scriptella.expression.LineIterator Maven / Gradle / Ivy
/*
* Copyright 2006-2012 The Scriptella Project Team.
*
* 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 scriptella.expression;
import scriptella.core.RuntimeIOException;
import scriptella.util.IOUtils;
import scriptella.util.StringUtils;
import java.io.BufferedReader;
import java.io.Closeable;
import java.io.IOException;
import java.io.Reader;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* An Iterator over the lines in a Reader, additionally properties substitution is performed.
* This class change the contract of {@link #hasNext()} method by
* throwing {@link scriptella.core.RuntimeIOException} on {@link IOException}.
*
Decorators should override {@link #format(String)} method.
*
This class is not threadsafe.
*
* @author Fyodor Kupolov
* @version 1.0
* @see PropertiesSubstitutor
*/
public class LineIterator implements Iterator, Closeable {
private PropertiesSubstitutor substitutor;
private BufferedReader reader;
private boolean trimLines;
private String line;
public LineIterator(Reader reader) {
this(reader, null, false);
}
public LineIterator(Reader reader, PropertiesSubstitutor substitutor) {
this(reader, substitutor, false);
}
/**
* Constructs iterator.
*
* @param reader reader to iterate.
* @param substitutor substitutor to use to expand properties or null to disable substitution.
* @param trimLines true if the returned lines should be trimmed.
*/
public LineIterator(Reader reader, PropertiesSubstitutor substitutor, boolean trimLines) {
if (reader == null) {
throw new IllegalArgumentException("reader cannot be null");
}
this.reader = IOUtils.asBuffered(reader);
this.substitutor = substitutor;
this.trimLines = trimLines;
}
/**
* @return true if a line is available for reading by {@link #next()}
* @throws RuntimeIOException if IO error occurs.
*/
public boolean hasNext() throws RuntimeIOException {
if (reader == null) {
return false;
}
if (line == null) {
try {
line = format(reader.readLine());
} catch (IOException e) {
throw new RuntimeIOException(e);
}
}
return line != null;
}
/**
* Applies additional formatting to the line read.
* May be overriden by decorators.
* @param line line of text, nulls allowed.
* @return formatted line.
*/
protected String format(String line) {
if (StringUtils.isEmpty(line)) {
return line;
}
if (trimLines) {
line = line.trim();
}
if (substitutor != null) {
line = substitutor.substitute(line);
}
return line;
}
/**
* Returns the next avalable line in a reader.
*
* @return the next avalable line in a reader.
* @throws RuntimeIOException if IO error occurs.
* @throws NoSuchElementException if has no more elements.
*/
public String next() throws RuntimeIOException, NoSuchElementException {
if (!hasNext()) {
throw new NoSuchElementException();
}
final String res = line;
line = null;
return res;
}
/**
* Skips N lines.
* @param n number of lines to skip.
* @return the actual number of lines skipped.
*/
public int skip(int n) {
for (int i = 0; i < n; i++) {
if (!hasNext()) {
return i;
}
next();
}
return n;
}
/**
* Returns specified line or null if EOF occured.
*
* @param n line number relative to the current line in the input. n>=0
* @return line n.
*/
public String getLineAt(int n) {
skip(n);
return hasNext() ? next() : null;
}
public void remove() throws UnsupportedOperationException {
throw new UnsupportedOperationException("remove not supported by " + getClass().getName());
}
public void close() throws IOException {
if (reader != null) {
reader.close();
reader = null;
}
}
}