对于我的论文研究，我需要在测试套件中为可定义的方法注入一段代码，其中我没有源代码（在本例中为DaCapo基准测试套件，http://dacapobench.org/）。以前的研究，我的论文的这一部分所基于的，使用字节码注入，这也导致我也这样做。
我使用Apache的BCEL库（http://commons.apache.org/proper/commons-bcel/）来构建一个小程序，这使我能够在其他语句之前将fibonacci算法注入方法体中。
现在，我已经做到了，但它无法正常工作。我注入的一些方法工作正常（因为它们因斐波那契代码而变慢），并且运行DaCapo框架效果很好，而其他注入方法则破坏了代码。
问题是，我不知道为什么，即使我知道哪些方法崩溃了，哪些方法成功了，我也无法在破碎的方法中找到重复出现的模式。
我可以粘贴一些失败的方法，但这会使这篇文章比现在更长。 所以我在想，是否有一些我没有想到或正在忽视的事情？
下面你会找到一个示例java文件，它的结果和我写的BCEL程序。
一个简单的例子，我有一个名为DemoClass.java的java文件：
public class DemoClass {
public static void main(String[] argv) {
System.out.println("Demo body");
test();
}
public static void test() {
System.out.println("Demo test");
}
}
在我的shell中调用以下java命令后：
javac DemoClass.java; java -cp bcel-5.2.jar:. InjectCodeBCEL DemoClass test 123456789 ; java DemoClass
（bcel-5.2.jar文件可以在前面提到的apache网站上找到）
程序将如下所示：
public class DemoClass {
public static void main(String[] argv) {
System.out.println("Demo body");
test();
}
public static void test() {
int[] fibNumbers = new int[100];
for (int i = 0; i < 123456789; i++) {
int j = i % 100;
if (i == 0) {
fibNumbers[i] = 0;
}
else if (i == 1) {
fibNumbers[i] = 1;
}
else {
int k = (i - 1) % 100;
int m = (i - 2) % 100;
int n = fibNumbers[k] + fibNumbers[m];
fibNumbers[j] = n;
}
}
System.out.println("Demo test");
}
}
这是InjectCodeBCEL.java的代码：
import java.io.IOException;
import org.apache.bcel.classfile.*;
import org.apache.bcel.generic.*;
import org.apache.bcel.*;
public class InjectCodeBCEL {
static public void main(String args[]) {
//Get class to modify from program argument
JavaClass mod = null;
String methodName = (args.length >= 2) ? args[1] : "";
int loopsize = (args.length >= 3) ? Integer.parseInt(args[2]) : 1;
try {
mod = Repository.lookupClass(args[0]);
}
catch (Exception e) {
System.err.println("Could not get class " + args[0]);
return;
}
//Create a generic class to modify
ClassGen modClass = new ClassGen(mod);
//Create a generic constantpool to modify
ConstantPoolGen cp = modClass.getConstantPool();
boolean methodEdited = false;
Method[] methods = mod.getMethods();
for (int i = 0; i < methods.length; i++) {
if (methods[i].getName().equals(methodName)) {
System.out.println("Method: " + methods[i]);
// System.out.println("before:\n" + methods[i].getCode());
modClass.removeMethod(methods[i]);
Method newMethod = insertCodeInMethod(mod, methods[i], cp, loopsize);
// System.out.println("after:\n" + newMethod.getCode());
modClass.addMethod(newMethod);
methodEdited = true;
}
}
if (methodEdited) {
modClass.update();
try {
//Write modified class
JavaClass newClass = modClass.getJavaClass();
String classname = args[0].replace(".","/");
newClass.dump(classname + ".class");
System.out.println("Class " + classname + " modified");
}
catch (IOException e) {
e.printStackTrace();
}
}
}
public static Method insertCodeInMethod(JavaClass mod, Method method, ConstantPoolGen cp, int loopsize) {
MethodGen mg = new MethodGen(method, mod.getClassName(), cp);
InstructionList il = mg.getInstructionList();
InstructionHandle ihs = il.getStart();
InstructionList ils = new InstructionList();
InstructionFactory f = new InstructionFactory(cp);
String CLASS_NAME = mod.getClassName();
int ARRAY_SIZE = 100;
int LOOP_SIZE = loopsize;
int INCREASE_ID = mg.isStatic() ? 0 : 1; // if not static, this has position 0 on the stack
Type[] types = mg.getArgumentTypes();
// Increase the stack location(?) so they don't collide with the methods parameters.
