Spring源码分析-配置文件加载流程

Spring配置文件加载流程

Spring配置文件是集成了Spring框架的项目的核心，引擎从哪里开始，中间都执行了哪些操作，小谈一下它的执行流程。

容器先是加载web .xml

 

接着是applicationContext.xml在web .xml里的注册

 

一种方法是加入ContextLoaderServlet这个servlet

<
context-param
>
        <
param-name
>
contextConfigLocation
</
param-name
>
        <
param-value
>
/WEB
-INF/applicationContext.xml
</
param-value
>
    </
context-param
>
     <
servlet
>
        <
servlet-name
>
context
</
servlet-name
>
        <
servlet-class
>
            org.springframework.web
.context.ContextLoaderServlet
        </
servlet-class
>
        <
load-on-startup
>
0
</
load-on-startup
>
    </
servlet
>

<context-param>
		<param-name>contextConfigLocation</param-name>
		<param-value>/WEB
-INF/applicationContext.xml</param-value>
	</context-param>
     <servlet>
		<servlet-name>context</servlet-name>
		<servlet-class>
			org.springframework.web
.context.ContextLoaderServlet
		</servlet-class>
		<load-on-startup>0</load-on-startup>
	</servlet>

还有一种是添加ContextLoaderListener这个监听器

<
context-param
>
    <
param-name
>
contextConfigLocation
</
param-name
>
    <
param-value
>
/WEB
-INF/applicationContext.xml
</
param-value
>
</
context-param
>

<
listener
>
    <
listener-class
>
org.springframework.web
.context.ContextLoaderListener
</
listener-class
>
</
listener
>

<context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>/WEB
-INF/applicationContext.xml</param-value>
</context-param>

<listener>
    <listener-class>org.springframework.web
.context.ContextLoaderListener</listener-class>
</listener>

 

 

下面是ContextLoaderServlet源代码

package
 org.springframework.web
.context;

import
 java.io.IOException;

import
 javax.servlet.ServletException;
import
 javax.servlet.http.HttpServlet;
import
 javax.servlet.http.HttpServletRequest;
import
 javax.servlet.http.HttpServletResponse;

public
 
class
 ContextLoaderServlet 
extends
 HttpServlet {

    private
 ContextLoader
 contextLoader
;


    /**
     * Initialize the root web
 application context.
     */

public
 
void
 init() 
throws
 ServletException {
        this
.contextLoader
 = createContextLoader();
        this
.contextLoader
.initWebApplicationContext(getServletContext());
    }   /**
     * Create the ContextLoader
 to use. Can be overridden in
 subclasses.
     * @return the new ContextLoader
     */
    protected
 ContextLoader
 createContextLoader() {
        return
 
new
 ContextLoader
();
    }

    /**
     * Return the ContextLoader
 used by this servlet.
     * @return the current ContextLoader
     */
    public
 ContextLoader
 getContextLoader() {
        return
 
this
.contextLoader
;
    }


    /**
     * Close the root web
 application context.
     */
    public
 
void
 destroy() {
        if
 (
this
.contextLoader
 != 
null
) {
            this
.contextLoader
.closeWebApplicationContext(getServletContext());
        }
    }


    /**
     * This should never even be called since no mapping to this servlet should
     * ever be created in
 web
.xml. That's why a correctly invoked Servlet 2.3
     * listener is much more appropriate for initialization work ;-)
     */
    public
 
void
 service(HttpServletRequest request, HttpServletResponse response) 
throws
 IOException {
        getServletContext().log(
                "Attempt to call service method on ContextLoaderServlet as ["
 +
                request.getRequestURI() + "] was ignored"
);
        response.sendError(HttpServletResponse.SC_BAD_REQUEST);
    }


    public
 String getServletInfo() {
        return
 
"ContextLoaderServlet for Servlet API 2.3 "
 +
            "(deprecated in
 favor of ContextLoaderListener for Servlet API 2.4)"
;
    }

}

package org.springframework.web
.context;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ContextLoaderServlet extends HttpServlet {

	private ContextLoader
 contextLoader
;


	/**
	 * Initialize the root web
 application context.
	 */

public void init() throws ServletException {
		this.contextLoader
 = createContextLoader();
		this.contextLoader
.initWebApplicationContext(getServletContext());
	}	/**
	 * Create the ContextLoader
 to use. Can be overridden in
 subclasses.
	 * @return the new ContextLoader

	 */
	protected ContextLoader
 createContextLoader() {
		return new ContextLoader
();
	}

	/**
	 * Return the ContextLoader
 used by this servlet. 
	 * @return the current ContextLoader

