/*
* Copyright 2004-2009 the original author or authors.
*
* 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.compass.core.converter.basic;
import org.compass.core.Property;
import org.compass.core.Resource;
import org.compass.core.converter.ConversionException;
import org.compass.core.converter.mapping.ContextResourcePropertyConverter;
import org.compass.core.mapping.Mapping;
import org.compass.core.mapping.ResourcePropertyMapping;
import org.compass.core.marshall.MarshallingContext;
/**
* An easy to use abstact class for Basic converters. Handles converters that usually deals with String
* as a result of the conversion.
*
* <p>Allows to override the actual marshalling and un-marshalling of object to strings. In order to override
* marshalling, override {@link #doToString(Object,org.compass.core.mapping.ResourcePropertyMapping,org.compass.core.marshall.MarshallingContext)}
* and in order to override un-marshalling overrode
* {@link #doFromString(String,org.compass.core.mapping.ResourcePropertyMapping,org.compass.core.marshall.MarshallingContext)}.
*
* @author kimchy
*/
public abstract class AbstractBasicConverter<T> implements ContextResourcePropertyConverter<T> {
public boolean marshall(Resource resource, T root, Mapping mapping, MarshallingContext context)
throws ConversionException {
ResourcePropertyMapping resourcePropertyMapping = (ResourcePropertyMapping) mapping;
// don't save a null value if the context does not states so
if (root == null && !handleNulls(resourcePropertyMapping, context)) {
return false;
}
String sValue;
if (root instanceof String && context.getResourceFactory().isNullValue((String) root)) {
// check if this is a null value (since sometimes we get injected with a null value for non string types)
sValue = (String) root;
} else {
sValue = toString(root, resourcePropertyMapping, context);
}
Property p = createProperty(sValue, resourcePropertyMapping, context);
doSetBoost(p, root, resourcePropertyMapping, context);
resource.addProperty(p);
return resourcePropertyMapping.getStore() != Property.Store.NO;
}
public T unmarshall(Resource resource, Mapping mapping, MarshallingContext context) throws ConversionException {
ResourcePropertyMapping resourcePropertyMapping = (ResourcePropertyMapping) mapping;
if (resourcePropertyMapping.getStore() == Property.Store.NO) {
// it is not stored, so don't bother with converting it
return null;
}
String propertyName = resourcePropertyMapping.getPath().getPath();
Property p = resource.getProperty(propertyName);
// don't set anything if null
if (p == null) {
return null;
}
return fromString(p.getStringValue(), resourcePropertyMapping, context);
}
/**
* Creates a new property to be added to the resource during the marshalling process. Allows
* sub classes to override ti in order to modify the created property.
*
* @param value The value of the property
* @param resourcePropertyMapping The resource mapping definition of the property
* @param context The context (allows to get the search engine from it)
* @return The property to be added to the Resource
*/
protected Property createProperty(String value, ResourcePropertyMapping resourcePropertyMapping, MarshallingContext context) {
return context.getResourceFactory().createProperty(value, resourcePropertyMapping);
}
/**
* <p>Should the converter handle nulls? Handling nulls means should the
* converter process nulls or not. Usually the converter will not
* persist null values, but sometimes it might be needed
* ({@link org.compass.core.marshall.MarshallingContext#handleNulls()}).
*
* <p>If a specific null value is configured with the {@link org.compass.core.mapping.ResourcePropertyMapping}
* then the converter will always handle nulls and write it.
*
* @param context The marshalling context
* @return <code>true</code> if the converter should handle null values
*/
protected boolean handleNulls(ResourcePropertyMapping resourcePropertyMapping, MarshallingContext context) {
return resourcePropertyMapping.hasNullValue() || context.handleNulls();
}
/**
* If the converter handle nulls, the value that will be stored in the
* search engine for <code>null</code> values (during the marshall process). Uses
* {@link org.compass.core.mapping.ResourcePropertyMapping#getNullValue()}.
*
* @param resourcePropertyMapping The resource proeprty mapping to get the null value from
* @param context The marshalling context
* @return Null value that will be inserted for <code>null</code>s.
*/
protected String getNullValue(ResourcePropertyMapping resourcePropertyMapping, MarshallingContext context) {
return resourcePropertyMapping.getNullValue();
}
/**
* Does this value represents a null value. If the {@link org.compass.core.mapping.ResourcePropertyMapping}
* is configured with a null value, then returns <code>true</code> if the null value equals the value read
* from the index. If the resource property mapping is not configured with a null value, checks if this
* it has the default value representing a null value.
