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Groovy: A powerful, dynamic language for the JVM
/*
* 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.
*/
package org.codehaus.groovy.control;
import groovy.lang.GroovyClassLoader;
import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.HashMap;
import java.util.Map;
import org.codehaus.groovy.GroovyBugError;
import org.codehaus.groovy.ast.ClassHelper;
import org.codehaus.groovy.ast.ClassNode;
import org.codehaus.groovy.classgen.Verifier;
import org.objectweb.asm.Opcodes;
/**
* This class is used as a pluggable way to resolve class names.
* An instance of this class has to be added to {@link CompilationUnit} using
* {@link CompilationUnit#setClassNodeResolver(ClassNodeResolver)}. The
* CompilationUnit will then set the resolver on the {@link ResolveVisitor} each
* time new. The ResolveVisitor will prepare name lookup and then finally ask
* the resolver if the class exists. This resolver then can return either a
* SourceUnit or a ClassNode. In case of a SourceUnit the compiler is notified
* that a new source is to be added to the compilation queue. In case of a
* ClassNode no further action than the resolving is done. The lookup result
* is stored in the helper class {@link LookupResult}. This class provides a
* class cache to cache lookups. If you don't want this, you have to override
* the methods {@link ClassNodeResolver#cacheClass(String, ClassNode)} and
* {@link ClassNodeResolver#getFromClassCache(String)}. Custom lookup logic is
* supposed to go into the method
* {@link ClassNodeResolver#findClassNode(String, CompilationUnit)} while the
* entry method is {@link ClassNodeResolver#resolveName(String, CompilationUnit)}
*
* @author Jochen "blackdrag" Theodorou
*/
public class ClassNodeResolver {
/**
* Helper class to return either a SourceUnit or ClassNode.
* @author Jochen "blackdrag" Theodorou
*/
public static class LookupResult {
private SourceUnit su;
private ClassNode cn;
/**
* creates a new LookupResult. You are not supposed to supply
* a SourceUnit and a ClassNode at the same time
*/
public LookupResult(SourceUnit su, ClassNode cn) {
this.su = su;
this.cn = cn;
if (su==null && cn==null) throw new IllegalArgumentException("Either the SourceUnit or the ClassNode must not be null.");
if (su!=null && cn!=null) throw new IllegalArgumentException("SourceUnit and ClassNode cannot be set at the same time.");
}
/**
* returns true if a ClassNode is stored
*/
public boolean isClassNode() { return cn!=null; }
/**
* returns true if a SourecUnit is stored
*/
public boolean isSourceUnit() { return su!=null; }
/**
* returns the SourceUnit
*/
public SourceUnit getSourceUnit() { return su; }
/**
* returns the ClassNode
*/
public ClassNode getClassNode() { return cn; }
}
// Map to store cached classes
private Map cachedClasses = new HashMap();
/**
* Internal helper used to indicate a cache hit for a class that does not exist.
* This way further lookups through a slow {@link #findClassNode(String, CompilationUnit)}
* path can be avoided.
* WARNING: This class is not to be used outside of ClassNodeResolver.
*/
protected static final ClassNode NO_CLASS = new ClassNode("NO_CLASS", Opcodes.ACC_PUBLIC,ClassHelper.OBJECT_TYPE){
public void setRedirect(ClassNode cn) {
throw new GroovyBugError("This is a dummy class node only! Never use it for real classes.");
}
};
/**
* Resolves the name of a class to a SourceUnit or ClassNode. If no
* class or source is found this method returns null. A lookup is done
* by first asking the cache if there is an entry for the class already available
* to then call {@link #findClassNode(String, CompilationUnit)}. The result
* of that method call will be cached if a ClassNode is found. If a SourceUnit
* is found, this method will not be asked later on again for that class, because
* ResolveVisitor will first ask the CompilationUnit for classes in the
* compilation queue and it will find the class for that SourceUnit there then.
* method return a ClassNode instead of a SourceUnit, the res
* @param name - the name of the class
* @param compilationUnit - the current CompilationUnit
* @return the LookupResult
*/
public LookupResult resolveName(String name, CompilationUnit compilationUnit) {
ClassNode res = getFromClassCache(name);
if (res==NO_CLASS) return null;
if (res!=null) return new LookupResult(null,res);
LookupResult lr = findClassNode(name, compilationUnit);
if (lr != null) {
if (lr.isClassNode()) cacheClass(name, lr.getClassNode());
return lr;
} else {
cacheClass(name, NO_CLASS);
return null;
}
}
/**
* caches a ClassNode
* @param name - the name of the class
* @param res - the ClassNode for that name
*/
public void cacheClass(String name, ClassNode res) {
cachedClasses.put(name, res);
}
/**
* returns whatever is stored in the class cache for the given name
* @param name - the name of the class
* @return the result of the lookup, which may be null
*/
public ClassNode getFromClassCache(String name) {
// We use here the class cache cachedClasses to prevent
// calls to ClassLoader#loadClass. Disabling this cache will
// cause a major performance hit.
