# Interface UnknownAttributeReader

public interface UnknownAttributeReader
Unknown (non-standard) attributes may be read via user-defined factory objects that can be registered with the Attribute.addAttributeReader method. These factory objects should implement this interface.

Since:
  6.0
See Also:
  - `Attribute`

- ## Method Summary

  Modifier and Type
  Method
  Description
  `Attribute`
  `createAttribute(int nameIndex, int length, DataInput file, ConstantPool constantPool)`
  When this attribute reader is added via the static method Attribute.addAttributeReader, an attribute name is associated with it.

- ## Method Details

  - ### createAttribute

    Attribute createAttribute(int nameIndex, int length, DataInput file, ConstantPool constantPool)
    When this attribute reader is added via the static method Attribute.addAttributeReader, an attribute name is associated with it. As the class file parser parses attributes, it will call various AttributeReaders based on the name of the attributes it is constructing.
    Parameters:
      `nameIndex` - An index into the constant pool, indexing a ConstantUtf8 that represents the name of the attribute.
      `length` - The length of the data contained in the attribute. This is written into the constant pool and should agree with what the factory expects the length to be.
      `file` - This is the data input that the factory needs to read its data from.
      `constantPool` - This is the constant pool associated with the Attribute that we are constructing.
    Returns:
      The user-defined AttributeReader should take this data and use it to construct an attribute. In the case of errors, a null can be returned which will cause the parsing of the class file to fail.
    See Also:
      - `Attribute.addAttributeReader(String, UnknownAttributeReader)`