自从上一篇:一个普通类就能干趴你的springboot，你信吗？后，很巧的是这次又发现一个问题，所以有了这篇文章，还是想沿用上篇的”流水帐“的方式查找问题和解决问题。这篇文章主要是因为使用POI导入一个20M的excel发生了OOM(OutOfMemoryError)异常。说来也惭愧，工作了这么多年，还真没导入过这种大小的文件，并且还发生了内存溢出。如果你百度下基本上清一色的告诉你:POI导入excel文件有两种方式，第一种是用户模式，这种模式用起来很简单直观，可以类比xml的dom方式解析(这里只针对excel2007，因为2003本身就有最大条数限制并且目前基本用的很少，这里直接忽略)，第二种是event模式，这种通常是网上说的解决POI导入大excel的”万金油“方法,可以类比为xml的sax解析方式。呵呵，我这篇文章首先就是要干趴这种方法（JVM使用-Xms512m -Xmx512m）。不信你随便写一个导入接口，导入如下20M大小的execl看看:链接: https://pan.baidu.com/s/1DUrS8ctLPp7Z6imOc1aIUQ 提取码: hd79 。
首先，既然要导入大点的excel2007，那么我们应该稍微了解一下这种文件如何存储数据，我们百度上可以发现，2007其实就是一个压缩包，可以直接修改后缀成zip然后解压打开文件看看，如下
上图可以看到最大的两个文件就两个:sharedStrings.xml和sheet1.xml。其中sheet2.xml这个可以不关注，直接从excel删掉都没事，这里没删除主要是没多大关系，这个excel文件也是测试直接提供给我的。由于sheet2比较小，与这个文章说到的内存溢出并无关系，请不要胡思乱想，被分散了注意。
直接用大文本编辑工具打开上图两个大文件，可以发现sharedString.xml里内容其实就是excel中每个单元格里的字符串内容（数字类型除外）,sheet.xml就是每个sheet里的结构xml，了解到这里基本上就了解了本文章说到问题的基本知识，然后下面进入正题。
先使用百度中查到的提供的event方式导入excel,代码如下:
package com.example.utils; import org.apache.poi.openxml4j.opc.OPCPackage; import org.apache.poi.xssf.eventusermodel.ReadOnlySharedStringsTable; import org.apache.poi.xssf.eventusermodel.XSSFReader; import org.apache.poi.xssf.usermodel.XSSFRichTextString; import org.xml.sax.Attributes; import org.xml.sax.InputSource; import org.xml.sax.SAXException; import org.xml.sax.XMLReader; import org.xml.sax.helpers.DefaultHandler; import org.xml.sax.helpers.XMLReaderFactory; import java.io.File; import java.io.InputStream; import java.sql.SQLException; import java.util.ArrayList; import java.util.Iterator; import java.util.List; /** * 百度上直接copy过来的 * XSSF and SAX (Event API) */ public abstract class BigDataParseExcelUtil extends DefaultHandler { private ReadOnlySharedStringsTable sst; private String lastContents; private boolean nextIsString; private int sheetIndex = -1; private List<String> rowlist = new ArrayList<String>(); private int curRow = 0; // 当前行 private int curCol = 0; // 当前列索引 private int preCol = 0; // 上一列列索引 private int titleRow = 0; // 标题行，一般情况下为0 private int rowsize = 0; // 列数 private List excelList = new ArrayList(); //excel全部转换为list // excel记录行操作方法，以sheet索引，行索引和行元素列表为参数，对sheet的一行元素进行操作，元素为String类型 public abstract void optRows(int sheetIndex, int curRow, List<String> rowlist, List excelList) throws SQLException, Exception; // 只遍历一个sheet，其中sheetId为要遍历的sheet索引，从1开始，1-3 /** * @param filename * @param sheetId sheetId为要遍历的sheet索引，从1开始，1-3 * @throws Exception */ public void processOneSheet(String filename, int sheetId) throws Exception { OPCPackage pkg = OPCPackage.open(filename); XSSFReader r = new XSSFReader(pkg); ReadOnlySharedStringsTable strings = new ReadOnlySharedStringsTable(pkg); XMLReader parser = fetchSheetParser(strings); // rId2 found by processing the Workbook // 根据 rId# 或 rSheet# 查找sheet InputStream sheet2 = r.getSheet("rId" + sheetId); sheetIndex++; InputSource sheetSource = new InputSource(sheet2); parser.parse(sheetSource); sheet2.close(); } @Override public void characters(char[] ch, int start, int length) throws SAXException { // 得到单元格内容的值 lastContents += new String(ch, start, length); } public void process(InputStream inputStream) throws Exception { OPCPackage pkg = OPCPackage.open(inputStream); XSSFReader r = new XSSFReader(pkg); ReadOnlySharedStringsTable strings = new ReadOnlySharedStringsTable(pkg); XMLReader parser = fetchSheetParser(strings); Iterator<InputStream> sheets = r.getSheetsData(); while (sheets.hasNext()) { curRow = 0; sheetIndex++; InputStream sheet = sheets.next(); InputSource sheetSource = new