Package net.bytebuddy.asm

Annotation Type Advice.FieldValue

  • @Documented
@Retention(RUNTIME)
@Target(PARAMETER)
public static @interface Advice.FieldValue

    Indicates that the annotated parameter should be mapped to a field in the scope of the instrumented type.

    Setting value() is optional. If the value is not set, the field value attempts to bind a setter's or getter's field if the intercepted method is an accessor method. Otherwise, the binding renders the target method to be an illegal candidate for binding.

    Important: Parameters with this option must not be used when from a constructor in combination with Advice.OnMethodEnter and a non-static field where the this reference is not available.

    Note: As the mapping is virtual, Byte Buddy might be required to reserve more space on the operand stack than the optimal value when accessing this parameter. This does not normally matter as the additional space requirement is minimal. However, if the runtime performance of class creation is secondary, one can require ASM to recompute the optimal frames by setting ClassWriter.COMPUTE_MAXS. This is however only relevant when writing to a non-static field.

    Important: Don't confuse this annotation with FieldValue or MemberSubstitution.FieldValue. This annotation should be used only in combination with Advice.

    See Also:
    Advice, Advice.OnMethodEnter, Advice.OnMethodExit

    • Optional Element Summary

      Optional Elements 
      Modifier and Type Optional Element Description
      java.lang.Class<?> declaringType
      Returns the type that declares the field that should be mapped to the annotated parameter.
      boolean readOnly
      Indicates if it is possible to write to this parameter.
      Assigner.Typing typing
      The typing that should be applied when assigning the field value.
      java.lang.String value
      Returns the name of the field.

    • Element Detail

      • value

        java.lang.String value
        Returns the name of the field.
        Returns:
        The name of the field.
        Default:
        ""

      • declaringType

        java.lang.Class<?> declaringType
        Returns the type that declares the field that should be mapped to the annotated parameter. If this property is set to void, the field is looked up implicitly within the instrumented class's class hierarchy. The value can also be set to TargetType in order to look up the type on the instrumented type.
        Returns:
        The type that declares the field, void if this type should be determined implicitly or TargetType for the instrumented type.
        Default:
        void.class

      • readOnly

        boolean readOnly

        Indicates if it is possible to write to this parameter. If this property is set to false, the annotated type must be equal to the type declaring the instrumented method if the typing is not also set to Assigner.Typing.DYNAMIC. If this property is set to true, the annotated parameter can be any super type of the instrumented method's declaring type.

        Important: This property must be set to true if the advice method is not inlined.

        Returns:
        true if this parameter is read-only.
        Default:
        true

      • typing

        Assigner.Typing typing
        The typing that should be applied when assigning the field value.
        Returns:
        The typing to apply upon assignment.
        Default:
        net.bytebuddy.implementation.bytecode.assign.Assigner.Typing.STATIC