I think POI is using too much memory! What can I do?This one comes up quite a lot, but often the reason isn't what you might initially think. So, the first thing to check is - what's the source of the problem? Your file? Your code? Your environment? Or Apache POI?

Next, use the example program ToCSV to try reading the a file in with HSSF or XSSF. Related is XLSX2CSV, which uses SAX parsing for .xlsx

我們看到了POI已經提出了針對這個問題的回答，而且正好在XLS2CSV中找到了很好的解決讀取大容量的方法.

在XLS2CSV中，即使是讀取300M的2007excel文件也沒有什么問題,占用的內存也是可以接受的。在這段代碼中的注釋中寫出了下面一段話：

*Data sheets are read using a SAX parser to keep thememory footprint relatively small, so this should be

able to read enormous workbooks. The styles table and

the shared-string table must be kept in memory. The

standard POI styles table class is used, but a custom

(read-only) class is used for the shared string table

because the standard POI SharedStringsTable grows

very quickly with the number of unique strings.

大概的意思就是說通用的處理方法會快速消耗掉內存，所以采用了 SAX parser方法來處理大容量的文件.public void processSheet(

StylesTable styles,

ReadOnlySharedStringsTable strings,

InputStream sheetInputStream)

throws IOException, ParserConfigurationException, SAXException {

InputSource sheetSource = new InputSource(sheetInputStream);

SAXParserFactory saxFactory = SAXParserFactory.newInstance();

SAXParser saxParser = saxFactory.newSAXParser();

XMLReader sheetParser = saxParser.getXMLReader();

ContentHandler handler = new MyXSSFSheetHandler(styles, strings, this.minColumns, this.output);

sheetParser.setContentHandler(handler);

sheetParser.parse(sheetSource);

}上面的一段代碼是比較核心的代碼，通過SAXParser解析xml文件，盡量不占用內存資源，從而達到讀取大文件的目的。

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