org.apache.commons.csv.CSVPrinter Maven / Gradle / Ivy
Show all versions of commons-csv Show documentation
/*
* 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.commons.csv;
import org.checkerframework.checker.nullness.qual.NonNull;
import org.checkerframework.checker.nullness.qual.Nullable;
import static org.apache.commons.csv.Constants.CR;
import static org.apache.commons.csv.Constants.LF;
import static org.apache.commons.csv.Constants.SP;
import java.io.Closeable;
import java.io.Flushable;
import java.io.IOException;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Arrays;
/**
* Prints values in a {@link CSVFormat CSV format}.
*
* Values can be appended to the output by calling the {@link #print(Object)} method.
* Values are printed according to {@link String#valueOf(Object)}.
* To complete a record the {@link #println()} method has to be called.
* Comments can be appended by calling {@link #printComment(String)}.
* However a comment will only be written to the output if the {@link CSVFormat} supports comments.
*
*
* The printer also supports appending a complete record at once by calling {@link #printRecord(Object...)}
* or {@link #printRecord(Iterable)}.
* Furthermore {@link #printRecords(Object...)}, {@link #printRecords(Iterable)} and {@link #printRecords(ResultSet)}
* methods can be used to print several records at once.
*
*
* Example:
*
*
* try (CSVPrinter printer = new CSVPrinter(new FileWriter("csv.txt"), CSVFormat.EXCEL)) {
* printer.printRecord("id", "userName", "firstName", "lastName", "birthday");
* printer.printRecord(1, "john73", "John", "Doe", LocalDate.of(1973, 9, 15));
* printer.println();
* printer.printRecord(2, "mary", "Mary", "Meyer", LocalDate.of(1985, 3, 29));
* } catch (IOException ex) {
* ex.printStackTrace();
* }
*
*
* This code will write the following to csv.txt:
*
* id,userName,firstName,lastName,birthday
* 1,john73,John,Doe,1973-09-15
*
* 2,mary,Mary,Meyer,1985-03-29
*
*/
public final class CSVPrinter implements Flushable, Closeable {
/** The place that the values get written. */
private final Appendable out;
private final CSVFormat format;
/** True if we just began a new record. */
private boolean newRecord = true;
/**
* Creates a printer that will print values to the given stream following the CSVFormat.
*
* Currently, only a pure encapsulation format or a pure escaping format is supported. Hybrid formats (encapsulation
* and escaping with a different character) are not supported.
*
*
* @param out
* stream to which to print. Must not be null.
* @param format
* the CSV format. Must not be null.
* @throws IOException
* thrown if the optional header cannot be printed.
* @throws IllegalArgumentException
* thrown if the parameters of the format are inconsistent or if either out or format are null.
*/
public CSVPrinter(final Appendable out, final CSVFormat format) throws IOException {
Assertions.notNull(out, "out");
Assertions.notNull(format, "format");
this.out = out;
this.format = format;
// TODO: Is it a good idea to do this here instead of on the first call to a print method?
// It seems a pain to have to track whether the header has already been printed or not.
if (format.getHeaderComments() != null) {
for (final String line : format.getHeaderComments()) {
if (line != null) {
this.printComment(line);
}
}
}
if (format.getHeader() != null && !format.getSkipHeaderRecord()) {
this.printRecord((Object[]) format.getHeader());
}
}
// ======================================================
// printing implementation
// ======================================================
@Override
public void close() throws IOException {
close(false);
}
/**
* Closes the underlying stream with an optional flush first.
* @param flush whether to flush before the actual close.
*
* @throws IOException
* If an I/O error occurs
* @since 1.6
*/
public void close(final boolean flush) throws IOException {
if (flush || format.getAutoFlush()) {
flush();
}
if (out instanceof Closeable) {
((Closeable) out).close();
}
}
/**
* Flushes the underlying stream.
*
* @throws IOException
* If an I/O error occurs
*/
@Override
public void flush() throws IOException {
if (out instanceof Flushable) {
((Flushable) out).flush();
}
}
/**
* Gets the target Appendable.
*
* @return the target Appendable.
*/
public Appendable getOut() {
return this.out;
}
/**
* Prints the string as the next value on the line. The value will be escaped or encapsulated as needed.
*
* @param value
* value to be output.
* @throws IOException
* If an I/O error occurs
*/
public void print(final @Nullable Object value) throws IOException {
format.print(value, out, newRecord);
newRecord = false;
}
/**
* Prints a comment on a new line among the delimiter separated values.
*
*
* Comments will always begin on a new line and occupy at least one full line. The character specified to start
* comments and a space will be inserted at the beginning of each new line in the comment.