InputSource(sheet); parser.parse(sheetSource); sheet.close(); } } /** * 遍历 excel 文件 */ public void process(File file) throws Exception { OPCPackage pkg = OPCPackage.open(file); XSSFReader r = new XSSFReader(pkg); ReadOnlySharedStringsTable strings = new ReadOnlySharedStringsTable(pkg); XMLReader parser = fetchSheetParser(strings); Iterator<InputStream> sheets = r.getSheetsData(); while (sheets.hasNext()) { curRow = 0; sheetIndex++; InputStream sheet = sheets.next(); InputSource sheetSource = new InputSource(sheet); parser.parse(sheetSource); sheet.close(); } } public XMLReader fetchSheetParser(ReadOnlySharedStringsTable sst) throws SAXException { XMLReader parser = XMLReaderFactory.createXMLReader(); // .createXMLReader("org.apache.xerces.parsers.SAXParser"); this.sst = sst; parser.setContentHandler(this); return parser; } @Override public void startElement(String uri, String localName, String name, Attributes attributes) throws SAXException { // c => 单元格 if (name.equals("c")) { // 如果下一个元素是 SST 的索引，则将nextIsString标记为true String cellType = attributes.getValue("t"); String rowStr = attributes.getValue("r"); curCol = this.getRowIndex(rowStr); if (cellType != null && cellType.equals("s")) { nextIsString = true; } else { nextIsString = false; } } // 置空 lastContents = ""; } @Override public void endElement(String uri, String localName, String name) throws SAXException { // 根据SST的索引值的到单元格的真正要存储的字符串 // 这时characters()方法可能会被调用多次 if (nextIsString) { try { int idx = Integer.parseInt(lastContents); lastContents = new XSSFRichTextString(sst.getEntryAt(idx)) .toString(); } catch (Exception e) { } } // v => 单元格的值，如果单元格是字符串则v标签的值为该字符串在SST中的索引 // 将单元格内容加入rowlist中，在这之前先去掉字符串前后的空白符 if (name.equals("v")) { String value = lastContents.trim(); value = value.equals("") ? " " : value; int cols = curCol - preCol; if (cols > 1) { for (int i = 0; i < cols - 1; i++) { rowlist.add(preCol, ""); } } preCol = curCol; rowlist.add(curCol - 1, value); } else { // 如果标签名称为 row ，这说明已到行尾，调用 optRows() 方法 if (name.equals("row")) { int tmpCols = rowlist.size(); if (curRow > this.titleRow && tmpCols < this.rowsize) { for (int i = 0; i < this.rowsize - tmpCols; i++) { rowlist.add(rowlist.size(), ""); } } try { optRows(sheetIndex, curRow, rowlist, excelList); } catch (SQLException e) { e.printStackTrace(); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } if (curRow == this.titleRow) { this.rowsize = rowlist.size(); } rowlist.clear(); curRow++; curCol = 0; preCol = 0; } } } // 得到列索引，每一列c元素的r属性构成为字母加数字的形式，字母组合为列索引，数字组合为行索引， // 如AB45,表示为第（A-A+1）*26+（B-A+1）*26列，45行 public int getRowIndex(String rowStr) { rowStr = rowStr.replaceAll("[^A-Z]", ""); byte[] rowAbc = rowStr.getBytes(); int len = rowAbc.length; float num = 0; for (int i = 0; i < len; i++) { num += (rowAbc[i] - 'A' + 1) * Math.pow(26, len - i - 1); } return (int) num; } }
package com.example.service; import com.example.utils.BigDataParseExcelUtil; import org.springframework.stereotype.Service; import java.io.InputStream; import java.sql.SQLException; import java.util.List; /** * @author: rongdi * @date: */ @Service public class ExcelService { public void import1(InputStream inputStream) throws Exception { BigDataParseExcelUtil xlx = new BigDataParseExcelUtil() { @Override public void optRows(int sheetIndex, int curRow, List<String> rowlist, List excelList) throws SQLException { System.out.println(rowlist); } }; xlx.process(inputStream); } }
