javassist.CodeConverter Maven / Gradle / Ivy
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/*
* Javassist, a Java-bytecode translator toolkit.
* Copyright (C) 1999- Shigeru Chiba. All Rights Reserved.
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. Alternatively, the contents of this file may be used under
* the terms of the GNU Lesser General Public License Version 2.1 or later,
* or the Apache License Version 2.0.
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*/
package javassist;
import javassist.bytecode.*;
import javassist.convert.*;
/**
* Simple translator of method bodies
* (also see the javassist.expr package).
*
* Instances of this class specifies how to instrument of the
* bytecodes representing a method body. They are passed to
* CtClass.instrument() or
* CtMethod.instrument() as a parameter.
*
*
Example:
*
* ClassPool cp = ClassPool.getDefault();
* CtClass point = cp.get("Point");
* CtClass singleton = cp.get("Singleton");
* CtClass client = cp.get("Client");
* CodeConverter conv = new CodeConverter();
* conv.replaceNew(point, singleton, "makePoint");
* client.instrument(conv);
*
*
* This program substitutes "Singleton.makePoint()"
* for all occurrences of "new Point()"
* appearing in methods declared in a Client class.
*
* @see javassist.CtClass#instrument(CodeConverter)
* @see javassist.CtMethod#instrument(CodeConverter)
* @see javassist.expr.ExprEditor
*/
public class CodeConverter {
protected Transformer transformers = null;
/**
* Modify a method body so that instantiation of the specified class
* is replaced with a call to the specified static method. For example,
* replaceNew(ctPoint, ctSingleton, "createPoint")
* (where ctPoint and ctSingleton are
* compile-time classes for class Point and class
* Singleton, respectively)
* replaces all occurrences of:
*
*
new Point(x, y)
*
* in the method body with:
*
* Singleton.createPoint(x, y)
*
* This enables to intercept instantiation of Point
* and change the samentics. For example, the following
* createPoint() implements the singleton pattern:
*
*
public static Point createPoint(int x, int y) {
* if (aPoint == null)
* aPoint = new Point(x, y);
* return aPoint;
* }
*
*
* The static method call substituted for the original new
* expression must be
* able to receive the same set of parameters as the original
* constructor. If there are multiple constructors with different
* parameter types, then there must be multiple static methods
* with the same name but different parameter types.
*
*
The return type of the substituted static method must be
* the exactly same as the type of the instantiated class specified by
* newClass.
*
* @param newClass the instantiated class.
* @param calledClass the class in which the static method is
* declared.
* @param calledMethod the name of the static method.
*/
public void replaceNew(CtClass newClass,
CtClass calledClass, String calledMethod) {
transformers = new TransformNew(transformers, newClass.getName(),
calledClass.getName(), calledMethod);
}
/**
* Modify a method body so that instantiation of the class
* specified by oldClass
* is replaced with instantiation of another class newClass.
* For example,
* replaceNew(ctPoint, ctPoint2)
* (where ctPoint and ctPoint2 are
* compile-time classes for class Point and class
* Point2, respectively)
* replaces all occurrences of:
*
*
new Point(x, y)
*
* in the method body with:
*
* new Point2(x, y)
*
* Note that Point2 must be type-compatible with Point.
* It must have the same set of methods, fields, and constructors as the
* replaced class.
*/
public void replaceNew(CtClass oldClass, CtClass newClass) {
transformers = new TransformNewClass(transformers, oldClass.getName(),
newClass.getName());
}
/**
* Modify a method body so that field read/write expressions access
* a different field from the original one.
*
*
Note that this method changes only the filed name and the class
* declaring the field; the type of the target object does not change.
* Therefore, the substituted field must be declared in the same class
* or a superclass of the original class.
*
*
Also, clazz and newClass must specify
* the class directly declaring the field. They must not specify
* a subclass of that class.
*
* @param field the originally accessed field.
* @param newClass the class declaring the substituted field.
* @param newFieldname the name of the substituted field.
*/
public void redirectFieldAccess(CtField field,
CtClass newClass, String newFieldname) {
transformers = new TransformFieldAccess(transformers, field,
newClass.getName(),
newFieldname);
}
/**
* Modify a method body so that an expression reading the specified
* field is replaced with a call to the specified static method.
* This static method receives the target object of the original
* read expression as a parameter. It must return a value of
* the same type as the field.
