com.github.bingoohuang.utils.lang.Substituters Maven / Gradle / Ivy
package com.github.bingoohuang.utils.lang;
import ognl.Ognl;
import ognl.OgnlException;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.HashSet;
import java.util.Set;
/**
* 从PropertyPlaceholderConfigurer.java代码中摘出的字符串变量解析的辅助类。
* 字符串中变量引用形式：
* 1) ${variable}
* 2) ${variable:defaultValue}
* 3) ${variabl${letter}} Recursive invocation
* 4) mixed above
*
* @author Bingoo Huang
*/
@SuppressWarnings("unchecked")
public abstract class Substituters {
/**
* Default Holder prefix: "${" .
*/
public static final String DEF_HOLDER_PREFIX = "${";
/**
* Default Holder suffix: "}".
*/
public static final String DEF_HOLDER_SUFFIX = "}";
/**
* Check system properties if not resolvable in the specified properties.
* This is the default.
*/
public static final int SYS_PROPS_MODE_FALLBACK = 1;
/**
* Check system properties first, before trying the specified properties.
* This allows system properties to override any other property source.
*/
public static final int SYS_PROPS_MODE_OVERRIDE = 2;
private static final int DEF_HOLDER_PREFIX_LEN = DEF_HOLDER_PREFIX.length();
private static final int DEF_HOLDER_SUFFIX_LEN = DEF_HOLDER_SUFFIX.length();
private static Logger log = LoggerFactory.getLogger(Substituters.class);
/**
* Parse the given String value recursively, to be able to resolve
* nested Holders (when resolved property values in turn contain
* Holders again).
*
* @param strVal the String value to parse
* @return 进行值填充后的字符串
*/
public static String parse(String strVal) {
Set visitedHolders = new HashSet();
return parse(strVal, null, visitedHolders, false);
}
/**
* Parse the given String value recursively, to be able to resolve
* nested Holders (when resolved property values in turn contain
* Holders again).
*
* @param strVal the String value to parse
* @param props the Properties to resolve Holders against
* @return 进行值填充后的字符串
*/
public static String parse(String strVal, Object props) {
Set visitedHolders = new HashSet();
return parse(strVal, props, visitedHolders, false);
}
public static String parse(String strVal, Object sub, Object props) {
Set visitedHolders = new HashSet();
return parse(strVal, sub, props, visitedHolders, false);
}
private static String parse(String strVal, Object sub, Object props, Set visitedHolders, boolean ignoreBadHolders) {
StringBuffer buf = new StringBuffer(strVal);
int startIndex = strVal.indexOf(DEF_HOLDER_PREFIX);
while (startIndex != -1) {
int endIndex = findHolderEndIndex(buf, startIndex);
if (endIndex != -1) {
String holder = buf.substring(startIndex + DEF_HOLDER_PREFIX_LEN, endIndex);
String defValue = null;
int defIndex = StringUtils.lastIndexOf(holder, ":");
if (defIndex >= 0) {
defValue = StringUtils.trim(holder.substring(defIndex + 1));
holder = StringUtils.trim(holder.substring(0, defIndex));
}
if (!visitedHolders.add(holder)) {
throw new RuntimeException("Circular PlaceHolder reference '"
+ holder + "' in property definitions");
}
// Recursive invocation, parsing Holders contained in the Holder keyValue.
holder = parse(holder, props, visitedHolders, ignoreBadHolders);
// Now obtain the value for the fully resolved keyValue...
String propVal = resolveHolder(holder, sub, props, SYS_PROPS_MODE_FALLBACK, defValue);
if (propVal != null) {
// Recursive invocation, parsing Holders contained in the
// previously resolved Holder value.
propVal = parse(propVal, props, visitedHolders, ignoreBadHolders);
buf.replace(startIndex, endIndex + DEF_HOLDER_SUFFIX_LEN, propVal);
startIndex = buf.indexOf(DEF_HOLDER_PREFIX, startIndex + propVal.length());
} else if (ignoreBadHolders) {
// Proceed with unprocessed value.
startIndex = buf.indexOf(DEF_HOLDER_PREFIX, endIndex + DEF_HOLDER_SUFFIX_LEN);
} else {
throw new RuntimeException("Could not resolve Placeholder '" + holder + "'");
}
visitedHolders.remove(holder);
} else {
startIndex = -1;
}
}
return buf.toString();
}
private static String resolveHolder(String holder, Object sub, Object props, int sysPropsMode, String defaultValue) {
String propVal = null;
if (sysPropsMode == SYS_PROPS_MODE_OVERRIDE) {
propVal = resolveSystemProperty(holder);
}
if (propVal == null) {
propVal = resolveHolder(holder, props, defaultValue);
}
if (propVal == null && sysPropsMode == SYS_PROPS_MODE_FALLBACK) {
propVal = resolveSystemProperty(holder);
}
if (propVal == null) {
propVal = resolveHolder(holder, sub, defaultValue);
}
return propVal;
}
/**
* Parse the given String value recursively, to be able to resolve
* nested Holders (when resolved property values in turn contain
* Holders again).
*
* @param strVal the String value to parse
* @param ignoreBadHolders 是否忽略没有的占位符号
* @return 进行值填充后的字符串
*/
public static String parse(String strVal, boolean ignoreBadHolders) {
Set visitedHolders = new HashSet();
return parse(strVal, null, visitedHolders, ignoreBadHolders);
}
/**
* Parse the given String value recursively, to be able to resolve
* nested Holders (when resolved property values in turn contain
* Holders again).
