package net.bytebuddy.implementation;
import lombok.EqualsAndHashCode;
import net.bytebuddy.description.field.FieldDescription;
import net.bytebuddy.description.method.MethodDescription;
import net.bytebuddy.description.method.ParameterDescription;
import net.bytebuddy.description.type.TypeDescription;
import net.bytebuddy.dynamic.scaffold.InstrumentedType;
import net.bytebuddy.implementation.bytecode.ByteCodeAppender;
import net.bytebuddy.implementation.bytecode.StackManipulation;
import net.bytebuddy.implementation.bytecode.assign.Assigner;
import net.bytebuddy.implementation.bytecode.constant.*;
import net.bytebuddy.implementation.bytecode.member.FieldAccess;
import net.bytebuddy.implementation.bytecode.member.MethodReturn;
import net.bytebuddy.implementation.bytecode.member.MethodVariableAccess;
import net.bytebuddy.utility.JavaConstant;
import net.bytebuddy.utility.JavaType;
import net.bytebuddy.utility.RandomString;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import static net.bytebuddy.matcher.ElementMatchers.named;
/**
* This implementation returns a fixed value for a method. Other than the {@link net.bytebuddy.implementation.StubMethod}
* implementation, this implementation allows to determine a specific value which must be assignable to the returning value
* of any instrumented method. Otherwise, an exception will be thrown.
*
* @see FieldAccessor
*/
@EqualsAndHashCode
public abstract class FixedValue implements Implementation {
/**
* The assigner that is used for assigning the fixed value to a method's return type.
*/
protected final Assigner assigner;
/**
* Indicates if dynamic type castings should be attempted for incompatible assignments.
*/
protected final Assigner.Typing typing;
/**
* Creates a new fixed value implementation.
*
* @param assigner The assigner to use for assigning the fixed value to the return type of the instrumented value.
* @param typing Indicates if dynamic type castings should be attempted for incompatible assignments.
*/
protected FixedValue(Assigner assigner, Assigner.Typing typing) {
this.assigner = assigner;
this.typing = typing;
}
/**
* <p>
* Returns a fixed value from any intercepted method. The fixed value is stored in the constant pool if this is possible.
* Java is capable of storing any primitive value, {@link String} values and {@link Class} references in the constant pool.
* Since Java 7, {@code MethodHandle} as well as {@code MethodType} references are also supported. Alternatively, the fixed
* value is stored in a static field.
* </p>
* <p>
* When a value is stored in the class's constant pool, its identity is lost. If an object's identity is important, the
* {@link FixedValue#reference(Object)} method should be used instead.
* </p>
* <p>
* <b>Important</b>: When supplying a method handle or a method type, all types that are implied must be visible to the instrumented
* type or an {@link IllegalAccessException} will be thrown at runtime.
* </p>
*
* @param fixedValue The fixed value to return from the method.
* @return An implementation for the given {@code value}.
*/
public static AssignerConfigurable value(Object fixedValue) {
Class<?> type = fixedValue.getClass();
if (type == String.class) {
return new ForPoolValue(new TextConstant((String) fixedValue), TypeDescription.STRING);
} else if (type == Class.class) {
return new ForPoolValue(ClassConstant.of(new TypeDescription.ForLoadedType((Class<?>) fixedValue)), TypeDescription.CLASS);
} else if (type == Boolean.class) {
return new ForPoolValue(IntegerConstant.forValue((Boolean) fixedValue), boolean.class);
} else if (type == Byte.class) {
return new ForPoolValue(IntegerConstant.forValue((Byte) fixedValue), byte.class);
} else if (type == Short.class) {
return new ForPoolValue(IntegerConstant.forValue((Short) fixedValue), short.class);
} else if (type == Character.class) {
return new ForPoolValue(IntegerConstant.forValue((Character) fixedValue), char.class);
} else if (type == Integer.class) {
return new ForPoolValue(IntegerConstant.forValue((Integer) fixedValue), int.class);
} else if (type == Long.class) {
return new ForPoolValue(LongConstant.forValue((Long) fixedValue), long.class);
} else if (type == Float.class) {
return new ForPoolValue(FloatConstant.forValue((Float) fixedValue), float.class);
} else if (type == Double.class) {
return new ForPoolValue(DoubleConstant.forValue((Double) fixedValue), double.class);
} else if (JavaType.METHOD_HANDLE.getTypeStub().isAssignableFrom(type)) {
return new ForPoolValue(new JavaConstantValue(JavaConstant.MethodHandle.ofLoaded(fixedValue)), type);
} else if (JavaType.METHOD_TYPE.getTypeStub().represents(type)) {
return new ForPoolValue(new JavaConstantValue(JavaConstant.MethodType.ofLoaded(fixedValue)), type);
} else {
return reference(fixedValue);
}
}
/**
* Other than {@link net.bytebuddy.implementation.FixedValue#value(Object)}, this function
* will create a fixed value implementation that will always defined a field in the instrumented class. As a result,
* object identity will be preserved between the given {@code value} and the value that is returned by
* instrumented methods. The field name can be explicitly determined. The field name is generated from the fixed value's
* hash code.
