RuntimeExceptionDeclared.java

/*
 * fb-contrib - Auxiliary detectors for Java programs
 * Copyright (C) 2005-2017 Dave Brosius
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package com.mebigfatguy.fbcontrib.detect;

import java.util.HashSet;
import java.util.Set;

import org.apache.bcel.Repository;
import org.apache.bcel.classfile.ExceptionTable;
import org.apache.bcel.classfile.JavaClass;
import org.apache.bcel.classfile.Method;

import com.mebigfatguy.fbcontrib.utils.BugType;
import com.mebigfatguy.fbcontrib.utils.Values;

import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.Detector;
import edu.umd.cs.findbugs.StringAnnotation;
import edu.umd.cs.findbugs.ba.ClassContext;
import edu.umd.cs.findbugs.visitclass.PreorderVisitor;

/**
 * looks for methods that declare Runtime exceptions in their throws clause. While doing so is not illegal, it may represent a misunderstanding as to the
 * exception in question. If a RuntimeException is declared, it implies that this exception type is expected to happen, which if true, should be handled in
 * code, and not propagated.
 */
public class RuntimeExceptionDeclared extends PreorderVisitor implements Detector {
    private static JavaClass runtimeExceptionClass;

    static {
        try {
            runtimeExceptionClass = Repository.lookupClass(Values.SLASHED_JAVA_LANG_RUNTIMEEXCEPTION);
        } catch (ClassNotFoundException cnfe) {
            runtimeExceptionClass = null;
        }
    }

    private final BugReporter bugReporter;
    private final Set<String> runtimeExceptions = new HashSet<>();

    /**
     * constructs a DRE detector given the reporter to report bugs on
     *
     * @param bugReporter
     *            the sync of bug reports
     */
    public RuntimeExceptionDeclared(final BugReporter bugReporter) {
        this.bugReporter = bugReporter;
        runtimeExceptions.add(Values.DOTTED_JAVA_LANG_RUNTIMEEXCEPTION);
    }

    /**
     * overrides the visitor and accepts if the Exception class was loaded
     *
     * @param classContext
     *            the context object for the currently parsed class
     */
    @Override
    public void visitClassContext(final ClassContext classContext) {
        if (runtimeExceptionClass != null) {
            classContext.getJavaClass().accept(this);
        }
    }

    /**
     * overrides the visitor to find declared runtime exceptions
     *
     * @param obj
     *            the method object of the currently parsed method
     */
    @Override
    public void visitMethod(final Method obj) {
        if (obj.isSynthetic()) {
            return;
        }
        ExceptionTable et = obj.getExceptionTable();
        if (et != null) {
            String[] exNames = et.getExceptionNames();
            Set<String> methodRTExceptions = new HashSet<>(6);
            int priority = LOW_PRIORITY;
            boolean foundRuntime = false;
            for (String ex : exNames) {
                boolean isRuntime = false;
                if (runtimeExceptions.contains(ex)) {
                    isRuntime = true;
                } else {
                    try {
                        JavaClass exClass = Repository.lookupClass(ex);
                        if (exClass.instanceOf(runtimeExceptionClass)) {
                            runtimeExceptions.add(ex);
                            if (ex.startsWith("java.lang.")) {
                                priority = NORMAL_PRIORITY;
                            }
                            isRuntime = true;
                        }
                    } catch (ClassNotFoundException cnfe) {
                        bugReporter.reportMissingClass(cnfe);
                    }
                }
                if (isRuntime) {
                    foundRuntime = true;
                    methodRTExceptions.add(ex);
                }
            }

            if (foundRuntime) {
                BugInstance bug = new BugInstance(this, BugType.DRE_DECLARED_RUNTIME_EXCEPTION.name(), priority).addClass(this).addMethod(this);

                for (String ex : methodRTExceptions) {
                    bug.add(new StringAnnotation(ex));
                }

                bugReporter.reportBug(bug);
            }
        }
    }

    /**
     * implementation of the detector, with null implementation
     */
    @Override
    public void report() {
        // not used, needed for the Detector interface
    }

}