propertyplaceholderconfigurer.java

spring的源代码

		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
	 */
	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
	 */
	public void setBeanFactory(BeanFactory beanFactory) {
		this.beanFactory = beanFactory;
	}


	protected void processProperties(ConfigurableListableBeanFactory beanFactoryToProcess, Properties props)
			throws BeansException {

		BeanDefinitionVisitor visitor = new PlaceholderResolvingBeanDefinitionVisitor(props);
		String[] beanNames = beanFactoryToProcess.getBeanDefinitionNames();
		for (int i = 0; i < beanNames.length; i++) {
			// Check that we're not parsing our own bean definition,
			// to avoid failing on unresolvable placeholders in properties file locations.
			if (!(beanNames[i].equals(this.beanName) && beanFactoryToProcess.equals(this.beanFactory))) {
				BeanDefinition bd = beanFactoryToProcess.getBeanDefinition(beanNames[i]);
				try {
					visitor.visitBeanDefinition(bd);
				}
				catch (BeanDefinitionStoreException ex) {
					throw new BeanDefinitionStoreException(bd.getResourceDescription(), beanNames[i], ex.getMessage());
				}
			}
		}
	}

	/**
	 * Parse the given String value recursively, to be able to resolve
	 * nested placeholders (when resolved property values in turn contain
	 * placeholders again).
	 * @param strVal the String value to parse
	 * @param props the Properties to resolve placeholders against
	 * @param originalPlaceholder the original placeholder, used to detect
	 * circular references between placeholders. Only non-null if we're
	 * parsing a nested placeholder.
	 * @throws BeanDefinitionStoreException if invalid values are encountered
	 * @see #resolvePlaceholder(String, java.util.Properties, int)
	 */
	protected String parseStringValue(String strVal, Properties props, String originalPlaceholder)
	    throws BeanDefinitionStoreException {

		StringBuffer buf = new StringBuffer(strVal);

		// The following code does not use JDK 1.4's StringBuffer.indexOf(String)
		// method to retain JDK 1.3 compatibility. The slight loss in performance
		// is not really relevant, as this code will typically just run on startup.

		int startIndex = strVal.indexOf(this.placeholderPrefix);
		while (startIndex != -1) {
			int endIndex = buf.toString().indexOf(
			    this.placeholderSuffix, startIndex + this.placeholderPrefix.length());
			if (endIndex != -1) {
				String placeholder = buf.substring(startIndex + this.placeholderPrefix.length(), endIndex);
				String originalPlaceholderToUse = null;

				if (originalPlaceholder != null) {
					originalPlaceholderToUse = originalPlaceholder;
					if (placeholder.equals(originalPlaceholder)) {
						throw new BeanDefinitionStoreException(
								"Circular placeholder reference '" + placeholder + "' in property definitions");
					}
				}
				else {
					originalPlaceholderToUse = placeholder;
				}

				String propVal = resolvePlaceholder(placeholder, props, this.systemPropertiesMode);
				if (propVal != null) {
					// Recursive invocation, parsing placeholders contained in the
					// previously resolved placeholder value.
					propVal = parseStringValue(propVal, props, originalPlaceholderToUse);
					buf.replace(startIndex, endIndex + this.placeholderSuffix.length(), propVal);
					if (logger.isDebugEnabled()) {
						logger.debug("Resolved placeholder '" + placeholder + "' to value [" + propVal + "]");
					}
					startIndex = buf.toString().indexOf(this.placeholderPrefix, startIndex + propVal.length());
				}
				else if (this.ignoreUnresolvablePlaceholders) {
					// Proceed with unprocessed value.
					startIndex = buf.toString().indexOf(this.placeholderPrefix, endIndex + this.placeholderSuffix.length());
				}
				else {
					throw new BeanDefinitionStoreException("Could not resolve placeholder '" + placeholder + "'");
				}
			}
			else {
				startIndex = -1;
			}
		}

		return buf.toString();
	}

	/**
	 * Resolve the given placeholder using the given properties, performing
	 * a system properties check according to the given mode.
	 * <p>Default implementation delegates to <code>resolvePlaceholder
	 * (placeholder, props)</code> before/after the system properties check.
	 * <p>Subclasses can override this for custom resolution strategies,
	 * including customized points for the system properties check.
	 * @param placeholder the placeholder to resolve
	 * @param props the merged properties of this configurer
	 * @param systemPropertiesMode the system properties mode,
	 * according to the constants in this class
	 * @return the resolved value, of null if none
	 * @see #setSystemPropertiesMode
	 * @see System#getProperty
	 * @see #resolvePlaceholder(String, java.util.Properties)
	 */
	protected String resolvePlaceholder(String placeholder, Properties props, int systemPropertiesMode) {
		String propVal = null;
		if (systemPropertiesMode == SYSTEM_PROPERTIES_MODE_OVERRIDE) {
			propVal = resolveSystemProperty(placeholder);
		}
		if (propVal == null) {
			propVal = resolvePlaceholder(placeholder, props);
		}
		if (propVal == null && systemPropertiesMode == SYSTEM_PROPERTIES_MODE_FALLBACK) {
			propVal = resolveSystemProperty(placeholder);
		}
		return propVal;
	}

	/**
	 * Resolve the given placeholder using the given properties.
	 * Default implementation simply checks for a corresponding property key.
	 * <p>Subclasses can override this for customized placeholder-to-key mappings
	 * or custom resolution strategies, possibly just using the given properties
	 * as fallback.
	 * <p>Note that system properties will still be checked before respectively
	 * after this method is invoked, according to the system properties mode.
	 * @param placeholder the placeholder to resolve
	 * @param props the merged properties of this configurer
	 * @return the resolved value, of <code>null</code> if none
	 * @see #setSystemPropertiesMode
	 */
	protected String resolvePlaceholder(String placeholder, Properties props) {
		return props.getProperty(placeholder);
	}

	/**
	 * Resolve the given key as JVM system property, and optionally also as
	 * system environment variable if no matching system property has been found.
	 * @param key the placeholder to resolve as system property key
	 * @return the system property value, or <code>null</code> if not found
	 * @see #setSearchSystemEnvironment
	 * @see java.lang.System#getProperty(String)
	 * @see java.lang.System#getenv(String)
	 */
	protected String resolveSystemProperty(String key) {
		String value = System.getProperty(key);
		if (value == null && this.searchSystemEnvironment) {
			value = System.getenv(key);
		}
		return value;
	}


	/**
	 * BeanDefinitionVisitor that resolves placeholders in String values,
	 * deleagating to the <code>parseStringValue</code> method of the
	 * containing clas.
	 */
	private class PlaceholderResolvingBeanDefinitionVisitor extends BeanDefinitionVisitor {

		private final Properties props;

		public PlaceholderResolvingBeanDefinitionVisitor(Properties props) {
			this.props = props;
		}

		protected String resolveStringValue(String strVal) throws BeansException {
			return parseStringValue(strVal, this.props, null);
		}
	}

}