org.brekka.stillingar.spring.pc.ConfigurationPlaceholderConfigurer.java Source code

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Here is the source code for org.brekka.stillingar.spring.pc.ConfigurationPlaceholderConfigurer.java

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/*
 * Copyright 2011 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.brekka.stillingar.spring.pc;

import org.brekka.stillingar.api.ConfigurationSource;
import org.brekka.stillingar.spring.expr.DefaultPlaceholderParser;
import org.brekka.stillingar.spring.expr.PlaceholderParser;
import org.springframework.beans.BeansException;
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.beans.factory.InitializingBean;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.BeanDefinitionVisitor;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.config.PropertyPlaceholderConfigurer;
import org.springframework.util.StringValueResolver;

/**
 * Identifies and replaces placeholders defined within a Spring configuration with values obtained from a
 * {@link ConfigurationSource}.
 * 
 * Inspired by the reloadable properties example found here: http://www.wuenschenswert.net/wunschdenken/archives/127.
 * 
 * @author Andrew Taylor
 */
public class ConfigurationPlaceholderConfigurer
        implements BeanFactoryPostProcessor, BeanFactoryAware, BeanNameAware, InitializingBean {

    /**
     * The source for configuration values
     */
    private final ConfigurationSource configurationSource;

    /**
     * The bean factory that loaded this instance
     */
    private BeanFactory beanFactory;

    /**
     * The name of this bean within the container.
     */
    private String beanName;

    /**
     * Used to parse the placeholder string.
     */
    private PlaceholderParser placeholderParser;

    /**
     * @param configurationSource The source for configuration values
     */
    public ConfigurationPlaceholderConfigurer(ConfigurationSource configurationSource) {
        this.configurationSource = configurationSource;
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        if (placeholderParser == null) {
            placeholderParser = new DefaultPlaceholderParser("${", "}");
        }
    }

    /**
     * Copied in its entirety from the {@link PropertyPlaceholderConfigurer} method of the same name. The only changes
     * are to the valueResolver and BeanDefinitionVisitor instances.
     */
    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactoryToProcess) throws BeansException {

        String[] beanNames = beanFactoryToProcess.getBeanDefinitionNames();
        for (String curName : beanNames) {
            CustomStringValueResolver valueResolver = new CustomStringValueResolver(this.placeholderParser,
                    this.configurationSource, this.beanFactory);

            // 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 beanDef = beanFactoryToProcess.getBeanDefinition(curName);
                try {
                    BeanDefinitionVisitor visitor = new CustomBeanDefinitionVisitor(curName, beanDef.isSingleton(),
                            valueResolver);
                    visitor.visitBeanDefinition(beanDef);
                } catch (Exception ex) {
                    throw new BeanDefinitionStoreException(beanDef.getResourceDescription(), curName, ex);
                }
            }
        }

        StringValueResolver valueResolver = new CustomStringValueResolver(this.placeholderParser,
                this.configurationSource, this.beanFactory);

        // 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);
    }

    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        this.beanFactory = beanFactory;
    }

    @Override
    public void setBeanName(String name) {
        this.beanName = name;
    }

    public void setPlaceholderParser(PlaceholderParser placeholderParser) {
        this.placeholderParser = placeholderParser;
    }
}