*
* @param fixedValue The fixed value to be returned by methods that are instrumented by this implementation.
* @return An implementation for the given {@code value}.
*/
public static AssignerConfigurable reference(Object fixedValue) {
return new ForValue(fixedValue);
}
/**
* Other than {@link net.bytebuddy.implementation.FixedValue#value(Object)}, this function
* will create a fixed value implementation that will always defined a field in the instrumented class. As a result,
* object identity will be preserved between the given {@code value} and the value that is returned by
* instrumented methods. The field name can be explicitly determined.
*
* @param fixedValue The fixed value to be returned by methods that are instrumented by this implementation.
* @param fieldName The name of the field for storing the fixed value.
* @return An implementation for the given {@code value}.
*/
public static AssignerConfigurable reference(Object fixedValue, String fieldName) {
return new ForValue(fieldName, fixedValue);
}
/**
* Returns the given type in form of a loaded type. The value is loaded from the written class's constant pool.
*
* @param fixedValue The type to return from the method.
* @return An implementation for the given {@code value}.
*/
public static AssignerConfigurable value(TypeDescription fixedValue) {
return new ForPoolValue(ClassConstant.of(fixedValue), TypeDescription.CLASS);
}
/**
* Returns the loaded version of the given {@link JavaConstant}. The value is loaded from the written class's constant pool.
*
* @param fixedValue The type to return from the method.
* @return An implementation for the given {@code value}.
*/
public static AssignerConfigurable value(JavaConstant fixedValue) {
return new ForPoolValue(fixedValue.asStackManipulation(), fixedValue.getType());
}
/**
* Returns the argument at the specified index.
*
* @param index The index of the argument to return.
* @return An implementation of a method that returns the argument at the specified index.
*/
public static AssignerConfigurable argument(int index) {
if (index < 0) {
throw new IllegalArgumentException("Argument index cannot be negative: " + index);
}
return new ForArgument(index);
}
/**
* Returns {@code this} from an instrumented method.
*
* @return An implementation that returns {@code this} from a method.
*/
public static AssignerConfigurable self() {
return new ForThisValue();
}
/**
* Returns a {@code null} value from an instrumented method.
*
* @return An implementation that returns {@code null} from a method.
*/
public static Implementation nullValue() {
return ForNullValue.INSTANCE;
}
/**
* Returns the origin type from an instrumented method.
*
* @return An implementation that returns the origin type of the current instrumented type.
*/
public static AssignerConfigurable originType() {
return new ForOriginType();
}
/**
* Blueprint method that for applying the actual implementation.
*
* @param methodVisitor The method visitor to which the implementation is applied to.
* @param implementationContext The implementation context for the given implementation.
* @param instrumentedMethod The instrumented method that is target of the implementation.
* @param fixedValueType A description of the type of the fixed value that is loaded by the
* {@code valueLoadingInstruction}.
* @param valueLoadingInstruction A stack manipulation that represents the loading of the fixed value onto the
* operand stack.
* @return A representation of the stack and variable array sized that are required for this implementation.
*/
protected ByteCodeAppender.Size apply(MethodVisitor methodVisitor,
Context implementationContext,
MethodDescription instrumentedMethod,
TypeDescription.Generic fixedValueType,
StackManipulation valueLoadingInstruction) {
StackManipulation assignment = assigner.assign(fixedValueType, instrumentedMethod.getReturnType(), typing);
if (!assignment.isValid()) {
throw new IllegalArgumentException("Cannot return value of type " + fixedValueType + " for " + instrumentedMethod);
}
StackManipulation.Size stackSize = new StackManipulation.Compound(
valueLoadingInstruction,
assignment,
MethodReturn.of(instrumentedMethod.getReturnType())
).apply(methodVisitor, implementationContext);
return new ByteCodeAppender.Size(stackSize.getMaximalSize(), instrumentedMethod.getStackSize());
}
/**
* Represents a fixed value implementation that is using a default assigner for attempting to assign
* the fixed value to the return type of the instrumented method.
