springioc容器学习第三篇----ApplicationContext容器初始化

前两篇已经学习了springIOC容器BeanFactory的实现DefaultListableBeanFactory的编程式使用，以及XmlBeanFactory的实现和使用，对springIOC容器如何加载xml文件中的类定义，加载bean的过程；

       本篇主要了解springIoc容器的初始化过程，这里了解的是ApplicationContext；这里以ApplicationContext的实现类ClassPathXmlApplicationContext来举例；

/*
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 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


package org.springframework.context.support;


import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;
import org.springframework.util.Assert;


/**
 * Standalone XML application context, taking the context definition files
 * from the class path, interpreting plain paths as class path resource names
 * that include the package path (e.g. "mypackage/myresource.txt"). Useful for
 * test harnesses as well as for application contexts embedded within JARs.
 *
 * <p>The config location defaults can be overridden via {@link #getConfigLocations},
 * Config locations can either denote concrete files like "/myfiles/context.xml"
 * or Ant-style patterns like "/myfiles/*-context.xml" (see the
 * {@link org.springframework.util.AntPathMatcher} javadoc for pattern details).
 *
 * <p>Note: In case of multiple config locations, later bean definitions will
 * override ones defined in earlier loaded files. This can be leveraged to
 * deliberately override certain bean definitions via an extra XML file.
 *
 * <p><b>This is a simple, one-stop shop convenience ApplicationContext.
 * Consider using the {@link GenericApplicationContext} class in combination
 * with an {@link org.springframework.beans.factory.xml.XmlBeanDefinitionReader}
 * for more flexible context setup.</b>
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see #getResource
 * @see #getResourceByPath
 * @see GenericApplicationContext
 */
public class ClassPathXmlApplicationContext extends AbstractXmlApplicationContext {


private Resource[] configResources;




/**
* Create a new ClassPathXmlApplicationContext for bean-style configuration.
* @see #setConfigLocation
* @see #setConfigLocations
* @see #afterPropertiesSet()
*/
public ClassPathXmlApplicationContext() {
}


/**
* Create a new ClassPathXmlApplicationContext for bean-style configuration.
* @param parent the parent context
* @see #setConfigLocation
* @see #setConfigLocations
* @see #afterPropertiesSet()
*/
public ClassPathXmlApplicationContext(ApplicationContext parent) {
super(parent);
}


/**
* Create a new ClassPathXmlApplicationContext, loading the definitions
* from the given XML file and automatically refreshing the context.
* @param configLocation resource location
* @throws BeansException if context creation failed
*/
public ClassPathXmlApplicationContext(String configLocation) throws BeansException {
this(new String[] {configLocation}, true, null);
}


/**
* Create a new ClassPathXmlApplicationContext, loading the definitions
* from the given XML files and automatically refreshing the context.
* @param configLocations array of resource locations
* @throws BeansException if context creation failed
*/
public ClassPathXmlApplicationContext(String... configLocations) throws BeansException {
this(configLocations, true, null);
}


/**
* Create a new ClassPathXmlApplicationContext with the given parent,
* loading the definitions from the given XML files and automatically
* refreshing the context.
* @param configLocations array of resource locations
* @param parent the parent context
* @throws BeansException if context creation failed
*/
public ClassPathXmlApplicationContext(String[] configLocations, ApplicationContext parent) throws BeansException {
this(configLocations, true, parent);
}


/**
* Create a new ClassPathXmlApplicationContext, loading the definitions
* from the given XML files.
* @param configLocations array of resource locations
* @param refresh whether to automatically refresh the context,
* loading all bean definitions and creating all singletons.
* Alternatively, call refresh manually after further configuring the context.
* @throws BeansException if context creation failed
* @see #refresh()
*/
public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh) throws BeansException {
this(configLocations, refresh, null);
}


/**
* Create a new ClassPathXmlApplicationContext with the given parent,
* loading the definitions from the given XML files.
* @param configLocations array of resource locations
* @param refresh whether to automatically refresh the context,
* loading all bean definitions and creating all singletons.
* Alternatively, call refresh manually after further configuring the context.
* @param parent the parent context
* @throws BeansException if context creation failed
* @see #refresh()
*/
public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent)
throws BeansException {


super(parent);
setConfigLocations(configLocations);
if (refresh) {
refresh();
}
}




/**
* Create a new ClassPathXmlApplicationContext, loading the definitions
* from the given XML file and automatically refreshing the context.
* <p>This is a convenience method to load class path resources relative to a
* given Class. For full flexibility, consider using a GenericApplicationContext
* with an XmlBeanDefinitionReader and a ClassPathResource argument.
* @param path relative (or absolute) path within the class path
* @param clazz the class to load resources with (basis for the given paths)
* @throws BeansException if context creation failed
* @see org.springframework.core.io.ClassPathResource#ClassPathResource(String, Class)
* @see org.springframework.context.support.GenericApplicationContext
* @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader
*/
public ClassPathXmlApplicationContext(String path, Class clazz) throws BeansException {
this(new String[] {path}, clazz);
}


/**
* Create a new ClassPathXmlApplicationContext, loading the definitions
* from the given XML files and automatically refreshing the context.
* @param paths array of relative (or absolute) paths within the class path
* @param clazz the class to load resources with (basis for the given paths)
* @throws BeansException if context creation failed
* @see org.springframework.core.io.ClassPathResource#ClassPathResource(String, Class)
* @see org.springframework.context.support.GenericApplicationContext
* @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader
*/
public ClassPathXmlApplicationContext(String[] paths, Class clazz) throws BeansException {
this(paths, clazz, null);
}


/**
* Create a new ClassPathXmlApplicationContext with the given parent,
* loading the definitions from the given XML files and automatically
* refreshing the context.
* @param paths array of relative (or absolute) paths within the class path
* @param clazz the class to load resources with (basis for the given paths)
* @param parent the parent context
* @throws BeansException if context creation failed
* @see org.springframework.core.io.ClassPathResource#ClassPathResource(String, Class)
* @see org.springframework.context.support.GenericApplicationContext
* @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader
*/
public ClassPathXmlApplicationContext(String[] paths, Class clazz, ApplicationContext parent)
throws BeansException {


super(parent);
Assert.notNull(paths, "Path array must not be null");
Assert.notNull(clazz, "Class argument must not be null");
this.configResources = new Resource[paths.length];
for (int i = 0; i < paths.length; i++) {
this.configResources[i] = new ClassPathResource(paths[i], clazz);
}
refresh();
}




@Override
protected Resource[] getConfigResources() {
return this.configResources;
}


}

通过ClassPathXmlApplicationContext的源码可以看出ClassPathXmlApplicationContext是通过refresh（）实现初始化的；

public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
prepareRefresh();


// Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();


// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);


try {
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);

// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);


// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);


// Initialize message source for this context.
initMessageSource();


// Initialize event multicaster for this context.
initApplicationEventMulticaster();


// Initialize other special beans in specific context subclasses.
onRefresh();


// Check for listener beans and register them.
registerListeners();


// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);


// Last step: publish corresponding event.
finishRefresh();
}


catch (BeansException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - " +
"cancelling refresh attempt: " + ex);
}


// Destroy already created singletons to avoid dangling resources.
destroyBeans();


// Reset 'active' flag.
cancelRefresh(ex);


// Propagate exception to caller.
throw ex;
}
}
}