net.bytebuddy.instrumentation

Class FixedValue

java.lang.Object

net.bytebuddy.instrumentation.FixedValue

All Implemented Interfaces:

Instrumentation

Direct Known Subclasses:

FixedValue.ForPoolValue, FixedValue.ForStaticField

public abstract class FixedValue
extends Object
implements Instrumentation

This instrumentation returns a fixed value for a method. Other than the StubMethod instrumentation, 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 instrumentation 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 instrumentation 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 instrumentation that represents its fixed value as a static field of the instrumented class.

Nested classes/interfaces inherited from interface net.bytebuddy.instrumentation.Instrumentation

Instrumentation.Compound, Instrumentation.Context, Instrumentation.ForAbstractMethod, Instrumentation.Simple, Instrumentation.SpecialMethodInvocation, Instrumentation.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 boolean	considerRuntimeType Determines if the runtime type of a fixed value should be considered for the assignment to a return type.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	FixedValue(Assigner assigner, boolean considerRuntimeType) Creates a new fixed value instrumentation.

Method Summary

Modifier and Type	Method and Description
protected ByteCodeAppender.Size	apply(org.objectweb.asm.MethodVisitor methodVisitor, Instrumentation.Context instrumentationContext, MethodDescription instrumentedMethod, TypeDescription fixedValueType, StackManipulation valueLoadingInstruction) Blueprint method that for applying the actual instrumentation.
boolean	equals(Object other)
int	hashCode()
static Instrumentation	nullValue() Creates a fixed value instrumentation that returns null as a fixed value.
static FixedValue.AssignerConfigurable	reference(Object fixedValue) Other than value(Object), this function will create a fixed value instrumentation 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 instrumentation that will always defined a field in the instrumented class.
static FixedValue.AssignerConfigurable	value(Object fixedValue) Creates a fixed value instrumentation that returns a fixed value.

Methods inherited from class java.lang.Object

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

Methods inherited from interface net.bytebuddy.instrumentation.Instrumentation

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.

considerRuntimeType

protected final boolean considerRuntimeType

Determines if the runtime type of a fixed value should be considered for the assignment to a return type.

Constructor Detail

FixedValue

protected FixedValue(Assigner assigner,
                     boolean considerRuntimeType)

Creates a new fixed value instrumentation.

Parameters:

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

considerRuntimeType - If true, the runtime type of the given value will be considered for assigning the return type.

Method Detail

nullValue

public static Instrumentation nullValue()

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

Returns:

An instrumentation that represents the null value.

value

public static FixedValue.AssignerConfigurable value(Object fixedValue)

Creates a fixed value instrumentation 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.
• All primitive types and their wrapper type, i.e. Boolean, Byte, Short, Character, Integer, Long, Float and Double.
• A null reference.

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 the Java 7 types java.lang.invoke.MethodHandle and java.lang.invoke.MethodType are are currently not supported for constant pool storage.

Parameters:

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

Returns:

An instrumentation for the given fixedValue.

reference

public static FixedValue.AssignerConfigurable reference(Object fixedValue)

Other than value(Object), this function will create a fixed value instrumentation 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 instrumentation.

Returns:

An instrumentation 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 instrumentation 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 instrumentation but will cause an exception.

Parameters:

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

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

Returns:

An instrumentation for the given fixedValue.

apply

protected ByteCodeAppender.Size apply(org.objectweb.asm.MethodVisitor methodVisitor,
                                      Instrumentation.Context instrumentationContext,
                                      MethodDescription instrumentedMethod,
                                      TypeDescription fixedValueType,
                                      StackManipulation valueLoadingInstruction)

Blueprint method that for applying the actual instrumentation.

Parameters:

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

instrumentationContext - The instrumentation context for the given instrumentation.

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

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 instrumentation.

equals

public boolean equals(Object other)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object