[NIO.2] 第三十四篇 编写一个文件搜索应用

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：

[list]
[*] 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。
[/list]

[b][size=x-large]通过名称搜索[/size][/b]

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。

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.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!");
        }
    }
}

[b][size=x-large]通过区块匹配搜索[/size][/b]

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);
    }
}

[b][size=x-large]通过文件内容进行搜索[/size][/b]

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*”，将使用第三方包。

[b][size=large]搜索 PDF 格式[/size][/b]

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; 
   } 
}

[b][size=large]
搜索 Microsoft Word、 Excel 和 PowerPoint[/size][/b]

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; 
   } 
}

[b][size=large]搜索文本文件[/size][/b]

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; 
    } 
 }

[b][size=large]编写一个完整的按内容搜索应用程序[/size][/b]

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：[url]http://www.aptusource.org/2014/04/nio-2-writing-a-rile-search-application/[/url]