content: /*
   * Parameter.java July 2009
   *
   * Copyright (C) 2009, Niall Gallagher <niallg@users.sf.net>
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or 
   * implied. See the License for the specific language governing 
   * permissions and limitations under the License.
   */
  
  package com.aliyun.odps.simpleframework.xml.core;
  
  import java.lang.annotation.Annotation;
  
  /**
   * The <code>Parameter</code> is used to represent a constructor 
   * parameter. It contains the XML annotation used on the parameter
   * as well as the name of the parameter and its position index.
   * A parameter is used to validate against the annotated methods 
   * and fields and also to determine the deserialized values that
   * should be injected in to the constructor to instantiate it.
   * 
   * @author Niall Gallagher
   */
  interface Parameter {
     
     /**
      * This is the key used to represent the parameter. The key is
      * used to store the parameter in hash containers. Unlike the
      * path is not necessarily the path for the parameter.
      * 
      * @return this is the key used to represent the parameter
      */
     Object getKey();
     
     /**
      * This is used to acquire the annotated type class. The class
      * is the type that is to be deserialized from the XML. This
      * is used to validate against annotated fields and methods.
      * 
      * @return this returns the type used for the parameter
      */
     Class getType();
     
     /**
      * This returns the index position of the parameter in the
      * constructor. This is used to determine the order of values
      * that are to be injected in to the constructor.
      * 
      * @return this returns the index for the parameter
      */
     int getIndex();
     
     /**
      * This is used to acquire the annotation that is used for the
      * parameter. The annotation provided will be an XML annotation
      * such as the <code>Element</code> or <code>Attribute</code>
      * annotation.
      * 
      * @return this returns the annotation used on the parameter
      */
     Annotation getAnnotation();
  
     /**
      * This method is used to return an XPath expression that is 
      * used to represent the position of this parameter. If there is 
      * no XPath expression associated with this then an empty path 
      * is returned. This will never return a null expression.
      * 
      * @return the XPath expression identifying the location
      */
     Expression getExpression(); 
     
     /**
      * This is used to acquire the name of the parameter that this
      * represents. The name is determined using annotation and 
      * the name attribute of that annotation, if one is provided.
      * 
      * @return this returns the name of the annotated parameter
      */
     String getName();
     
     /**
      * This is used to acquire the path of the element or attribute
      * represented by this parameter. The path is determined by
      * acquiring the XPath expression and appending the name of the
      * label to form a fully qualified path.
      * 
      * @return returns the path that is used for this parameter
      */
     String getPath();
     
     /**
      * This is used to determine if the parameter is required. If 
      * an attribute is not required then it can be null. Which 
      * means that we can inject a null value. Also, this means we
      * can match constructors in a more flexible manner.
      * 
      * @return this returns true if the parameter is required
      */
     boolean isRequired();
     
     /**
      * This is used to determine if the parameter is primitive. A
      * primitive parameter must not be null. As there is no way to
      * provide the value to the constructor. A default value is 
      * not a good solution as it affects the constructor score.
      * 
      * @return this returns true if the parameter is primitive
      */
     boolean isPrimitive();
     
     /**
      * This method is used to determine if the parameter represents 
      * an attribute. This is used to style the name so that elements
      * are styled as elements and attributes are styled as required.
      * 
      * @return this is used to determine if this is an attribute
      */
     boolean isAttribute();
     
     /**
      * This is used to determine if the parameter represents text. 
      * If this represents text it typically does not have a name,
      * instead the empty string represents the name. Also text
      * parameters can not exist with other text parameters.
      * 
      * @return returns true if this parameter represents text
      */
     boolean isText();
     
     /**
      * This is used to provide a textual representation of the 
      * parameter. Providing a string describing the parameter is
      * useful for debugging and for exception messages.
      * 
      * @return this returns the string representation for this
      */
     String toString();
  }
  