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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2022 Saxonica Limited
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
package net.sf.saxon.trans;
import net.sf.saxon.Configuration;
import net.sf.saxon.Version;
import net.sf.saxon.lib.IDynamicLoader;
import net.sf.saxon.lib.Logger;
import net.sf.saxon.serialize.MessageEmitter;
import java.io.InputStream;
import java.lang.reflect.Constructor;
import java.util.HashMap;
/**
* Utility class used to perform dynamic loading of user-hook implementations
*/
public class DynamicLoader implements IDynamicLoader {
private ClassLoader classLoader;
protected HashMap> knownClasses = new HashMap<>(20);
public DynamicLoader() {
registerKnownClasses();
}
/**
* Register classes that might be dynamically loaded even though they are contained
* within Saxon itself. This typically occurs for default implementations of classes that
* can be substituted or subclassed by the user.
*/
protected void registerKnownClasses() {
knownClasses.put("net.sf.saxon.serialize.MessageEmitter", MessageEmitter.class);
//knownClasses.put("net.sf.saxon.java.JavaPlatform", JavaPlatform.class); // not available on .NET
knownClasses.put("net.sf.saxon.Configuration", Configuration.class);
}
/**
* Set a ClassLoader to be used when loading external classes. Examples of classes that are
* loaded include SAX parsers, localization modules for formatting numbers and dates,
* extension functions, external object models. In an environment such as Eclipse that uses
* its own ClassLoader, this ClassLoader should be nominated to ensure that any class loaded
* by Saxon is identical to a class of the same name loaded by the external environment.
*
* @param loader the ClassLoader to be used in this configuration
*/
public void setClassLoader(ClassLoader loader) {
classLoader = loader;
}
/**
* Get the ClassLoader supplied using the method {@link #setClassLoader}.
* If none has been supplied, return null.
*
* @return the ClassLoader used in this configuration
*/
public ClassLoader getClassLoader() {
return classLoader;
}
/**
* Load a class using the class name provided.
* Note that the method does not check that the object is of the right class.
* This method is intended for internal use only.
*
* @param className A string containing the name of the
* class, for example "com.microstar.sax.LarkDriver"
* @param traceOut if diagnostic tracing is required, the destination for the output; otherwise null
* @param classLoader The ClassLoader to be used to load the class. If this is null, then
* the classLoader used will be the first one available of: the classLoader registered
* with the Configuration using {@link #setClassLoader}; the context class loader for
* the current thread; or failing that, the class loader invoked implicitly by a call
* of Class.forName() (which is the ClassLoader that was used to load the Configuration
* object itself).
* @return an instance of the class named, or null if it is not
* loadable.
* @throws XPathException if the class cannot be loaded.
*/
public Class getClass(String className, Logger traceOut, ClassLoader classLoader) throws XPathException {
Class known = knownClasses.get(className);
if (known != null) {
return known;
}
boolean tracing = traceOut != null;
if (tracing) {
traceOut.info("Loading " + className);
}
try {
ClassLoader loader = classLoader;
if (loader == null) {
loader = this.classLoader;
}
if (loader == null) {
loader = Thread.currentThread().getContextClassLoader();
}
if (loader != null) {
try {
return loader.loadClass(className);
} catch (Throwable ex) {
// Catching Exception is not enough; Java sometimes throws a NoClassDefFoundError
return Class.forName(className);
}
} else {
return Class.forName(className);
}
} catch (Throwable e) {
if (tracing) {
// The exception is often masked, especially when calling extension
// functions
traceOut.error("The class " + className + " could not be loaded: " + e.getMessage());
}
throw new XPathException("Failed to load " + className + getMissingJarFileMessage(className), e);
}
}
/**
* Instantiate a class using the class name provided.
* Note that the method does not check that the object is of the right class.
* This method is intended for internal use only.
*
* @param className A string containing the name of the
* class, for example "com.microstar.sax.LarkDriver"
* @param classLoader The ClassLoader to be used to load the class. If this is null, then
* the classLoader used will be the first one available of: the classLoader registered
* with the Configuration using {@link #setClassLoader}; the context class loader for
* the current thread; or failing that, the class loader invoked implicitly by a call
* of Class.forName() (which is the ClassLoader that was used to load the Configuration
* object itself).
* @return an instance of the class named, or null if it is not
* loadable.
* @throws XPathException if the class cannot be loaded.
*/
public Object getInstance(String className, /*@Nullable*/ ClassLoader classLoader) throws XPathException {
Class theclass = getClass(className, null, classLoader);
try {
Constructor constructor = theclass.getConstructor();
return constructor.newInstance();
} catch (NoSuchMethodException err) {
throw new XPathException("Failed to instantiate class " + className +
" (it has no public zero-argument constructor)", err);
} catch (Exception err) {
throw new XPathException("Failed to instantiate class " + className, err);
}
}
/**
* Instantiate a class using the class name provided, with the option of tracing
* Note that the method does not check that the object is of the right class.
* This method is intended for internal use only.
*
* @param className A string containing the name of the
* class, for example "com.microstar.sax.LarkDriver"
* @param traceOut if attempts to load classes are to be traced, then the destination
* for the trace output; otherwise null
* @param classLoader The ClassLoader to be used to load the class. If this is null, then
* the classLoader used will be the first one available of: the classLoader registered
* with the Configuration using {@link #setClassLoader}; the context class loader for
* the current thread; or failing that, the class loader invoked implicitly by a call
* of Class.forName() (which is the ClassLoader that was used to load the Configuration
* object itself).
* @return an instance of the class named, or null if it is not
* loadable.
* @throws XPathException if the class cannot be loaded.
*/
public Object getInstance(String className, Logger traceOut, /*@Nullable*/ ClassLoader classLoader) throws XPathException {
Class theclass = getClass(className, traceOut, classLoader);
try {
Constructor constructor = theclass.getConstructor();
return constructor.newInstance();
} catch (NoSuchMethodException err) {
throw new XPathException("Failed to instantiate class " + className +
" (it has no public zero-argument constructor)", err);
} catch (NoClassDefFoundError err) {
throw new XPathException("Failed to load instance of class " + className + getMissingJarFileMessage(className), err);
} catch (Exception err) {
throw new XPathException("Failed to instantiate class " + className, err);
}
}
/**
* If a Saxon class is in a particular JAR file, identify the JAR file
* @param className the name of a class
* @return the name of the JAR file that the class should be found in, if known; otherwise null
*/
private String getJarFileForClass(String className) {
if (className.startsWith("net.sf.saxon.option.sql.")) {
return "saxon-sql-" + Version.getProductVersion() + ".jar";
} else if (className.startsWith("com.ibm.icu.")) {
return "icu4j-59.1.jar";
} else if (className.startsWith("com.saxonica")) {
return "saxon-" + Version.softwareEdition.toLowerCase() + "-" + Version.getProductVersion() + ".jar";
} else {
return null;
}
}
private String getMissingJarFileMessage(String className) {
String jar = getJarFileForClass(className);
return jar==null ? "" : ". Check that " + jar + " is on the classpath";
}
public InputStream getResourceAsStream(String name) {
ClassLoader loader = getClassLoader();
if (loader == null) {
loader = Thread.currentThread().getContextClassLoader();
}
return loader.getResourceAsStream(name);
}
}