大多数操作系统都提供了独立的工具用于文件搜索(例如,Linux 上的 find 命令,Windows 上的文件搜索工具)。从简单到高级,这些工具提供的搜索模式都大同小异:用户提供搜索条件,等待搜索工具返回
搜索结果。如果你想自己编写搜索程序,那么可以利用 FileVisitor
接口。你可以编写按
文件名、按文件扩展名、按区域匹配、按文件内容来搜索文件的功能。
利用 FileVisitor 来编写搜索工具,需要明确以下几点:
- visitFile() 是用于比较当前文件和搜索条件的最佳地方。在这里,你可以获取当前文件名、文件扩展名、文件属性或者打开文件读取文件内容。这个方法不会搜索目录。
- 如果要搜索目录,必须将比较代码放入 preVisitDirectory() 或 postVisitDirectory() 方法中,至于放入哪个方法,取决于你的需求。
- 如果文件还未搜索出来, visitFileFailed() 需要返回 FileVisitResult.CONTINUE,因为你并不需要让整个搜索过程停止。
- 如果只需要返回一个结果,那么在搜索到结果之后需要在 visitFile() 方法中返回 FileVisitResult.TERMINATE 否则要返回 FileVisitResult.CONTINUE。
- 搜索过程可以将软连接处理为目标文件,但是在递归删除的时候,建议只删除软链接自身。
通过名称搜索
下面代码演示了如何通过文件名称进行搜索。代码中将会在整个默认文件系统中搜索名为 rafa_1.jpg 的文件,并在搜索到结果后停止。
class="java">import java.io.IOException;
import java.nio.file.Filesystems.html" target="_blank">Systems;
import java.nio.file.FileVisitOption;
import java.nio.file.FileVisitResult;
import java.nio.file.FileVisitor;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.EnumSet;
class Search implements FileVisitor {
private final Path searchedFile;
public boolean found;
public Search(Path searchedFile) {
this.searchedFile = searchedFile;
this.found = false;
}
void search(Path file) throws IOException {
Path name = file.getFileName();
if (name != null && name.equals(searchedFile)) {
System.out.println("Searched file was found: " + searchedFile
+ " in " + file.toRealPath().toString());
found = true;
}
}
@Override
public FileVisitResult postVisitDirectory(Object dir, IOException exc)
throws IOException {
System.out.println("Visited: " + (Path) dir);
return FileVisitResult.CONTINUE;
}
@Override
public FileVisitResult preVisitDirectory(Object dir, BasicFileAttributes attrs)
throws IOException {
return FileVisitResult.CONTINUE;
}
@Override
public FileVisitResult visitFile(Object file, BasicFileAttributes attrs)
throws IOException {
search((Path) file);
if (!found) {
return FileVisitResult.CONTINUE;
} else {
return FileVisitResult.TERMINATE;
}
}
@Override
public FileVisitResult visitFileFailed(Object file, IOException exc)
throws IOException {
//report an error if necessary
return FileVisitResult.CONTINUE;
}
}
class Main {
public static void main(String[] args) throws IOException {
Path searchFile = Paths.get("rafa_1.jpg");
Search walk = new Search(searchFile);
EnumSet opts = EnumSet.of(FileVisitOption.FOLLOW_LINKS);
Iterable<Path> dirs = FileSystems.getDefault().getRootDirectories();
for (Path root : dirs) {
if (!walk.found) {
Files.walkFileTree(root, opts, Integer.MAX_VALUE, walk);
}
}
if (!walk.found) {
System.out.println("The file " + searchFile + " was not found!");
}
}
}
通过区块匹配搜索
有的时候,你可能只知道部分文件名,那么就可以使用区块匹配功能。下面的代码将演示如何在 C:\rafaelnadal 目录树中查找 *.jpg 的文件。整个目录树搜索完才会停止。
import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.FileVisitOption;
import java.nio.file.FileVisitResult;
import java.nio.file.FileVisitor;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.PathMatcher;
import java.nio.file.Paths;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.EnumSet;
class Search implements FileVisitor {
private final PathMatcher matcher;
public Search(String glob) {
matcher = FileSystems.getDefault().getPathMatcher("glob:" + glob);
}
void search(Path file) throws IOException {
Path name = file.getFileName();
if (name != null && matcher.matches(name)) {