package com.example.controller; import com.example.service.ExcelService; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestParam; import org.springframework.web.bind.annotation.ResponseBody; import org.springframework.web.multipart.MultipartFile; /** * @author: rongdi * @date: */ @Controller public class ExcelController { @Autowired private ExcelService excelService; @RequestMapping("/excel/import1") @ResponseBody public String import1(@RequestParam("file") MultipartFile multipartFile) throws Exception { excelService.import1(multipartFile.getInputStream()); return "ok"; } }
使用postman等工具，导入上面说的20M的文件22.xlsx，报错如下:
那我们优化一下不使用inputStream，直接使用一个File传入看看
public void import2(File file) throws Exception { BigDataParseExcelUtil xlx = new BigDataParseExcelUtil() { @Override public void optRows(int sheetIndex, int curRow, List<String> rowlist, List excelList) throws SQLException { System.out.println(rowlist); } }; xlx.process(file); } @RequestMapping("/excel/import2") @ResponseBody public String import2(@RequestParam("file") MultipartFile multipartFile) throws Exception { // 延迟解析比率 ZipSecureFile.setMinInflateRatio(-1.0d); File tmp = Files.createTempFile("tmp-", ".xlsx").toFile(); Files.copy(multipartFile.getInputStream(), Paths.get(tmp.getPath()), StandardCopyOption.REPLACE_EXISTING); excelService.import2(tmp); return "ok"; }
使用postman上传文件运行效果如下：
这时候就发现很尴尬了，难道是POI自己代码里就有bug，我们可以使用断点调试确认一下这个strings里到底是不是全部放了sharedStrings.xml里的内容。
由上证明就是这个strings装多了导致内存溢出了，从这里可以看出网上说使用event事件解析excel的方案基本都是行不通的，哎，我也不懂为啥百度上都是这种答案，难道他们压根都没遇到过大数据导入吗?当然也有可能我冤枉了他们，因为sharedStrings.xml中存放的是每个单元格的字符串内容，这个存放是排重过的，如果虽然excel里单元格很多，但是大多都是整型或者大多都是重复的，那确实可以跳过这一步一路之后会一路畅通了，因为毕竟sax解析xml确实可以节省很多内存。
从上分析可以看到POI就两种方式导入：一种是用户方式写代码简单，基本按顺序数格子就好，但是类比dom方式解析xml，很耗内存。第二种事件方式，类比sax方式解析xml确实很省内存，但是POI提供的类里把解析出的大量字符串放入了集合中，还是会导致内存溢出。那么我们怎么解决这个问题，这里很常规的想法是到底这个strings是用来干啥的，怎么用的，如果可以保持strings相同逻辑功能的前提下，修改了ReadOnlySharedStringsTable这个类的逻辑，就可以解决这里的内存溢出了。那么我们可以直接搜索ReadOnlySharedStringsTable类里所有用到strings的方法上打上断点，特别是从strings里取值的方法上，然后调大jvm内存避免内存溢出的情况下断点调试如下
我们是不是可以直接往strings里添加字符串和获取字符串的方法那里替换掉，不要使用strings这个集合存储所有字符串。但是既然excel里设计成使用一个sharedStrings.xml存放公共的字符串，而不是像csv格式那样，每次读一行取一行数据就好了。那么这个sharedStrings.xml中的数据总要解析出来，总要有个地方存储里面的数据，不然怎么结合sheet.xml的格式获取到每一行的数据呢？所以这里就很尴尬了，不能每次解析sharedStrings.xml时不保存每次需要获取strings的时候，再去解析一下这个xm吧,如果从本文章的xml上来看，要重复解析25W次，效率极其低。现在问题可以简化成我们需要把sharedStrings.xml解析出的所有字符串放在一个地方，还能方便解析，由于怕内存溢出，肯定不能放在内存中了。那么这里就有一些选择，比如解析出的字符串按加入strings集合的顺序放入数据库，文件，外部存储或者缓存(限制内存大小，多余写入文件)存储中。然后使用的时候按照索引位置idx去一一取出。本文章先使用临时文件来放这些数据，因为不想搞那么复杂，导入任务不管再多复杂的系统中，最终执行的都会是一个单节点，在单节点中先使用本机资源这种就近资源是最方便的。如下直接先复制源码，然后修改上述说的两个地方。
package com.example.utils; import org.apache.poi.ooxml.util.SAXHelper; import org.apache.poi.openxml4j.opc.OPCPackage; import org.apache.poi.openxml4j.opc.PackagePart; import org.apache.poi.ss.usermodel.RichTextString; import org.apache.poi.util.Removal; import org.apache.poi.xssf.model.SharedStrings; import org.apache.poi.xssf.usermodel.XSSFRelation; import org.apache.poi.xssf.usermodel.XSSFRichTextString; import org.xml.sax.Attributes; import org.xml.sax.InputSource; import org.xml.sax.SAXException; import org.xml.sax.XMLReader; import org.xml.sax.helpers.DefaultHandler; import javax.xml.parsers.ParserConfigurationException; import java.io.File; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.FileReader; import java.io.IOException; import java.io.InputStream; import java.io.LineNumberReader; import java.io.PushbackInputStream; import java.nio.file.Files; import java.util.ArrayList; import java.util.LinkedHashMap; import java.util.List; import java.util.Map; import