	 */
	public ContextLoader
 getContextLoader() {
		return this.contextLoader
;
	}


	/**
	 * Close the root web
 application context.
	 */
	public void destroy() {
		if (this.contextLoader
 != null) {
			this.contextLoader
.closeWebApplicationContext(getServletContext());
		}
	}


	/**
	 * This should never even be called since no mapping to this servlet should
	 * ever be created in
 web
.xml. That's why a correctly invoked Servlet 2.3
	 * listener is much more appropriate for initialization work ;-)
	 */
	public void service(HttpServletRequest request, HttpServletResponse response) throws IOException {
		getServletContext().log(
				"Attempt to call service method on ContextLoaderServlet as [" +
				request.getRequestURI() + "] was ignored");
		response.sendError(HttpServletResponse.SC_BAD_REQUEST);
	}


	public String getServletInfo() {
		return "ContextLoaderServlet for Servlet API 2.3 " +
		    "(deprecated in
 favor of ContextLoaderListener for Servlet API 2.4)";
	}

}

 

ContextLoaderListener源代码

package
 org.springframework.web
.context;

import
 javax.servlet.ServletContextEvent;
import
 javax.servlet.ServletContextListener;

public
 
class
 ContextLoaderListener 
implements
 ServletContextListener {

    private
 ContextLoader
 contextLoader
;


    /**
     * Initialize the root web
 application context.
     */
    public
 
void
 contextInitialized(ServletContextEvent event) {
               this
.contextLoader
 = createContextLoader();
        this
.contextLoader
.initWebApplicationContext(event.getServletContext());
    }

    /**
     * Create the ContextLoader
 to use. Can be overridden in
 subclasses.
     * @return the new ContextLoader
     */
    protected
 ContextLoader
 createContextLoader() {
        return
 
new
 ContextLoader
();
    }

    /**
     * Return the ContextLoader
 used by this listener.
     * @return the current ContextLoader
     */
    public
 ContextLoader
 getContextLoader() {
        return
 
this
.contextLoader
;
    }


    /**
     * Close the root web
 application context.
     */
    public
 
void
 contextDestroyed(ServletContextEvent event) {
        if
 (
this
.contextLoader
 != 
null
) {
            this
.contextLoader
.closeWebApplicationContext(event.getServletContext());
        }
    }

}

package org.springframework.web
.context;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class ContextLoaderListener implements ServletContextListener {

	private ContextLoader
 contextLoader
;


	/**
	 * Initialize the root web
 application context.
	 */
	public void contextInitialized(ServletContextEvent event) {
               this.contextLoader
 = createContextLoader();
		this.contextLoader
.initWebApplicationContext(event.getServletContext());
	}

	/**
	 * Create the ContextLoader
 to use. Can be overridden in
 subclasses.
	 * @return the new ContextLoader

	 */
	protected ContextLoader
 createContextLoader() {
		return new ContextLoader
();
	}

	/**
	 * Return the ContextLoader
 used by this listener.
	 * @return the current ContextLoader

	 */
	public ContextLoader
 getContextLoader() {
		return this.contextLoader
;
	}


	/**
	 * Close the root web
 application context.
	 */
	public void contextDestroyed(ServletContextEvent event) {
		if (this.contextLoader
 != null) {
			this.contextLoader
.closeWebApplicationContext(event.getServletContext());
		}
	}

}

 以上都提到了ContextLoader 这个类

package
 org.springframework.web
.context;

public
 
class
 ContextLoader
 {

    public
 
static
 
final
 String CONTEXT_CLASS_PARAM = 
"contextClass"
;

    public
 
static
 
final
 String CONFIG_LOCATION_PARAM = 
"contextConfigLocation"
;

       public
 
static
 
final
 String LOCATOR_FACTORY_SELECTOR_PARAM = 
"locatorFactorySelector"
;

    public
 
static
 
final
 String LOCATOR_FACTORY_KEY_PARAM = 
"parentContextKey"
;

    private
 
static
 
final
 String DEFAULT_STRATEGIES_PATH = 
"ContextLoader
.properties"
;


    private
 
static
 
final
 Properties defaultStrategies;

    static
 {
                try
 {
            ClassPathResource resource = new
 ClassPathResource(DEFAULT_STRATEGIES_PATH, ContextLoader
.
class
);
            defaultStrategies = PropertiesLoaderUtils.loadProperties(resource);
        }
        catch
 (IOException ex) {
            throw
 
new
 IllegalStateException(
"Could not load 'ContextLoader
.properties': "
 + ex.getMessage());
        }
    }


    private
 
static
 
final
 Log logger = LogFactory.getLog(ContextLoader
.
class
);