System.out.println("Searched file was found: " + name
+ " in " + file.toRealPath().toString());
}
}
@Override
public FileVisitResult postVisitDirectory(Object dir, IOException exc)
throws IOException {
System.out.println("Visited: " + (Path) dir);
return FileVisitResult.CONTINUE;
}
@Override
public FileVisitResult preVisitDirectory(Object dir, BasicFileAttributes attrs)
throws IOException {
return FileVisitResult.CONTINUE;
}
@Override
public FileVisitResult visitFile(Object file, BasicFileAttributes attrs)
throws IOException {
search((Path) file);
return FileVisitResult.CONTINUE;
}
@Override
public FileVisitResult visitFileFailed(Object file, IOException exc)
throws IOException {
//report an error if necessary
return FileVisitResult.CONTINUE;
}
}
class Main {
public static void main(String[] args) throws IOException {
String glob = "*.jpg";
Path fileTree = Paths.get("C:/rafaelnadal/");
Search walk = new Search(glob);
EnumSet opts = EnumSet.of(FileVisitOption.FOLLOW_LINKS);
Files.walkFileTree(fileTree, opts, Integer.MAX_VALUE, walk);
}
}
如果你知道文件的更多属性,那么可以编写更复杂的过滤条件。例如,除了文件名外,你可能还知道文件大小小于多少 KB、或者文件的创建时间、文件的最后编辑时间、文件是否只读、文件是否隐藏、文件所有者是谁等。这些都是文件属性中的一部分,下面的代码将搜索按 *.jpg 匹配并且文件大小小于 100 KB 的文件。
import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.FileVisitOption;
import java.nio.file.FileVisitResult;
import java.nio.file.FileVisitor;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.PathMatcher;
import java.nio.file.Paths;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.EnumSet;
class Search implements FileVisitor {
private final PathMatcher matcher;
private final long accepted_size;
public Search(String glob, long accepted_size) {
matcher = FileSystems.getDefault().getPathMatcher("glob:" + glob);
this.accepted_size = accepted_size;
}
void search(Path file) throws IOException {
Path name = file.getFileName();
long size = (Long) Files.getAttribute(file, "basic:size");
if (name != null && matcher.matches(name) && size <= accepted_size) {
System.out.println("Searched file was found: " + name + " in "
+ file.toRealPath().toString() + " size (bytes):" + size);
}
}
@Override
public FileVisitResult postVisitDirectory(Object dir, IOException exc)
throws IOException {
System.out.println("Visited: " + (Path) dir);
return FileVisitResult.CONTINUE;
}
@Override
public FileVisitResult preVisitDirectory(Object dir, BasicFileAttributes attrs)
throws IOException {
return FileVisitResult.CONTINUE;
}
@Override
public FileVisitResult visitFile(Object file, BasicFileAttributes attrs)
throws IOException {
search((Path) file);
return FileVisitResult.CONTINUE;
}
@Override
public FileVisitResult visitFileFailed(Object file, IOException exc)
throws IOException {
//report an error if necessary
return FileVisitResult.CONTINUE;
}
}
class Main {
public static void main(String[] args) throws IOException {
String glob = "*.jpg";
long size = 102400; //100 kilobytes in bytes
Path fileTree = Paths.get("C:/rafaelnadal/");
Search walk = new Search(glob, size);
EnumSet opts = EnumSet.of(FileVisitOption.FOLLOW_LINKS);
Files.walkFileTree(fileTree, opts, Integer.MAX_VALUE, walk);
}
}
通过文件内容进行搜索
文件搜索中比较高级的功能是通过文件内容来进行搜索。你传入一句话或几个
单词,返回文件内容中包含这些文本的文件。这种搜索非常消耗时间,因为它需要访问每个文件(每个文件都需要打开、读取、关闭操作)。另外,很多文件格式都支持文本,例如 PDF、
Microsoft Word、 Excel、 PowerPoint、 简单文本文件、