static org.apache.poi.xssf.usermodel.XSSFRelation.NS_SPREADSHEETML; public class ReadOnlySharedStringsTable extends DefaultHandler implements SharedStrings { protected final boolean includePhoneticRuns; /** * An integer representing the total count of strings in the workbook. This count does not * include any numbers, it counts only the total of text strings in the workbook. */ protected int count; /** * An integer representing the total count of unique strings in the Shared String Table. * A string is unique even if it is a copy of another string, but has different formatting applied * at the character level. */ protected int uniqueCount; /** * The shared strings table. */ private List<String> strings; private File tmp = null; FileOutputStream fos = null; private int counts; private Map<Integer,String> map = new LinkedHashMap<Integer,String>(); public ReadOnlySharedStringsTable(OPCPackage pkg) throws IOException, SAXException { this(pkg, true); } public ReadOnlySharedStringsTable(OPCPackage pkg, boolean includePhoneticRuns) throws IOException, SAXException { this.includePhoneticRuns = includePhoneticRuns; ArrayList<PackagePart> parts = pkg.getPartsByContentType(XSSFRelation.SHARED_STRINGS.getContentType()); // Some workbooks have no shared strings table. if (parts.size() > 0) { PackagePart sstPart = parts.get(0); readFrom(sstPart.getInputStream()); } } /** * Like POIXMLDocumentPart constructor * * Calls {@link #ReadOnlySharedStringsTable(PackagePart, boolean)}, with a * value of <code>true</code> to include phonetic runs. * * @since POI 3.14-Beta1 */ public ReadOnlySharedStringsTable(PackagePart part) throws IOException, SAXException { this(part, true); } /** * Like POIXMLDocumentPart constructor * * @since POI 3.14-Beta3 */ public ReadOnlySharedStringsTable(PackagePart part, boolean includePhoneticRuns) throws IOException, SAXException { this.includePhoneticRuns = includePhoneticRuns; readFrom(part.getInputStream()); } /** * Read this shared strings table from an XML file. * * @param is The input stream containing the XML document. * @throws IOException if an error occurs while reading. * @throws SAXException if parsing the XML data fails. */ public void readFrom(InputStream is) throws IOException, SAXException { // test if the file is empty, otherwise parse it PushbackInputStream pis = new PushbackInputStream(is, 1); int emptyTest = pis.read(); if (emptyTest > -1) { pis.unread(emptyTest); InputSource sheetSource = new InputSource(pis); try { XMLReader sheetParser = SAXHelper.newXMLReader(); sheetParser.setContentHandler(this); sheetParser.parse(sheetSource); } catch(ParserConfigurationException e) { throw new RuntimeException("SAX parser appears to be broken - " + e.getMessage()); } } } /** * Return an integer representing the total count of strings in the workbook. This count does not * include any numbers, it counts only the total of text strings in the workbook. * * @return the total count of strings in the workbook */ @Override public int getCount() { return this.count; } /** * Returns an integer representing the total count of unique strings in the Shared String Table. * A string is unique even if it is a copy of another string, but has different formatting applied * at the character level. * * @return the total count of unique strings in the workbook */ @Override public int getUniqueCount() { return this.uniqueCount; } /** * Return the string at a given index. * Formatting is ignored. * * @param idx index of item to return. * @return