for (int i = 0; i < types.length; i++) {
INCREASE_ID += types[i].getSize();
}
int VAR_ARRAY = 0 + INCREASE_ID;
int VAR_I = 1 + INCREASE_ID;
int VAR_II = 2 + INCREASE_ID;
int VAR_I_MIN_1 = 3 + INCREASE_ID;
int VAR_I_MIN_2 = 4 + INCREASE_ID;
int VAR_SUM = 5 + INCREASE_ID;
int VAR_JUMPTO = 6 + INCREASE_ID;
// init array
ils.append(new PUSH(cp, ARRAY_SIZE));
ils.append(new NEWARRAY(Type.INT));
ils.append(new ASTORE(VAR_ARRAY));
// create iterator = 0 for while
ils.append(new PUSH(cp, 0));
ils.append(new ISTORE(VAR_I));
// Main while loop:
InstructionHandle beforeWhile = ils.append(new ILOAD(VAR_I));
ils.append(new PUSH(cp, LOOP_SIZE));
// While condition:
BranchHandle whileCondition = ils.append(new IF_ICMPLT(null)); // if (VAR_I < LOOP_SIZE): jump to "whileBody"
BranchHandle whileConditionFalseGoto = ils.append(new GOTO(null)); // if not: jump to "afterWhile"
// While body:
InstructionHandle whileBody = ils.append(new ILOAD(VAR_I));
ils.append(new PUSH(cp, ARRAY_SIZE));
ils.append(new IREM());
ils.append(new ISTORE(VAR_II)); // create int ii = i % ARRAY_SIZE;
// if (i == 0)
ils.append(new ILOAD(VAR_I));
ils.append(new PUSH(cp, 0));
BranchHandle ifIteratorIs0 = ils.append(new IF_ICMPEQ(null));
BranchHandle ifIteratorIs0FalseGoto = ils.append(new GOTO(null));
// If true body
InstructionHandle ifIteratorIs0Body = ils.append(new ALOAD(VAR_ARRAY));
ils.append(new ILOAD(VAR_I));
ils.append(new PUSH(cp, 0));
ils.append(new IASTORE());
BranchHandle ifIteratorIs0Done = ils.append(new GOTO(null));
// "else" if (i != 1)
InstructionHandle beginIfIteratorIsNot1 = ils.append(new ILOAD(VAR_I));
ils.append(new PUSH(cp, 1));
BranchHandle ifIteratorIsNot1 = ils.append(new IF_ICMPNE(null));
// false: else: so in this case: if (!(i != 1)):
ils.append(new ALOAD(VAR_ARRAY));
ils.append(new ILOAD(VAR_I));
ils.append(new PUSH(cp, 1));
ils.append(new IASTORE());
// done, go to i++;
BranchHandle ifIteratorIsNot1FalseGoto = ils.append(new GOTO(null));
// If true body (so if i != 1)..
// create variable VAR_I_MIN_1 for array index (i-1)
InstructionHandle ifIteratorIsNot1Body = ils.append(new ILOAD(VAR_I));
ils.append(new PUSH(cp, 1));
ils.append(new ISUB());
ils.append(new PUSH(cp, ARRAY_SIZE));
ils.append(new IREM());
ils.append(new ISTORE(VAR_I_MIN_1)); // create int i_min_1 = (i - 1) % ARRAY_SIZE;
// create variable VAR_I_MIN_2 for array index (i-2)
ils.append(new ILOAD(VAR_I));
ils.append(new PUSH(cp, 2));
ils.append(new ISUB());
ils.append(new PUSH(cp, ARRAY_SIZE));
ils.append(new IREM());
ils.append(new ISTORE(VAR_I_MIN_2)); // create int i_min_2 = (i - 2) % ARRAY_SIZE;
// load the array values:
ils.append(new ALOAD(VAR_ARRAY));
ils.append(new ILOAD(VAR_I_MIN_1));
ils.append(new IALOAD());
ils.append(new ALOAD(VAR_ARRAY));
ils.append(new ILOAD(VAR_I_MIN_2));
ils.append(new IALOAD());
// add the two values, and save them
ils.append(new IADD());
ils.append(new ISTORE(VAR_SUM));
// add the new calculated number to the array
ils.append(new ALOAD(VAR_ARRAY));
ils.append(new ILOAD(VAR_II));
ils.append(new ILOAD(VAR_SUM));
ils.append(new IASTORE());
// Done; go to i++;
BranchHandle ifIteratorIsNot1Done = ils.append(new GOTO(null));
// Increment i with 1
InstructionHandle generalIfDoneGoto = ils.append(new IINC(VAR_I,1));
// Goto that whil restart this loop:
BranchHandle whileGotoBegin = ils.append(new GOTO(null)); // jumps to "beforeWhile"
// We need something to jump to when done with the outer loop.
