I add cached property support to tapestry. A cached
property is actually a method in the form of a getter,
which will return an object could be used by page
components for several times, and worth cache it. For
example, a selection model containing data retrieved
from database, and the selection model could be used
several times in the template and the page class.
The implementation consists of the following:
1. an EnhancementWorker class - CachePropertyWorker
2. hivemind config
========================
<service-point id="CachePropertyWorker"
interface="org.apache.tapestry.enhance.EnhancementWorker">
<invoke-factory>
<construct
class="com.newtouch.newtouchone.tapestry.CachePropertyWorker"
/>
</invoke-factory>
</service-point>
<contribution
configuration-id="tapestry.enhance.EnhancementWorkers">
<command id="cache-properties"
object="service:CachePropertyWorker"
before="tapestry.enhance.abstract-property" />
</contribution>
================================================
3. page spec definition, an specified property named
_cache will be defined, with its initial value as the
properties need to be cached. For example,
<property name="_cache"
initial-value="literal:foo,bar" />
which will cache the result of getFoo() and getBar().
Maybe a better solution would be add an special tag,
such as <cache property="foo" />, but the
implementation might be more complex.
Yunfeng Hou
CachePropertyWorker.java
==============================
package com.newtouch.newtouchone.tapestry;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.HashMap;
import java.util.Map;
import java.util.StringTokenizer;
import org.apache.hivemind.ErrorLog;
import org.apache.hivemind.Location;
import org.apache.hivemind.service.MethodSignature;
import org.apache.hivemind.util.StringUtils;
import org.apache.tapestry.enhance.EnhanceUtils;
import
org.apache.tapestry.enhance.EnhancementOperation;
import org.apache.tapestry.enhance.EnhancementWorker;
import org.apache.tapestry.event.PageDetachListener;
import
org.apache.tapestry.spec.IComponentSpecification;
import
org.apache.tapestry.spec.IPropertySpecification;
public class CachePropertyWorker implements
EnhancementWorker {
private static final String LITERAL_PREFIX =
"literal:";
private static final Class[] NULL_ARGS = new
Class[0];
private ErrorLog _errorLog;
private static final String GETTERBODY = "return
_cache.containsKey(\"XXX\")?"
+ "(TTT) _cache.get(\"XXX\"): "
+ "(TTT)
com.newtouch.newtouchone.tapestry.CachePropertyWorker"
+ ".cachedObject(\"XXX\", _cache, super.getXXX());";
public void performEnhancement(EnhancementOperation
op,
IComponentSpecification spec) {
Location location = (Location) spec.getLocation();
IPropertySpecification propSpec = spec
.getPropertySpecification("_cache");
if (propSpec == null)
return;
String names = propSpec.getInitialValue();
if (names == null ||
!names.startsWith(LITERAL_PREFIX))
return;
String pageClassName = spec.getComponentClassName();
Class pageClass = null;
try {
pageClass = Class.forName(pageClassName);
} catch (ClassNotFoundException e) {
_errorLog.error("page class not found:" +
pageClassName, location,
e);
return;
}
op.addInjectedField("_cache", java.util.Map.class,
new HashMap());
// createGetCacheMethod(op, location);
names = names.substring(LITERAL_PREFIX.length());
StringTokenizer st = new StringTokenizer(names, ",;
");
while (st.hasMoreTokens()) {
String name = st.nextToken();
String getterName = "get" + name.substring(0,
1).toUpperCase()
+ name.substring(1);
try {
Method getter = pageClass.getMethod(getterName,
NULL_ARGS);
createProperty(op, getter, location);
} catch (Exception e) {
_errorLog.error("getter not found:" +
getterName,
location, e);
}
}
}
private void createProperty(EnhancementOperation op,
Method getter,
Location location) {
String name = getter.getName().substring(3);
String body = StringUtils.replace(GETTERBODY, "XXX",
name);
body = StringUtils.replace(body, "TTT",
getter.getReturnType()
.getName());
op
.addMethod(Modifier.PUBLIC, new
MethodSignature(getter
.getReturnType(),
getter.getName(), null, null),
body,
location);
op.extendMethodImplementation(PageDetachListener.class,
EnhanceUtils.PAGE_DETACHED_SIGNATURE,
"_cache.clear();");
}
public void setErrorLog(ErrorLog errorLog) {
_errorLog = errorLog;
}
public static Object cachedObject(String name, Map
cache, Object obj) {
cache.put(name, obj);
return obj;
}
}
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<?xml version="1.0"?>
<module id="tapestry.spring" version="1.0.0">
<service-point id="CachePropertyWorker"
interface="org.apache.tapestry.enhance.EnhancementWorker">
<invoke-factory>
<construct
class="com.newtouch.newtouchone.tapestry.CachePropertyWorker" />
</invoke-factory>
</service-point>
<contribution
configuration-id="tapestry.enhance.EnhancementWorkers">
<command id="cache-properties"
object="service:CachePropertyWorker" before="tapestry.enhance.abstract-property" />
</contribution>
</module>
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