/*
* Copyright 2014 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.springframework.data.hadoop.store.partition;
import java.util.Map;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.fs.Path;
import org.springframework.data.hadoop.store.expression.MapExpressionMethods;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpressionParser;
/**
* A {@link PartitionStrategy} which is used to provide a generic partitioning support using Spring SpEL.
*
* @author Janne Valkealahti
*
*/
public class DefaultPartitionStrategy<T extends Object> extends AbstractPartitionStrategy<T,Map<String,Object>> {
private final static Log log = LogFactory.getLog(DefaultPartitionStrategy.class);
/**
* Instantiates a new default partition strategy.
*
* @param expression the expression
*/
public DefaultPartitionStrategy(Expression expression) {
this(expression, null);
}
/**
* Instantiates a new default partition strategy with
* {@link EvaluationContext}.
*
* @param expression the expression
* @param evaluationContext the evaluation context
*/
public DefaultPartitionStrategy(Expression expression, EvaluationContext evaluationContext) {
super(new MapPartitionResolver(expression, evaluationContext), new MapPartitionKeyResolver<T>());
}
/**
* Instantiates a new default partition strategy.
*
* @param expression the expression
*/
public DefaultPartitionStrategy(String expression) {
this(expression, null);
}
/**
* Instantiates a new default partition strategy with
* {@link EvaluationContext}.
*
* @param expression the expression
* @param evaluationContext the evaluation context
*/
public DefaultPartitionStrategy(String expression, EvaluationContext evaluationContext) {
super(new MapPartitionResolver(expression, evaluationContext), new MapPartitionKeyResolver<T>());
}
/**
* A {@link PartitionResolver} which uses an {@link Expression} together with
* {@link MapExpressionMethods} to evaluate new {@link Path}s.
*/
private static class MapPartitionResolver implements PartitionResolver<Map<String,Object>> {
private final Expression expression;
private final MapExpressionMethods methods;
public MapPartitionResolver(String expression, EvaluationContext evaluationContext) {
ExpressionParser parser = new SpelExpressionParser();
this.expression = parser.parseExpression(expression);
this.methods = new MapExpressionMethods(evaluationContext);
log.info("Using expression=[" + this.expression.getExpressionString() + "]");
}
public MapPartitionResolver(Expression expression, EvaluationContext evaluationContext) {
this.expression = expression;
this.methods = new MapExpressionMethods(evaluationContext);
log.info("Using expression=[" + this.expression.getExpressionString() + "]");
}
@Override
public Path resolvePath(Map<String,Object> partitionKey) {
return new Path(methods.getValue(expression, partitionKey, String.class));
}
}
/**
* A {@link PartitionKeyResolver} which simply creates a new {@link Map}
* as a partition key using an passed in entity.
*/
private static class MapPartitionKeyResolver<T extends Object> implements PartitionKeyResolver<T,Map<String,Object>> {
@Override
public Map<String,Object> resolvePartitionKey(T entity) {
return new DefaultPartitionKey(entity);
}
}
}