the item at the specified position in this Shared String table. * @deprecated use <code>getItemAt</code> instead */ @Removal(version = "4.2") @Deprecated public String getEntryAt(int idx) { /** * 这里就是修改部分了，直接从按行存储的临时文件读取需要的字符串 */ String value = map.get(idx + 1); if(value == null) { return readString(idx,1000,this.uniqueCount); } else { return value; } } /** * 从指定位置读取size个字符串，这里是使用局部性原理，每次读取size个字符串， * 以免每次需要读取文件，性能极低 * @return */ private String readString(int idx,int size,int numbers) { map.clear(); int currNumber = idx + 1; if (currNumber < 0 || currNumber > numbers) { return null; } try { FileReader in = new FileReader(tmp); LineNumberReader reader = new LineNumberReader(in); try { String line = ""; for(int i = 1;i <= numbers;i ++) { line = reader.readLine(); if(i >= currNumber && i < currNumber + size) { map.put(i, line); } } } finally { reader.close(); in.close(); } } catch (Exception e) { System.out.println(e.getMessage()); } return map.get(idx + 1); } /** * Returns all the strings. * Formatting is ignored. * * @return a list with all the strings * @deprecated use <code>getItemAt</code> instead */ @Removal(version = "4.2") @Deprecated public List<String> getItems() { return strings; } @Override public RichTextString getItemAt(int idx) { return new XSSFRichTextString(getEntryAt(idx)); } //// ContentHandler methods //// private StringBuilder characters; private boolean tIsOpen; private boolean inRPh; @Override public void startElement(String uri, String localName, String name, Attributes attributes) throws SAXException { if (uri != null && ! uri.equals(NS_SPREADSHEETML)) { return; } if ("sst".equals(localName)) { String count = attributes.getValue("count"); if(count != null) this.count = Integer.parseInt(count); String uniqueCount = attributes.getValue("uniqueCount"); if(uniqueCount != null) this.uniqueCount = Integer.parseInt(uniqueCount); try { tmp = Files.createTempFile("tmp-", ".xlsx").toFile(); } catch (IOException e) { e.printStackTrace(); } // this.strings = new ArrayList<>(this.uniqueCount); characters = new StringBuilder(64); try { fos = new FileOutputStream(tmp,true); } catch (FileNotFoundException e) { e.printStackTrace(); } } else if ("si".equals(localName)) { characters.setLength(0); } else if ("t".equals(localName)) { tIsOpen = true; } else if ("rPh".equals(localName)) { inRPh = true; //append space...this assumes that rPh always comes after regular <t> if (includePhoneticRuns && characters.length() > 0) { characters.append(" "); } } } @Override public void endElement(String uri, String localName, String name) throws SAXException { if (uri != null && ! uri.equals(NS_SPREADSHEETML)) { return; } if ("si".equals(localName)) { // strings.add(characters.toString().intern()); try { /** * 这里就是修改的一部分，这里直接把字符串按行存入临时文件 */ counts ++; fos.write((characters.toString() + " ").getBytes()); if(counts == this.uniqueCount) { fos.close(); } } catch (IOException e) { e.printStackTrace(); } } else if ("t".equals(localName)) { tIsOpen = false; } else if ("rPh".equals(localName)) { inRPh = false; } } /** * Captures characters only if a t(ext) element is open. */ @Override public void characters(char[] ch, int start, int length) throws SAXException { if (tIsOpen) { if (inRPh && includePhoneticRuns) { characters.append(ch, start, length); } else if (! inRPh){ characters.append(ch, start, length); } } } }
然后在自己代码里把包换成自己的包，替换POI里该类的包，运行JVM堆情况如下毫无压力
自此内存溢出问题大功告成！针对使用POI导入大Excel遇到的问题总结如下：
1）网上给出的方案不管是用户模式还是事件模式，往往都不能支持大excel的导入
