infra.beans.factory.config.PreferencesPlaceholderConfigurer Maven / Gradle / Ivy
/*
* Copyright 2017 - 2024 the original author or authors.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see [https://www.gnu.org/licenses/]
*/
package infra.beans.factory.config;
import java.util.Properties;
import java.util.prefs.BackingStoreException;
import java.util.prefs.Preferences;
import infra.beans.factory.BeanDefinitionStoreException;
import infra.beans.factory.InitializingBean;
import infra.lang.Nullable;
/**
* Subclass of PropertyPlaceholderConfigurer that supports JDK 1.4's
* Preferences API ({@code java.util.prefs}).
*
* Tries to resolve placeholders as keys first in the user preferences,
* then in the system preferences, then in this configurer's properties.
* Thus, behaves like PropertyPlaceholderConfigurer if no corresponding
* preferences defined.
*
*
Supports custom paths for the system and user preferences trees. Also
* supports custom paths specified in placeholders ("myPath/myPlaceholderKey").
* Uses the respective root node if not specified.
*
* @author Juergen Hoeller
* @author Harry Yang
* @see #setSystemTreePath
* @see #setUserTreePath
* @see java.util.prefs.Preferences
* @since 4.0 2022/3/9 9:13
*/
public class PreferencesPlaceholderConfigurer extends PropertyPlaceholderConfigurer implements InitializingBean {
@Nullable
private String systemTreePath;
@Nullable
private String userTreePath;
private Preferences systemPrefs = Preferences.systemRoot();
private Preferences userPrefs = Preferences.userRoot();
/**
* Set the path in the system preferences tree to use for resolving
* placeholders. Default is the root node.
*/
public void setSystemTreePath(@Nullable String systemTreePath) {
this.systemTreePath = systemTreePath;
}
/**
* Set the path in the system preferences tree to use for resolving
* placeholders. Default is the root node.
*/
public void setUserTreePath(@Nullable String userTreePath) {
this.userTreePath = userTreePath;
}
/**
* This implementation eagerly fetches the Preferences instances
* for the required system and user tree nodes.
*/
@Override
public void afterPropertiesSet() {
if (systemTreePath != null) {
this.systemPrefs = systemPrefs.node(systemTreePath);
}
if (userTreePath != null) {
this.userPrefs = userPrefs.node(userTreePath);
}
}
/**
* This implementation tries to resolve placeholders as keys first
* in the user preferences, then in the system preferences, then in
* the passed-in properties.
*/
@Override
protected String resolvePlaceholder(String placeholder, Properties props) {
String path = null;
String key = placeholder;
int endOfPath = placeholder.lastIndexOf('/');
if (endOfPath != -1) {
path = placeholder.substring(0, endOfPath);
key = placeholder.substring(endOfPath + 1);
}
String value = resolvePlaceholder(path, key, userPrefs);
if (value == null) {
value = resolvePlaceholder(path, key, systemPrefs);
if (value == null) {
value = props.getProperty(placeholder);
}
}
return value;
}
/**
* Resolve the given path and key against the given Preferences.
*
* @param path the preferences path (placeholder part before '/')
* @param key the preferences key (placeholder part after '/')
* @param preferences the Preferences to resolve against
* @return the value for the placeholder, or {@code null} if none found
*/
@Nullable
protected String resolvePlaceholder(@Nullable String path, String key, Preferences preferences) {
if (path != null) {
// Do not create the node if it does not exist...
try {
if (preferences.nodeExists(path)) {
return preferences.node(path).get(key, null);
}
else {
return null;
}
}
catch (BackingStoreException ex) {
throw new BeanDefinitionStoreException("Cannot access specified node path [" + path + "]", ex);
}
}
else {
return preferences.get(key, null);
}
}
}