/*
* Copyright 2002-2013 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.core.env;
/**
* {@link Environment} implementation suitable for use in 'standard' (i.e. non-web)
* applications.
*
* <p>In addition to the usual functions of a {@link ConfigurableEnvironment} such as
* property resolution and profile-related operations, this implementation configures two
* default property sources, to be searched in the following order:
* <ul>
* <li>{@linkplain AbstractEnvironment#getSystemProperties() system properties}
* <li>{@linkplain AbstractEnvironment#getSystemEnvironment() system environment variables}
* </ul>
*
* That is, if the key "xyz" is present both in the JVM system properties as well as in
* the set of environment variables for the current process, the value of key "xyz" from
* system properties will return from a call to {@code environment.getProperty("xyz")}.
* This ordering is chosen by default because system properties are per-JVM, while
* environment variables may be the same across many JVMs on a given system. Giving
* system properties precedence allows for overriding of environment variables on a
* per-JVM basis.
*
* <p>These default property sources may be removed, reordered, or replaced; and
* additional property sources may be added using the {@link MutablePropertySources}
* instance available from {@link #getPropertySources()}. See
* {@link ConfigurableEnvironment} Javadoc for usage examples.
*
* <p>See {@link SystemEnvironmentPropertySource} javadoc for details on special handling
* of property names in shell environments (e.g. Bash) that disallow period characters in
* variable names.
*
* @author Chris Beams
* @since 3.1
* @see ConfigurableEnvironment
* @see SystemEnvironmentPropertySource
* @see org.springframework.web.context.support.StandardServletEnvironment
*/
public class StandardEnvironment extends AbstractEnvironment {
/** System environment property source name: {@value} */
public static final String SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME = "systemEnvironment";
/** JVM system properties property source name: {@value} */
public static final String SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME = "systemProperties";
/**
* Customize the set of property sources with those appropriate for any standard
* Java environment:
* <ul>
* <li>{@value #SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME}
* <li>{@value #SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME}
* </ul>
* <p>Properties present in {@value #SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME} will
* take precedence over those in {@value #SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME}.
* @see AbstractEnvironment#customizePropertySources(MutablePropertySources)
* @see #getSystemProperties()
* @see #getSystemEnvironment()
*/
@Override
protected void customizePropertySources(MutablePropertySources propertySources) {
propertySources.addLast(new MapPropertySource(SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME, getSystemProperties()));
propertySources.addLast(new SystemEnvironmentPropertySource(SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME, getSystemEnvironment()));
}
}