package org.apache.velocity.util;
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
import java.io.InputStream;
import org.apache.velocity.context.InternalContextAdapter;
import org.apache.velocity.exception.MethodInvocationException;
import org.apache.velocity.exception.VelocityException;
import org.apache.velocity.runtime.parser.node.SimpleNode;
import org.apache.velocity.runtime.parser.node.ASTMethod.MethodCacheKey;
import org.apache.velocity.util.introspection.Info;
import org.apache.velocity.util.introspection.IntrospectionCacheData;
import org.apache.velocity.util.introspection.VelMethod;
/**
* Simple utility functions for manipulating classes and resources
* from the classloader.
*
* @author <a href="mailto:[email protected]">Will Glass-Husain</a>
* @version $Id: ClassUtils.java 898032 2010-01-11 19:51:03Z nbubna $
* @since 1.5
*/
public class ClassUtils {
/**
* Utility class; cannot be instantiated.
*/
private ClassUtils()
{
}
/**
* Return the specified class. Checks the ThreadContext classloader first,
* then uses the System classloader. Should replace all calls to
* <code>Class.forName( claz )</code> (which only calls the System class
* loader) when the class might be in a different classloader (e.g. in a
* webapp).
*
* @param clazz the name of the class to instantiate
* @return the requested Class object
* @throws ClassNotFoundException
*/
public static Class getClass(String clazz) throws ClassNotFoundException
{
/**
* Use the Thread context classloader if possible
*/
ClassLoader loader = Thread.currentThread().getContextClassLoader();
if (loader != null)
{
try
{
return Class.forName(clazz, true, loader);
}
catch (ClassNotFoundException E)
{
/**
* If not found with ThreadContext loader, fall thru to
* try System classloader below (works around bug in ant).
*/
}
}
/**
* Thread context classloader isn't working out, so use system loader.
*/
return Class.forName(clazz);
}
/**
* Return a new instance of the given class. Checks the ThreadContext
* classloader first, then uses the System classloader. Should replace all
* calls to <code>Class.forName( claz ).newInstance()</code> (which only
* calls the System class loader) when the class might be in a different
* classloader (e.g. in a webapp).
*
* @param clazz the name of the class to instantiate
* @return an instance of the specified class
* @throws ClassNotFoundException
* @throws IllegalAccessException
* @throws InstantiationException
*/
public static Object getNewInstance(String clazz)
throws ClassNotFoundException,IllegalAccessException,InstantiationException
{
return getClass(clazz).newInstance();
}
/**
* Finds a resource with the given name. Checks the Thread Context
* classloader, then uses the System classloader. Should replace all
* calls to <code>Class.getResourceAsString</code> when the resource
* might come from a different classloader. (e.g. a webapp).
* @param claz Class to use when getting the System classloader (used if no Thread
* Context classloader available or fails to get resource).
* @param name name of the resource
* @return InputStream for the resource.
*/
public static InputStream getResourceAsStream(Class claz, String name)
{
InputStream result = null;
/**
* remove leading slash so path will work with classes in a JAR file
*/
while (name.startsWith("/"))
{
name = name.substring(1);
}
ClassLoader classLoader = Thread.currentThread()
.getContextClassLoader();
if (classLoader == null)
{
classLoader = claz.getClassLoader();
result = classLoader.getResourceAsStream( name );
}
else
{
result= classLoader.getResourceAsStream( name );
/**
* for compatibility with texen / ant tasks, fall back to
* old method when resource is not found.
*/
if (result == null)
{
classLoader = claz.getClassLoader();
if (classLoader != null)
result = classLoader.getResourceAsStream( name );
}
}
return result;
}
/**
* Lookup a VelMethod object given the method signature that is specified in
* the passed in parameters. This method first searches the cache, if not found in
* the cache then uses reflections to inspect Object o, for the given method.
* @param methodName Name of method
* @param params Array of objects that are parameters to the method
* @param paramClasses Array of Classes coresponding to the types in params.
* @param o Object to introspect for the given method.
* @param context Context from which the method cache is aquirred
* @param node ASTNode, used for error reporting.
* @param strictRef If no method is found, throw an exception, never return null in this case
* @return VelMethod object if the object is found, null if not matching method is found
*/
public static VelMethod getMethod(String methodName, Object[] params,
Class[] paramClasses, Object o, InternalContextAdapter context,
SimpleNode node, boolean strictRef)
{
VelMethod method = null;
try
{
/*
* check the cache
*/
MethodCacheKey mck = new MethodCacheKey(methodName, paramClasses);
IntrospectionCacheData icd = context.icacheGet(mck);
/*
* like ASTIdentifier, if we have cache information, and the Class of
* Object o is the same as that in the cache, we are safe.
*/
if (icd != null && (o != null && icd.contextData == o.getClass()))
{
/*
* get the method from the cache
*/
method = (VelMethod) icd.thingy;
}
else
{
/*
* otherwise, do the introspection, and then cache it
*/
method = node.getRuntimeServices().getUberspect().getMethod(o, methodName, params,
new Info(node.getTemplateName(), node.getLine(), node.getColumn()));
if ((method != null) && (o != null))
{
icd = new IntrospectionCacheData();
icd.contextData = o.getClass();
icd.thingy = method;
context.icachePut(mck, icd);
}
}
/*
* if we still haven't gotten the method, either we are calling a method
* that doesn't exist (which is fine...) or I screwed it up.
*/
if (method == null)
{
if (strictRef)
{
// Create a parameter list for the exception error message
StringBuffer plist = new StringBuffer();
for (int i = 0; i < params.length; i++)
{
Class param = paramClasses[i];
plist.append(param == null ? "null" : param.getName());
if (i < params.length - 1)
plist.append(", ");
}
throw new MethodInvocationException("Object '"
+ o.getClass().getName() + "' does not contain method "
+ methodName + "(" + plist + ")", null, methodName, node
.getTemplateName(), node.getLine(), node.getColumn());
}
else
{
return null;
}
}
}
catch (MethodInvocationException mie)
{
/*
* this can come from the doIntrospection(), as the arg values are
* evaluated to find the right method signature. We just want to propogate
* it here, not do anything fancy
*/
throw mie;
}
catch (RuntimeException e)
{
/**
* pass through application level runtime exceptions
*/
throw e;
}
catch (Exception e)
{
/*
* can come from the doIntropection() also, from Introspector
*/
String msg = "ASTMethod.execute() : exception from introspection";
throw new VelocityException(msg, e);
}
return method;
}
}
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