*/
public interface AssignerConfigurable extends Implementation {
/**
* Defines an explicit assigner to this fixed value implementation.
*
* @param assigner The assigner to use for assigning the fixed value to the return type of the
* instrumented value.
* @param typing Indicates if dynamic type castings should be attempted for incompatible assignments.
* @return A fixed value implementation that makes use of the given assigner.
*/
Implementation withAssigner(Assigner assigner, Assigner.Typing typing);
}
/**
* A fixed value of {@code null}.
*/
protected enum ForNullValue implements Implementation, ByteCodeAppender {
/**
* The singleton instance.
*/
INSTANCE;
@Override
public ByteCodeAppender appender(Target implementationTarget) {
return this;
}
@Override
public InstrumentedType prepare(InstrumentedType instrumentedType) {
return instrumentedType;
}
@Override
public Size apply(MethodVisitor methodVisitor, Context implementationContext, MethodDescription instrumentedMethod) {
if (instrumentedMethod.getReturnType().isPrimitive()) {
throw new IllegalStateException("Cannot return null from " + instrumentedMethod);
}
return new ByteCodeAppender.Simple(
NullConstant.INSTANCE,
MethodReturn.REFERENCE
).apply(methodVisitor, implementationContext, instrumentedMethod);
}
}
/**
* A fixed value that appends the origin type of the instrumented type.
*/
protected static class ForOriginType extends FixedValue implements AssignerConfigurable {
/**
* Creates a new fixed value appender for the origin type.
*/
protected ForOriginType() {
this(Assigner.DEFAULT, Assigner.Typing.STATIC);
}
/**
* Creates a new fixed value appender for the origin type.
*
* @param assigner The assigner to use for assigning the fixed value to the return type of the instrumented value.
* @param typing Indicates if dynamic type castings should be attempted for incompatible assignments.
*/
private ForOriginType(Assigner assigner, Assigner.Typing typing) {
super(assigner, typing);
}
@Override
public Implementation withAssigner(Assigner assigner, Assigner.Typing typing) {
return new ForOriginType(assigner, typing);
}
@Override
public ByteCodeAppender appender(Target implementationTarget) {
return new Appender(implementationTarget.getOriginType().asErasure());
}
@Override
public InstrumentedType prepare(InstrumentedType instrumentedType) {
return instrumentedType;
}
/**
* An appender for writing the origin type.
*/
protected class Appender implements ByteCodeAppender {
/**
* The instrumented type.
*/
private final TypeDescription originType;
/**
* Creates a new appender.
*
* @param originType The instrumented type.
*/
protected Appender(TypeDescription originType) {
this.originType = originType;
}
@Override
public Size apply(MethodVisitor methodVisitor, Context implementationContext, MethodDescription instrumentedMethod) {
return ForOriginType.this.apply(methodVisitor,
implementationContext,
instrumentedMethod,
TypeDescription.CLASS.asGenericType(),
ClassConstant.of(originType));
}
/**
* Returns the outer instance.
*
* @return The outer instance.
*/
private ForOriginType getOuter() {
return ForOriginType.this;
}
@Override // HE: Remove when Lombok support for getOuter is added.
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Appender appender = (Appender) o;
return originType.equals(appender.originType)
&& getOuter().equals(appender.getOuter());
}
@Override // HE: Remove when Lombok support for getOuter is added.
public int hashCode() {
return 31 * getOuter().hashCode() + originType.hashCode();
}
}
}
/**
* A fixed value of {@code this}.
*/
protected static class ForThisValue extends FixedValue implements AssignerConfigurable {
/**
* Creates an implementation that returns the instance of the instrumented type.
*/
protected ForThisValue() {
super(Assigner.DEFAULT, Assigner.Typing.STATIC);
}
/**
* Creates an implementation that returns the instance of the instrumented type.
*
* @param assigner The assigner to use for assigning the fixed value to the return type of the instrumented value.
* @param typing Indicates if dynamic type castings should be attempted for incompatible assignments.
*/
private ForThisValue(Assigner assigner, Assigner.Typing typing) {
super(assigner, typing);
}
@Override
public ByteCodeAppender appender(Target implementationTarget) {
return new Appender(implementationTarget.getInstrumentedType());
}
@Override
public InstrumentedType prepare(InstrumentedType instrumentedType) {
return instrumentedType;
}
@Override
public Implementation withAssigner(Assigner assigner, Assigner.Typing typing) {
return new ForThisValue(assigner, typing);
}
/**
* A byte code appender for returning {@code this}.
