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;
/* The config location defaults can be overridden via {@link #getConfigLocations}, Note: In case of multiple config locations, later bean definitions will This is a simple, one-stop shop convenience ApplicationContext. This is a convenience method to load class path resources relative to a
* Copyright 2002-2010 the original author or authors.
*
* 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.
*
*
* 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).
*
*
* override ones defined in earlier loaded files. This can be leveraged to
* deliberately override certain bean definitions via an extra XML file.
*
*
* Consider using the {@link GenericApplicationContext} class in combination
* with an {@link org.springframework.beans.factory.xml.XmlBeanDefinitionReader}
* for more flexible context setup.
*
* @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.
*
* 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;
}
}
}