*
*
For example, the program below
*
*
Point p = new Point();
* int newX = p.x + 3;
*
* can be translated into:
*
*
Point p = new Point();
* int newX = Accessor.readX(p) + 3;
*
* where
*
*
public class Accessor {
* public static int readX(Object target) { ... }
* }
*
* The type of the parameter of readX() must
* be java.lang.Object independently of the actual
* type of target. The return type must be the same
* as the field type.
*
* @param field the field.
* @param calledClass the class in which the static method is
* declared.
* @param calledMethod the name of the static method.
*/
public void replaceFieldRead(CtField field,
CtClass calledClass, String calledMethod) {
transformers = new TransformReadField(transformers, field,
calledClass.getName(),
calledMethod);
}
/**
* Modify a method body so that an expression writing the specified
* field is replaced with a call to the specified static method.
* This static method receives two parameters: the target object of
* the original
* write expression and the assigned value. The return type of the
* static method is void.
*
*
For example, the program below
*
*
Point p = new Point();
* p.x = 3;
*
* can be translated into:
*
*
Point p = new Point();
* Accessor.writeX(3);
*
* where
*
*
public class Accessor {
* public static void writeX(Object target, int value) { ... }
* }
*
* The type of the first parameter of writeX() must
* be java.lang.Object independently of the actual
* type of target. The type of the second parameter
* is the same as the field type.
*
* @param field the field.
* @param calledClass the class in which the static method is
* declared.
* @param calledMethod the name of the static method.
*/
public void replaceFieldWrite(CtField field,
CtClass calledClass, String calledMethod) {
transformers = new TransformWriteField(transformers, field,
calledClass.getName(),
calledMethod);
}
/**
* Modify a method body, so that ALL accesses to an array are replaced with
* calls to static methods within another class. In the case of reading an
* element from the array, this is replaced with a call to a static method with
* the array and the index as arguments, the return value is the value read from
* the array. If writing to an array, this is replaced with a call to a static
* method with the array, index and new value as parameters, the return value of
* the static method is void.
*
*
The calledClass parameter is the class containing the static methods to be used
* for array replacement. The names parameter points to an implementation of
* ArrayAccessReplacementMethodNames which specifies the names of the method to be
* used for access for each type of array. For example reading from an int[] will
* require a different method than if writing to an int[], and writing to a long[]
* will require a different method than if writing to a byte[]. If the implementation
* of ArrayAccessReplacementMethodNames does not contain the name for access for a
* type of array, that access is not replaced.
*
*
A default implementation of ArrayAccessReplacementMethodNames called
* DefaultArrayAccessReplacementMethodNames has been provided and is what is used in the
* following example. This also assumes that 'foo.ArrayAdvisor' is the name of the
* CtClass passed in.
*
*
If we have the following class:
*
class POJO{
* int[] ints = new int[]{1, 2, 3, 4, 5};
* long[] longs = new int[]{10, 20, 30};
* Object objects = new Object[]{true, false};
* Integer[] integers = new Integer[]{new Integer(10)};
* }
*
* and this is accessed as:
* POJO p = new POJO();
*
* //Write to int array
* p.ints[2] = 7;
*
* //Read from int array
* int i = p.ints[2];
*
* //Write to long array
* p.longs[2] = 1000L;
*
* //Read from long array
* long l = p.longs[2];
*
* //Write to Object array
* p.objects[2] = "Hello";
*
* //Read from Object array
* Object o = p.objects[2];
*
* //Write to Integer array
* Integer integer = new Integer(5);
* p.integers[0] = integer;
*
* //Read from Object array
* integer = p.integers[0];
*
*
* Following instrumentation we will have
* POJO p = new POJO();
*
* //Write to int array
* ArrayAdvisor.arrayWriteInt(p.ints, 2, 7);
*
* //Read from int array
* int i = ArrayAdvisor.arrayReadInt(p.ints, 2);
*
* //Write to long array
* ArrayAdvisor.arrayWriteLong(p.longs, 2, 1000L);
*
* //Read from long array
* long l = ArrayAdvisor.arrayReadLong(p.longs, 2);
*
* //Write to Object array
* ArrayAdvisor.arrayWriteObject(p.objects, 2, "Hello");
*
* //Read from Object array
* Object o = ArrayAdvisor.arrayReadObject(p.objects, 2);
*
* //Write to Integer array
* Integer integer = new Integer(5);
* ArrayAdvisor.arrayWriteObject(p.integers, 0, integer);
*
* //Read from Object array
* integer = ArrayAdvisor.arrayWriteObject(p.integers, 0);
*
*
* @see DefaultArrayAccessReplacementMethodNames
*
* @param calledClass the class containing the static methods.
