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/*
* ElementLabel.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.Element;
import org.simpleframework.xml.strategy.Type;
import org.simpleframework.xml.stream.Format;
import org.simpleframework.xml.stream.Style;
/**
* The ElementLabel represents a label that is used to
* represent an XML element in a class schema. This element can be
* used to convert an XML node into either a primitive value such as
* a string or composite object value, which is itself a schema for
* a section of XML within the XML document.
*
* @author Niall Gallagher
*
* @see org.simpleframework.xml.Element
*/
class ElementLabel extends TemplateLabel {
/**
* This is the decorator that is associated with the element.
*/
private Decorator decorator;
/**
* The contact that this element label represents.
*/
private Introspector detail;
/**
* This is a cache of the expression for this element.
*/
private Expression cache;
/**
* References the annotation that was used by the field.
*/
private Element label;
/**
* This is the format used to style this element label.
*/
private Format format;
/**
* This is the name of the element for this label instance.
*/
private String override;
/**
* This is the path of the XML element from the annotation.
*/
private String path;
/**
* This is the name of the XML element from the annotation.
*/
private String name;
/**
* This is the expected type that has been declared for this.
*/
private Class expect;
/**
* This is the type of the class that the field references.
*/
private Class type;
/**
* This is used to determine if the element is required.
*/
private boolean required;
/**
* This is used to determine if the element is data.
*/
private boolean data;
/**
* Constructor for the ElementLabel object. This is
* used to create a label that can convert a XML node into a
* composite object or a primitive type from an XML element.
*
* @param contact this is the field that this label represents
* @param label this is the annotation for the contact
* @param format this is the format used to style this element
*/
public ElementLabel(Contact contact, Element label, Format format) {
this.detail = new Introspector(contact, this, format);
this.decorator = new Qualifier(contact);
this.required = label.required();
this.type = contact.getType();
this.override = label.name();
this.expect = label.type();
this.data = label.data();
this.format = format;
this.label = 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
*/
public Decorator getDecorator() throws Exception {
return decorator;
}
/**
* 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
*/
public Type getType(Class type){
Type contact = getContact();
if(expect == void.class) {
return contact;
}
return new OverrideType(contact, expect);
}
/**
* Creates a converter that can be used to transform an XML node to
* an object and vice versa. The converter created will handles
* only XML elements and requires the context object to be provided.
*
* @param context this is the context object used for serialization
*
* @return this returns a converter for serializing XML elements
*/
public Converter getConverter(Context context) throws Exception {
Type type = getContact();
if(context.isPrimitive(type)) {
return new Primitive(context, type);
}
if(expect == void.class) {
return new Composite(context, type);
}
return new Composite(context, type, expect);
}
/**
* 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
*/
public Object getEmpty(Context context) {
return null;
}
/**
* 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
*/
public String getName() throws Exception{
if(name == null) {
Style style = format.getStyle();
String value = detail.getName();
name = style.getElement(value);
}
return name;
}
/**
* 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
*/
public String getPath() throws Exception {
if(path == null) {
Expression expression = getExpression();
String name = getName();
path = expression.getElement(name);
}
return path;
}
/**
* 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
*/
public Expression getExpression() throws Exception {
if(cache == null) {
cache = detail.getExpression();
}
return cache;
}
/**
* 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
*/
public Annotation getAnnotation() {
return label;
}
/**
* 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 contact that this label is representing
*/
public Contact getContact() {
return detail.getContact();
}
/**
* 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
*/
public String getOverride() {
return override;
}
/**
* This acts as a convenience method used to determine the type of
* contact 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 contact class
*/
public Class getType() {
if(expect == void.class) {
return type;
}
return expect;
}
/**
* This is used to determine whether the XML 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
*/
public boolean isRequired() {
return required;
}
/**
* 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
*/
public boolean isData() {
return data;
}
/**
* 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 will provide enough information
* such that the problem can be isolated correctly.
*
* @return this returns a string representation of the label
*/
public String toString() {
return detail.toString();
}
}