com.github.bingoohuang.utils.config.impl.CSVReader Maven / Gradle / Ivy
package com.github.bingoohuang.utils.config.impl;
import org.apache.commons.lang3.StringUtils;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.Reader;
import java.util.ArrayList;
import java.util.List;
/**
* CSV读取器。
* @author BingooHuang
*
*/
public class CSVReader {
/** The default separator to use if none is supplied to the constructor. */
public static final char DEFAULT_SEPARATOR = ',';
/**
* The default quote character to use if none is supplied to the
* constructor.
*/
public static final char DEFAULT_QUOTE_CHARACTER = '"';
/**
* The default line to start reading.
*/
public static final int DEFAULT_SKIP_LINES = 0;
private BufferedReader br;
private boolean hasNext = true;
private char separator; // 分隔符
private char quotechar; // 引号符
private int skipLines; //
private boolean linesSkiped; //转移线
/**
* Constructs CSVReader using a comma for the separator.
*
* @param reader
* the reader to an underlying CSV source.
*/
public CSVReader(Reader reader) {
this(reader, DEFAULT_SEPARATOR);
}
/**
* Constructs CSVReader with supplied separator.
*
* @param reader
* the reader to an underlying CSV source.
* @param separator
* the delimiter to use for separating entries.
*/
public CSVReader(Reader reader, char separator) {
this(reader, separator, DEFAULT_QUOTE_CHARACTER);
}
/**
* Constructs CSVReader with supplied separator and quote char.
*
* @param reader
* the reader to an underlying CSV source.
* @param separator
* the delimiter to use for separating entries
* @param quotechar
* the character to use for quoted elements
*/
public CSVReader(Reader reader, char separator, char quotechar) {
this(reader, separator, quotechar, DEFAULT_SKIP_LINES);
}
/**
* Constructs CSVReader with supplied separator and quote char.
*
* @param reader
* the reader to an underlying CSV source.
* @param separator
* the delimiter to use for separating entries
* @param quotechar
* the character to use for quoted elements
* @param line
* the line number to skip for start reading
*/
public CSVReader(Reader reader, char separator, char quotechar, int line) {
br = new BufferedReader(reader);
this.separator = separator;
this.quotechar = quotechar;
skipLines = line;
}
/**
* Reads the entire file into a List with each element being a String[] of
* tokens.
*
* @return a List of String[], with each String[] representing a line of the
* file.
*
* @throws java.io.IOException
* if bad things happen during the read
*/
public List readAll() throws IOException {
List allElements = new ArrayList();
while (hasNext) {
String[] nextLineAsTokens = readNext();
if (nextLineAsTokens != null) {
allElements.add(nextLineAsTokens);
}
}
return allElements;
}
/**
* Reads the next line from the buffer and converts to a string array.
*
* @return a string array with each comma-separated element as a separate
* entry.
*
* @throws java.io.IOException
* if bad things happen during the read
*/
public String[] readNext() throws IOException {
String nextLine = getNextLine();
if (nextLine == null) {
return null;
}
if (!StringUtils.startsWith(StringUtils.trim(nextLine), "#")) {
return hasNext ? parseLine(nextLine) : null;
}
return readNext();
}
/**
* Reads the next line from the file.
*
* @return the next line from the file without trailing newline
* @throws java.io.IOException
* if bad things happen during the read
*/
private String getNextLine() throws IOException {
if (!linesSkiped) {
for (int i = 0; i < skipLines; i++) {
br.readLine();
}
linesSkiped = true;
}
String nextLine = br.readLine();
if (nextLine == null) {
hasNext = false;
}
return hasNext ? nextLine : null;
}
/**
* Parses an incoming String and returns an array of elements.
*
* @param nextLine
* the string to parse
* @return the comma-tokenized list of elements, or null if nextLine is null
* @throws java.io.IOException
* if bad things happen during the read
*/
private String[] parseLine(String nextLine) throws IOException {
List tokensOnThisLine = new ArrayList();
StringBuilder sb = new StringBuilder();
boolean inQuotes = false;
do {
if (inQuotes) {
// continuing a quoted section, reappend newline
sb.append("\n");
nextLine = getNextLine();
if (nextLine == null) {
break;
}
}
for (int i = 0; i < nextLine.length(); i++) {
char c = nextLine.charAt(i);
if (c == quotechar) {
// this gets complex... the quote may end a quoted block, or
// escape another quote.
// do a 1-char lookahead:
if (inQuotes // we are in quotes, therefore there can be
// escaped quotes in here.
&& nextLine.length() > i + 1 // there is indeed
// another character
// to check.
&& nextLine.charAt(i + 1) == quotechar) { // ..and
// that
// char.
// is a
// quote
// also.
// we have two quote chars in a row == one quote char,
// so consume them both and
// put one on the token. we do *not* exit the quoted
// text.
sb.append(nextLine.charAt(i + 1));
i++;
}
else {
inQuotes = !inQuotes;
// the tricky case of an embedded quote in the middle:
// a,bc"d"ef,g
if (i > 2 // not on the begining of the line
&& nextLine.charAt(i - 1) != separator // not
// at
// the
// begining
// of
// an
// escape
// sequence
&& nextLine.length() > i + 1
&& nextLine.charAt(i + 1) != separator // not
// at
// the
// end
// of
// an
// escape
// sequence
) {
sb.append(c);
}
}
}
else if (c == separator && !inQuotes) {
tokensOnThisLine.add(sb.toString());
sb = new StringBuilder(); // start work on next token
}
else {
sb.append(c);
}
}
}
while (inQuotes);
tokensOnThisLine.add(sb.toString());
return tokensOnThisLine.toArray(new String[0]);
}
/**
* Closes the underlying reader.
*
* @throws java.io.IOException
* if the close fails
*/
public void close() throws IOException {
br.close();
}
}
© 2015 - 2025 Weber Informatics LLC | Privacy Policy