2）excel本质上是一堆excel的压缩包（这里只考虑2007忽略2003）改了个后缀名成xlsx
3）使用事件导入时应先将上传文件存入文件，再使用文件OPCPackage.open(file)，如果直接传入输入流，由于里面逻辑会将输入流的所有内容先存入ByteArrayOutputStream 中，这个输出流实际上是一个内存中的字节流，所以也会导致内存溢出。
4）用户模式不用考虑，事件模式会先将sharedString.xml这个大xml解析出来放入一个List中，不管通过什么方式都绕不开需要解析这个类，因为每个单元格的字符串都放在这个xml中，而要解析这个xml最常规的方法就是保存在内存使用list和map之内的容器存放我相信不会有人会想刚解析出一个xml还要存回文件中把，这里基本就绕不开ReadOnlySharedStringsTable或者SharedStringsTable,就算你侥幸绕开了，想自己解析，或许还是重复这两个类的悲剧，这就是另外一种内存溢出的根源。
回顾一下上述实现直接把sharedStrings.xml中的内容粗略的保存到文件中，然后再从文件中获取是属于很低劣的实现，只能说能满足不内存溢出，性能方面堪忧！下面直接借鉴easyexcel源码中用到的ReadCache来实现保存sharedStrings.xml中的内容
package com.example.advanceevent; import com.example.utils.FileUtils; import org.ehcache.Cache; import org.ehcache.CacheManager; import org.ehcache.config.CacheConfiguration; import org.ehcache.config.builders.CacheConfigurationBuilder; import org.ehcache.config.builders.CacheManagerBuilder; import org.ehcache.config.builders.ResourcePoolsBuilder; import org.ehcache.config.units.MemoryUnit; import org.ehcache.core.Ehcache; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import java.io.File; import java.util.HashMap; import java.util.UUID; /** * @author: rongdi * @date: */ public class ReadCache { private static final Logger LOGGER = LoggerFactory.getLogger(Ehcache.class); private int index = 0; private HashMap<Integer, String> dataMap = new HashMap(1334); private static CacheManager fileCacheManager; private static CacheConfiguration<Integer, HashMap> fileCacheConfiguration; private static CacheManager activeCacheManager; private CacheConfiguration<Integer, HashMap> activeCacheConfiguration; private Cache<Integer, HashMap> fileCache; private Cache<Integer, HashMap> activeCache; private String cacheAlias; private int cacheMiss = 0; public ReadCache(int maxCacheActivateSize) { this.activeCacheConfiguration = CacheConfigurationBuilder.newCacheConfigurationBuilder(Integer.class, HashMap.class, ResourcePoolsBuilder.newResourcePoolsBuilder().heap((long)maxCacheActivateSize, MemoryUnit.MB)).withSizeOfMaxObjectGraph(1000000L).withSizeOfMaxObjectSize((long)maxCacheActivateSize, MemoryUnit.MB).build(); init(); } private void init() { this.cacheAlias = UUID.randomUUID().toString(); this.fileCache = fileCacheManager.createCache(this.cacheAlias, fileCacheConfiguration); this.activeCache = activeCacheManager.createCache(this.cacheAlias, this.activeCacheConfiguration); } public void put(String value) { this.dataMap.put(this.index, value); if ((this.index + 1) % 1000 == 0) { this.fileCache.put(this.index / 1000, this.dataMap); this.dataMap = new HashMap(1334); } ++this.index; if (LOGGER.isDebugEnabled() && this.index % 1000000 == 0) { LOGGER.debug("Already put :{}", this.index); } } public String get(Integer key) { if (key != null && key >= 0) { int route = key / 1000; HashMap<Integer, String> dataMap = (HashMap)this.activeCache.get(route); if (dataMap == null) { dataMap = (HashMap)this.fileCache.get(route); this.activeCache.put(route, dataMap); if (LOGGER.isDebugEnabled() && this.cacheMiss++ % 1000 == 0) { LOGGER.debug("Cache misses count:{}", this.cacheMiss); } } return (String)dataMap.get(key); } else { return null; } } public void putFinished() { if (this.dataMap != null) { this.fileCache.put(this.index / 1000, this.dataMap); } } public void destroy() { fileCacheManager.removeCache(this.cacheAlias); activeCacheManager.removeCache(this.cacheAlias); } static { File cacheFile = FileUtils.createCacheTmpFile(); fileCacheManager = CacheManagerBuilder.newCacheManagerBuilder().with(CacheManagerBuilder.persistence(cacheFile)).build(true); activeCacheManager = CacheManagerBuilder.newCacheManagerBuilder().build(true); fileCacheConfiguration = CacheConfigurationBuilder.newCacheConfigurationBuilder(Integer.class, HashMap.class, ResourcePoolsBuilder.newResourcePoolsBuilder().disk(10L, MemoryUnit.GB)).withSizeOfMaxObjectGraph(1000000L).withSizeOfMaxObjectSize(10L, MemoryUnit.GB).build(); } }