*/
@EqualsAndHashCode
protected static class Appender implements ByteCodeAppender {
/**
* The instrumented type.
*/
private final TypeDescription instrumentedType;
/**
* Creates a new byte code appender for returning {@code this}.
*
* @param instrumentedType The instrumented type.
*/
protected Appender(TypeDescription instrumentedType) {
this.instrumentedType = instrumentedType;
}
@Override
public Size apply(MethodVisitor methodVisitor, Context implementationContext, MethodDescription instrumentedMethod) {
if (instrumentedMethod.isStatic() || !instrumentedType.isAssignableTo(instrumentedMethod.getReturnType().asErasure())) {
throw new IllegalStateException("Cannot return 'this' from " + instrumentedMethod);
}
return new ByteCodeAppender.Simple(
MethodVariableAccess.loadThis(),
MethodReturn.REFERENCE
).apply(methodVisitor, implementationContext, instrumentedMethod);
}
}
}
/**
* A fixed value implementation that returns a method's argument.
*/
@EqualsAndHashCode(callSuper = true)
protected static class ForArgument extends FixedValue implements AssignerConfigurable, ByteCodeAppender {
/**
* The argument index.
*/
private final int index;
/**
* Creates a new fixed value implementation that returns a method's argument.
*
* @param index The argument's index.
*/
protected ForArgument(int index) {
this(Assigner.DEFAULT, Assigner.Typing.STATIC, index);
}
/**
* Creates a new fixed value implementation that returns a method's argument.
*
* @param assigner The assigner to use for assigning the fixed value to the return type of the
* instrumented value.
* @param typing Indicates if dynamic type castings should be attempted for incompatible assignments.
* @param index The argument's index.
*/
private ForArgument(Assigner assigner, Assigner.Typing typing, int index) {
super(assigner, typing);
this.index = index;
}
@Override
public Size apply(MethodVisitor methodVisitor, Context implementationContext, MethodDescription instrumentedMethod) {
if (instrumentedMethod.getParameters().size() <= index) {
throw new IllegalStateException(instrumentedMethod + " does not define a parameter with index " + index);
}
ParameterDescription parameterDescription = instrumentedMethod.getParameters().get(index);
StackManipulation stackManipulation = new StackManipulation.Compound(
MethodVariableAccess.load(parameterDescription),
assigner.assign(parameterDescription.getType(), instrumentedMethod.getReturnType(), typing),
MethodReturn.of(instrumentedMethod.getReturnType())
);
if (!stackManipulation.isValid()) {
throw new IllegalStateException("Cannot assign " + instrumentedMethod.getReturnType() + " to " + parameterDescription);
}
return new Size(stackManipulation.apply(methodVisitor, implementationContext).getMaximalSize(), instrumentedMethod.getStackSize());
}
@Override
public ByteCodeAppender appender(Target implementationTarget) {
return this;
}
@Override
public InstrumentedType prepare(InstrumentedType instrumentedType) {
return instrumentedType;
}
@Override
public Implementation withAssigner(Assigner assigner, Assigner.Typing typing) {
return new ForArgument(assigner, typing, index);
}
}
/**
* A fixed value implementation that represents its fixed value as a value that is written to the instrumented
* class's constant pool.
*/
@EqualsAndHashCode(callSuper = true)
protected static class ForPoolValue extends FixedValue implements AssignerConfigurable, ByteCodeAppender {
/**
* The stack manipulation which is responsible for loading the fixed value onto the operand stack.
*/
private final StackManipulation valueLoadInstruction;
/**
* The type of the fixed value.
*/
private final TypeDescription loadedType;
/**
* Creates a new constant pool fixed value implementation.
*
* @param valueLoadInstruction The instruction that is responsible for loading the constant pool value onto the
* operand stack.
* @param loadedType A type description representing the loaded type.
*/
protected ForPoolValue(StackManipulation valueLoadInstruction, Class<?> loadedType) {
this(valueLoadInstruction, new TypeDescription.ForLoadedType(loadedType));
}
/**
* Creates a new constant pool fixed value implementation.
*
* @param valueLoadInstruction The instruction that is responsible for loading the constant pool value onto the
* operand stack.
* @param loadedType A type description representing the loaded type.
*/
protected ForPoolValue(StackManipulation valueLoadInstruction, TypeDescription loadedType) {
this(Assigner.DEFAULT, Assigner.Typing.STATIC, valueLoadInstruction, loadedType);
}
/**
* Creates a new constant pool fixed value implementation.
*
* @param valueLoadInstruction The instruction that is responsible for loading the constant pool value onto the
* operand stack.