* @param names contains the names of the methods to replace
* the different kinds of array access with.
*/
public void replaceArrayAccess(CtClass calledClass, ArrayAccessReplacementMethodNames names)
throws NotFoundException
{
transformers = new TransformAccessArrayField(transformers, calledClass.getName(), names);
}
/**
* Modify method invocations in a method body so that a different
* method will be invoked.
*
* Note that the target object, the parameters, or
* the type of invocation
* (static method call, interface call, or private method call)
* are not modified. Only the method name is changed. The substituted
* method must have the same signature that the original one has.
* If the original method is a static method, the substituted method
* must be static.
*
* @param origMethod original method
* @param substMethod substituted method
*/
public void redirectMethodCall(CtMethod origMethod,
CtMethod substMethod)
throws CannotCompileException
{
String d1 = origMethod.getMethodInfo2().getDescriptor();
String d2 = substMethod.getMethodInfo2().getDescriptor();
if (!d1.equals(d2))
throw new CannotCompileException("signature mismatch: "
+ substMethod.getLongName());
int mod1 = origMethod.getModifiers();
int mod2 = substMethod.getModifiers();
if (Modifier.isStatic(mod1) != Modifier.isStatic(mod2)
|| (Modifier.isPrivate(mod1) && !Modifier.isPrivate(mod2))
|| origMethod.getDeclaringClass().isInterface()
!= substMethod.getDeclaringClass().isInterface())
throw new CannotCompileException("invoke-type mismatch "
+ substMethod.getLongName());
transformers = new TransformCall(transformers, origMethod,
substMethod);
}
/**
* Correct invocations to a method that has been renamed.
* If a method is renamed, calls to that method must be also
* modified so that the method with the new name will be called.
*
*
The method must be declared in the same class before and
* after it is renamed.
*
*
Note that the target object, the parameters, or
* the type of invocation
* (static method call, interface call, or private method call)
* are not modified. Only the method name is changed.
*
* @param oldMethodName the old name of the method.
* @param newMethod the method with the new name.
* @see javassist.CtMethod#setName(String)
*/
public void redirectMethodCall(String oldMethodName,
CtMethod newMethod)
throws CannotCompileException
{
transformers
= new TransformCall(transformers, oldMethodName, newMethod);
}
/**
* Insert a call to another method before an existing method call.
* That "before" method must be static. The return type must be
* void. As parameters, the before method receives
* the target object and all the parameters to the originally invoked
* method. For example, if the originally invoked method is
* move():
*
*
class Point {
* Point move(int x, int y) { ... }
* }
*
* Then the before method must be something like this:
*
*
class Verbose {
* static void print(Point target, int x, int y) { ... }
* }
*
* The CodeConverter would translate bytecode
* equivalent to:
*
*
Point p2 = p.move(x + y, 0);
*
* into the bytecode equivalent to:
*
*
int tmp1 = x + y;
* int tmp2 = 0;
* Verbose.print(p, tmp1, tmp2);
* Point p2 = p.move(tmp1, tmp2);
*
* @param origMethod the method originally invoked.
* @param beforeMethod the method invoked before
* origMethod.
*/
public void insertBeforeMethod(CtMethod origMethod,
CtMethod beforeMethod)
throws CannotCompileException
{
try {
transformers = new TransformBefore(transformers, origMethod,
beforeMethod);
}
catch (NotFoundException e) {
throw new CannotCompileException(e);
}
}
/**
* Inserts a call to another method after an existing method call.
* That "after" method must be static. The return type must be
* void. As parameters, the after method receives
* the target object and all the parameters to the originally invoked
* method. For example, if the originally invoked method is
* move():
*
*
class Point {
* Point move(int x, int y) { ... }
* }
*
* Then the after method must be something like this:
*
*
class Verbose {
* static void print(Point target, int x, int y) { ... }
* }
*
* The CodeConverter would translate bytecode
* equivalent to:
*
*
Point p2 = p.move(x + y, 0);
*
* into the bytecode equivalent to:
*
*
int tmp1 = x + y;
* int tmp2 = 0;
* Point p2 = p.move(tmp1, tmp2);
* Verbose.print(p, tmp1, tmp2);
*
* @param origMethod the method originally invoked.
