經(jīng)常有人問我怎么將類似word，pdf這樣的文檔轉(zhuǎn)換為文本然后索引，.net 這方面的解決方案不是很多，為了方便大家，我花了一天時間自己做了一個。
Java 版本的 lucence 提供了一個 tika 的工具用于將 word, excel, pdf 等文檔轉(zhuǎn)換為文本，然后進行索引。但這個工具沒有 .net 版本，要在 .net 下用，需要用 IKVM.net，很麻煩。而且這個工具實際上底層是調(diào)用 POI 和 PDFParse 來轉(zhuǎn)換的。從網(wǎng)上搜索到的信息看,POI 對 office 2007 以上版本的文檔處理有問題，不知道最新版本是否解決了，我沒有試過。 PDFParse 這個東西，我用過 .net 版本，對中文不支持，不知道 Java 版本是否支持。
其實 .net 下完全不需要用這些開源解決方案來解決，因為微軟提供了一個官方的解決方案，這個解決方案叫 IFilter，這個過濾器是為 sql server 的全文索引設(shè)計的，但第三方軟件可以調(diào)用API來完成文檔的提取工作。
為了方便大家，我把 IFilter 轉(zhuǎn)換的功能封裝到了一個開源的組件中去，大家可以到下面地址去下載源碼：HBTextParse .
調(diào)用很簡單：
這個是提取文件中的文本到字符串的代碼
if (openFileDialog.ShowDialog() == DialogResult.OK)
{
//要轉(zhuǎn)換的文件
textBoxFilePath.Text = openFileDialog.FileName;
//實例化 TextParse ，傳入要轉(zhuǎn)換的文件路徑
TextParse textParse = new TextParse(textBoxFilePath.Text);
//提取文件中的文本，并輸出
richTextBoxView.Text = textParse.ConvertToString();
}這個是將文件轉(zhuǎn)換為文本文件的代碼：
if (saveFileDialog.ShowDialog() == DialogResult.OK)
{
try
{
//實例化 TextParse，傳入要轉(zhuǎn)換的文件的路徑
TextParse textParse = new TextParse(textBoxFilePath.Text);
//將文件轉(zhuǎn)換到 saveFileDialog.FileName 指定的文本文件中
textParse.ConvertToFile(saveFileDialog.FileName);
}
catch (Exception ex)
{
MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}要注意的問題是提取 Pdf 文檔，如果機器是 64為操作系統(tǒng)，必須要安裝 Adobe PDF iFilter 9 for 64-bit platforms. 否則會報異常。這個問題我搞了將近一天才搞定。
支持的文檔類型：
目前這個組件可以支持所有 Microsoft office 提供的文檔類型，包括 *.rtf, *.doc, *.docx, *.xls, *.xlsx, *.ppt, *.pptx 等等
除了微軟Office的文檔外，還可以轉(zhuǎn)換
html 文檔:可以把html文檔中的文本提取出來（不包含標(biāo)簽）
Pdf 文檔:我測試過，對中文支持沒有問題
Txt 文檔
這個代碼的核心部分是一個叫 FilterCode 的類。這個類是從 http://ifilter.codeplex.com/ 這個地方下載的，我對這個類做了改進，加入了轉(zhuǎn)換到文件的方法。我把這個類的代碼貼出來，如果對如何調(diào)用IFilter的windows API感興趣，可以參考這段代碼
IFilter 的相關(guān)API函數(shù)如下：通常這些API函數(shù)就可以通過IFilter接口提取文本。
[DllImport("query.dll", SetLastError = true, CharSet = CharSet.Unicode)]
static extern int LoadIFilter(string pwcsPath,
[MarshalAs(UnmanagedType.IUnknown)] object pUnkOuter,
ref IFilter ppIUnk);
[ComImport, Guid("89BCB740-6119-101A-BCB7-00DD010655AF")]
[InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
public interface IFilter
{
/// <summary>
/// The IFilter::Init method initializes a filtering session.
/// </summary>
[PreserveSig]
IFilterReturnCodes Init(
//[in] Flag settings from the IFILTER_INIT enumeration for
// controlling text standardization, property output, embedding
// scope, and IFilter access patterns.
IFILTER_INIT grfFlags,
// [in] The size of the attributes array. When nonzero, cAttributes
// takes
// precedence over attributes specified in grfFlags. If no
// attribute flags
// are specified and cAttributes is zero, the default is given by
// the
// PSGUID_STORAGE storage property set, which contains the date and
// time
// of the last write to the file, size, and so on; and by the
// PID_STG_CONTENTS
// 'contents' property, which maps to the main contents of the
// file.
// For more information about properties and property sets, see
// Property Sets.
int cAttributes,
//[in] Array of pointers to FULLPROPSPEC structures for the
// requested properties.
// When cAttributes is nonzero, only the properties in aAttributes
// are returned.
IntPtr aAttributes,
// [out] Information about additional properties available to the
// caller; from the IFILTER_FLAGS enumeration.
out IFILTER_FLAGS pdwFlags);
/// <summary>
/// The IFilter::GetChunk method positions the filter at the beginning
/// of the next chunk,
/// or at the first chunk if this is the first call to the GetChunk
/// method, and returns a description of the current chunk.
/// </summary>
[PreserveSig]
IFilterReturnCodes GetChunk(out STAT_CHUNK pStat);
/// <summary>
/// The IFilter::GetText method retrieves text (text-type properties)
/// from the current chunk,
/// which must have a CHUNKSTATE enumeration value of CHUNK_TEXT.
/// </summary>
[PreserveSig]
IFilterReturnCodes GetText(
// [in/out] On entry, the size of awcBuffer array in wide/Unicode
// characters. On exit, the number of Unicode characters written to
// awcBuffer.
