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/*
* ClassInstantiator.java December 2009
*
* Copyright (C) 2009, 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.util.ArrayList;
import java.util.List;
/**
* The ClassInstantiator is used for instantiating
* objects using either the default no argument constructor or one
* that takes deserialized values as parameters. This also exposes
* the parameters and constructors used to instantiate the object.
*
* @author Niall Gallagher
*/
class ClassInstantiator implements Instantiator {
/**
* This contains a list of all the creators for the class.
*/
private final List creators;
/**
* This is used to acquire a parameter by the parameter name.
*/
private final ParameterMap registry;
/**
* This represents the default no argument constructor used.
*/
private final Creator primary;
/**
* This contains the details for the class to instantiate.
*/
private final Detail detail;
/**
* Constructor for the ClassCreator object. This is
* used to create an object that contains all information that
* relates to the construction of an instance.
*
* @param creators contains the list of all constructors available
* @param primary this is the default no argument constructor
* @param registry contains all parameters for the constructors
* @param detail contains the details for the instantiated class
*/
public ClassInstantiator(List creators, Creator primary, ParameterMap registry, Detail detail) {
this.creators = creators;
this.registry = registry;
this.primary = primary;
this.detail = detail;
}
/**
* This is used to determine if this Creator has a
* default constructor. If the class does contain a no argument
* constructor then this will return true.
*
* @return true if the class has a default constructor
*/
public boolean isDefault() {
int count = creators.size();
if(count <= 1) {
return primary != null;
}
return false;
}
/**
* This is used to instantiate the object using the default no
* argument constructor. If for some reason the object can not be
* instantiated then this will throw an exception with the reason.
*
* @return this returns the object that has been instantiated
*/
public Object getInstance() throws Exception {
return primary.getInstance();
}
/**
* This is used to instantiate the object using a constructor that
* takes deserialized objects as arguments. The object that have
* been deserialized can be taken from the Criteria
* object which contains the deserialized values.
*
* @param criteria this contains the criteria to be used
*
* @return this returns the object that has been instantiated
*/
public Object getInstance(Criteria criteria) throws Exception {
Creator creator = getCreator(criteria);
if(creator == null) {
throw new PersistenceException("Constructor not matched for %s", detail);
}
return creator.getInstance(criteria);
}
/**
* This is used to acquire an Instantiator which is used
* to instantiate the object. If there is no match for the instantiator
* then the default constructor is provided.
*
* @param criteria this contains the criteria to be used for this
*
* @return this returns the instantiator that has been matched
*/
private Creator getCreator(Criteria criteria) throws Exception {
Creator result = primary;
double max = 0.0;
for(Creator instantiator : creators) {
double score = instantiator.getScore(criteria);
if(score > max) {
result = instantiator;
max = score;
}
}
return result;
}
/**
* This is used to acquire the named Parameter from
* the creator. A parameter is taken from the constructor which
* contains annotations for each object that is required. These
* parameters must have a matching field or method.
*
* @param name this is the name of the parameter to be acquired
*
* @return this returns the named parameter for the creator
*/
public Parameter getParameter(String name) {
return registry.get(name);
}
/**
* This is used to acquire all parameters annotated for the class
* schema. Providing all parameters ensures that they can be
* validated against the annotated methods and fields to ensure
* that each parameter is valid and has a corresponding match.
*
* @return this returns the parameters declared in the schema
*/
public List getParameters() {
return registry.getAll();
}
/**
* This is used to acquire all of the Instantiator
* objects used to create an instance of the object. Each represents
* a constructor and contains the parameters to the constructor.
* This is primarily used to validate each constructor against the
* fields and methods annotated to ensure they are compatible.
*
* @return this returns a list of instantiators for the creator
*/
public List getCreators() {
return new ArrayList(creators);
}
/**
* This is used to acquire a description of the creator. This is
* useful when debugging an issue as it allows a representation
* of the instance to be viewed with the class it represents.
*
* @return this returns a visible description of the creator
*/
public String toString() {
return String.format("creator for %s", detail);
}
}