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/*
* Label.java July 2006
*
* Copyright (C) 2006, Niall Gallagher
*
* 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 org.simpleframework.xml.core;
import java.lang.annotation.Annotation;
import org.simpleframework.xml.strategy.Type;
/**
* The Label interface is used to describe an reference to
* a field annotated with an XML schema annotation. Because each field
* and annotation is different, there are different ways in which the
* annotation can be accessed. This provides a uniform means for
* accessing the field annotation details and the field properties.
*
* This also exposes a Converter object, which is used to
* convert an XML node into a property that can be assigned to the
* annotated field. Each converter returned is specific to the label
* and knows, based on the annotation, how to serialize the field.
*
* @author Niall Gallagher
*/
interface Label {
/**
* This is used to acquire the Decorator for this.
* A decorator is an object that adds various details to the
* node without changing the overall structure of the node. For
* example comments and namespaces can be added to the node with
* a decorator as they do not affect the deserialization.
*
* @return this returns the decorator associated with this
*/
Decorator getDecorator() throws Exception;
/**
* This is used to acquire the Type that the type
* provided is represented by. Typically this will return the
* field or method represented by the label. However, in the
* case of unions this will provide an override type.
*
* @param type this is the class to acquire the type for
*
* @return this returns the type represented by this class
*/
Type getType(Class type) throws Exception;
/**
* This is used to acquire the Label that the type
* provided is represented by. Typically this will return the
* same instance. However, in the case of unions this will
* look for an individual label to match the type provided.
*
* @param type this is the type to acquire the label for
*
* @return this returns the label represented by this type
*/
Label getLabel(Class type) throws Exception;
/**
* This returns a Collection of element names. This
* will typically contain both the name and path of the label.
* However, if this is a union it can contain many names and
* paths. This method should never return null.
*
* @return this returns the names of each of the elements
*/
String[] getNames() throws Exception;
/**
* This returns a Collection of element paths. This
* will typically contain only the path of the label, which is
* composed using the Path annotation and the name
* of the label. However, if this is a union it can contain many
* paths. This method should never return null.
*
* @return this returns the names of each of the elements
*/
String[] getPaths() throws Exception;
/**
* This is used to provide a configured empty value used when the
* annotated value is null. This ensures that XML can be created
* with required details regardless of whether values are null or
* not. It also provides a means for sensible default values.
*
* @param context this is the context object for the serialization
*
* @return this returns the string to use for default values
*/
Object getEmpty(Context context) throws Exception;
/**
* This method returns a Converter which can be used to
* convert an XML node into an object value and vice versa. The
* converter requires only the context object in order to perform
* serialization or deserialization of the provided XML node.
*
* @param context this is the context object for the serialization
*
* @return this returns an object that is used for conversion
*/
Converter getConverter(Context context) throws Exception;
/**
* This is used to acquire the name of the element or attribute
* that is used by the class schema. The name is determined by
* checking for an override within the annotation. If it contains
* a name then that is used, if however the annotation does not
* specify a name the the field or method name is used instead.
*
* @return returns the name that is used for the XML property
*/
String getName() throws Exception;
/**
* This is used to acquire the path of the element or attribute
* that is used by the class schema. 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 the XML property
*/
String getPath() throws Exception;
/**
* This method is used to return an XPath expression that is
* used to represent the position of this label. 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() throws Exception;
/**
* This returns the dependent type for the annotation. This type
* is the type other than the annotated field or method type that
* the label depends on. For the ElementList and
* the ElementArray this is the component type that
* is deserialized individually and inserted into the container.
*
* @return this is the type that the annotation depends on
*/
Type getDependent() throws Exception;
/**
* This is used to either provide the entry value provided within
* the annotation or compute a entry value. If the entry string
* is not provided the the entry value is calculated as the type
* of primitive the object is as a simplified class name.
*
* @return this returns the name of the XML entry element used
*/
String getEntry() throws Exception;
/**
* This is the key used to represent this label. The key is used
* to store the parameter in hash containers. Typically the
* key is generated from the paths associated with the label.
*
* @return this is the key used to represent the label
*/
Object getKey() throws Exception;
/**
* This acquires the annotation associated with this label. This
* is typically the annotation acquired from the field or method.
* However, in the case of unions this will return the actual
* annotation within the union group that this represents.
*
* @return this returns the annotation that this represents
*/
Annotation getAnnotation();
/**
* This is used to acquire the contact object for this label. The
* contact retrieved can be used to set any object or primitive that
* has been deserialized, and can also be used to acquire values to
* be serialized in the case of object persistence. All contacts
* that are retrieved from this method will be accessible.
*
* @return returns the field that this label is representing
*/
Contact getContact();
/**
* This acts as a convenience method used to determine the type of
* the field this represents. This is used when an object is written
* to XML. It determines whether a class attribute
* is required within the serialized XML element, that is, if the
* class returned by this is different from the actual value of the
* object to be serialized then that type needs to be remembered.
*
* @return this returns the type of the field class
*/
Class getType();
/**
* This is used to acquire the name of the element or attribute
* as taken from the annotation. If the element or attribute
* explicitly specifies a name then that name is used for the
* XML element or attribute used. If however no overriding name
* is provided then the method or field is used for the name.
*
* @return returns the name of the annotation for the contact
*/
String getOverride();
/**
* This is used to determine whether the annotation requires it
* and its children to be written as a CDATA block. This is done
* when a primitive or other such element requires a text value
* and that value needs to be encapsulated within a CDATA block.
*
* @return this returns true if the element requires CDATA
*/
boolean isData();
/**
* Determines whether the XML attribute or element is required.
* This ensures that if an XML element is missing from a document
* that deserialization can continue. Also, in the process of
* serialization, if a value is null it does not need to be
* written to the resulting XML document.
*
* @return true if the label represents a some required data
*/
boolean isRequired();
/**
* This method is used to determine if the label 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 label is a collection. If the
* label represents a collection then any original assignment to
* the field or method can be written to without the need to
* create a new collection. This allows obscure collections to be
* used and also allows initial entries to be maintained.
*
* @return true if the label represents a collection value
*/
boolean isCollection();
/**
* This is used to determine whether the label represents an
* inline XML entity. The ElementList annotation
* and the Text annotation represent inline
* items. This means that they contain no containing element
* and so can not specify overrides or special attributes.
*
* @return this returns true if the annotation is inline
*/
boolean isInline();
/**
* This is used to determine if the label represents text. If
* a label represents text it typically does not have a name,
* instead the empty string represents the name. Also text
* labels can not exist with other text labels, or elements.
*
* @return this returns true if this label represents text
*/
boolean isText();
/**
* This is used to determine if an annotated list is a text
* list. A text list is a list of elements that also accepts
* free text. Typically this will be an element list union that
* will allow unstructured XML such as XHTML to be parsed.
*
* @return returns true if the label represents a text list
*/
boolean isTextList();
/**
* This is used to determine if this label is a union. If this
* is true then this label represents a number of labels and
* is simply a wrapper for these labels.
*
* @return this returns true if the label represents a union
*/
boolean isUnion();
/**
* This is used to describe the annotation and method or field
* that this label represents. This is used to provide error
* messages that can be used to debug issues that occur when
* processing a method. This should provide enough information
* such that the problem can be isolated correctly.
*
* @return this returns a string representation of the label
*/
String toString();
}