157      * but may also be translated into a conventional by-name lookup based on the name
158      * of the given type. For more extensive retrieval operations across sets of beans,
159      * use {@link ListableBeanFactory} and/or {@link BeanFactoryUtils}.
160      * @return an instance of the single bean matching the required type
161      * @throws NoSuchBeanDefinitionException if no bean of the given type was found
162      * @throws NoUniqueBeanDefinitionException if more than one bean of the given type was found
163      * @since 3.0
164      * @see ListableBeanFactory
165      */
166     <T> T getBean(Class<T> requiredType) throws BeansException;
167
168     /**
169      * Return an instance, which may be shared or independent, of the specified bean.
170      * <p>Allows for specifying explicit constructor arguments / factory method arguments,
171      * overriding the specified default arguments (if any) in the bean definition.
172      * @param name the name of the bean to retrieve
173      * @param args arguments to use if creating a prototype using explicit arguments to a
174      * static factory method. It is invalid to use a non-null args value in any other case.
175      * @return an instance of the bean
176      * @throws NoSuchBeanDefinitionException if there is no such bean definition
177      * @throws BeanDefinitionStoreException if arguments have been given but
178      * the affected bean isn‘t a prototype
179      * @throws BeansException if the bean could not be created
180      * @since 2.5
181      */
182     Object getBean(String name, Object... args) throws BeansException;
183
184     /**
185      * Does this bean factory contain a bean definition or externally registered singleton
186      * instance with the given name?
187      * <p>If the given name is an alias, it will be translated back to the corresponding
188      * canonical bean name.
189      * <p>If this factory is hierarchical, will ask any parent factory if the bean cannot
190      * be found in this factory instance.
191      * <p>If a bean definition or singleton instance matching the given name is found,
192      * this method will return {@code true} whether the named bean definition is concrete
193      * or abstract, lazy or eager, in scope or not. Therefore, note that a {@code true}
194      * return value from this method does not necessarily indicate that {@link #getBean}
195      * will be able to obtain an instance for the same name.
196      * @param name the name of the bean to query
197      * @return whether a bean with the given name is present
198      */
199     boolean containsBean(String name);
200
201     /**
202      * Is this bean a shared singleton? That is, will {@link #getBean} always
203      * return the same instance?
204      * <p>Note: This method returning {@code false} does not clearly indicate
205      * independent instances. It indicates non-singleton instances, which may correspond
206      * to a scoped bean as well. Use the {@link #isPrototype} operation to explicitly
207      * check for independent instances.
208      * <p>Translates aliases back to the corresponding canonical bean name.
209      * Will ask the parent factory if the bean cannot be found in this factory instance.
210      * @param name the name of the bean to query
211      * @return whether this bean corresponds to a singleton instance
212      * @throws NoSuchBeanDefinitionException if there is no bean with the given name
213      * @see #getBean
214      * @see #isPrototype
215      */
216     boolean isSingleton(String name) throws NoSuchBeanDefinitionException;
217
218     /**
219      * Is this bean a prototype? That is, will {@link #getBean} always return
220      * independent instances?
221      * <p>Note: This method returning {@code false} does not clearly indicate
222      * a singleton object. It indicates non-independent instances, which may correspond
223      * to a scoped bean as well. Use the {@link #isSingleton} operation to explicitly
224      * check for a shared singleton instance.
225      * <p>Translates aliases back to the corresponding canonical bean name.
226      * Will ask the parent factory if the bean cannot be found in this factory instance.
227      * @param name the name of the bean to query
228      * @return whether this bean will always deliver independent instances
229      * @throws NoSuchBeanDefinitionException if there is no bean with the given name
230      * @since 2.0.3
231      * @see #getBean
232      * @see #isSingleton
233      */
234     boolean isPrototype(String name) throws NoSuchBeanDefinitionException;
235
236     /**
237      * Check whether the bean with the given name matches the specified type.
238      * More specifically, check whether a {@link #getBean} call for the given name
239      * would return an object that is assignable to the specified target type.
240      * <p>Translates aliases back to the corresponding canonical bean name.
241      * Will ask the parent factory if the bean cannot be found in this factory instance.
242      * @param name the name of the bean to query
243      * @param targetType the type to match against
244      * @return {@code true} if the bean type matches,
245      * {@code false} if it doesn‘t match or cannot be determined yet
246      * @throws NoSuchBeanDefinitionException if there is no bean with the given name
247      * @since 2.0.1
248      * @see #getBean
249      * @see #getType
250      */
251     boolean isTypeMatch(String name, Class<?> targetType) throws NoSuchBeanDefinitionException;
252
253     /**
254      * Determine the type of the bean with the given name. More specifically,
255      * determine the type of object that {@link #getBean} would return for the given name.
256      * <p>For a {@link FactoryBean}, return the type of object that the FactoryBean creates,
257      * as exposed by {@link FactoryBean#getObjectType()}.
258      * <p>Translates aliases back to the corresponding canonical bean name.
259      * Will ask the parent factory if the bean cannot be found in this factory instance.
260      * @param name the name of the bean to query
261      * @return the type of the bean, or {@code null} if not determinable
262      * @throws NoSuchBeanDefinitionException if there is no bean with the given name
263      * @since 1.1.2
264      * @see #getBean
265      * @see #isTypeMatch
266      */
267     Class<?> getType(String name) throws NoSuchBeanDefinitionException;
268
269     /**
270      * Return the aliases for the given bean name, if any.
271      * All of those aliases point to the same bean when used in a {@link #getBean} call.
272      * <p>If the given name is an alias, the corresponding original bean name
273      * and other aliases (if any) will be returned, with the original bean name
274      * being the first element in the array.
275      * <p>Will ask the parent factory if the bean cannot be found in this factory instance.
276      * @param name the bean name to check for aliases
277      * @return the aliases, or an empty array if none
278      * @see #getBean
279      */
280     String[] getAliases(String name);
281
282 }