ClassNode cached = cachedClasses.get(name);
return cached;
}
/**
* Extension point for custom lookup logic of finding ClassNodes. Per default
* this will use the CompilationUnit class loader to do a lookup on the class
* path and load the needed class using that loader. Or if a script is found
* and that script is seen as "newer", the script will be used instead of the
* class.
*
* @param name - the name of the class
* @param compilationUnit - the current compilation unit
* @return the lookup result
*/
public LookupResult findClassNode(String name, CompilationUnit compilationUnit) {
return tryAsLoaderClassOrScript(name, compilationUnit);
}
/**
* This method is used to realize the lookup of a class using the compilation
* unit class loader. Should no class be found we fall abck to a script lookup.
* If a class is found we check if there is also a script and maybe use that
* one in case it is newer.
*/
private LookupResult tryAsLoaderClassOrScript(String name, CompilationUnit compilationUnit) {
GroovyClassLoader loader = compilationUnit.getClassLoader();
Class cls;
try {
// NOTE: it's important to do no lookup against script files
// here since the GroovyClassLoader would create a new CompilationUnit
cls = loader.loadClass(name, false, true);
} catch (ClassNotFoundException cnfe) {
LookupResult lr = tryAsScript(name, compilationUnit, null);
return lr;
} catch (CompilationFailedException cfe) {
throw new GroovyBugError("The lookup for "+name+" caused a failed compilaton. There should not have been any compilation from this call.", cfe);
}
//TODO: the case of a NoClassDefFoundError needs a bit more research
// a simple recompilation is not possible it seems. The current class
// we are searching for is there, so we should mark that somehow.
// Basically the missing class needs to be completely compiled before
// we can again search for the current name.
/*catch (NoClassDefFoundError ncdfe) {
cachedClasses.put(name,SCRIPT);
return false;
}*/
if (cls == null) return null;
//NOTE: we might return false here even if we found a class,
// because we want to give a possible script a chance to
// recompile. This can only be done if the loader was not
// the instance defining the class.
if (cls.getClassLoader() != loader) {
return tryAsScript(name, compilationUnit, cls);
}
ClassNode cn = ClassHelper.make(cls);
return new LookupResult(null,cn);
}
/**
* try to find a script using the compilation unit class loader.
*/
private static LookupResult tryAsScript(String name, CompilationUnit compilationUnit, Class oldClass) {
LookupResult lr = null;
if (oldClass!=null) {
ClassNode cn = ClassHelper.make(oldClass);
lr = new LookupResult(null,cn);
}
if (name.startsWith("java.")) return lr;
//TODO: don't ignore inner static classes completely
if (name.indexOf('$') != -1) return lr;
// try to find a script from classpath*/
GroovyClassLoader gcl = compilationUnit.getClassLoader();
URL url = null;
try {
url = gcl.getResourceLoader().loadGroovySource(name);
} catch (MalformedURLException e) {
// fall through and let the URL be null
}
if (url != null && ( oldClass==null || isSourceNewer(url, oldClass))) {
SourceUnit su = compilationUnit.addSource(url);
return new LookupResult(su,null);
}
return lr;
}
/**
* get the time stamp of a class
* NOTE: copied from GroovyClassLoader
*/
private static long getTimeStamp(Class cls) {
return Verifier.getTimestamp(cls);
}
/**
* returns true if the source in URL is newer than the class
* NOTE: copied from GroovyClassLoader
*/
private static boolean isSourceNewer(URL source, Class cls) {
try {
long lastMod;
// Special handling for file:// protocol, as getLastModified() often reports
// incorrect results (-1)
if (source.getProtocol().equals("file")) {
// Coerce the file URL to a File
String path = source.getPath().replace('/', File.separatorChar).replace('|', ':');
File file = new File(path);
lastMod = file.lastModified();
} else {
URLConnection conn = source.openConnection();
lastMod = conn.getLastModified();
conn.getInputStream().close();
}
return lastMod > getTimeStamp(cls);
} catch (IOException e) {
// if the stream can't be opened, let's keep the old reference
return false;
}
}
}