InstructionHandle afterWhile = ils.append(new PUSH(cp, 0));
ils.append(new ISTORE(VAR_JUMPTO));
// While targets:
whileCondition.setTarget(whileBody);
whileConditionFalseGoto.setTarget(afterWhile);
whileGotoBegin.setTarget(beforeWhile);
// if (i == 0)
ifIteratorIs0.setTarget(ifIteratorIs0Body);
ifIteratorIs0FalseGoto.setTarget(beginIfIteratorIsNot1);
ifIteratorIs0Done.setTarget(generalIfDoneGoto);
// if (i == 1)
ifIteratorIsNot1.setTarget(ifIteratorIsNot1Body);
ifIteratorIsNot1FalseGoto.setTarget(generalIfDoneGoto);
ifIteratorIsNot1Done.setTarget(generalIfDoneGoto);
InstructionHandle ihss = il.insert(ihs,ils);
il.redirectBranches(ihs, ihss);
il.update();
mg.setMaxStack();
mg.setMaxLocals();
mg.update();
return mg.getMethod();
}
}
更新
下面你可以看到net.sourceforge.pmd.AbstractRuleChainVisitor中注入了visitAll方法失败后的完整错误
===== DaCapo 9.12 pmd starting =====
java.lang.reflect.InvocationTargetException
java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.dacapo.harness.Pmd.iterate(Pmd.java:58)
at org.dacapo.harness.Benchmark.run(Benchmark.java:166)
at org.dacapo.harness.TestHarness.runBenchmark(TestHarness.java:218)
at org.dacapo.harness.TestHarness.main(TestHarness.java:171)
at Harness.main(Harness.java:17)
Caused by: java.lang.ClassFormatError: LVTT entry for 'nodes' in class file net/sourceforge/pmd/AbstractRuleChainVisitor does not match any LVT entry
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at org.dacapo.harness.DacapoClassLoader.loadClass(DacapoClassLoader.java:124)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at org.dacapo.harness.DacapoClassLoader.loadClass(DacapoClassLoader.java:124)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
at net.sourceforge.pmd.RuleSets.<init>(RuleSets.java:27)
at net.sourceforge.pmd.RuleSetFactory.createRuleSets(RuleSetFactory.java:82)
at net.sourceforge.pmd.RuleSetFactory.createRuleSets(RuleSetFactory.java:70)
at net.sourceforge.pmd.PMD.doPMD(PMD.java:359)
at net.sourceforge.pmd.PMD.main(PMD.java:415)
... 9 more
此方法的代码（由JD-GUI生成）：
public void visitAll(List<CompilationUnit> astCompilationUnits, RuleContext ctx)
{
initialize();
clear();
long start = System.nanoTime();
indexNodes(astCompilationUnits, ctx);
long end = System.nanoTime();
Benchmark.mark(8, end - start, 1L);
for (RuleSet ruleSet : this.ruleSetRules.keySet())
if (ruleSet.applies(ctx.getSourceCodeFile()))
{
visits = 0;
start = System.nanoTime();
for (Rule rule : (List)this.ruleSetRules.get(ruleSet)) {
List nodeNames = rule.getRuleChainVisits();
for (int j = 0; j < nodeNames.size(); j++) {
List nodes = (List)this.nodeNameToNodes.get(nodeNames.get(j));
for (SimpleNode node : nodes)
{
while ((rule instanceof RuleReference)) {
rule = ((RuleReference)rule).getRule();
}
visit(rule, node, ctx);
}
visits += nodes.size();
}
end = System.nanoTime();
Benchmark.mark(1, rule.getName(), end - start, visits);
start = end;
}
}
int visits;
}
当我的代码错过了'insertCodeInMethod'中的堆栈位置增加部分时，这是一个类似的错误。这导致了参数，当不是静态时，它与斐波那契代码中定义的变量发生碰撞。
答案 0 :(得分：3)
LVTT代表LocalVariableTypeTable，LVT代表LocalVariableTable。这些是在更改方法时必须调整或删除的调试信息。
顺便说一句，这不是成功将大量代码注入方法的好方法，因为它会产生各种错误来源，意味着重新发明轮子（构建编译器）并导致转换中的代码重复类。大多数使用代码注入/类文件转换的应用程序只会注入预编译方法的小型调用。