Glassfish example source code file (BtraceClientGenerator.java)

This example Glassfish source code file (BtraceClientGenerator.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Glassfish tags/keywords

annotationvisitor, btraceclientgenerator, class, classwriter, file, file, fileoutputstream, fileoutputstream, generatoradapter, io, lcom/sun/btrace/annotations/btrace, method, method, reflection, security, string, string, util

The Glassfish BtraceClientGenerator.java source code

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright (c) 2009-2010 Oracle and/or its affiliates. All rights reserved.
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License.  You can
 * obtain a copy of the License at
 * https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
 * or packager/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 *
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at packager/legal/LICENSE.txt.
 *
 * GPL Classpath Exception:
 * Oracle designates this particular file as subject to the "Classpath"
 * exception as provided by Oracle in the GPL Version 2 section of the License
 * file that accompanied this code.
 *
 * Modifications:
 * If applicable, add the following below the License Header, with the fields
 * enclosed by brackets [] replaced by your own identifying information:
 * "Portions Copyright [year] [name of copyright owner]"
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 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
 * holder.
 */

package org.glassfish.flashlight.impl.client;

/**
 * @author Mahesh Kannan
 * Started: Jul 20, 2008
 * @author Byron Nevins, August 2009
 */
import com.sun.enterprise.util.SystemPropertyConstants;
import org.glassfish.flashlight.provider.FlashlightProbe;
import org.glassfish.flashlight.provider.ProbeRegistry;
import org.objectweb.asm.AnnotationVisitor;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.Label;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;
import org.objectweb.asm.commons.GeneratorAdapter;
import org.objectweb.asm.commons.Method;

import java.io.File;
import java.io.FileOutputStream;
import java.io.PrintStream;
import java.lang.reflect.InvocationTargetException;
import java.security.PrivilegedActionException;
import java.security.ProtectionDomain;
import java.util.Collection;

public class BtraceClientGenerator {
    private BtraceClientGenerator() {
        // all static class -- no instances allowed
    }

    public static byte[] generateBtraceClientClassData(int clientID, Collection<FlashlightProbe> probes) {
        // create a unique name.  It does not matter what the name is.
        String generatedClassName = "com/sun/btrace/flashlight/BTrace_Flashlight_" + clientID;
        //Start of writing a class using ASM, which will be our BTrace Client
        int cwFlags = ClassWriter.COMPUTE_FRAMES + ClassWriter.COMPUTE_MAXS;
        ClassWriter cw = new ClassWriter(cwFlags);

        //Define the access identifiers for the BTrace Client class
        int access = Opcodes.ACC_PUBLIC + Opcodes.ACC_FINAL;
        cw.visit(Opcodes.V1_5, access, generatedClassName, null,
                "java/lang/Object", null);
        //Need a @OnMethod annotation, so prepare your Annotation Visitor for that
        AnnotationVisitor av = cw.visitAnnotation("Lcom/sun/btrace/annotations/BTrace;", true);