XML、 HTML、 XHTML 等等。这些文件类型的读取各不相同,它们都需要单独的代码来进行内容提取。
下面,我们将开发按文件内容搜索的应用。搜索条件是一系列单词或逗号分隔的句子。例如“Rafael Nadal,tennis,winner of Roland Garros,BNP Paribas tournament draws”。使用 StringTokenizer 类按逗号分隔,将每个单词存入 ArrayList:
…
String words="Rafael Nadal,tennis,winner of Roland Garros,BNP Paribas tournament draws";
ArrayList<String> wordsarray = new ArrayList<>();
…
StringTokenizer st = new StringTokenizer(words, ",");
while (st.hasMoreTokens()) {
wordsarray.add(st.nextToken());
}
编写 searchText() 方法,将文件中提取的文本传入,
循环前面 ArrayList 依次比较文本是否匹配:
//search text
private boolean searchText(String text) {
boolean flag = false;
for (int j = 0; j < wordsarray.size(); j++) {
if ((text.toLowerCase()).contains(wordsarray.get(j).toLowerCase())) {
flag = true;
break;
}
}
return flag;
}
下面将用一组方法来提取不同格式的文件。为了“不重复发明轮子”,将使用第三方包。
搜索 PDF 格式
读取 PDF 内容,可以使用比较流行的 iText 和 Apache PDFBox。这两个包可以到 http://itextpdf.com/ 和 http://pdfbox.apache.org/ 下载。下面的代码基于 iText 5.1.2 和 PDFBox 1.6.0。
//使用 iText 搜索 PDF 文件
boolean searchInPDF_iText(String file) {
PdfReader reader = null;
boolean flag = false;
try {
reader = new PdfReader(file);
int n = reader.getNumberOfPages();
OUTERMOST:
for (int i = 1; i <= n; i++) {
String str = PdfTextExtractor.getTextFromPage(reader, i);
flag = searchText(str);
if (flag) {
break OUTERMOST;
}
}
} catch (Exception e) {
} finally {
if (reader != null) {
reader.close();
}
return flag;
}
}
如果你更熟悉 PDFBox,那么可以使用下面代码:
boolean searchInPDF_PDFBox(String file) {
PDFParser parser = null;
String parsedText = null;
PDFTextStripper pdfStripper = null;
PDDocument pdDoc = null;
COSDocument cosDoc = null;
boolean flag = false;
int page = 0;
File pdf = new File(file);
try {
parser = new PDFParser(new FileInputStream(pdf));
parser.parse();
cosDoc = parser.getDocument();
pdfStripper = new PDFTextStripper();
pdDoc = new PDDocument(cosDoc);
OUTERMOST:
while (page < pdDoc.getNumberOfPages()) {
page++;
pdfStripper.setStartPage(page);
pdfStripper.setEndPage(page + 1);
parsedText = pdfStripper.getText(pdDoc);
flag = searchText(parsedText);
if (flag) {
break OUTERMOST;
}
}
} catch (Exception e) {
} finally {
try {
if (cosDoc != null) {
cosDoc.close();
}
if (pdDoc != null) {
pdDoc.close();
}
} catch (Exception e) {}
return flag;
}
}
搜索 Microsoft Word、 Excel 和 PowerPoint
Microsoft office 可以用 Apache POI 包来
解析,可访问 http://poi.apache.org/ 下载,下面的代码基于 3.7
版本。
处理 word:
boolean searchInWord(String file) {
POIFSFileSystem fs = null;
boolean flag = false;
try {
fs = new POIFSFileSystem(new FileInputStream(file));
HWPFDocument doc = new HWPFDocument(fs);
WordExtractor we = new WordExtractor(doc);
String[] paragraphs = we.getParagraphText();
OUTERMOST:
for (int i = 0; i < paragraphs.length; i++) {
flag = searchText(paragraphs[i]);
if (flag) {
break OUTERMOST;
}
}
} catch (Exception e) {
} finally {
return flag;
}
}
处理 excel:
boolean searchInExcel(String file) {
Row row;
Cell cell;
String text;
boolean flag = false;
InputStream xls = null;
try {
xls = new FileInputStream(file);
HSSFWorkbook wb = new HSSFWorkbook(xls);
int sheets = wb.getNumberOfSheets();
OUTERMOST:
for (int i = 0; i < sheets; i++) {
HSSFSheet sheet = wb.getSheetAt(i);
Iterator<Row> row_iterator = sheet.rowIterator();
while (row_iterator.hasNext()) {
row = (Row) row_iterator.next();
Iterator<Cell> cell_iterator = row.cellIterator();