*
*
*
* If comments are disabled in the current CSV format this method does nothing.
*
*
* This method detects line breaks inside the comment string and inserts {@link CSVFormat#getRecordSeparator()}
* to start a new line of the comment. Note that this might produce unexpected results for formats that do not use
* line breaks as record separator.
*
* @param comment
* the comment to output
* @throws IOException
* If an I/O error occurs
*/
@SuppressWarnings("nullness") // getCommentMarker() isn't affected by side effects in this method
public void printComment(final String comment) throws IOException {
if (!format.isCommentMarkerSet()) {
return;
}
if (!newRecord) {
println();
}
out.append(format.getCommentMarker().charValue());
out.append(SP);
for (int i = 0; i < comment.length(); i++) {
final char c = comment.charAt(i);
switch (c) {
case CR:
if (i + 1 < comment.length() && comment.charAt(i + 1) == LF) {
i++;
}
//$FALL-THROUGH$ break intentionally excluded.
case LF:
println();
out.append(format.getCommentMarker().charValue());
out.append(SP);
break;
default:
out.append(c);
break;
}
}
println();
}
/**
* Outputs the record separator.
*
* @throws IOException
* If an I/O error occurs
*/
public void println() throws IOException {
format.println(out);
newRecord = true;
}
/**
* Prints the given values a single record of delimiter separated values followed by the record separator.
*
*
* The values will be quoted if needed. Quotes and newLine characters will be escaped. This method adds the record
* separator to the output after printing the record, so there is no need to call {@link #println()}.
*
*
* @param values
* values to output.
* @throws IOException
* If an I/O error occurs
*/
public void printRecord(final Iterable values) throws IOException {
for (final Object value : values) {
print(value);
}
println();
}
/**
* Prints the given values a single record of delimiter separated values followed by the record separator.
*
*
* The values will be quoted if needed. Quotes and newLine characters will be escaped. This method adds the record
* separator to the output after printing the record, so there is no need to call {@link #println()}.
*
*
* @param values
* values to output.
* @throws IOException
* If an I/O error occurs
*/
public void printRecord(final Object... values) throws IOException {
format.printRecord(out, values);
newRecord = true;
}
/**
* Prints all the objects in the given collection handling nested collections/arrays as records.
*
*
* If the given collection only contains simple objects, this method will print a single record like
* {@link #printRecord(Iterable)}. If the given collections contains nested collections/arrays those nested elements
* will each be printed as records using {@link #printRecord(Object...)}.
*
*
*
* Given the following data structure:
*
*
*
*
* List<String[]> data = ...
* data.add(new String[]{ "A", "B", "C" });
* data.add(new String[]{ "1", "2", "3" });
* data.add(new String[]{ "A1", "B2", "C3" });
*
*
*
*
* Calling this method will print:
*
*
*
*
* A, B, C
* 1, 2, 3
* A1, B2, C3
*
*
*
* @param values
* the values to print.
* @throws IOException
* If an I/O error occurs
*/
public void printRecords(final Iterable values) throws IOException {
for (final Object value : values) {
if (value instanceof Object[]) {
this.printRecord((Object[]) value);
} else if (value instanceof Iterable) {
this.printRecord((Iterable) value);
} else {
this.printRecord(value);
}
}
}
/**
* Prints all the objects in the given array handling nested collections/arrays as records.
*
*
* If the given array only contains simple objects, this method will print a single record like
* {@link #printRecord(Object...)}. If the given collections contains nested collections/arrays those nested
* elements will each be printed as records using {@link #printRecord(Object...)}.
*
*
*
* Given the following data structure:
*
*
*
*
* String[][] data = new String[3][]
* data[0] = String[]{ "A", "B", "C" };
* data[1] = new String[]{ "1", "2", "3" };
* data[2] = new String[]{ "A1", "B2", "C3" };
*
*
*
*
* Calling this method will print:
*
*
*
*
* A, B, C
* 1, 2, 3
* A1, B2, C3
*
*
*
* @param values
* the values to print.
* @throws IOException
* If an I/O error occurs
*/
public void printRecords(final Object... values) throws IOException {
printRecords(Arrays.asList(values));
}
/**
* Prints all the objects in the given JDBC result set.
*
* @param resultSet
* result set the values to print.
* @throws IOException
* If an I/O error occurs
* @throws SQLException
* if a database access error occurs
*/
public void printRecords(final ResultSet resultSet) throws SQLException, IOException {
final int columnCount = resultSet.getMetaData().getColumnCount();
while (resultSet.next()) {
for (int i = 1; i <= columnCount; i++) {
print(resultSet.getObject(i));
}
println();
}
}
}