* @param afterMethod the method invoked after
* origMethod.
*/
public void insertAfterMethod(CtMethod origMethod,
CtMethod afterMethod)
throws CannotCompileException
{
try {
transformers = new TransformAfter(transformers, origMethod,
afterMethod);
}
catch (NotFoundException e) {
throw new CannotCompileException(e);
}
}
/**
* Performs code conversion.
*/
protected void doit(CtClass clazz, MethodInfo minfo, ConstPool cp)
throws CannotCompileException
{
Transformer t;
CodeAttribute codeAttr = minfo.getCodeAttribute();
if (codeAttr == null || transformers == null)
return;
for (t = transformers; t != null; t = t.getNext())
t.initialize(cp, clazz, minfo);
CodeIterator iterator = codeAttr.iterator();
while (iterator.hasNext()) {
try {
int pos = iterator.next();
for (t = transformers; t != null; t = t.getNext())
pos = t.transform(clazz, pos, iterator, cp);
}
catch (BadBytecode e) {
throw new CannotCompileException(e);
}
}
int locals = 0;
int stack = 0;
for (t = transformers; t != null; t = t.getNext()) {
int s = t.extraLocals();
if (s > locals)
locals = s;
s = t.extraStack();
if (s > stack)
stack = s;
}
for (t = transformers; t != null; t = t.getNext())
t.clean();
if (locals > 0)
codeAttr.setMaxLocals(codeAttr.getMaxLocals() + locals);
if (stack > 0)
codeAttr.setMaxStack(codeAttr.getMaxStack() + stack);
try {
minfo.rebuildStackMapIf6(clazz.getClassPool(),
clazz.getClassFile2());
}
catch (BadBytecode b) {
throw new CannotCompileException(b.getMessage(), b);
}
}
/**
* Interface containing the method names to be used
* as array access replacements.
*
* @author Kabir Khan
* @version $Revision: 1.16 $
*/
public interface ArrayAccessReplacementMethodNames
{
/**
* Returns the name of a static method with the signature
* (Ljava/lang/Object;I)B to replace reading from a byte[].
*/
String byteOrBooleanRead();
/**
* Returns the name of a static method with the signature
* (Ljava/lang/Object;IB)V to replace writing to a byte[].
*/
String byteOrBooleanWrite();
/**
* @return the name of a static method with the signature
* (Ljava/lang/Object;I)C to replace reading from a char[].
*/
String charRead();
/**
* Returns the name of a static method with the signature
* (Ljava/lang/Object;IC)V to replace writing to a byte[].
*/
String charWrite();
/**
* Returns the name of a static method with the signature
* (Ljava/lang/Object;I)D to replace reading from a double[].
*/
String doubleRead();
/**
* Returns the name of a static method with the signature
* (Ljava/lang/Object;ID)V to replace writing to a double[].
*/
String doubleWrite();
/**
* Returns the name of a static method with the signature
* (Ljava/lang/Object;I)F to replace reading from a float[].
*/
String floatRead();
/**
* Returns the name of a static method with the signature
* (Ljava/lang/Object;IF)V to replace writing to a float[].
*/
String floatWrite();
/**
* Returns the name of a static method with the signature
* (Ljava/lang/Object;I)I to replace reading from a int[].
*/
String intRead();
/**
* Returns the name of a static method with the signature
* (Ljava/lang/Object;II)V to replace writing to a int[].
*/
String intWrite();
/**
* Returns the name of a static method with the signature
* (Ljava/lang/Object;I)J to replace reading from a long[].
*/
String longRead();
/**
* Returns the name of a static method with the signature
* (Ljava/lang/Object;IJ)V to replace writing to a long[].
*/
String longWrite();
/**
* Returns the name of a static method with the signature
* (Ljava/lang/Object;I)Ljava/lang/Object;
* to replace reading from a Object[] (or any subclass of object).
*/
String objectRead();
/**
* Returns the name of a static method with the signature
* (Ljava/lang/Object;ILjava/lang/Object;)V
* to replace writing to a Object[] (or any subclass of object).
