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package com.sun.appserv.web.cache;
import java.util.Map;
import java.util.logging.Logger;
import java.util.logging.Level;
import java.util.ResourceBundle;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import com.sun.enterprise.web.logging.pwc.LogDomains;
import com.sun.appserv.web.cache.mapping.Constants;
import com.sun.appserv.web.cache.mapping.CacheMapping;
import com.sun.appserv.web.cache.mapping.ConstraintField;
import com.sun.appserv.web.cache.mapping.Field;
/** DefaultCacheHelper interface is the built-in implementation of the
* <code>CacheHelper</code> interface to aide in:
* a) the key generation b) whether to cache the response.
* There is one CacheHelper instance per web application.
*/
public class DefaultCacheHelper implements CacheHelper {
private static final String[] KEY_PREFIXES = {
"", "ca.", "rh.", "rp.", "rc.", "ra.", "sa.", "si." };
public static final String ATTR_CACHING_FILTER_NAME =
"com.sun.ias.web.cachingFilterName";
public static final String PROP_KEY_GENERATOR_ATTR_NAME =
"cacheKeyGeneratorAttrName";
// PWC_LOGGER
private static Logger _logger;
private static boolean _isTraceEnabled = false;
/**
* The resource bundle containing the localized message strings.
*/
private static ResourceBundle _rb = null;
ServletContext context;
// cache manager
CacheManager manager;
String attrKeyGenerator = null;
boolean isKeyGeneratorChecked = false;
CacheKeyGenerator keyGenerator;
/**
* set the CacheManager for this application
* @param manager associated with this application
*/
public void setCacheManager(CacheManager manager) {
this.manager = manager;
}
/*** CacheHelper methods **/
/**
* initialize this helper
* @param context the web application context this helper belongs to
* @param props helper properties
*/
public void init(ServletContext context, Map props) {
this.context = context;
attrKeyGenerator = (String)props.get(PROP_KEY_GENERATOR_ATTR_NAME);
// web container logger
_logger = LogDomains.getLogger(LogDomains.PWC_LOGGER);
_isTraceEnabled = _logger.isLoggable(Level.FINE);
_rb = _logger.getResourceBundle();
}
/**
* cache-mapping for this servlet-name or the URLpattern
* @param request incoming request
* @return cache-mapping object; uses servlet name or the URL pattern
* to lookup in the CacheManager for the mapping.
*/
private CacheMapping lookupCacheMapping(HttpServletRequest request) {
String name = (String)request.getAttribute(ATTR_CACHING_FILTER_NAME);
return manager.getCacheMapping(name);
}
/** getCacheKey: generate the key to be used to cache this request
* @param request incoming <code>HttpServletRequest</code>
* @return key string used to access the cache entry.
* Key is composed of: servletPath + a concatenation of the field values in
* the request; all key field names must be found in the appropriate scope.
*/
public String getCacheKey(HttpServletRequest request) {
// cache mapping associated with the request
CacheMapping mapping = lookupCacheMapping(request);
if (isKeyGeneratorChecked == false && attrKeyGenerator != null) {
try {
keyGenerator = (CacheKeyGenerator)
context.getAttribute(attrKeyGenerator);
} catch (ClassCastException cce){
_logger.log(Level.WARNING, "cache.defaultHelp.illegalKeyGenerator", cce);
}
isKeyGeneratorChecked = true;
}
if (keyGenerator != null) {
String key = keyGenerator.getCacheKey(context, request);
if (key != null)
return key;
}
StringBuffer sb = new StringBuffer(128);
/** XXX: the StringBuffer append is a (uncontended) synchronized method.
* performance hit?
*/
sb.append(request.getServletPath());
// append the key fields
Field[] keys = mapping.getKeyFields();
for (int i = 0; i < keys.length; i++) {
Object value = keys[i].getValue(context, request);
// all defined key field must be present
if (value == null) {
if (_isTraceEnabled) {
_logger.fine("DefaultCacheHelper: cannot find all the required key fields in the request " + request.getServletPath());
}
return null;
}
sb.append(";");
sb.append(KEY_PREFIXES[keys[i].getScope()]);
sb.append(keys[i].getName());
sb.append("=");
sb.append(value);
}
return sb.toString();
}
/** isCacheable: is the response to given request cachebale?
* @param request incoming <code>HttpServletRequest</code> object
* @return <code>true</code> if the response could be cached.
* or return <code>false</code> if the results of this request
* must not be cached.
*
* Applies pre-configured cacheability constraints in the cache-mapping;
* all constraints must pass for this to be cacheable.
*/
public boolean isCacheable(HttpServletRequest request) {
boolean result = false;
// cache mapping associated with the request
CacheMapping mapping = lookupCacheMapping(request);
// check if the method is in the allowed methods list
if (mapping.findMethod(request.getMethod())) {
result = true;
ConstraintField fields[] = mapping.getConstraintFields();
// apply all the constraints
for (int i = 0; i < fields.length; i++) {
if (!fields[i].applyConstraints(context, request)) {
result = false;
break;
}
}
}
return result;
}
/** isRefreshNeeded: is the response to given request be refreshed?
* @param request incoming <code>HttpServletRequest</code> object
* @return <code>true</code> if the response needs to be refreshed.
* or return <code>false</code> if the results of this request
* don't need to be refreshed.
*
* XXX: 04/16/02 right now there is no configurability for this in
* ias-web.xml; should add a refresh-field element there:
* <refresh-field name="refresh" scope="request.parameter" />
*/
public boolean isRefreshNeeded(HttpServletRequest request) {
boolean result = false;
// cache mapping associated with the request
CacheMapping mapping = lookupCacheMapping(request);
Field field = mapping.getRefreshField();
if (field != null) {
Object value = field.getValue(context, request);
// the field's string representation must be "true" or "false"
if (value != null && "true".equals(value.toString())) {
result = true;
}
}
return result;
}
/** get timeout for the cacheable data in this request
* @param request incoming <code>HttpServletRequest</code> object
* @return either the statically specified value or from the request
* fields. If not specified, get the timeout defined for the
* cache element.
*/
public int getTimeout(HttpServletRequest request) {
// cache mapping associated with the request
CacheMapping mapping = lookupCacheMapping(request);
// get the statically configured value, if any
int result = mapping.getTimeout();
// if the field is not defined, return the configured value
Field field = mapping.getTimeoutField();
if (field != null) {
Object value = field.getValue(context, request);
if (value != null) {
try {
// Integer type timeout object
Integer timeoutAttr = Integer.valueOf(value.toString());
result = timeoutAttr.intValue();
} catch (NumberFormatException cce) { }
}
}
// Note: this could be CacheHelper.TIMEOUT_NOT_SET
return result;
}
/**
* Stop this Context component.
* @exception Exception if a shutdown error occurs
*/
public void destroy() throws Exception {
}
}