// Note that this value is not the number of bytes in the buffer.
ref int pcwcBuffer,
// Text retrieved from the current chunk. Do not terminate the
// buffer with a character.
[Out(), MarshalAs(UnmanagedType.LPWStr)]
StringBuilder awcBuffer);
/// <summary>
/// The IFilter::GetValue method retrieves a value (public
/// value-type property) from a chunk,
/// which must have a CHUNKSTATE enumeration value of CHUNK_VALUE.
/// </summary>
[PreserveSig]
IFilterReturnCodes GetValue(
// Allocate the PROPVARIANT structure with CoTaskMemAlloc. Some
// PROPVARIANT
// structures contain pointers, which can be freed by calling the
// PropVariantClear function.
// It is up to the caller of the GetValue method to call the
// PropVariantClear method.
// ref IntPtr ppPropValue
// [MarshalAs(UnmanagedType.Struct)]
ref IntPtr PropVal);
/// <summary>
/// The IFilter::BindRegion method retrieves an interface representing
/// the specified portion of the object.
/// Currently reserved for future use.
/// </summary>
[PreserveSig]
IFilterReturnCodes BindRegion(ref FILTERREGION origPos,
ref Guid riid, ref object ppunk);
}從文檔中提取文本的代碼如下：
/// <summary>
/// Utilizes IFilter interface in Windows to parse the contents of files.
/// </summary>
/// <param name="path">Path - Location of file to parse</param>
/// <param name="buffer">Buffer - Return text artifacts</param>
/// <returns>Raw set of strings from the document in plain text format.</returns>
public void GetTextFromDocument(string path, ref StringBuilder buffer)
{
IFilter filter = null;
int hresult;
IFilterReturnCodes rtn;
// Initialize the return buffer to 64K.
buffer = new StringBuilder(64 * 1024);
// Try to load the filter for the path given.
hresult = LoadIFilter(path, new IntPtr(0), ref filter);
if (hresult == 0)
{
IFILTER_FLAGS uflags;
// Init the filter provider.
rtn = filter.Init(
IFILTER_INIT.IFILTER_INIT_CANON_PARAGRAPHS |
IFILTER_INIT.IFILTER_INIT_CANON_HYPHENS |
IFILTER_INIT.IFILTER_INIT_CANON_SPACES |
IFILTER_INIT.IFILTER_INIT_APPLY_INDEX_ATTRIBUTES |
IFILTER_INIT.IFILTER_INIT_INDEXING_ONLY,
0, new IntPtr(0), out uflags);
if (rtn == IFilterReturnCodes.S_OK)
{
STAT_CHUNK statChunk;
// Outer loop will read chunks from the document at a time. For those
// chunks that have text, the contents will be pulled and put into the
// return buffer.
bool bMoreChunks = true;
while (bMoreChunks)
{
rtn = filter.GetChunk(out statChunk);
if (rtn == IFilterReturnCodes.S_OK)
{
// Ignore all non-text chunks.
if (statChunk.flags != CHUNKSTATE.CHUNK_TEXT)
continue;
// Check for white space items and add the appropriate breaks.
switch (statChunk.breakType)
{
case CHUNK_BREAKTYPE.CHUNK_NO_BREAK:
break;
case CHUNK_BREAKTYPE.CHUNK_EOW:
buffer.Append(' ');
break;
case CHUNK_BREAKTYPE.CHUNK_EOC:
case CHUNK_BREAKTYPE.CHUNK_EOP:
case CHUNK_BREAKTYPE.CHUNK_EOS:
buffer.AppendLine();
break;
}
// At this point we have a text chunk. The following code will pull out
// all of it and add it to the buffer.
bool bMoreText = true;
while (bMoreText)
{
// Create a temporary string buffer we can use for the parsing algorithm.
int cBuffer = DefaultBufferSize;
StringBuilder sbBuffer = new StringBuilder(DefaultBufferSize);
// Read the next piece of data up to the size of our local buffer.
rtn = filter.GetText(ref cBuffer, sbBuffer);
if (rtn == IFilterReturnCodes.S_OK || rtn == IFilterReturnCodes.FILTER_S_LAST_TEXT)
{
// If any data was returned, scrub it and then add it to the buffer.
CleanUpCharacters(cBuffer, sbBuffer);
buffer.Append(sbBuffer.ToString());
// If we got back some text but there is no more, terminate the loop.
if (rtn == IFilterReturnCodes.FILTER_S_LAST_TEXT)
{
bMoreText = false;
break;
}
}
// Once all data is exhausted, we are done so terminate.
else if (rtn == IFilterReturnCodes.FILTER_E_NO_MORE_TEXT)
{
bMoreText = false;
break;
}
// Check for any fatal errors. It is a bug if you land here.
else if (rtn == IFilterReturnCodes.FILTER_E_NO_TEXT)
{
System.Diagnostics.Debug.Assert(false, "Should not get here");
throw new InvalidOperationException();
}
}
}
// Once all chunks have been read, we are done with the file.
else if (rtn == IFilterReturnCodes.FILTER_E_END_OF_CHUNKS)
{
bMoreChunks = false;
break;
}
else if (rtn == IFilterReturnCodes.FILTER_E_EMBEDDING_UNAVAILABLE ||
rtn == IFilterReturnCodes.FILTER_E_LINK_UNAVAILABLE)
{
continue;
}
else
{
throw new COMException("IFilter COM error: " + rtn.ToString());
}
}
}
}
else
{
// If you get here there is no filter for the file type you asked for. Throw an
// exception for the caller.
throw new InvalidOperationException("Failed to find IFilter for file " + path);
}
}
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