while (cell_iterator.hasNext()) {
cell = cell_iterator.next();
int type = cell.getCellType();
if (type == HSSFCell.CELL_TYPE_STRING) {
text = cell.getStringCellValue();
flag = searchText(text);
if (flag) {
break OUTERMOST;
}
}
}
}
}
} catch (IOException e) {
} finally {
try {
if (xls != null) {
xls.close();
}
} catch (IOException e) {}
return flag;
}
}
处理 PPT:
boolean searchInPPT(String file) {
boolean flag = false;
InputStream fis = null;
String text;
try {
fis = new FileInputStream(new File(file));
POIFSFileSystem fs = new POIFSFileSystem(fis);
HSLFSlideShow show = new HSLFSlideShow(fs);
SlideShow ss = new SlideShow(show);
Slide[] slides = ss.getSlides();
OUTERMOST:
for (int i = 0; i < slides.length; i++) {
TextRun[] runs = slides[i].getTextRuns();
for (int j = 0; j < runs.length; j++) {
TextRun run = runs[j];
if (run.getRunType() == TextHeaderAtom.TITLE_TYPE) {
text = run.getText();
} else {
text = run.getRunType() + " " + run.getText();
}
flag = searchText(text);
if (flag) {
break OUTERMOST;
}
}
Notes notes = slides[i].getNotesSheet();
if (notes != null) {
runs = notes.getTextRuns();
for (int j = 0; j < runs.length; j++) {
text = runs[j].getText();
flag = searchText(text);
if (flag) {
break OUTERMOST;
}
}
}
}
} catch (IOException e) {
} finally {
try {
if (fis != null) {
fis.close();
}
} catch (IOException e) {}
return flag;
}
}
搜索文本文件
文本文件(.txt, .html, .xml 等)不需要第三方包,只需要原始的 NIO.2 功能即可完成:
boolean searchInText(Path file) {
boolean flag = false;
Charset charset = Charset.forName("UTF-8");
try (BufferedReader reader = Files.newBufferedReader(file, charset)) {
String line = null;
OUTERMOST:
while ((line = reader.readLine()) != null) {
flag = searchText(line);
if (flag) {
break OUTERMOST;
}
}
} catch (IOException e) {
} finally {
return flag;
}
}
编写一个完整的按内容搜索应用程序
好了,有了以上的基础,我们把所有代码
结合起来:
import com.itextpdf.text.pdf.PdfReader;
import com.itextpdf.text.pdf.parser.PdfTextExtractor;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.Charset;
import java.nio.file.FileSystems;
import java.nio.file.FileVisitOption;
import java.nio.file.FileVisitResult;
import java.nio.file.FileVisitor;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.ArrayList;
import java.util.EnumSet;
import java.util.Iterator;
import java.util.StringTokenizer;
import org.apache.pdfbox.cos.COSDocument;
import org.apache.pdfbox.pdfparser.PDFParser;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.util.PDFTextStripper;
import org.apache.poi.hslf.HSLFSlideShow;
import org.apache.poi.hslf.model.Notes;
import org.apache.poi.hslf.model.Slide;
import org.apache.poi.hslf.model.TextRun;
import org.apache.poi.hslf.record.TextHeaderAtom;
import org.apache.poi.hslf.usermodel.SlideShow;
import org.apache.poi.hssf.usermodel.HSSFCell;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.hwpf.HWPFDocument;
import org.apache.poi.hwpf.extractor.WordExtractor;
import org.apache.poi.poifs.filesystem.POIFSFileSystem;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
class Search implements FileVisitor {
ArrayList<String> wordsarray = new ArrayList<>();
ArrayList<String> documents = new ArrayList<>();
boolean found = false;
public Search(String words) {
wordsarray.clear();
documents.clear();
StringTokenizer st = new StringTokenizer(words, ",");
while (st.hasMoreTokens()) {