* @param loadedType A type description representing the loaded type.
* @param assigner The assigner to use for assigning the fixed value to the return type of the
* instrumented value.
* @param typing Indicates if dynamic type castings should be attempted for incompatible assignments.
*/
private ForPoolValue(Assigner assigner, Assigner.Typing typing, StackManipulation valueLoadInstruction, TypeDescription loadedType) {
super(assigner, typing);
this.valueLoadInstruction = valueLoadInstruction;
this.loadedType = loadedType;
}
@Override
public Implementation withAssigner(Assigner assigner, Assigner.Typing typing) {
return new ForPoolValue(assigner, typing, valueLoadInstruction, loadedType);
}
@Override
public InstrumentedType prepare(InstrumentedType instrumentedType) {
return instrumentedType;
}
@Override
public ByteCodeAppender appender(Target implementationTarget) {
return this;
}
@Override
public Size apply(MethodVisitor methodVisitor, Context implementationContext, MethodDescription instrumentedMethod) {
return apply(methodVisitor, implementationContext, instrumentedMethod, loadedType.asGenericType(), valueLoadInstruction);
}
}
/**
* A fixed value implementation that represents its fixed value as a static field of the instrumented class.
*/
@EqualsAndHashCode(callSuper = true, exclude = "fieldType")
protected static class ForValue extends FixedValue implements AssignerConfigurable {
/**
* The prefix of the static field that is created for storing the fixed value.
*/
private static final String PREFIX = "value";
/**
* The name of the field in which the fixed value is stored.
*/
private final String fieldName;
/**
* The value that is to be stored in the static field.
*/
private final Object value;
/**
* The type if the field for storing the fixed value.
*/
private final TypeDescription.Generic fieldType;
/**
* Creates a new static field fixed value implementation with a random name for the field containing the fixed
* value.
*
* @param value The fixed value to be returned.
*/
protected ForValue(Object value) {
this(String.format("%s$%s", PREFIX, RandomString.hashOf(value.hashCode())), value);
}
/**
* Creates a new static field fixed value implementation.
*
* @param fieldName The name of the field for storing the fixed value.
* @param value The fixed value to be returned.
*/
protected ForValue(String fieldName, Object value) {
this(Assigner.DEFAULT, Assigner.Typing.STATIC, fieldName, value);
}
/**
* Creates a new static field fixed value implementation.
*
* @param fieldName The name of the field for storing the fixed value.
* @param value The fixed value to be returned.
* @param assigner The assigner to use for assigning the fixed value to the return type of the
* instrumented value.
* @param typing Indicates if dynamic type castings should be attempted for incompatible assignments.
*/
private ForValue(Assigner assigner, Assigner.Typing typing, String fieldName, Object value) {
super(assigner, typing);
this.fieldName = fieldName;
this.value = value;
fieldType = new TypeDescription.Generic.OfNonGenericType.ForLoadedType(value.getClass());
}
@Override
public Implementation withAssigner(Assigner assigner, Assigner.Typing typing) {
return new ForValue(assigner, typing, fieldName, value);
}
@Override
public InstrumentedType prepare(InstrumentedType instrumentedType) {
return instrumentedType
.withField(new FieldDescription.Token(fieldName, Opcodes.ACC_SYNTHETIC | Opcodes.ACC_STATIC | Opcodes.ACC_PUBLIC, fieldType))
.withInitializer(new LoadedTypeInitializer.ForStaticField(fieldName, value));
}
@Override
public ByteCodeAppender appender(Target implementationTarget) {
return new StaticFieldByteCodeAppender(implementationTarget.getInstrumentedType());
}
/**
* A byte code appender for returning the fixed value that was stored in a static field.
*/
@EqualsAndHashCode
private class StaticFieldByteCodeAppender implements ByteCodeAppender {
/**
* The stack manipulation that loads the fixed value onto the operand stack.
*/
private final StackManipulation fieldGetAccess;
/**
* Creates a new byte code appender for returning a value of a static field from an instrumented method.
*
* @param instrumentedType The instrumented type that is subject of the instrumentation.
*/
private StaticFieldByteCodeAppender(TypeDescription instrumentedType) {
fieldGetAccess = FieldAccess.forField(instrumentedType.getDeclaredFields().filter((named(fieldName))).getOnly()).read();
}
@Override
public Size apply(MethodVisitor methodVisitor, Context implementationContext, MethodDescription instrumentedMethod) {
return ForValue.this.apply(methodVisitor, implementationContext, instrumentedMethod, fieldType, fieldGetAccess);
}
}
}
}