Java example source code file (Trace.java)

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Java - Java tags/keywords

bad, error, eventthread, ioexception, jdi, launchingconnector, make, map, printwriter, streamredirectthread, string, stringbuffer, trace, util, virtualmachine

The Trace.java Java example source code

/*
 * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/*
 * This source code is provided to illustrate the usage of a given feature
 * or technique and has been deliberately simplified. Additional steps
 * required for a production-quality application, such as security checks,
 * input validation and proper error handling, might not be present in
 * this sample code.
 */


package com.sun.tools.example.trace;

import com.sun.jdi.VirtualMachine;
import com.sun.jdi.Bootstrap;
import com.sun.jdi.connect.*;

import java.util.Map;
import java.util.List;

import java.io.PrintWriter;
import java.io.FileWriter;
import java.io.IOException;

/**
 * This program traces the execution of another program.
 * See "java Trace -help".
 * It is a simple example of the use of the Java Debug Interface.
 *
 * @author Robert Field
 */
public class Trace {

    // Running remote VM
    private final VirtualMachine vm;

    // Thread transferring remote error stream to our error stream
    private Thread errThread = null;

    // Thread transferring remote output stream to our output stream
    private Thread outThread = null;

    // Mode for tracing the Trace program (default= 0 off)
    private int debugTraceMode = 0;

    //  Do we want to watch assignments to fields
    private boolean watchFields = false;

    // Class patterns for which we don't want events
    private String[] excludes = {"java.*", "javax.*", "sun.*",
                                 "com.sun.*"};

    /**
     * main
     */
    public static void main(String[] args) {
        new Trace(args);
    }

    /**
     * Parse the command line arguments.
     * Launch target VM.
     * Generate the trace.
     */
    Trace(String[] args) {
        PrintWriter writer = new PrintWriter(System.out);
        int inx;
        for (inx = 0; inx < args.length; ++inx) {
            String arg = args[inx];
            if (arg.charAt(0) != '-') {
                break;
            }
            if (arg.equals("-output")) {
                try {
                    writer = new PrintWriter(new FileWriter(args[++inx]));
                } catch (IOException exc) {
                    System.err.println("Cannot open output file: " + args[inx]
                                       + " - " +  exc);
                    System.exit(1);
                }
            } else if (arg.equals("-all")) {
                excludes = new String[0];
            } else if (arg.equals("-fields")) {
                watchFields = true;
            } else if (arg.equals("-dbgtrace")) {
                debugTraceMode = Integer.parseInt(args[++inx]);
            } else if (arg.equals("-help")) {
                usage();
                System.exit(0);
            } else {
                System.err.println("No option: " + arg);
                usage();
                System.exit(1);
            }
        }
        if (inx >= args.length) {
            System.err.println("<class> missing");
            usage();
            System.exit(1);
        }
        StringBuffer sb = new StringBuffer();
        sb.append(args[inx]);
        for (++inx; inx < args.length; ++inx) {
            sb.append(' ');
            sb.append(args[inx]);
        }
        vm = launchTarget(sb.toString());
        generateTrace(writer);
    }


    /**
     * Generate the trace.
     * Enable events, start thread to display events,
     * start threads to forward remote error and output streams,
     * resume the remote VM, wait for the final event, and shutdown.
     */
    void generateTrace(PrintWriter writer) {
        vm.setDebugTraceMode(debugTraceMode);
        EventThread eventThread = new EventThread(vm, excludes, writer);
        eventThread.setEventRequests(watchFields);
        eventThread.start();
        redirectOutput();
        vm.resume();

        // Shutdown begins when event thread terminates
        try {
            eventThread.join();
            errThread.join(); // Make sure output is forwarded
            outThread.join(); // before we exit
        } catch (InterruptedException exc) {
            // we don't interrupt
        }
        writer.close();
    }

    /**
     * Launch target VM.
     * Forward target's output and error.
     */
    VirtualMachine launchTarget(String mainArgs) {
        LaunchingConnector connector = findLaunchingConnector();
        Map<String, Connector.Argument> arguments =
           connectorArguments(connector, mainArgs);
        try {
            return connector.launch(arguments);
        } catch (IOException exc) {
            throw new Error("Unable to launch target VM: " + exc);
        } catch (IllegalConnectorArgumentsException exc) {
            throw new Error("Internal error: " + exc);
        } catch (VMStartException exc) {
            throw new Error("Target VM failed to initialize: " +
                            exc.getMessage());
        }
    }

    void redirectOutput() {
        Process process = vm.process();

        // Copy target's output and error to our output and error.
        errThread = new StreamRedirectThread("error reader",
                                             process.getErrorStream(),
                                             System.err);
        outThread = new StreamRedirectThread("output reader",
                                             process.getInputStream(),
                                             System.out);
        errThread.start();
        outThread.start();
    }

    /**
     * Find a com.sun.jdi.CommandLineLaunch connector
     */
    LaunchingConnector findLaunchingConnector() {
        List<Connector> connectors = Bootstrap.virtualMachineManager().allConnectors();
        for (Connector connector : connectors) {
            if (connector.name().equals("com.sun.jdi.CommandLineLaunch")) {
                return (LaunchingConnector)connector;
            }
        }
        throw new Error("No launching connector");
    }

    /**
     * Return the launching connector's arguments.
     */
    Map<String, Connector.Argument> connectorArguments(LaunchingConnector connector, String mainArgs) {
        Map<String, Connector.Argument> arguments = connector.defaultArguments();
        Connector.Argument mainArg =
                           (Connector.Argument)arguments.get("main");
        if (mainArg == null) {
            throw new Error("Bad launching connector");
        }
        mainArg.setValue(mainArgs);

        if (watchFields) {
            // We need a VM that supports watchpoints
            Connector.Argument optionArg =
                (Connector.Argument)arguments.get("options");
            if (optionArg == null) {
                throw new Error("Bad launching connector");
            }
            optionArg.setValue("-classic");
        }
        return arguments;
    }

    /**
     * Print command line usage help
     */
    void usage() {
        System.err.println("Usage: java Trace <options>  ");
        System.err.println("<options> are:");
        System.err.println(
"  -output <filename>   Output trace to ");
        System.err.println(
"  -all                 Include system classes in output");
        System.err.println(
"  -help                Print this help message");
        System.err.println("<class> is the program to trace");
        System.err.println("<args> are the arguments to ");
    }
}