package com.example.advanceevent; import org.apache.poi.ooxml.util.SAXHelper; import org.apache.poi.openxml4j.opc.OPCPackage; import org.apache.poi.openxml4j.opc.PackagePart; import org.apache.poi.ss.usermodel.RichTextString; import org.apache.poi.util.Removal; import org.apache.poi.xssf.model.SharedStrings; import org.apache.poi.xssf.usermodel.XSSFRelation; import org.apache.poi.xssf.usermodel.XSSFRichTextString; import org.xml.sax.Attributes; import org.xml.sax.InputSource; import org.xml.sax.SAXException; import org.xml.sax.XMLReader; import org.xml.sax.helpers.DefaultHandler; import javax.xml.parsers.ParserConfigurationException; import java.io.IOException; import java.io.InputStream; import java.io.PushbackInputStream; import java.util.ArrayList; import java.util.List; import static org.apache.poi.xssf.usermodel.XSSFRelation.NS_SPREADSHEETML; public class ReadOnlySharedStringsTable extends DefaultHandler implements SharedStrings { protected final boolean includePhoneticRuns; /** * An integer representing the total count of strings in the workbook. This count does not * include any numbers, it counts only the total of text strings in the workbook. */ protected int count; /** * An integer representing the total count of unique strings in the Shared String Table. * A string is unique even if it is a copy of another string, but has different formatting applied * at the character level. */ protected int uniqueCount; /** * 缓存 */ ReadCache readCache = new ReadCache(100); private int counts; public ReadOnlySharedStringsTable(OPCPackage pkg) throws IOException, SAXException { this(pkg, true); } public ReadOnlySharedStringsTable(OPCPackage pkg, boolean includePhoneticRuns) throws IOException, SAXException { this.includePhoneticRuns = includePhoneticRuns; ArrayList<PackagePart> parts = pkg.getPartsByContentType(XSSFRelation.SHARED_STRINGS.getContentType()); // Some workbooks have no shared strings table. if (parts.size() > 0) { PackagePart sstPart = parts.get(0); readFrom(sstPart.getInputStream()); } } /** * Like POIXMLDocumentPart constructor * * Calls {@link #ReadOnlySharedStringsTable(PackagePart, boolean)}, with a * value of <code>true</code> to include phonetic runs. * * @since POI 3.14-Beta1 */ public ReadOnlySharedStringsTable(PackagePart part) throws IOException, SAXException { this(part, true); } /** * Like POIXMLDocumentPart constructor * * @since POI 3.14-Beta3 */ public ReadOnlySharedStringsTable(PackagePart part, boolean includePhoneticRuns) throws IOException, SAXException { this.includePhoneticRuns = includePhoneticRuns; readFrom(part.getInputStream()); } /** * Read this shared strings table from an XML file. * * @param is The input stream containing the XML document. * @throws IOException if an error occurs while reading. * @throws SAXException if parsing the XML data fails. */ public void readFrom(InputStream is) throws IOException, SAXException { // test if the file is empty, otherwise parse it PushbackInputStream pis = new PushbackInputStream(is, 1); int emptyTest = pis.read(); if (emptyTest > -1) { pis.unread(emptyTest); InputSource sheetSource = new InputSource(pis); try { XMLReader sheetParser = SAXHelper.newXMLReader(); sheetParser.setContentHandler(this); sheetParser.parse(sheetSource); } catch(ParserConfigurationException e) { throw new RuntimeException("SAX parser appears to be broken - " + e.getMessage()); } } } /** * Return an integer representing the total count of strings in the workbook. This count does not * include any numbers, it counts only the total of text strings in the workbook. * * @return the total count of strings in the workbook */ @Override public int getCount() { return this.count; } /** * Returns an integer representing the total count of unique strings in the Shared String Table. * A string is unique even if it is a copy of another string, but has different formatting applied * at the character level. * * @return the total count of unique strings in the workbook */ @Override public int getUniqueCount() { return this.uniqueCount; } /** * Return the string at a given index. * Formatting is ignored. * * @param idx index of item to return. * @return the item at the specified position in this Shared String table. * @deprecated use <code>getItemAt</code> instead */ @Removal(version = "4.2") @Deprecated public String getEntryAt(int idx) { /** * 这里就是修改部分了，直接从按行存储的临时文件读取需要的字符串 */ return readCache.get(idx); } /** * Returns all the strings. * Formatting is ignored. * * @return a list with all the strings * @deprecated use <code>getItemAt</code> instead */ @Removal(version = "4.2") @Deprecated public List<String> getItems() { return null; } @Override public RichTextString getItemAt(int idx) { return new XSSFRichTextString(getEntryAt(idx)); } //// ContentHandler methods //// private StringBuilder characters; private boolean tIsOpen; private boolean inRPh; @Override public void startElement(String uri, String localName, String name, Attributes attributes) throws SAXException { if (uri != null && ! uri.equals(NS_SPREADSHEETML)) { return; } if ("sst".equals(localName)) { String count = attributes.getValue("count"); if(count != null) this.count = Integer.parseInt(count); String uniqueCount = attributes.getValue("uniqueCount"); if(uniqueCount != null) this.uniqueCount = Integer.parseInt(uniqueCount); // this.strings = new ArrayList<>(this.uniqueCount); characters = new StringBuilder(64); } else if ("si".equals(localName)) { characters.setLength(0); } else if ("t".equals(localName)) { tIsOpen = true; } else if ("rPh".equals(localName)) { inRPh = true; //append space...this assumes that rPh always comes after regular <t> if (includePhoneticRuns && characters.length() > 0) { characters.append(" "); } } } @Override public void endElement(String uri, String localName, String name) throws SAXException { if (uri != null && ! uri.equals(NS_SPREADSHEETML)) { return; } if ("si".equals(localName)) { // strings.add(characters.toString().intern()); readCache.put(characters.toString()); /** * 这里就是修改的一部分，这里直接把字符串按行存入临时文件 */ counts ++; if(counts == this.uniqueCount) { readCache.putFinished(); } } else if ("t".equals(localName)) { tIsOpen = false; } else if ("rPh".equals(localName)) { inRPh = false; } } /** * Captures characters only if a t(ext) element is open. */ @Override public void characters(char[] ch, int start, int length) throws SAXException { if (tIsOpen) { if (inRPh && includePhoneticRuns) { characters.append(ch, start, length); } else if (! inRPh){ characters.append(ch, start, length); } } } }
至此代码效率有了相当大的提高，而且内存溢出问题也得到解决。详细测试代码：https://github.com/rongdi/poi-example.git