    private
 
static
 
final
 Map currentContextPerThread = CollectionFactory.createConcurrentMapIfPossible(
1
);

    private
 WebApplicationContext context;

    private
 BeanFactoryReference parentContextRef;

    public
 WebApplicationContext initWebApplicationContext(ServletContext servletContext)

          throws
 IllegalStateException, BeansException {

        if
 (servletContext.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE) != 
null
) {
            throw
 
new
 IllegalStateException(
                    "Cannot initialize context because there is already a root application context present - "
 +
                    "check
 whether
 you
 have
 multiple
 ContextLoader
* definitions
 in
 your
 web
.xml!"
);
        }

        servletContext.log("Initializing Spring root WebApplicationContext"
);
        if
 (logger.isInfoEnabled()) {
            logger.info("Root WebApplicationContext: initialization started"
);
        }
        long
 startTime = System.currentTimeMillis();

        try
 {
            // Determine parent for root web
 application context, if any.
            ApplicationContext parent = loadParentContext(servletContext);

            // Store context in
 local instance variable, to guarantee that
            // it is available on ServletContext shutdown.
            this
.context = createWebApplicationContext(servletContext, parent);
            servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this
.context);
            currentContextPerThread.put(Thread.currentThread().getContextClassLoader(), this
.context);

            if
 (logger.isDebugEnabled()) {
                logger.debug("Published root WebApplicationContext as ServletContext attribute with name ["
 +
                        WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE + "]"
);
            }
            if
 (logger.isInfoEnabled()) {
                long
 elapsedTime = System.currentTimeMillis() - startTime;
                logger.info("Root WebApplicationContext: initialization completed in
 "
 + elapsedTime + 
" ms"
);
            }

            return
 
this
.context;
        }
        catch
 (RuntimeException ex) {
            logger.error("Context initialization failed"
, ex);
            servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, ex);
            throw
 ex;
        }
        catch
 (Error err) {
            logger.error("Context initialization failed"
, err);
            servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, err);
            throw
 err;
        }
    }

    protected
 WebApplicationContext createWebApplicationContext(
            ServletContext servletContext, ApplicationContext parent) throws
 BeansException {

        Class contextClass = determineContextClass(servletContext);
        if
 (!ConfigurableWebApplicationContext.
class
.isAssignableFrom(contextClass)) {
            throw
 
new
 ApplicationContextException(
"Custom context class ["
 + contextClass.getName() +
                    "] is not of type ["
 + ConfigurableWebApplicationContext.
class
.getName() + 
"]"
);
        }

        ConfigurableWebApplicationContext wac =
                (ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);
        wac.setParent(parent);
        wac.setServletContext(servletContext);
        <span style="color: rgb(0, 0, 0);"
>wac.setConfigLocation(servletContext.getInitParameter(CONFIG_LOCATION_PARAM));</span>






customizeContext(servletContext, wac);
        wac.refresh();

        return
 wac;
    }

        protected
 Class determineContextClass(ServletContext servletContext) 
throws
 ApplicationContextException {
        String contextClassName = servletContext.getInitParameter(CONTEXT_CLASS_PARAM);
        if
 (contextClassName != 
null
) {
            try
 {
                return
 ClassUtils.forName(contextClassName);
            }
            catch
 (ClassNotFoundException ex) {
                throw
 
new
 ApplicationContextException(
                        "Failed to load custom context class ["
 + contextClassName + 
"]"
, ex);
            }
        }
        else
 {
            contextClassName = defaultStrategies.getProperty(WebApplicationContext.class
.getName());
            try
 {
                return
 ClassUtils.forName(contextClassName, ContextLoader
.
class
.getClassLoader());
            }
            catch
 (ClassNotFoundException ex) {
                throw
 
new
 ApplicationContextException(
                        "Failed to load default context class ["
 + contextClassName + 
"]"
, ex);
            }
        }
    }

        protected
 
void
 customizeContext(
            ServletContext servletContext, ConfigurableWebApplicationContext applicationContext) {
    }

    protected
 ApplicationContext loadParentContext(ServletContext servletContext)
            throws
 BeansException {

