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Java example source code file (BreakpointSpec.java)

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

Learn more about this Java project at its project page.

Java - Java tags/keywords

absentinformationexception, ambiguousmethodexception, breakpointspec, eventrequest, invalidtypeexception, jdi, linenotfoundexception, list, location, method, nosuchmethodexception, object, override, string, stringbuffer, util

The BreakpointSpec.java Java example source code

/*
 * Copyright (c) 1998, 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.debug.tty;

import com.sun.jdi.*;
import com.sun.jdi.request.*;

import java.util.ArrayList;
import java.util.List;

class BreakpointSpec extends EventRequestSpec {
    String methodId;
    List<String> methodArgs;
    int lineNumber;

    BreakpointSpec(ReferenceTypeSpec refSpec, int lineNumber) {
        super(refSpec);
        this.methodId = null;
        this.methodArgs = null;
        this.lineNumber = lineNumber;
    }

    BreakpointSpec(ReferenceTypeSpec refSpec, String methodId,
                   List<String> methodArgs) throws MalformedMemberNameException {
        super(refSpec);
        this.methodId = methodId;
        this.methodArgs = methodArgs;
        this.lineNumber = 0;
        if (!isValidMethodName(methodId)) {
            throw new MalformedMemberNameException(methodId);
        }
    }

    /**
     * The 'refType' is known to match, return the EventRequest.
     */
    @Override
    EventRequest resolveEventRequest(ReferenceType refType)
                           throws AmbiguousMethodException,
                                  AbsentInformationException,
                                  InvalidTypeException,
                                  NoSuchMethodException,
                                  LineNotFoundException {
        Location location = location(refType);
        if (location == null) {
            throw new InvalidTypeException();
        }
        EventRequestManager em = refType.virtualMachine().eventRequestManager();
        EventRequest bp = em.createBreakpointRequest(location);
        bp.setSuspendPolicy(suspendPolicy);
        bp.enable();
        return bp;
    }

    String methodName() {
        return methodId;
    }

    int lineNumber() {
        return lineNumber;
    }

    List<String> methodArgs() {
        return methodArgs;
    }

    boolean isMethodBreakpoint() {
        return (methodId != null);
    }

    @Override
    public int hashCode() {
        return refSpec.hashCode() + lineNumber +
            ((methodId != null) ? methodId.hashCode() : 0) +
            ((methodArgs != null) ? methodArgs.hashCode() : 0);
    }

    @Override
    public boolean equals(Object obj) {
        if (obj instanceof BreakpointSpec) {
            BreakpointSpec breakpoint = (BreakpointSpec)obj;

            return ((methodId != null) ?
                        methodId.equals(breakpoint.methodId)
                      : methodId == breakpoint.methodId) &&
                   ((methodArgs != null) ?
                        methodArgs.equals(breakpoint.methodArgs)
                      : methodArgs == breakpoint.methodArgs) &&
                   refSpec.equals(breakpoint.refSpec) &&
                   (lineNumber == breakpoint.lineNumber);
        } else {
            return false;
        }
    }

    @Override
    String errorMessageFor(Exception e) {
        if (e instanceof AmbiguousMethodException) {
            return (MessageOutput.format("Method is overloaded; specify arguments",
                                         methodName()));
            /*
             * TO DO: list the methods here
             */
        } else if (e instanceof NoSuchMethodException) {
            return (MessageOutput.format("No method in",
                                         new Object [] {methodName(),
                                                        refSpec.toString()}));
        } else if (e instanceof AbsentInformationException) {
            return (MessageOutput.format("No linenumber information for",
                                         refSpec.toString()));
        } else if (e instanceof LineNotFoundException) {
            return (MessageOutput.format("No code at line",
                                         new Object [] {new Long (lineNumber()),
                                                        refSpec.toString()}));
        } else if (e instanceof InvalidTypeException) {
            return (MessageOutput.format("Breakpoints can be located only in classes.",
                                         refSpec.toString()));
        } else {
            return super.errorMessageFor( e);
        }
    }

    @Override
    public String toString() {
        StringBuffer buffer = new StringBuffer(refSpec.toString());
        if (isMethodBreakpoint()) {
            buffer.append('.');
            buffer.append(methodId);
            if (methodArgs != null) {
                boolean first = true;
                buffer.append('(');
                for (String arg : methodArgs) {
                    if (!first) {
                        buffer.append(',');
                    }
                    buffer.append(arg);
                    first = false;
                }
                buffer.append(")");
            }
        } else {
            buffer.append(':');
            buffer.append(lineNumber);
        }
        return MessageOutput.format("breakpoint", buffer.toString());
    }

    private Location location(ReferenceType refType) throws
                                    AmbiguousMethodException,
                                    AbsentInformationException,
                                    NoSuchMethodException,
                                    LineNotFoundException {
        Location location = null;
        if (isMethodBreakpoint()) {
            Method method = findMatchingMethod(refType);
            location = method.location();
        } else {
            // let AbsentInformationException be thrown
            List<Location> locs = refType.locationsOfLine(lineNumber());
            if (locs.size() == 0) {
                throw new LineNotFoundException();
            }
            // TO DO: handle multiple locations
            location = locs.get(0);
            if (location.method() == null) {
                throw new LineNotFoundException();
            }
        }
        return location;
    }

    private boolean isValidMethodName(String s) {
        return isJavaIdentifier(s) ||
               s.equals("<init>") ||
               s.equals("<clinit>");
    }

