/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.apache.howl.data.schema;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.howl.common.HowlException;
/**
* HowlSchema. This class is NOT thread-safe.
*/
public class HowlSchema implements Serializable{
private static final long serialVersionUID = 1L;
private final List<HowlFieldSchema> fieldSchemas;
private final Map<String,Integer> fieldPositionMap;
private final List<String> fieldNames;
/**
*
* @param fieldSchemas is now owned by HowlSchema. Any subsequent modifications
* on fieldSchemas won't get reflected in HowlSchema.
*/
public HowlSchema(final List<HowlFieldSchema> fieldSchemas){
this.fieldSchemas = new ArrayList<HowlFieldSchema>(fieldSchemas);
int idx = 0;
fieldPositionMap = new HashMap<String,Integer>();
fieldNames = new ArrayList<String>();
for (HowlFieldSchema field : fieldSchemas){
fieldPositionMap.put(field.getName(), idx);
fieldNames.add(field.getName());
idx++;
}
}
public void append(final HowlFieldSchema hfs) throws HowlException{
if(hfs == null || fieldSchemas == null){
throw new HowlException("Attempt to append null HowlFieldSchema in HowlSchema.");
}
//TODO Addition of existing field should not be allowed in Schema.
//Need to enforce that. For that to happen, field schema needs to implement Comparable.
// Also, HowlSchema needs to implement Comparable.
this.fieldSchemas.add(hfs);
String fieldName = hfs.getName();
this.fieldNames.add(fieldName);
this.fieldPositionMap.put(fieldName, this.size()-1);
}
/**
* Users are not allowed to modify the list directly, since HowlSchema
* maintains internal state. Use append/remove to modify the schema.
*/
public List<HowlFieldSchema> getFields(){
return Collections.unmodifiableList(this.fieldSchemas);
}
/**
* @param fieldName
* @return the index of field named fieldName in Schema. If field is not
* present, returns null.
*/
public Integer getPosition(String fieldName) {
return fieldPositionMap.get(fieldName);
}
public HowlFieldSchema get(String fieldName) throws HowlException {
return get(getPosition(fieldName));
}
public List<String> getFieldNames(){
return this.fieldNames;
}
public HowlFieldSchema get(int position) {
return fieldSchemas.get(position);
}
public int size(){
return fieldSchemas.size();
}
public void remove(final HowlFieldSchema howlFieldSchema) throws HowlException {
if(!fieldSchemas.contains(howlFieldSchema)){
throw new HowlException("Attempt to delete a non-existent column from Howl Schema: "+ howlFieldSchema);
}
fieldSchemas.remove(howlFieldSchema);
fieldPositionMap.remove(howlFieldSchema);
fieldNames.remove(howlFieldSchema.getName());
}
@Override
public String toString() {
boolean first = true;
StringBuilder sb = new StringBuilder();
for (HowlFieldSchema hfs : fieldSchemas){
if (!first){
sb.append(",");
}else{
first = false;
}
if (hfs.getName() != null){
sb.append(hfs.getName());
sb.append(":");
}
sb.append(hfs.toString());
}
return sb.toString();
}
}