code: private void fieldInsn(final int opcode, final Type ownerType,
              final String name, final Type fieldType) {
          mv.visitFieldInsn(opcode, ownerType.getInternalName(), name,
                  fieldType.getDescriptor());
      }
docs: Generates a get field or set field instruction.
  
  @param opcode
  the instruction's opcode.
  @param ownerType
  the class in which the field is defined.
  @param name
  the name of the field.
  @param fieldType
  the type of the field.