*
* @param strVal the String value to parse
* @param props the Properties to resolve Holders against
* @param visitedHolders the Holders that have already been visited
* @param ignoreBadHolders during the current resolution attempt (used to detect circular references
* between Holders). Only non-null if we're parsing a nested Holder.
* @return 进行值填充后的字符串
*/
public static String parse(String strVal, Object props, Set visitedHolders,
boolean ignoreBadHolders) {
StringBuffer buf = new StringBuffer(strVal);
int startIndex = strVal.indexOf(DEF_HOLDER_PREFIX);
while (startIndex != -1) {
int endIndex = findHolderEndIndex(buf, startIndex);
if (endIndex != -1) {
String holder = buf.substring(startIndex + DEF_HOLDER_PREFIX_LEN, endIndex);
String defValue = null;
int defIndex = StringUtils.lastIndexOf(holder, ":");
if (defIndex >= 0) {
defValue = StringUtils.trim(holder.substring(defIndex + 1));
holder = StringUtils.trim(holder.substring(0, defIndex));
}
if (!visitedHolders.add(holder)) {
throw new RuntimeException("Circular PlaceHolder reference '"
+ holder + "' in property definitions");
}
// Recursive invocation, parsing Holders contained in the Holder keyValue.
holder = parse(holder, props, visitedHolders, ignoreBadHolders);
// Now obtain the value for the fully resolved keyValue...
String propVal = resolveHolder(holder, props, SYS_PROPS_MODE_FALLBACK, defValue);
if (propVal != null) {
// Recursive invocation, parsing Holders contained in the
// previously resolved Holder value.
propVal = parse(propVal, props, visitedHolders, ignoreBadHolders);
buf.replace(startIndex, endIndex + DEF_HOLDER_SUFFIX_LEN, propVal);
startIndex = buf.indexOf(DEF_HOLDER_PREFIX, startIndex + propVal.length());
} else if (ignoreBadHolders) {
// Proceed with unprocessed value.
startIndex = buf.indexOf(DEF_HOLDER_PREFIX, endIndex + DEF_HOLDER_SUFFIX_LEN);
} else {
throw new RuntimeException("Could not resolve Placeholder '" + holder + "'");
}
visitedHolders.remove(holder);
} else {
startIndex = -1;
}
}
return buf.toString();
}
private static int findHolderEndIndex(CharSequence buf, int startIndex) {
int index = startIndex + DEF_HOLDER_PREFIX_LEN;
int withinNestedHolder = 0;
while (index < buf.length()) {
if (substringMatch(buf, index, DEF_HOLDER_SUFFIX)) {
if (withinNestedHolder > 0) {
withinNestedHolder--;
index = index + DEF_HOLDER_SUFFIX_LEN;
} else {
return index;
}
} else if (substringMatch(buf, index, DEF_HOLDER_PREFIX)) {
withinNestedHolder++;
index = index + DEF_HOLDER_PREFIX_LEN;
} else {
index++;
}
}
return -1;
}
/**
* Test whether the given string matches the given substring at the given index.
*
* @param str the original string (or StringBuffer)
* @param index the index in the original string to start matching against
* @param substring the substring to match at the given index
* @return true/false
*/
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;
}
/**
* Resolve the given Holder using the given properties, performing
* a system properties check according to the given mode.
* Default implementation delegates to resolveHolder
* (Holder, props) before/after the system properties check.
*
Subclasses can override this for custom resolution strategies,
* including customized points for the system properties check.
*
* @param holder the Holder to resolve
* @param props the merged properties of this configurer
* @param sysPropsMode the system properties mode,
* according to the constants in this class
* @return the resolved value, of null if none
* @see System#getProperty
*/
private static String resolveHolder(String holder, Object props, int sysPropsMode,
String defaultValue) {
String propVal = null;
if (sysPropsMode == SYS_PROPS_MODE_OVERRIDE) {
propVal = resolveSystemProperty(holder);
}
if (propVal == null) {
propVal = resolveHolder(holder, props, defaultValue);
}
if (propVal == null && sysPropsMode == SYS_PROPS_MODE_FALLBACK) {
propVal = resolveSystemProperty(holder);
}
return propVal;
}
/**
* Resolve the given Holder using the given properties.
* The default implementation simply checks for a corresponding property keyValue.
*
Subclasses can override this for customized Holder-to-keyValue mappings
* or custom resolution strategies, possibly just using the given properties
* as fallback.
*
Note that system properties will still be checked before respectively
* after this method is invoked, according to the system properties mode.
*
* @param holder the Holder to resolve
* @param props the merged properties of this configurer
* @param defaultValue 默认值
* @return the resolved value, of null if none
*/
protected static String resolveHolder(String holder, Object props, String defaultValue) {
if (props != null) {
Object value = ognlGetValue(holder, props);
// Object value = props.get(holder);
if (value != null) {
return "" + value;
} else if (defaultValue != null) {
return defaultValue;
}
}
return defaultValue;
}
private static Object ognlGetValue(String holder, Object props) {
try {
return Ognl.getValue(holder, props);
} catch (OgnlException e) {
log.debug("", e);
}
return null;
}
/**
* Resolve the given keyValue as JVM system property, and optionally also as
* system environment variable if no matching system property has been found.
*
* @param key the Holder to resolve as system property keyValue
* @return the system property value, or null if not found
* @see System#getProperty(String)
* @see System#getenv(String)
*/
private static String resolveSystemProperty(String key) {
try {
String value = System.getProperty(key);
if (value == null) {
value = System.getenv(key);
}
return value;
} catch (Exception ex) {
return null;
}
}
}