wordsarray.add(st.nextToken().trim());
}
}
void search(Path file) throws IOException {
found = false;
String name = file.getFileName().toString();
int mid = name.lastIndexOf(".");
String ext = name.substring(mid + 1, name.length());
if (ext.equalsIgnoreCase("pdf")) {
found = searchInPDF_iText(file.toString());
if (!found) {
found = searchInPDF_PDFBox(file.toString());
}
}
if (ext.equalsIgnoreCase("doc") || ext.equalsIgnoreCase("docx")) {
found = searchInWord(file.toString());
}
if (ext.equalsIgnoreCase("ppt")) {
searchInPPT(file.toString());
}
if (ext.equalsIgnoreCase("xls")) {
searchInExcel(file.toString());
}
if ((ext.equalsIgnoreCase("txt")) || (ext.equalsIgnoreCase("xml")
|| ext.equalsIgnoreCase("html"))
|| ext.equalsIgnoreCase("htm") || ext.equalsIgnoreCase("xhtml")
|| ext.equalsIgnoreCase("rtf")) {
searchInText(file);
}
if (found) {
documents.add(file.toString());
}
}
//search in text files
boolean searchInText(Path file) {
boolean flag = false;
Charset charset = Charset.forName("UTF-8");
try (BufferedReader reader = Files.newBufferedReader(file, charset)) {
String line = null;
OUTERMOST:
while ((line = reader.readLine()) != null) {
flag = searchText(line);
if (flag) {
break OUTERMOST;
}
}
} catch (IOException e) {
} finally {
return flag;
}
}
//search in Excel files
boolean searchInExcel(String file) {
Row row;
Cell cell;
String text;
boolean flag = false;
InputStream xls = null;
try {
xls = new FileInputStream(file);
HSSFWorkbook wb = new HSSFWorkbook(xls);
int sheets = wb.getNumberOfSheets();
OUTERMOST:
for (int i = 0; i < sheets; i++) {
HSSFSheet sheet = wb.getSheetAt(i);
Iterator<Row> row_iterator = sheet.rowIterator();
while (row_iterator.hasNext()) {
row = (Row) row_iterator.next();
Iterator<Cell> cell_iterator = row.cellIterator();
while (cell_iterator.hasNext()) {
cell = cell_iterator.next();
int type = cell.getCellType();
if (type == HSSFCell.CELL_TYPE_STRING) {
text = cell.getStringCellValue();
flag = searchText(text);
if (flag) {
break OUTERMOST;
}
}
}
}
}
} catch (IOException e) {
} finally {
try {
if (xls != null) {
xls.close();
}
} catch (IOException e) {
}
return flag;
}
}
//search in PowerPoint files
boolean searchInPPT(String file) {
boolean flag = false;
InputStream fis = null;
String text;
try {
fis = new FileInputStream(new File(file));
POIFSFileSystem fs = new POIFSFileSystem(fis);
HSLFSlideShow show = new HSLFSlideShow(fs);
SlideShow ss = new SlideShow(show);
Slide[] slides = ss.getSlides();
OUTERMOST:
for (int i = 0; i < slides.length; i++) {
TextRun[] runs = slides[i].getTextRuns();
for (int j = 0; j < runs.length; j++) {
TextRun run = runs[j];
if (run.getRunType() == TextHeaderAtom.TITLE_TYPE) {
text = run.getText();
} else {
text = run.getRunType() + " " + run.getText();
}
flag = searchText(text);
if (flag) {
break OUTERMOST;
}
}
Notes notes = slides[i].getNotesSheet();
if (notes != null) {
runs = notes.getTextRuns();
for (int j = 0; j < runs.length; j++) {
text = runs[j].getText();
flag = searchText(text);
if (flag) {
break OUTERMOST;
}
}
}
}
} catch (IOException e) {
} finally {
try {
if (fis != null) {
fis.close();
}
} catch (IOException e) {
}
return flag;
}
}
//search in Word files
boolean searchInWord(String file) {
POIFSFileSystem fs = null;
boolean flag = false;
try {
