/*
* Copyright 2002-2016 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.beans.factory.config;
import org.springframework.beans.factory.BeanDefinitionStoreException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.BeanNameAware;
import org.springframework.util.StringValueResolver;
/**
* Abstract base class for property resource configurers that resolve placeholders
* in bean definition property values. Implementations <em>pull</em> values from a
* properties file or other {@linkplain org.springframework.core.env.PropertySource
* property source} into bean definitions.
*
* <p>The default placeholder syntax follows the Ant / Log4J / JSP EL style:
*
* <pre class="code">${...}</pre>
*
* Example XML bean definition:
*
* <pre class="code">
* <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource"/>
* <property name="driverClassName" value="${driver}"/>
* <property name="url" value="jdbc:${dbname}"/>
* </bean>
* </pre>
*
* Example properties file:
*
* <pre class="code">driver=com.mysql.jdbc.Driver
* dbname=mysql:mydb</pre>
*
* Annotated bean definitions may take advantage of property replacement using
* the {@link org.springframework.beans.factory.annotation.Value @Value} annotation:
*
* <pre class="code">@Value("${person.age}")</pre>
*
* Implementations check simple property values, lists, maps, props, and bean names
* in bean references. Furthermore, placeholder values can also cross-reference
* other placeholders, like:
*
* <pre class="code">rootPath=myrootdir
* subPath=${rootPath}/subdir</pre>
*
* In contrast to {@link PropertyOverrideConfigurer}, subclasses of this type allow
* filling in of explicit placeholders in bean definitions.
*
* <p>If a configurer cannot resolve a placeholder, a {@link BeanDefinitionStoreException}
* will be thrown. If you want to check against multiple properties files, specify multiple
* resources via the {@link #setLocations locations} property. You can also define multiple
* configurers, each with its <em>own</em> placeholder syntax. Use {@link
* #ignoreUnresolvablePlaceholders} to intentionally suppress throwing an exception if a
* placeholder cannot be resolved.
*
* <p>Default property values can be defined globally for each configurer instance
* via the {@link #setProperties properties} property, or on a property-by-property basis
* using the default value separator which is {@code ":"} by default and
* customizable via {@link #setValueSeparator(String)}.
*
* <p>Example XML property with default value:
*
* <pre class="code">
* <property name="url" value="jdbc:${dbname:defaultdb}"/>
* </pre>
*
* @author Chris Beams
* @author Juergen Hoeller
* @since 3.1
* @see PropertyPlaceholderConfigurer
* @see org.springframework.context.support.PropertySourcesPlaceholderConfigurer
*/
public abstract class PlaceholderConfigurerSupport extends PropertyResourceConfigurer
implements BeanNameAware, BeanFactoryAware {
/** Default placeholder prefix: {@value} */
public static final String DEFAULT_PLACEHOLDER_PREFIX = "${";
/** Default placeholder suffix: {@value} */
public static final String DEFAULT_PLACEHOLDER_SUFFIX = "}";
/** Default value separator: {@value} */
public static final String DEFAULT_VALUE_SEPARATOR = ":";
/** Defaults to {@value #DEFAULT_PLACEHOLDER_PREFIX} */
protected String placeholderPrefix = DEFAULT_PLACEHOLDER_PREFIX;
/** Defaults to {@value #DEFAULT_PLACEHOLDER_SUFFIX} */
protected String placeholderSuffix = DEFAULT_PLACEHOLDER_SUFFIX;
/** Defaults to {@value #DEFAULT_VALUE_SEPARATOR} */
protected String valueSeparator = DEFAULT_VALUE_SEPARATOR;
protected boolean trimValues = false;
protected String nullValue;
protected boolean ignoreUnresolvablePlaceholders = false;
private String beanName;
private BeanFactory beanFactory;
/**
* Set the prefix that a placeholder string starts with.
* The default is {@value #DEFAULT_PLACEHOLDER_PREFIX}.
*/
public void setPlaceholderPrefix(String placeholderPrefix) {
this.placeholderPrefix = placeholderPrefix;
}
/**
* Set the suffix that a placeholder string ends with.
* The default is {@value #DEFAULT_PLACEHOLDER_SUFFIX}.
*/
public void setPlaceholderSuffix(String placeholderSuffix) {
this.placeholderSuffix = placeholderSuffix;
}
/**
* Specify the separating character between the placeholder variable
* and the associated default value, or {@code null} if no such
* special character should be processed as a value separator.
* The default is {@value #DEFAULT_VALUE_SEPARATOR}.
*/
public void setValueSeparator(String valueSeparator) {
this.valueSeparator = valueSeparator;
}
/**
* Specify whether to trim resolved values before applying them,
* removing superfluous whitespace from the beginning and end.
* <p>Default is {@code false}.
* @since 4.3
*/
public void setTrimValues(boolean trimValues) {
this.trimValues = trimValues;
}
/**
* Set a value that should be treated as {@code null} when resolved
* as a placeholder value: e.g. "" (empty String) or "null".
* <p>Note that this will only apply to full property values,
* not to parts of concatenated values.
* <p>By default, no such null value is defined. This means that
* there is no way to express {@code null} as a property value
* unless you explicitly map a corresponding value here.
*/
public void setNullValue(String nullValue) {
this.nullValue = nullValue;
}
/**
* Set whether to ignore unresolvable placeholders.
* <p>Default is "false": An exception will be thrown if a placeholder fails
* to resolve. Switch this flag to "true" in order to preserve the placeholder
* String as-is in such a case, leaving it up to other placeholder configurers
* to resolve it.
*/
public void setIgnoreUnresolvablePlaceholders(boolean ignoreUnresolvablePlaceholders) {
this.ignoreUnresolvablePlaceholders = ignoreUnresolvablePlaceholders;
}
/**
* Only necessary to check that we're not parsing our own bean definition,
* to avoid failing on unresolvable placeholders in properties file locations.
* The latter case can happen with placeholders for system properties in
* resource locations.
* @see #setLocations
* @see org.springframework.core.io.ResourceEditor
*/
@Override
public void setBeanName(String beanName) {
this.beanName = beanName;
}
/**
* Only necessary to check that we're not parsing our own bean definition,
* to avoid failing on unresolvable placeholders in properties file locations.
* The latter case can happen with placeholders for system properties in
* resource locations.
* @see #setLocations
* @see org.springframework.core.io.ResourceEditor
*/
@Override
public void setBeanFactory(BeanFactory beanFactory) {
this.beanFactory = beanFactory;
}
protected void doProcessProperties(ConfigurableListableBeanFactory beanFactoryToProcess,
StringValueResolver valueResolver) {
BeanDefinitionVisitor visitor = new BeanDefinitionVisitor(valueResolver);
String[] beanNames = beanFactoryToProcess.getBeanDefinitionNames();
for (String curName : beanNames) {
// Check that we're not parsing our own bean definition,
// to avoid failing on unresolvable placeholders in properties file locations.
if (!(curName.equals(this.beanName) && beanFactoryToProcess.equals(this.beanFactory))) {
BeanDefinition bd = beanFactoryToProcess.getBeanDefinition(curName);
try {
visitor.visitBeanDefinition(bd);
}
catch (Exception ex) {
throw new BeanDefinitionStoreException(bd.getResourceDescription(), curName, ex.getMessage(), ex);
}
}
}
// New in Spring 2.5: resolve placeholders in alias target names and aliases as well.
beanFactoryToProcess.resolveAliases(valueResolver);
// New in Spring 3.0: resolve placeholders in embedded values such as annotation attributes.
beanFactoryToProcess.addEmbeddedValueResolver(valueResolver);
}
}