Java tutorial
/** * 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.hadoop.hive.serde2; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.hive.serde.serdeConstants; import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector; import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorFactory; import org.apache.hadoop.hive.serde2.objectinspector.StructField; import org.apache.hadoop.hive.serde2.objectinspector.StructObjectInspector; import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory; import org.apache.hadoop.hive.serde2.objectinspector.primitive.StringObjectInspector; import org.apache.hadoop.io.Text; import org.apache.hadoop.io.Writable; import java.io.CharArrayReader; import java.io.IOException; import java.io.Reader; import java.io.StringWriter; import java.io.Writer; import java.util.ArrayList; import java.util.Arrays; import java.util.List; import java.util.Properties; import au.com.bytecode.opencsv.CSVReader; import au.com.bytecode.opencsv.CSVWriter; /** * OpenCSVSerde use opencsv to deserialize CSV format. * Users can specify custom separator, quote or escape characters. And the default separator(\), * quote("), and escape characters(\) are the same as the opencsv library. * */ @SerDeSpec(schemaProps = { serdeConstants.LIST_COLUMNS, OpenCSVSerde.SEPARATORCHAR, OpenCSVSerde.QUOTECHAR, OpenCSVSerde.ESCAPECHAR }) public final class OpenCSVSerde extends AbstractSerDe { public static final Log LOG = LogFactory.getLog(OpenCSVSerde.class.getName()); private ObjectInspector inspector; private String[] outputFields; private int numCols; private List<String> row; private char separatorChar; private char quoteChar; private char escapeChar; public static final String SEPARATORCHAR = "separatorChar"; public static final String QUOTECHAR = "quoteChar"; public static final String ESCAPECHAR = "escapeChar"; @Override public void initialize(final Configuration conf, final Properties tbl) throws SerDeException { final List<String> columnNames = Arrays.asList(tbl.getProperty(serdeConstants.LIST_COLUMNS).split(",")); numCols = columnNames.size(); final List<ObjectInspector> columnOIs = new ArrayList<ObjectInspector>(numCols); for (int i = 0; i < numCols; i++) { columnOIs.add(PrimitiveObjectInspectorFactory.javaStringObjectInspector); } inspector = ObjectInspectorFactory.getStandardStructObjectInspector(columnNames, columnOIs); outputFields = new String[numCols]; row = new ArrayList<String>(numCols); for (int i = 0; i < numCols; i++) { row.add(null); } separatorChar = getProperty(tbl, SEPARATORCHAR, CSVWriter.DEFAULT_SEPARATOR); quoteChar = getProperty(tbl, QUOTECHAR, CSVWriter.DEFAULT_QUOTE_CHARACTER); escapeChar = getProperty(tbl, ESCAPECHAR, CSVWriter.DEFAULT_ESCAPE_CHARACTER); } private char getProperty(final Properties tbl, final String property, final char def) { final String val = tbl.getProperty(property); if (val != null) { return val.charAt(0); } return def; } @Override public Writable serialize(Object obj, ObjectInspector objInspector) throws SerDeException { final StructObjectInspector outputRowOI = (StructObjectInspector) objInspector; final List<? extends StructField> outputFieldRefs = outputRowOI.getAllStructFieldRefs(); if (outputFieldRefs.size() != numCols) { throw new SerDeException("Cannot serialize the object because there are " + outputFieldRefs.size() + " fields but the table has " + numCols + " columns."); } // Get all data out. for (int c = 0; c < numCols; c++) { final Object field = outputRowOI.getStructFieldData(obj, outputFieldRefs.get(c)); final ObjectInspector fieldOI = outputFieldRefs.get(c).getFieldObjectInspector(); // The data must be of type String final StringObjectInspector fieldStringOI = (StringObjectInspector) fieldOI; // Convert the field to Java class String, because objects of String type // can be stored in String, Text, or some other classes. outputFields[c] = fieldStringOI.getPrimitiveJavaObject(field); } final StringWriter writer = new StringWriter(); final CSVWriter csv = newWriter(writer, separatorChar, quoteChar, escapeChar); try { csv.writeNext(outputFields); csv.close(); return new Text(writer.toString()); } catch (final IOException ioe) { throw new SerDeException(ioe); } } @Override public Object deserialize(final Writable blob) throws SerDeException { Text rowText = (Text) blob; CSVReader csv = null; try { csv = newReader(new CharArrayReader(rowText.toString().toCharArray()), separatorChar, quoteChar, escapeChar); final String[] read = csv.readNext(); for (int i = 0; i < numCols; i++) { if (read != null && i < read.length) { row.set(i, read[i]); } else { row.set(i, null); } } return row; } catch (final Exception e) { throw new SerDeException(e); } finally { if (csv != null) { try { csv.close(); } catch (final Exception e) { LOG.error("fail to close csv writer ", e); } } } } private CSVReader newReader(final Reader reader, char separator, char quote, char escape) { // CSVReader will throw an exception if any of separator, quote, or escape is the same, but // the CSV format specifies that the escape character and quote char are the same... very weird if (CSVWriter.DEFAULT_ESCAPE_CHARACTER == escape) { return new CSVReader(reader, separator, quote); } else { return new CSVReader(reader, separator, quote, escape); } } private CSVWriter newWriter(final Writer writer, char separator, char quote, char escape) { if (CSVWriter.DEFAULT_ESCAPE_CHARACTER == escape) { return new CSVWriter(writer, separator, quote, ""); } else { return new CSVWriter(writer, separator, quote, escape, ""); } } @Override public ObjectInspector getObjectInspector() throws SerDeException { return inspector; } @Override public Class<? extends Writable> getSerializedClass() { return Text.class; } @Override public SerDeStats getSerDeStats() { return null; } }