/*
 * Copyright 2002-2018 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
 *
 *      https://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 javax.servlet.ServletConfig;
import javax.servlet.ServletContext;

import org.springframework.core.env.Environment;
import org.springframework.core.env.MutablePropertySources;
import org.springframework.core.env.PropertySource;
import org.springframework.core.env.PropertySource.StubPropertySource;
import org.springframework.core.env.StandardEnvironment;
import org.springframework.jndi.JndiLocatorDelegate;
import org.springframework.jndi.JndiPropertySource;
import org.springframework.lang.Nullable;
import org.springframework.web.context.ConfigurableWebEnvironment;

Environment implementation to be used by Servlet-based web applications. All web-related (servlet-based) ApplicationContext classes initialize an instance by default. 
Contributes ServletConfig, ServletContext, and JNDI-based PropertySource instances. See customizePropertySources method documentation for details. 
Author:
Chris Beams
See Also:
StandardEnvironment
Since:
3.1/**
 * {@link Environment} implementation to be used by {@code Servlet}-based web
 * applications. All web-related (servlet-based) {@code ApplicationContext} classes
 * initialize an instance by default.
 *
 * <p>Contributes {@code ServletConfig}, {@code ServletContext}, and JNDI-based
 * {@link PropertySource} instances. See {@link #customizePropertySources} method
 * documentation for details.
 *
 * @author Chris Beams
 * @since 3.1
 * @see StandardEnvironment
 */
public class StandardServletEnvironment extends StandardEnvironment implements ConfigurableWebEnvironment {

	
Servlet context init parameters property source name: "servletContextInitParams". /** Servlet context init parameters property source name: {@value}. */
	public static final String SERVLET_CONTEXT_PROPERTY_SOURCE_NAME = "servletContextInitParams";

	
Servlet config init parameters property source name: "servletConfigInitParams". /** Servlet config init parameters property source name: {@value}. */
	public static final String SERVLET_CONFIG_PROPERTY_SOURCE_NAME = "servletConfigInitParams";

	
JNDI property source name: "jndiProperties". /** JNDI property source name: {@value}. */
	public static final String JNDI_PROPERTY_SOURCE_NAME = "jndiProperties";


	
Customize the set of property sources with those contributed by superclasses as
well as those appropriate for standard servlet-based environments:

"servletConfigInitParams" 
"servletContextInitParams" 
"jndiProperties" 
Properties present in "servletConfigInitParams" will take precedence over those in "servletContextInitParams", and properties found in either of the above take precedence over those found in "jndiProperties". 
Properties in any of the above will take precedence over system properties and environment variables contributed by the StandardEnvironment superclass. 
The Servlet-related property sources are added as stubs at this stage, and will be fully initialized once the actual ServletContext object becomes available. 
See Also:
StandardEnvironment.customizePropertySources
AbstractEnvironment.customizePropertySources
ServletConfigPropertySource
ServletContextPropertySource
JndiPropertySource
initPropertySources.initPropertySources
initPropertySources(ServletContext, ServletConfig)/**
	 * Customize the set of property sources with those contributed by superclasses as
	 * well as those appropriate for standard servlet-based environments:
	 * <ul>
	 * <li>{@value #SERVLET_CONFIG_PROPERTY_SOURCE_NAME}
	 * <li>{@value #SERVLET_CONTEXT_PROPERTY_SOURCE_NAME}
	 * <li>{@value #JNDI_PROPERTY_SOURCE_NAME}
	 * </ul>
	 * <p>Properties present in {@value #SERVLET_CONFIG_PROPERTY_SOURCE_NAME} will
	 * take precedence over those in {@value #SERVLET_CONTEXT_PROPERTY_SOURCE_NAME}, and
	 * properties found in either of the above take precedence over those found in
	 * {@value #JNDI_PROPERTY_SOURCE_NAME}.
	 * <p>Properties in any of the above will take precedence over system properties and
	 * environment variables contributed by the {@link StandardEnvironment} superclass.
	 * <p>The {@code Servlet}-related property sources are added as
	 * {@link StubPropertySource stubs} at this stage, and will be
	 * {@linkplain #initPropertySources(ServletContext, ServletConfig) fully initialized}
	 * once the actual {@link ServletContext} object becomes available.
	 * @see StandardEnvironment#customizePropertySources
	 * @see org.springframework.core.env.AbstractEnvironment#customizePropertySources
	 * @see ServletConfigPropertySource
	 * @see ServletContextPropertySource
	 * @see org.springframework.jndi.JndiPropertySource
	 * @see org.springframework.context.support.AbstractApplicationContext#initPropertySources
	 * @see #initPropertySources(ServletContext, ServletConfig)
	 */
	@Override
	protected void customizePropertySources(MutablePropertySources propertySources) {
		propertySources.addLast(new StubPropertySource(SERVLET_CONFIG_PROPERTY_SOURCE_NAME));
		propertySources.addLast(new StubPropertySource(SERVLET_CONTEXT_PROPERTY_SOURCE_NAME));
		if (JndiLocatorDelegate.isDefaultJndiEnvironmentAvailable()) {
			propertySources.addLast(new JndiPropertySource(JNDI_PROPERTY_SOURCE_NAME));
		}
		super.customizePropertySources(propertySources);
	}

	@Override
	public void initPropertySources(@Nullable ServletContext servletContext, @Nullable ServletConfig servletConfig) {
		WebApplicationContextUtils.initServletPropertySources(getPropertySources(), servletContext, servletConfig);
	}

}