/*
* FindBugs - Find Bugs in Java programs
* Copyright (C) 2003-2007 University of Maryland
*
* 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 edu.umd.cs.findbugs.detect;
import org.apache.bcel.classfile.Code;
import edu.umd.cs.findbugs.BugAccumulator;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.ba.AnalysisContext;
import edu.umd.cs.findbugs.ba.INullnessAnnotationDatabase;
import edu.umd.cs.findbugs.ba.NullnessAnnotation;
import edu.umd.cs.findbugs.ba.SignatureParser;
import edu.umd.cs.findbugs.ba.XMethod;
import edu.umd.cs.findbugs.bcel.OpcodeStackDetector;
/**
* Base class for simple type checking detectors which tests if the method
* returns null references for specific types.
*
* @author alison
* @author Andrey Loskutov
*/
public abstract class TypeReturnNull extends OpcodeStackDetector {
BugAccumulator bugAccumulator;
public TypeReturnNull(BugReporter bugReporter) {
this.bugAccumulator = new BugAccumulator(bugReporter);
}
@Override
public void visit(Code code) {
SignatureParser sp = new SignatureParser(getMethodSig());
// Check to see if the method has expected return type
String returnSignature = sp.getReturnTypeSignature();
if (!matchesReturnSignature(returnSignature)){
return;
}
if (isExplicitlyNullable()){
return;
}
super.visit(code); // make callbacks to sawOpcode for all opcodes
bugAccumulator.reportAccumulatedBugs();
}
private boolean isExplicitlyNullable() {
AnalysisContext analysisContext = AnalysisContext.currentAnalysisContext();
INullnessAnnotationDatabase nullnessAnnotationDatabase = analysisContext.getNullnessAnnotationDatabase();
XMethod xMethod = getXMethod();
NullnessAnnotation na = nullnessAnnotationDatabase.getResolvedAnnotation(xMethod, true);
return na != null && na != NullnessAnnotation.NONNULL;
}
@Override
public void sawOpcode(int seen) {
if (seen == ARETURN && getPrevOpcode(1) == ACONST_NULL){
accumulateBug();
}
}
/**
* @return true if the given return signature matches expected type
*/
protected abstract boolean matchesReturnSignature(String returnSignature);
/**
* creates individual bug instance on match
*/
protected abstract void accumulateBug();
}