        //Iterate through the probes, so you will create one method for each probe
        int methodCounter = 0;
        for (FlashlightProbe probe : probes) {
            //Preparing the class method header and params (type) for @OnMethod annotation
            String typeDesc = "void ";
            String methodDesc = "void __" + probe.getProviderJavaMethodName() + "__" + clientID + "_" + methodCounter + "_";
            methodDesc += "(";
            typeDesc += "(";
            String delim = "";
            String typeDelim = "";
            Class[] paramTypes = probe.getParamTypes();
            for (int index = 0; index < paramTypes.length; index++) {
                Class paramType = paramTypes[index];
                methodDesc += delim + paramType.getName();
                // Dont add the param type for type desc, if self is the first index
                if (!(probe.hasSelf() && (index == 0))) {
                    typeDesc += typeDelim + paramType.getName();
                    typeDelim = ",";
                }
                delim = ", ";
            }
            methodDesc += ")";
            typeDesc += ")";
            //Creating the class method
            Method m = Method.getMethod(methodDesc);
            GeneratorAdapter gen = new GeneratorAdapter(Opcodes.ACC_PUBLIC + Opcodes.ACC_STATIC, m, null, null, cw);
            // Add the @Self annotation
            if (probe.hasSelf()) {
                String[] paramNames = probe.getProbeParamNames();
                for (int index = 0; index < paramNames.length; index++) {
                    if (paramNames[index].equalsIgnoreCase(FlashlightProbe.SELF)) {
                        AnnotationVisitor paramVisitor = gen.visitParameterAnnotation(index, "Lcom/sun/btrace/annotations/Self;", true);
                        paramVisitor.visitEnd();
                    }
                }
            }
            //Add the @OnMethod annotation to this method
            av = gen.visitAnnotation("Lcom/sun/btrace/annotations/OnMethod;", true);
            av.visit("clazz", "" + probe.getProviderClazz().getName());
            av.visit("method", probe.getProviderJavaMethodName());
            av.visit("type", typeDesc);
            av.visitEnd();
            //Add the body
            gen.push(probe.getId());
            gen.loadArgArray();
            gen.invokeStatic(Type.getType(
                    ProbeRegistry.class), Method.getMethod("void invokeProbe(int, Object[])"));
            gen.returnValue();
            gen.endMethod();
            methodCounter++;
        }
        BtraceClientGenerator.generateConstructor(cw);
        cw.visitEnd();
        byte[] classData = cw.toByteArray();
        writeClass(classData, generatedClassName);
        return classData;
    }

    private static void writeClass(byte[] classData, String generatedClassName) {
        // only do this if we are in "debug" mode
        if(Boolean.parseBoolean(System.getenv("AS_DEBUG")) == false)
            return;

        System.out.println("**** Generated BTRACE Client " + generatedClassName);

        try {
            int index = generatedClassName.lastIndexOf('/');
            String rootPath = System.getProperty(SystemPropertyConstants.INSTALL_ROOT_PROPERTY) +
                    File.separator + "lib" + File.separator;

            String fileName = rootPath + generatedClassName.substring(index + 1) + ".class";
            //System.out.println("***ClassFile: " + fileName);
            File file = new File(fileName);

            FileOutputStream fos = new FileOutputStream(file);
            fos.write(classData);
            fos.flush();
            fos.close();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    private static void generateConstructor(ClassWriter cw) {
        Method m = Method.getMethod("void <init> ()");
        GeneratorAdapter gen = new GeneratorAdapter(Opcodes.ACC_PUBLIC, m, null, null, cw);
        gen.loadThis();
        gen.invokeConstructor(Type.getType(Object.class), m);
        //return the value from constructor
        gen.returnValue();
        gen.endMethod();
    }
}


/****  Example generated class (bnevins, August 2009)
 *
 * package com.sun.btrace.flashlight.org.glassfish.web.admin.monitor;

import com.sun.btrace.annotations.BTrace;
import com.sun.btrace.annotations.OnMethod;
import javax.servlet.Servlet;
import org.glassfish.flashlight.provider.ProbeRegistry;

@BTrace
public final class ServletStatsProvider_BTrace_7_
{
  @OnMethod(clazz="org.glassfish.web.admin.monitor.ServletProbeProvider", method="servletInitializedEvent", type="void (javax.servlet.Servlet, java.lang.String, java.lang.String)")
  public static void __servletInitializedEvent__7_0_(Servlet paramServlet, String paramString1, String paramString2)
  {
    ProbeRegistry.invokeProbe(78, new Object[] { paramServlet, paramString1, paramString2 });
  }

  @OnMethod(clazz="org.glassfish.web.admin.monitor.ServletProbeProvider", method="servletDestroyedEvent", type="void (javax.servlet.Servlet, java.lang.String, java.lang.String)")
  public static void __servletDestroyedEvent__7_1_(Servlet paramServlet, String paramString1, String paramString2)
  {
    ProbeRegistry.invokeProbe(79, new Object[] { paramServlet, paramString1, paramString2 });
  }
}
 */