/*
* Copyright 2002-2005 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.util.Properties;
import javax.servlet.ServletContext;
import org.springframework.beans.factory.config.PropertyPlaceholderConfigurer;
import org.springframework.web.context.ServletContextAware;
/**
* Subclass of PropertyPlaceholderConfigurer that resolves placeholders as
* ServletContext init parameters (that is, <code>web.xml</code> context-param
* entries).
*
* <p>Can be combined with "locations" and/or "properties" values in addition
* to web.xml context-params. Alternatively, can be defined without local
* properties, to resolve all placeholders as <code>web.xml</code> context-params
* (or JVM system properties).
*
* <p>If a placeholder could not be resolved against the provided local
* properties within the application, this configurer will fall back to
* ServletContext parameters. Can also be configured to let ServletContext
* init parameters override local properties (contextOverride=true).
*
* <p>Optionally supports searching for ServletContext <i>attributes</i>: If turned
* on, an otherwise unresolvable placeholder will matched against the corresponding
* ServletContext attribute, using its stringified value if found. This can be
* used to feed dynamic values into Spring's placeholder resolution.
*
* <p>If not running within a WebApplicationContext (or any other context that
* is able to satisfy the ServletContextAware callback), this class will behave
* like the default PropertyPlaceholderConfigurer. This allows for keeping
* ServletContextPropertyPlaceholderConfigurer definitions in test suites.
*
* @author Juergen Hoeller
* @since 1.1.4
* @see #setLocations
* @see #setProperties
* @see #setSystemPropertiesModeName
* @see #setContextOverride
* @see #setSearchContextAttributes
* @see javax.servlet.ServletContext#getInitParameter(String)
* @see javax.servlet.ServletContext#getAttribute(String)
*/
public class ServletContextPropertyPlaceholderConfigurer extends PropertyPlaceholderConfigurer
implements ServletContextAware {
private boolean contextOverride = false;
private boolean searchContextAttributes = false;
private ServletContext servletContext;
/**
* Set whether ServletContext init parameters (and optionally also ServletContext
* attributes) should override local properties within the application.
* Default is "false": ServletContext settings serve as fallback.
* <p>Note that system properties will still override ServletContext settings,
* if the system properties mode is set to "SYSTEM_PROPERTIES_MODE_OVERRIDE".
* @see #setSearchContextAttributes
* @see #setSystemPropertiesModeName
* @see #SYSTEM_PROPERTIES_MODE_OVERRIDE
*/
public void setContextOverride(boolean contextOverride) {
this.contextOverride = contextOverride;
}
/**
* Set whether to search for matching a ServletContext attribute before
* checking a ServletContext init parameter. Default is "false": only
* checking init parameters.
* <p>If turned on, the configurer will look for a ServletContext attribute with
* the same name as the placeholder, and use its stringified value if found.
* Exposure of such ServletContext attributes can be used to dynamically override
* init parameters defined in <code>web.xml</code>, for example in a custom
* context listener.
* @see javax.servlet.ServletContext#getInitParameter(String)
* @see javax.servlet.ServletContext#getAttribute(String)
*/
public void setSearchContextAttributes(boolean searchContextAttributes) {
this.searchContextAttributes = searchContextAttributes;
}
/**
* Set the ServletContext to resolve placeholders against.
* Will be auto-populated when running in a WebApplicationContext.
* <p>If not set, this configurer will simply not resolve placeholders
* against the ServletContext: It will effectively behave like a plain
* PropertyPlaceholderConfigurer in such a scenario.
*/
public void setServletContext(ServletContext servletContext) {
this.servletContext = servletContext;
}
@Override
protected String resolvePlaceholder(String placeholder, Properties props) {
String value = null;
if (this.contextOverride && this.servletContext != null) {
value = resolvePlaceholder(placeholder, this.servletContext, this.searchContextAttributes);
}
if (value == null) {
value = super.resolvePlaceholder(placeholder, props);
}
if (value == null && this.servletContext != null) {
value = resolvePlaceholder(placeholder, this.servletContext, this.searchContextAttributes);
}
return value;
}
/**
* Resolves the given placeholder using the init parameters
* and optionally also the attributes of the given ServletContext.
* <p>Default implementation checks ServletContext attributes before
* init parameters. Can be overridden to customize this behavior,
* potentially also applying specific naming patterns for parameters
* and/or attributes (instead of using the exact placeholder name).
* @param placeholder the placeholder to resolve
* @param servletContext the ServletContext to check
* @param searchContextAttributes whether to search for a matching
* ServletContext attribute
* @return the resolved value, of null if none
* @see javax.servlet.ServletContext#getInitParameter(String)
* @see javax.servlet.ServletContext#getAttribute(String)
*/
protected String resolvePlaceholder(
String placeholder, ServletContext servletContext, boolean searchContextAttributes) {
String value = null;
if (searchContextAttributes) {
Object attrValue = servletContext.getAttribute(placeholder);
if (attrValue != null) {
value = attrValue.toString();
}
}
if (value == null) {
value = servletContext.getInitParameter(placeholder);
}
return value;
}
}
|