fs = new POIFSFileSystem(new FileInputStream(file));
HWPFDocument doc = new HWPFDocument(fs);
WordExtractor we = new WordExtractor(doc);
String[] paragraphs = we.getParagraphText();
OUTERMOST:
for (int i = 0; i < paragraphs.length; i++) {
flag = searchText(paragraphs[i]);
if (flag) {
break OUTERMOST;
}
}
} catch (Exception e) {
} finally {
return flag;
}
}
//search in PDF files using PDFBox library
boolean searchInPDF_PDFBox(String file) {
PDFParser parser = null;
String parsedText = null;
PDFTextStripper pdfStripper = null;
PDDocument pdDoc = null;
COSDocument cosDoc = null;
boolean flag = false;
int page = 0;
File pdf = new File(file);
try {
parser = new PDFParser(new FileInputStream(pdf));
parser.parse();
cosDoc = parser.getDocument();
pdfStripper = new PDFTextStripper();
pdDoc = new PDDocument(cosDoc);
OUTERMOST:
while (page < pdDoc.getNumberOfPages()) {
page++;
pdfStripper.setStartPage(page);
pdfStripper.setEndPage(page + 1);
parsedText = pdfStripper.getText(pdDoc);
flag = searchText(parsedText);
if (flag) {
break OUTERMOST;
}
}
} catch (Exception e) {
} finally {
try {
if (cosDoc != null) {
cosDoc.close();
}
if (pdDoc != null) {
pdDoc.close();
}
} catch (Exception e) {
}
return flag;
}
}
//search in PDF files using iText library
boolean searchInPDF_iText(String file) {
PdfReader reader = null;
boolean flag = false;
try {
reader = new PdfReader(file);
int n = reader.getNumberOfPages();
OUTERMOST:
for (int i = 1; i <= n; i++) {
String str = PdfTextExtractor.getTextFromPage(reader, i);
flag = searchText(str);
if (flag) {
break OUTERMOST;
}
}
} catch (Exception e) {
} finally {
if (reader != null) {
reader.close();
}
return flag;
}
}
//search text
private boolean searchText(String text) {
boolean flag = false;
for (int j = 0; j < wordsarray.size(); j++) {
if ((text.toLowerCase()).contains(wordsarray.get(j).toLowerCase())) {
flag = true;
break;
}
}
return flag;
}
@Override
public FileVisitResult postVisitDirectory(Object dir, IOException exc)
throws IOException {
System.out.println("Visited: " + (Path) dir);
return FileVisitResult.CONTINUE;
}
@Override
public FileVisitResult preVisitDirectory(Object dir, BasicFileAttributes attrs)
throws IOException {
return FileVisitResult.CONTINUE;
}
@Override
public FileVisitResult visitFile(Object file, BasicFileAttributes attrs)
throws IOException {
search((Path) file);
return FileVisitResult.CONTINUE;
}
@Override
public FileVisitResult visitFileFailed(Object file, IOException exc)
throws IOException {
//report an error if necessary
return FileVisitResult.CONTINUE;
}
}
class Main {
public static void main(String[] args) throws IOException {
String words = "Rafael Nadal, tennis, winner of Roland Garros, BNP Paribas tournament draws";
Search walk = new Search(words);
EnumSet opts = EnumSet.of(FileVisitOption.FOLLOW_LINKS);
Iterable<Path> dirs = FileSystems.getDefault().getRootDirectories();
for (Path root : dirs) {
Files.walkFileTree(root, opts, Integer.MAX_VALUE, walk);
}
System.out.println("____________________________________________________________");
for (String path_string : walk.documents) {
System.out.println(path_string);
}
System.out.println("____________________________________________________________");
}
}
文章来源:http://www.aptusource.org/2014/04/nio-2-writing-a-rile-search-application/