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/**
* Copyright (c) 2004-2011 QOS.ch
* All rights reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
*/
/**
*
*/
package org.slf4j.instrumentation;
import static org.slf4j.helpers.MessageFormatter.format;
import java.io.ByteArrayInputStream;
import java.lang.instrument.ClassFileTransformer;
import java.security.ProtectionDomain;
import javassist.CannotCompileException;
import javassist.ClassPool;
import javassist.CtBehavior;
import javassist.CtClass;
import javassist.CtField;
import javassist.NotFoundException;
import org.slf4j.helpers.MessageFormatter;
/**
*
* LogTransformer does the work of analyzing each class, and if appropriate add
* log statements to each method to allow logging entry/exit.
*
*
* This class is based on the article Add Logging at Class Load Time with Java Instrumentation.
*
*/
public class LogTransformer implements ClassFileTransformer {
/**
* Builder provides a flexible way of configuring some of many options on the
* parent class instead of providing many constructors.
*
* http://rwhansen.blogspot.com/2007/07/theres-builder-pattern-that-joshua.html
*
*/
public static class Builder {
/**
* Build and return the LogTransformer corresponding to the options set in
* this Builder.
*
* @return
*/
public LogTransformer build() {
if (verbose) {
System.err.println("Creating LogTransformer");
}
return new LogTransformer(this);
}
boolean addEntryExit;
/**
* Should each method log entry (with parameters) and exit (with parameters
* and return value)?
*
* @param b
* value of flag
* @return
*/
public Builder addEntryExit(boolean b) {
addEntryExit = b;
return this;
}
boolean addVariableAssignment;
// private Builder addVariableAssignment(boolean b) {
// System.err.println("cannot currently log variable assignments.");
// addVariableAssignment = b;
// return this;
// }
boolean verbose;
/**
* Should LogTransformer be verbose in what it does? This currently list the
* names of the classes being processed.
*
* @param b
* @return
*/
public Builder verbose(boolean b) {
verbose = b;
return this;
}
String[] ignore = { "org/slf4j/", "ch/qos/logback/", "org/apache/log4j/" };
public Builder ignore(String[] strings) {
this.ignore = strings;
return this;
}
private String level = "info";
public Builder level(String level) {
level = level.toLowerCase();
if (level.equals("info") || level.equals("debug") || level.equals("trace")) {
this.level = level;
} else {
if (verbose) {
System.err.println("level not info/debug/trace : " + level);
}
}
return this;
}
}
private final String level;
private final String levelEnabled;
private LogTransformer(Builder builder) {
String s = "WARNING: javassist not available on classpath for javaagent, log statements will not be added";
try {
if (Class.forName("javassist.ClassPool") == null) {
System.err.println(s);
}
} catch (ClassNotFoundException e) {
System.err.println(s);
}
this.addEntryExit = builder.addEntryExit;
// this.addVariableAssignment = builder.addVariableAssignment;
this.verbose = builder.verbose;
this.ignore = builder.ignore;
this.level = builder.level;
this.levelEnabled = "is" + builder.level.substring(0, 1).toUpperCase() + builder.level.substring(1) + "Enabled";
}
private final boolean addEntryExit;
// private boolean addVariableAssignment;
private final boolean verbose;
private final String[] ignore;
public byte[] transform(ClassLoader loader, String className, Class clazz, ProtectionDomain domain, byte[] bytes) {
try {
return transform0(className, clazz, domain, bytes);
} catch (Exception e) {
System.err.println("Could not instrument " + className);
e.printStackTrace();
return bytes;
}
}
/**
* transform0 sees if the className starts with any of the namespaces to
* ignore, if so it is returned unchanged. Otherwise it is processed by
* doClass(...)
*
* @param className
* @param clazz
* @param domain
* @param bytes
* @return
*/
private byte[] transform0(String className, Class clazz, ProtectionDomain domain, byte[] bytes) {
try {
for (String s : ignore) {
if (className.startsWith(s)) {
return bytes;
}
}
String slf4jName = "org.slf4j.LoggerFactory";
try {
if (domain != null && domain.getClassLoader() != null) {
domain.getClassLoader().loadClass(slf4jName);
} else {
if (verbose) {
System.err.println("Skipping " + className + " as it doesn't have a domain or a class loader.");
}
return bytes;
}
} catch (ClassNotFoundException e) {
if (verbose) {
System.err.println("Skipping " + className + " as slf4j is not available to it");
}
return bytes;
}
if (verbose) {
System.err.println("Processing " + className);
}
return doClass(className, clazz, bytes);
} catch (Throwable e) {
System.out.println("e = " + e);
return bytes;
}
}
private String loggerName;
/**
* doClass() process a single class by first creates a class description from
* the byte codes. If it is a class (i.e. not an interface) the methods
* defined have bodies, and a static final logger object is added with the
* name of this class as an argument, and each method then gets processed with
* doMethod(...) to have logger calls added.
*
* @param name
* class name (slashes separate, not dots)
* @param clazz
* @param b
* @return
*/
private byte[] doClass(String name, Class clazz, byte[] b) {
ClassPool pool = ClassPool.getDefault();
CtClass cl = null;
try {
cl = pool.makeClass(new ByteArrayInputStream(b));
if (cl.isInterface() == false) {
loggerName = "_____log";
// We have to declare the log variable.
String pattern1 = "private static org.slf4j.Logger {};";
String loggerDefinition = format(pattern1, loggerName).getMessage();
CtField field = CtField.make(loggerDefinition, cl);
// and assign it the appropriate value.
String pattern2 = "org.slf4j.LoggerFactory.getLogger({}.class);";
String replace = name.replace('/', '.');
String getLogger = format(pattern2, replace).getMessage();
cl.addField(field, getLogger);
// then check every behaviour (which includes methods). We are
// only
// interested in non-empty ones, as they have code.
// NOTE: This will be changed, as empty methods should be
// instrumented too.
CtBehavior[] methods = cl.getDeclaredBehaviors();
for (CtBehavior method : methods) {
if (method.isEmpty() == false) {
doMethod(method);
}
}
b = cl.toBytecode();
}
} catch (Exception e) {
System.err.println("Could not instrument " + name + ", " + e);
e.printStackTrace(System.err);
} finally {
if (cl != null) {
cl.detach();
}
}
return b;
}
/**
* process a single method - this means add entry/exit logging if requested.
* It is only called for methods with a body.
*
* @param method
* method to work on
* @throws NotFoundException
* @throws CannotCompileException
*/
private void doMethod(CtBehavior method) throws NotFoundException, CannotCompileException {
String signature = JavassistHelper.getSignature(method);
String returnValue = JavassistHelper.returnValue(method);
if (addEntryExit) {
String messagePattern = "if ({}.{}()) {}.{}(\">> {}\");";
Object[] arg1 = new Object[] { loggerName, levelEnabled, loggerName, level, signature };
String before = MessageFormatter.arrayFormat(messagePattern, arg1).getMessage();
// System.out.println(before);
method.insertBefore(before);
String messagePattern2 = "if ({}.{}()) {}.{}(\"<< {}{}\");";
Object[] arg2 = new Object[] { loggerName, levelEnabled, loggerName, level, signature, returnValue };
String after = MessageFormatter.arrayFormat(messagePattern2, arg2).getMessage();
// System.out.println(after);
method.insertAfter(after);
}
}
}