        ApplicationContext parentContext = null
;
        String locatorFactorySelector = servletContext.getInitParameter(LOCATOR_FACTORY_SELECTOR_PARAM);
        String parentContextKey = servletContext.getInitParameter(LOCATOR_FACTORY_KEY_PARAM);

        if
 (parentContextKey != 
null
) {
            // locatorFactorySelector may be null, indicating the default "classpath*:beanRefContext.xml"
            BeanFactoryLocator locator = ContextSingletonBeanFactoryLocator.getInstance(locatorFactorySelector);
            if
 (logger.isDebugEnabled()) {
                logger.debug("Getting parent context definition: using parent context key of '"
 +
                        parentContextKey + "' with BeanFactoryLocator"
);
            }
            this
.parentContextRef = locator.useBeanFactory(parentContextKey);
            parentContext = (ApplicationContext) this
.parentContextRef.getFactory();
        }

        return
 parentContext;
    }

    public
 
void
 closeWebApplicationContext(ServletContext servletContext) {
        servletContext.log("Closing Spring root WebApplicationContext"
);
        try
 {
            if
 (
this
.context 
instanceof
 ConfigurableWebApplicationContext) {
                ((ConfigurableWebApplicationContext) this
.context).close();
            }
        }
        finally
 {
            currentContextPerThread.remove(Thread.currentThread().getContextClassLoader());
            servletContext.removeAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);
            if
 (
this
.parentContextRef != 
null
) {
                this
.parentContextRef.release();
            }
        }
    }


    public
 
static
 WebApplicationContext getCurrentWebApplicationContext() {
        return
 (WebApplicationContext) currentContextPerThread.get(Thread.currentThread().getContextClassLoader());
    }

}

package org.springframework.web
.context;

public class ContextLoader
 {

	public static final String CONTEXT_CLASS_PARAM = "contextClass";

	public static final String CONFIG_LOCATION_PARAM = "contextConfigLocation";

       public static final String LOCATOR_FACTORY_SELECTOR_PARAM = "locatorFactorySelector";

	public static final String LOCATOR_FACTORY_KEY_PARAM = "parentContextKey";

	private static final String DEFAULT_STRATEGIES_PATH = "ContextLoader
.properties";


	private static final Properties defaultStrategies;

	static {
				try {
			ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, ContextLoader
.class);
			defaultStrategies = PropertiesLoaderUtils.loadProperties(resource);
		}
		catch (IOException ex) {
			throw new IllegalStateException("Could not load 'ContextLoader
.properties': " + ex.getMessage());
		}
	}


	private static final Log logger = LogFactory.getLog(ContextLoader
.class);

	private static final Map currentContextPerThread = CollectionFactory.createConcurrentMapIfPossible(1);

	private WebApplicationContext context;

	private BeanFactoryReference parentContextRef;

	public WebApplicationContext initWebApplicationContext(ServletContext servletContext)

          throws IllegalStateException, BeansException {

		if (servletContext.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE) != null) {
			throw new IllegalStateException(
					"Cannot initialize context because there is already a root application context present - " +
					"check
 whether
 you
 have
 multiple
 ContextLoader
* definitions
 in
 your
 web
.xml!");
		}

		servletContext.log("Initializing Spring root WebApplicationContext");
		if (logger.isInfoEnabled()) {
			logger.info("Root WebApplicationContext: initialization started");
		}
		long startTime = System.currentTimeMillis();

		try {
			// Determine parent for root web
 application context, if any.
			ApplicationContext parent = loadParentContext(servletContext);

			// Store context in
 local instance variable, to guarantee that
			// it is available on ServletContext shutdown.
			this.context = createWebApplicationContext(servletContext, parent);
			servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context);
			currentContextPerThread.put(Thread.currentThread().getContextClassLoader(), this.context);

			if (logger.isDebugEnabled()) {
				logger.debug("Published root WebApplicationContext as ServletContext attribute with name [" +
						WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE + "]");
			}
			if (logger.isInfoEnabled()) {
				long elapsedTime = System.currentTimeMillis() - startTime;
				logger.info("Root WebApplicationContext: initialization completed in
 " + elapsedTime + " ms");
			}

			return this.context;
		}
		catch (RuntimeException ex) {
			logger.error("Context initialization failed", ex);
			servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, ex);
			throw ex;
		}
		catch (Error err) {
			logger.error("Context initialization failed", err);
			servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, err);
			throw err;
		}
	}

	protected WebApplicationContext createWebApplicationContext(
			ServletContext servletContext, ApplicationContext parent) throws BeansException {

		Class contextClass = determineContextClass(servletContext);
		if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {
			throw new ApplicationContextException("Custom context class [" + contextClass.getName() +
					"] is not of type [" + ConfigurableWebApplicationContext.class.getName() + "]");
		}

		ConfigurableWebApplicationContext wac =
				(ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);
		wac.setParent(parent);
		wac.setServletContext(servletContext);
		wac.setConfigLocation(servletContext.getInitParameter(CONFIG_LOCATION_PARAM));







customizeContext(servletContext, wac);
		wac.refresh();

		return wac;
	}

		protected Class determineContextClass(ServletContext servletContext)

  


  

    
    
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