*/
protected boolean isNullValue(String value, ResourcePropertyMapping resourcePropertyMapping, MarshallingContext context) {
if (value == null) {
return true;
}
if (resourcePropertyMapping.hasNullValue()) {
return resourcePropertyMapping.getNullValue().equals(value);
}
// the default null value is an empty string
return value.length() == 0;
}
/**
* <p>A simple extension point that allows to set the boost value for the created {@link Property}.
*
* <p>The default implemenation uses the statically defined boost value in the mapping definition
* ({@link org.compass.core.mapping.ResourcePropertyMapping#getBoost()}) to set the boost level
* using {@link Property#setBoost(float)}
*
* @param property The property to set the boost on
* @param root The object that is marshalled into a property
* @param resourcePropertyMapping The Resource Property Mapping definition
* @throws ConversionException
*/
protected void doSetBoost(Property property, T root, ResourcePropertyMapping resourcePropertyMapping,
MarshallingContext context) throws ConversionException {
property.setBoost(resourcePropertyMapping.getBoost());
}
/**
* Implementation calls {@link #toString(Object,org.compass.core.mapping.ResourcePropertyMapping,org.compass.core.marshall.MarshallingContext)}
* with <code>null</code> value for the context parameter.
*
* <p>Note, please don't override this method, please override {@link #doToString(Object,org.compass.core.mapping.ResourcePropertyMapping,org.compass.core.marshall.MarshallingContext)}
* to change the how the object gets marshalled into a String.
*/
public String toString(T o, ResourcePropertyMapping resourcePropertyMapping) {
return toString(o, resourcePropertyMapping, null);
}
/**
* Implementation handle nulls and if the object is not null, delegates to
* {@link #doToString(Object,org.compass.core.mapping.ResourcePropertyMapping,org.compass.core.marshall.MarshallingContext)}.
*
* <p>Note, please don't override this method, please override {@link #doToString(Object,org.compass.core.mapping.ResourcePropertyMapping,org.compass.core.marshall.MarshallingContext)}
* to change the how the object gets marshalled into a String.
*/
public String toString(T o, ResourcePropertyMapping resourcePropertyMapping, MarshallingContext context) {
String sValue;
if (o != null) {
if (o instanceof String) {
// if we got a string, try and convert it
// if we got a class cast exception, just assume that this is the value that we want to store
// (we expect number for example, but the use provided a String, assuming he knows what he wants)
try {
sValue = doToString(o, resourcePropertyMapping, context);
} catch (ClassCastException e) {
sValue = (String) o;
}
} else {
sValue = doToString(o, resourcePropertyMapping, context);
}
} else {
sValue = getNullValue(resourcePropertyMapping, context);
}
return sValue;
}
/**
* Allows to override to toString operation. Default implementation calls the object <code>toString</code>.
*
* <p>Note, the marshalling context might be null.
*/
protected String doToString(T o, ResourcePropertyMapping resourcePropertyMapping, MarshallingContext context) {
return o.toString();
}
/**
* Calls {@link #fromString(String, org.compass.core.mapping.ResourcePropertyMapping, org.compass.core.marshall.MarshallingContext)}
* with a null value for the context.
*/
public T fromString(String str, ResourcePropertyMapping resourcePropertyMapping) throws ConversionException {
return fromString(str, resourcePropertyMapping, null);
}
/**
* Performs null checks (by calling {@link #isNullValue(String, org.compass.core.mapping.ResourcePropertyMapping, org.compass.core.marshall.MarshallingContext)})
* and then calls {@link #doFromString(String, org.compass.core.mapping.ResourcePropertyMapping, org.compass.core.marshall.MarshallingContext)}
* if the value is not <code>null</code>.
*/
public T fromString(String str, ResourcePropertyMapping resourcePropertyMapping, MarshallingContext context) throws ConversionException {
if (isNullValue(str, resourcePropertyMapping, context)) {
return null;
}
return doFromString(str, resourcePropertyMapping, context);
}
/**
* Override the from String in order to un-marshall the String back into its object representation.
*/
protected abstract T doFromString(String str, ResourcePropertyMapping resourcePropertyMapping, MarshallingContext context) throws ConversionException;
/**
* Return <code>false</code>. Specific parsers that can convert on query string should override this method
* and return <code>true</code>.
*/
public boolean canNormalize() {
return false;
}
/**
* By default for all converters simply return <code>null</code>.
*/
public Property.Index suggestIndex() {
return null;
}
public Property.TermVector suggestTermVector() {
return null;
}
public Property.Store suggestStore() {
return null;
}
/**
* By default for all converters simply return <code>null</code>.
*/
public Boolean suggestOmitNorms() {
return null;
}
/**
* By default for all converters simply return <code>null</code>.
*/
public Boolean suggestOmitTf() {
return null;
}
}