public static void main(String[] args) {Properties properties = System.getProperties();properties.setProperty("prefixName", "read-code");ApplicationContext ac = new ClassPathXmlApplicationContext("classpath:${prefixName}-spring.xml");ReadCodeService readCodeService = (ReadCodeService) ac.getBean("readCodeService");readCodeService.say();}

View Code

public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent)throws BeansException {super(parent);setConfigLocations(configLocations);if (refresh) {refresh();}}

    /*** Set the config locations for this application context.* <p>If not set, the implementation may use a default as appropriate.*/public void setConfigLocations(String... locations) {if (locations != null) {Assert.noNullElements(locations, "Config locations must not be null");this.configLocations = new String[locations.length];for (int i = 0; i < locations.length; i++) {this.configLocations[i] = resolvePath(locations[i]).trim(); // 解析路劲
            }}else {this.configLocations = null;}}

    /*** Resolve the given path, replacing placeholders with corresponding* environment property values if necessary. Applied to config locations.* @param path the original file path* @return the resolved file path* @see org.springframework.core.env.Environment#resolveRequiredPlaceholders(String)*/protected String resolvePath(String path) {return getEnvironment().resolveRequiredPlaceholders(path);}

public String resolveRequiredPlaceholders(String text) throws IllegalArgumentException {if (this.strictHelper == null) {this.strictHelper = createPlaceholderHelper(false);}return doResolvePlaceholders(text, this.strictHelper);}

private String doResolvePlaceholders(String text, PropertyPlaceholderHelper helper) {return helper.replacePlaceholders(text, new PropertyPlaceholderHelper.PlaceholderResolver() {@Overridepublic String resolvePlaceholder(String placeholderName) {return getPropertyAsRawString(placeholderName);}});}

protected String getPropertyAsRawString(String key) {return getProperty(key, String.class, false);}

    protected <T> T getProperty(String key, Class<T> targetValueType, boolean resolveNestedPlaceholders) {boolean debugEnabled = logger.isDebugEnabled();if (logger.isTraceEnabled()) {logger.trace(String.format("getProperty(\"%s\", %s)", key, targetValueType.getSimpleName()));}if (this.propertySources != null) {for (PropertySource<?> propertySource : this.propertySources) {if (debugEnabled) {logger.debug(String.format("Searching for key '%s' in [%s]", key, propertySource.getName()));}Object value;if ((value = propertySource.getProperty(key)) != null) {Class<?> valueType = value.getClass();if (resolveNestedPlaceholders && value instanceof String) {value = resolveNestedPlaceholders((String) value);}if (debugEnabled) {logger.debug(String.format("Found key '%s' in [%s] with type [%s] and value '%s'",key, propertySource.getName(), valueType.getSimpleName(), value));}if (!this.conversionService.canConvert(valueType, targetValueType)) {throw new IllegalArgumentException(String.format("Cannot convert value [%s] from source type [%s] to target type [%s]",value, valueType.getSimpleName(), targetValueType.getSimpleName()));}return this.conversionService.convert(value, targetValueType);}}}if (debugEnabled) {logger.debug(String.format("Could not find key '%s' in any property source. Returning [null]", key));}return null;}

View Code

public String replacePlaceholders(String value, PlaceholderResolver placeholderResolver) {Assert.notNull(value, "'value' must not be null");return parseStringValue(value, placeholderResolver, new HashSet<String>());}

protected String parseStringValue(String strVal, PlaceholderResolver placeholderResolver, Set<String> visitedPlaceholders) {StringBuilder result = new StringBuilder(strVal);int startIndex = strVal.indexOf(this.placeholderPrefix);while (startIndex != -1) {int endIndex = findPlaceholderEndIndex(result, startIndex);if (endIndex != -1) {String placeholder = result.substring(startIndex + this.placeholderPrefix.length(), endIndex);String originalPlaceholder = placeholder;if (!visitedPlaceholders.add(originalPlaceholder)) {throw new IllegalArgumentException("Circular placeholder reference '" + originalPlaceholder + "' in property definitions");}// Recursive invocation, parsing placeholders contained in the placeholder key.
                placeholder = parseStringValue(placeholder, placeholderResolver, visitedPlaceholders);  // 递归查找// Now obtain the value for the fully resolved key...String propVal = placeholderResolver.resolvePlaceholder(placeholder);if (propVal == null && this.valueSeparator != null) {int separatorIndex = placeholder.indexOf(this.valueSeparator);if (separatorIndex != -1) {String actualPlaceholder = placeholder.substring(0, separatorIndex);String defaultValue = placeholder.substring(separatorIndex + this.valueSeparator.length());propVal = placeholderResolver.resolvePlaceholder(actualPlaceholder); // 这里是调用第四步骤的实现PropertyPlaceholderHelper内部接口PlaceholderResolver方法resolvePlaceholder ：占位符 key -> valueif (propVal == null) {propVal = defaultValue;}}}if (propVal != null) {// Recursive invocation, parsing placeholders contained in the// previously resolved placeholder value.propVal = parseStringValue(propVal, placeholderResolver, visitedPlaceholders);result.replace(startIndex, endIndex + this.placeholderSuffix.length(), propVal); // 替换占位符具体值if (logger.isTraceEnabled()) {logger.trace("Resolved placeholder '" + placeholder + "'");}startIndex = result.indexOf(this.placeholderPrefix, startIndex + propVal.length());}else if (this.ignoreUnresolvablePlaceholders) {// Proceed with unprocessed value.startIndex = result.indexOf(this.placeholderPrefix, endIndex + this.placeholderSuffix.length());}else {throw new IllegalArgumentException("Could not resolve placeholder '" +placeholder + "'" + " in string value \"" + strVal + "\"");}visitedPlaceholders.remove(originalPlaceholder);}else {startIndex = -1;}}return result.toString();}

private int findPlaceholderEndIndex(CharSequence buf, int startIndex) {int index = startIndex + this.placeholderPrefix.length();int withinNestedPlaceholder = 0;while (index < buf.length()) {if (StringUtils.substringMatch(buf, index, this.placeholderSuffix)) {if (withinNestedPlaceholder > 0) {withinNestedPlaceholder--;index = index + this.placeholderSuffix.length();}else {return index;}}else if (StringUtils.substringMatch(buf, index, this.simplePrefix)) {withinNestedPlaceholder++;index = index + this.simplePrefix.length();}else {index++;}}return -1;}

View Code

public static boolean substringMatch(CharSequence str, int index, CharSequence substring) {for (int j = 0; j < substring.length(); j++) {int i = index + j;if (i >= str.length() || str.charAt(i) != substring.charAt(j)) {return false;}}return true;}

View Code