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An auxiliary findbugs.sourceforge.net plugin for java bug detectors that fall outside the narrow scope of detectors to be packaged with the product itself.

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/*
 * fb-contrib - Auxiliary detectors for Java programs
 * Copyright (C) 2005-2018 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 org.apache.bcel.Repository;
import org.apache.bcel.classfile.Field;
import org.apache.bcel.classfile.JavaClass;

import com.mebigfatguy.fbcontrib.utils.BugType;

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

/**
 * looks for fields in serializable classes that are defined as both final and transient. As a transient field is not initialized when streamed, and is not
 * initialized in a constructor, it will remain null because it is defined final.
 */
public class NonFunctionalField extends PreorderVisitor implements Detector {

    private BugReporter bugReporter;
    private JavaClass serializableClass;

    /**
     * constructs a NFF detector given the reporter to report bugs on
     *
     * @param bugReporter
     *            the sync of bug reports
     */
    public NonFunctionalField(BugReporter bugReporter) {
        this.bugReporter = bugReporter;

        try {
            serializableClass = Repository.lookupClass("java/io/Serializable");
        } catch (ClassNotFoundException cnfe) {
            bugReporter.reportMissingClass(cnfe);
        }
    }

    /**
     * checks to see if the class is Serializable, then looks for fields that are both final and transient
     *
     * @param classContext
     *            the context object of the currently parsed class
     */
    @Override
    public void visitClassContext(ClassContext classContext) {
        try {
            JavaClass cls = classContext.getJavaClass();
            if ((serializableClass != null) && (cls.implementationOf(serializableClass))) {
                Field[] fields = cls.getFields();
                setupVisitorForClass(cls);
                for (Field f : fields) {
                    if (!f.isStatic() && f.isFinal() && f.isTransient()) {
                        bugReporter.reportBug(new BugInstance(this, BugType.NFF_NON_FUNCTIONAL_FIELD.name(), Priorities.NORMAL_PRIORITY).addClass(this)
                                .addField(cls.getClassName(), f.getName(), f.getSignature(), f.getAccessFlags()));
                    }
                }
            }
        } catch (ClassNotFoundException cnfe) {
            bugReporter.reportMissingClass(cnfe);
        }
    }

    /**
     * implements the visitor, but does nothing
     */
    @Override
    public void report() {
        // intentionally blank
    }
}