    /*
     * Compare a method's argument types with a Vector of type names.
     * Return true if each argument type has a name identical to the
     * corresponding string in the vector (allowing for varars)
     * and if the number of arguments in the method matches the
     * number of names passed
     */
    private boolean compareArgTypes(Method method, List<String> nameList) {
        List<String> argTypeNames = method.argumentTypeNames();

        // If argument counts differ, we can stop here
        if (argTypeNames.size() != nameList.size()) {
            return false;
        }

        // Compare each argument type's name
        int nTypes = argTypeNames.size();
        for (int i = 0; i < nTypes; ++i) {
            String comp1 = argTypeNames.get(i);
            String comp2 = nameList.get(i);
            if (! comp1.equals(comp2)) {
                /*
                 * We have to handle varargs.  EG, the
                 * method's last arg type is xxx[]
                 * while the nameList contains xxx...
                 * Note that the nameList can also contain
                 * xxx[] in which case we don't get here.
                 */
                if (i != nTypes - 1 ||
                    !method.isVarArgs()  ||
                    !comp2.endsWith("...")) {
                    return false;
                }
                /*
                 * The last types differ, it is a varargs
                 * method and the nameList item is varargs.
                 * We just have to compare the type names, eg,
                 * make sure we don't have xxx[] for the method
                 * arg type and yyy... for the nameList item.
                 */
                int comp1Length = comp1.length();
                if (comp1Length + 1 != comp2.length()) {
                    // The type names are different lengths
                    return false;
                }
                // We know the two type names are the same length
                if (!comp1.regionMatches(0, comp2, 0, comp1Length - 2)) {
                    return false;
                }
                // We do have xxx[] and xxx... as the last param type
                return true;
            }
        }

        return true;
    }


    /*
     * Remove unneeded spaces and expand class names to fully
     * qualified names, if necessary and possible.
     */
    private String normalizeArgTypeName(String name) {
        /*
         * Separate the type name from any array modifiers,
         * stripping whitespace after the name ends
         */
        int i = 0;
        StringBuffer typePart = new StringBuffer();
        StringBuffer arrayPart = new StringBuffer();
        name = name.trim();
        int nameLength = name.length();
        /*
         * For varargs, there can be spaces before the ... but not
         * within the ...  So, we will just ignore the ...
         * while stripping blanks.
         */
        boolean isVarArgs = name.endsWith("...");
        if (isVarArgs) {
            nameLength -= 3;
        }
        while (i < nameLength) {
            char c = name.charAt(i);
            if (Character.isWhitespace(c) || c == '[') {
                break;      // name is complete
            }
            typePart.append(c);
            i++;
        }
        while (i < nameLength) {
            char c = name.charAt(i);
            if ( (c == '[') || (c == ']')) {
                arrayPart.append(c);
            } else if (!Character.isWhitespace(c)) {
                throw new IllegalArgumentException
                    (MessageOutput.format("Invalid argument type name"));
            }
            i++;
        }
        name = typePart.toString();

        /*
         * When there's no sign of a package name already, try to expand the
         * the name to a fully qualified class name
         */
        if ((name.indexOf('.') == -1) || name.startsWith("*.")) {
            try {
                ReferenceType argClass = Env.getReferenceTypeFromToken(name);
                if (argClass != null) {
                    name = argClass.name();
                }
            } catch (IllegalArgumentException e) {
                // We'll try the name as is
            }
        }
        name += arrayPart.toString();
        if (isVarArgs) {
            name += "...";
        }
        return name;
    }

    /*
     * Attempt an unambiguous match of the method name and
     * argument specification to a method. If no arguments
     * are specified, the method must not be overloaded.
     * Otherwise, the argument types much match exactly
     */
    private Method findMatchingMethod(ReferenceType refType)
                                        throws AmbiguousMethodException,
                                               NoSuchMethodException {

        // Normalize the argument string once before looping below.
        List<String> argTypeNames = null;
        if (methodArgs() != null) {
            argTypeNames = new ArrayList<String>(methodArgs().size());
            for (String name : methodArgs()) {
                name = normalizeArgTypeName(name);
                argTypeNames.add(name);
            }
        }

        // Check each method in the class for matches
        Method firstMatch = null;  // first method with matching name
        Method exactMatch = null;  // (only) method with same name & sig
        int matchCount = 0;        // > 1 implies overload
        for (Method candidate : refType.methods()) {
            if (candidate.name().equals(methodName())) {
                matchCount++;

                // Remember the first match in case it is the only one
                if (matchCount == 1) {
                    firstMatch = candidate;
                }

                // If argument types were specified, check against candidate
                if ((argTypeNames != null)
                        && compareArgTypes(candidate, argTypeNames) == true) {
                    exactMatch = candidate;
                    break;
                }
            }
        }

        // Determine method for breakpoint
        Method method = null;
        if (exactMatch != null) {
            // Name and signature match
            method = exactMatch;
        } else if ((argTypeNames == null) && (matchCount > 0)) {
            // At least one name matched and no arg types were specified
            if (matchCount == 1) {
                method = firstMatch;       // Only one match; safe to use it
            } else {
                throw new AmbiguousMethodException();
            }
        } else {
            throw new NoSuchMethodException(methodName());
        }
        return method;
    }
}

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