net.bytebuddy.implementation

Class FixedValue

java.lang.Object

net.bytebuddy.implementation.FixedValue

All Implemented Interfaces:

Implementation

Direct Known Subclasses:

FixedValue.ForPoolValue, FixedValue.ForStaticField

public abstract class FixedValue
extends Object
implements Implementation

This implementation returns a fixed value for a method. Other than the 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.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	FixedValue.AssignerConfigurable 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.
protected static class	FixedValue.ForPoolValue A fixed value implementation that represents its fixed value as a value that is written to the instrumented class's constant pool.
protected static class	FixedValue.ForStaticField A fixed value implementation that represents its fixed value as a static field of the instrumented class.

Nested classes/interfaces inherited from interface net.bytebuddy.implementation.Implementation

Implementation.Composable, Implementation.Compound, Implementation.Context, Implementation.Simple, Implementation.SpecialMethodInvocation, Implementation.Target

Field Summary

Fields

Modifier and Type	Field and Description
protected Assigner	assigner The assigner that is used for assigning the fixed value to a method's return type.
protected Assigner.Typing	typing Indicates if dynamic type castings should be attempted for incompatible assignments.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	FixedValue(Assigner assigner, Assigner.Typing typing) Creates a new fixed value implementation.

Method Summary

Modifier and Type	Method and Description
protected ByteCodeAppender.Size	apply(MethodVisitor methodVisitor, Implementation.Context implementationContext, MethodDescription instrumentedMethod, TypeDescription fixedValueType, StackManipulation valueLoadingInstruction) Blueprint method that for applying the actual implementation.
boolean	equals(Object other)
int	hashCode()
static Implementation	nullValue() Creates a fixed value implementation that returns null as a fixed value.
static FixedValue.AssignerConfigurable	reference(Object fixedValue) Other than value(Object), this function will create a fixed value implementation that will always defined a field in the instrumented class.
static FixedValue.AssignerConfigurable	reference(Object fixedValue, String fieldName) Other than value(Object), this function will create a fixed value implementation that will always defined a field in the instrumented class.
static FixedValue.AssignerConfigurable	value(JavaInstance fixedValue) Returns the loaded version of the given JavaInstance.
static FixedValue.AssignerConfigurable	value(Object fixedValue) Creates a fixed value implementation that returns a fixed value.
static FixedValue.AssignerConfigurable	value(TypeDescription fixedValue) Returns the given type in form of a loaded type.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface net.bytebuddy.implementation.Implementation

appender, prepare

Field Detail

assigner

protected final Assigner assigner

The assigner that is used for assigning the fixed value to a method's return type.

typing

protected final Assigner.Typing typing

Indicates if dynamic type castings should be attempted for incompatible assignments.

Constructor Detail

FixedValue

protected FixedValue(Assigner assigner,
                     Assigner.Typing typing)

Creates a new fixed value implementation.

Parameters:

assigner - The assigner to use for assigning the fixed value to the return type of the instrumented value.

typing - Indicates if dynamic type castings should be attempted for incompatible assignments.

Method Detail

nullValue

public static Implementation nullValue()

Creates a fixed value implementation that returns null as a fixed value. This value is inlined into the method and does not create a field.

Returns:

An implementation that represents the null value.

value

public static FixedValue.AssignerConfigurable value(Object fixedValue)

Creates a fixed value implementation that returns a fixed value. If the value can be inlined into the created class, i.e. can be added to the constant pool of a class, no explicit type initialization will be required for the created dynamic class. Otherwise, a static field will be created in the dynamic type which will be initialized with the given value. The following Java types can be inlined:

• The String type.
• The Class type.
• All primitive types and their wrapper type, i.e. Boolean, Byte, Short, Character, Integer, Long, Float and Double.
• A null reference.
• From Java 7 on, instances of java.lang.invoke.MethodType and java.lang.invoke.MethodHandle.

If possible, the constant pool value is substituted by a byte code instruction that creates the value. (This is possible for integer types and types that are presented by integers inside the JVM (boolean, byte, short, char) and for the null value. Additionally, several common constants of the float, double and long types can be represented by opcode constants.

Note that method handles or (method) types require to be visible to a class's class loader.

Parameters:

fixedValue - The fixed value to be returned by methods that are instrumented by this implementation.

Returns:

An implementation for the given fixedValue.

reference

public static FixedValue.AssignerConfigurable reference(Object fixedValue)

Other than 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 fixedValue and the value that is returned by instrumented methods.

As an exception, the null value is always presented by a constant value and is never stored in a static field.

Parameters:

fixedValue - The fixed value to be returned by methods that are instrumented by this implementation.

Returns:

An implementation for the given fixedValue.

reference

public static FixedValue.AssignerConfigurable reference(Object fixedValue,
                                                        String fieldName)

Other than 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 fixedValue and the value that is returned by instrumented methods. The field name can be explicitly determined.

As an exception, the null value cannot be used for this implementation but will cause an exception.

Parameters:

fixedValue - The fixed value to be returned by methods that are instrumented by this implementation.

fieldName - The name of the field for storing the fixed value.

Returns:

An implementation for the given fixedValue.

value

public static FixedValue.AssignerConfigurable value(TypeDescription fixedValue)

Returns the given type in form of a loaded type. The value is loaded from the written class's constant pool.

Parameters:

fixedValue - The type to return from the method.

Returns:

An implementation for the given fixedValue.

value

public static FixedValue.AssignerConfigurable value(JavaInstance fixedValue)

Returns the loaded version of the given JavaInstance. The value is loaded from the written class's constant pool.

Parameters:

fixedValue - The type to return from the method.

Returns:

An implementation for the given fixedValue.

apply

protected ByteCodeAppender.Size apply(MethodVisitor methodVisitor,
                                      Implementation.Context implementationContext,
                                      MethodDescription instrumentedMethod,
                                      TypeDescription fixedValueType,
                                      StackManipulation valueLoadingInstruction)

Blueprint method that for applying the actual implementation.

Parameters:

methodVisitor - The method visitor to which the implementation is applied to.

implementationContext - The implementation context for the given implementation.

instrumentedMethod - The instrumented method that is target of the implementation.

fixedValueType - A description of the type of the fixed value that is loaded by the valueLoadingInstruction.

valueLoadingInstruction - A stack manipulation that represents the loading of the fixed value onto the operand stack.

Returns:

A representation of the stack and variable array sized that are required for this implementation.

equals

public boolean equals(Object other)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object