https://github.com/spring-projects/spring-framework: Spring Web (Spring IO)
  • Juergen Hoeller 
/*
 * Copyright 2002-2017 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.web.context.support;

import java.io.File;
import javax.servlet.ServletContext;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ApplicationObjectSupport;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.web.context.ServletContextAware;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.util.WebUtils;


Convenient superclass for application objects running in a WebApplicationContext. Provides getWebApplicationContext(), getServletContext(), and getTempDir() accessors. 
Note: It is generally recommended to use individual callback interfaces for the actual callbacks needed. This broad base class is primarily intended for use within the framework, in case of ServletContext access etc typically being needed. 
Author:Juergen Hoeller
See Also:
Since:28.08.2003
/**
 * Convenient superclass for application objects running in a {@link WebApplicationContext}.
 * Provides {@code getWebApplicationContext()}, {@code getServletContext()}, and
 * {@code getTempDir()} accessors.
 *
 * <p>Note: It is generally recommended to use individual callback interfaces for the actual
 * callbacks needed. This broad base class is primarily intended for use within the framework,
 * in case of {@link ServletContext} access etc typically being needed.
 *
 * @author Juergen Hoeller
 * @since 28.08.2003
 * @see SpringBeanAutowiringSupport
 */
public abstract class WebApplicationObjectSupport extends ApplicationObjectSupport implements ServletContextAware {

	@Nullable
	private ServletContext servletContext;


	@Override
	public final void setServletContext(ServletContext servletContext) {
		if (servletContext != this.servletContext) {
			this.servletContext = servletContext;
			initServletContext(servletContext);
		}
	}

	
Overrides the base class behavior to enforce running in an ApplicationContext.
All accessors will throw IllegalStateException if not running in a context.

See Also:
/**
	 * Overrides the base class behavior to enforce running in an ApplicationContext.
	 * All accessors will throw IllegalStateException if not running in a context.
	 * @see #getApplicationContext()
	 * @see #getMessageSourceAccessor()
	 * @see #getWebApplicationContext()
	 * @see #getServletContext()
	 * @see #getTempDir()
	 */
	@Override
	protected boolean isContextRequired() {
		return true;
	}

	
Calls initServletContext(ServletContext) if the given ApplicationContext is a WebApplicationContext. 
/**
	 * Calls {@link #initServletContext(javax.servlet.ServletContext)} if the
	 * given ApplicationContext is a {@link WebApplicationContext}.
	 */
	@Override
	protected void initApplicationContext(ApplicationContext context) {
		super.initApplicationContext(context);
		if (this.servletContext == null && context instanceof WebApplicationContext) {
			this.servletContext = ((WebApplicationContext) context).getServletContext();
			if (this.servletContext != null) {
				initServletContext(this.servletContext);
			}
		}
	}

	
Subclasses may override this for custom initialization based
on the ServletContext that this application object runs in.

The default implementation is empty. Called by initApplicationContext(ApplicationContext) as well as setServletContext(ServletContext). 
Params:
  • servletContext – the ServletContext that this application object runs in (never null)
/**
	 * Subclasses may override this for custom initialization based
	 * on the ServletContext that this application object runs in.
	 * <p>The default implementation is empty. Called by
	 * {@link #initApplicationContext(org.springframework.context.ApplicationContext)}
	 * as well as {@link #setServletContext(javax.servlet.ServletContext)}.
	 * @param servletContext the ServletContext that this application object runs in
	 * (never {@code null})
	 */
	protected void initServletContext(ServletContext servletContext) {
	}

	
Return the current application context as WebApplicationContext.

NOTE: Only use this if you actually need to access WebApplicationContext-specific functionality. Preferably use getApplicationContext() or getServletContext() else, to be able to run in non-WebApplicationContext environments as well. 
Throws:
See Also:
/**
	 * Return the current application context as WebApplicationContext.
	 * <p><b>NOTE:</b> Only use this if you actually need to access
	 * WebApplicationContext-specific functionality. Preferably use
	 * {@code getApplicationContext()} or {@code getServletContext()}
	 * else, to be able to run in non-WebApplicationContext environments as well.
	 * @throws IllegalStateException if not running in a WebApplicationContext
	 * @see #getApplicationContext()
	 */
	@Nullable
	protected final WebApplicationContext getWebApplicationContext() throws IllegalStateException {
		ApplicationContext ctx = getApplicationContext();
		if (ctx instanceof WebApplicationContext) {
			return (WebApplicationContext) getApplicationContext();
		}
		else if (isContextRequired()) {
			throw new IllegalStateException("WebApplicationObjectSupport instance [" + this +
					"] does not run in a WebApplicationContext but in: " + ctx);
		}
		else {
			return null;
		}
	}

	
Return the current ServletContext.

Throws:
  • IllegalStateException – if not running within a required ServletContext
See Also:
/**
	 * Return the current ServletContext.
	 * @throws IllegalStateException if not running within a required ServletContext
	 * @see #isContextRequired()
	 */
	@Nullable
	protected final ServletContext getServletContext() throws IllegalStateException {
		if (this.servletContext != null) {
			return this.servletContext;
		}
		ServletContext servletContext = null;
		WebApplicationContext wac = getWebApplicationContext();
		if (wac != null) {
			servletContext = wac.getServletContext();
		}
		if (servletContext == null && isContextRequired()) {
			throw new IllegalStateException("WebApplicationObjectSupport instance [" + this +
					"] does not run within a ServletContext. Make sure the object is fully configured!");
		}
		return servletContext;
	}

	
Return the temporary directory for the current web application,
as provided by the servlet container.

Throws:
See Also:
Returns:the File representing the temporary directory
/**
	 * Return the temporary directory for the current web application,
	 * as provided by the servlet container.
	 * @return the File representing the temporary directory
	 * @throws IllegalStateException if not running within a ServletContext
	 * @see org.springframework.web.util.WebUtils#getTempDir(javax.servlet.ServletContext)
	 */
	protected final File getTempDir() throws IllegalStateException {
		ServletContext servletContext = getServletContext();
		Assert.state(servletContext != null, "ServletContext is required");
		return WebUtils.getTempDir(servletContext);
	}

}