*/
String objectWrite();
/**
* Returns the name of a static method with the signature
* (Ljava/lang/Object;I)S to replace reading from a short[].
*/
String shortRead();
/**
* Returns the name of a static method with the signature
* (Ljava/lang/Object;IS)V to replace writing to a short[].
*/
String shortWrite();
}
/**
* Default implementation of the ArrayAccessReplacementMethodNames
* interface giving default values for method names to be used for replacing
* accesses to array elements.
*
* @author Kabir Khan
* @version $Revision: 1.16 $
*/
public static class DefaultArrayAccessReplacementMethodNames
implements ArrayAccessReplacementMethodNames
{
/**
* Returns "arrayReadByteOrBoolean" as the name of the static method with the signature
* (Ljava/lang/Object;I)B to replace reading from a byte[].
*/
public String byteOrBooleanRead()
{
return "arrayReadByteOrBoolean";
}
/**
* Returns "arrayWriteByteOrBoolean" as the name of the static method with the signature
* (Ljava/lang/Object;IB)V to replace writing to a byte[].
*/
public String byteOrBooleanWrite()
{
return "arrayWriteByteOrBoolean";
}
/**
* Returns "arrayReadChar" as the name of the static method with the signature
* (Ljava/lang/Object;I)C to replace reading from a char[].
*/
public String charRead()
{
return "arrayReadChar";
}
/**
* Returns "arrayWriteChar" as the name of the static method with the signature
* (Ljava/lang/Object;IC)V to replace writing to a byte[].
*/
public String charWrite()
{
return "arrayWriteChar";
}
/**
* Returns "arrayReadDouble" as the name of the static method with the signature
* (Ljava/lang/Object;I)D to replace reading from a double[].
*/
public String doubleRead()
{
return "arrayReadDouble";
}
/**
* Returns "arrayWriteDouble" as the name of the static method with the signature
* (Ljava/lang/Object;ID)V to replace writing to a double[].
*/
public String doubleWrite()
{
return "arrayWriteDouble";
}
/**
* Returns "arrayReadFloat" as the name of the static method with the signature
* (Ljava/lang/Object;I)F to replace reading from a float[].
*/
public String floatRead()
{
return "arrayReadFloat";
}
/**
* Returns "arrayWriteFloat" as the name of the static method with the signature
* (Ljava/lang/Object;IF)V to replace writing to a float[].
*/
public String floatWrite()
{
return "arrayWriteFloat";
}
/**
* Returns "arrayReadInt" as the name of the static method with the signature
* (Ljava/lang/Object;I)I to replace reading from a int[].
*/
public String intRead()
{
return "arrayReadInt";
}
/**
* Returns "arrayWriteInt" as the name of the static method with the signature
* (Ljava/lang/Object;II)V to replace writing to a int[].
*/
public String intWrite()
{
return "arrayWriteInt";
}
/**
* Returns "arrayReadLong" as the name of the static method with the signature
* (Ljava/lang/Object;I)J to replace reading from a long[].
*/
public String longRead()
{
return "arrayReadLong";
}
/**
* Returns "arrayWriteLong" as the name of the static method with the signature
* (Ljava/lang/Object;IJ)V to replace writing to a long[].
*/
public String longWrite()
{
return "arrayWriteLong";
}
/**
* Returns "arrayReadObject" as the name of the static method with the signature
* (Ljava/lang/Object;I)Ljava/lang/Object; to replace reading from a Object[] (or any subclass of object).
*/
public String objectRead()
{
return "arrayReadObject";
}
/**
* Returns "arrayWriteObject" as the name of the static method with the signature
* (Ljava/lang/Object;ILjava/lang/Object;)V to replace writing to a Object[] (or any subclass of object).
*/
public String objectWrite()
{
return "arrayWriteObject";
}
/**
* Returns "arrayReadShort" as the name of the static method with the signature
* (Ljava/lang/Object;I)S to replace reading from a short[].
*/
public String shortRead()
{
return "arrayReadShort";
}
/**
* Returns "arrayWriteShort" as the name of the static method with the signature
* (Ljava/lang/Object;IS)V to replace writing to a short[].
*/
public String shortWrite()
{
return "arrayWriteShort";
}
}
}