/**
* Copyright 2013 Cloudera Inc.
*
* 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.kitesdk.data;
import org.kitesdk.data.spi.partition.PartitionFunctions;
import com.google.common.base.Objects;
import com.google.common.collect.Lists;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.commons.jexl2.Expression;
import org.apache.commons.jexl2.JexlEngine;
import org.kitesdk.data.spi.FieldPartitioner;
/**
* Internal utility class for persisting partition strategies,
* not a part of the public API.
*/
class PartitionExpression {
private JexlEngine engine;
private Expression expression;
private boolean isStrict;
public PartitionExpression(String expression, boolean isStrict) {
this.engine = new JexlEngine();
Map<String, Object> fns = new HashMap<String, Object>();
fns.put(null, PartitionFunctions.class);
this.engine.setFunctions(fns);
this.engine.setStrict(true);
this.engine.setSilent(false);
this.engine.setCache(10);
this.expression = engine.createExpression(expression);
this.isStrict = isStrict;
}
public PartitionStrategy evaluate() {
Object object = expression.evaluate(null);
if (object instanceof FieldPartitioner) {
return new PartitionStrategy(
Lists.newArrayList((FieldPartitioner) object));
} else if (object instanceof Object[]) {
/*
* JEXL doesn't recognize that [hash(...), range(...)] is an array of
* FieldPartitioner. Instead, it thinks it's Object[].
*/
List<FieldPartitioner> partitioners = Lists.newArrayList();
for (Object o : ((Object[]) object)) {
partitioners.add((FieldPartitioner) o);
}
return new PartitionStrategy(partitioners);
} else {
throw new IllegalArgumentException(
"Partition expression did not produce FieldPartitioner result (or array) for value:"
+ object);
}
}
/**
* Convert a PartitionStrategy into a serialized expression. This can be used
* to set a PartitionStrategy in an Avro property if the PartitionStrategy is
* passed as an object.
*/
public static String toExpression(PartitionStrategy partitionStrategy) {
List<FieldPartitioner> fieldPartitioners = partitionStrategy
.getFieldPartitioners();
if (fieldPartitioners.size() == 1) {
return PartitionFunctions.toExpression(fieldPartitioners.get(0));
}
StringBuilder sb = new StringBuilder();
sb.append("[");
for (FieldPartitioner fieldPartitioner : fieldPartitioners) {
if (sb.length() > 1) {
sb.append(", ");
}
sb.append(PartitionFunctions.toExpression(fieldPartitioner));
}
sb.append("]");
return sb.toString();
}
@Override
public String toString() {
return Objects.toStringHelper(this).add("expression", expression)
.add("isStrict", isStrict).add("engine", engine).toString();
}
}