上一篇文章提过，HSSF的用户模式会导致读取海量数据时很慢，所以我们采用的是事件驱动模式。这个模式类似于xml的sax解析。需要实现一个接口，HSSFListener接口。
原理：根据excel底层存储（07以版本采用xml存储，以下版本采用二进制）标签决定事件出发点。
目标：在解析完一行(row)数据时进行触发。
优点：读取大数据时，不会导致内存溢出
缺点：用户在解析数据时比较困难。读取数据时速度不快的，因为读取数据的同时根据每个标签进行事件触发。
HSSF事件驱动读取文件的封装类解析。
主要用到两个类（一个是抽象类，一个是工具类）和一个接口：
第一个：工具类：HxlsRead.java:
package yycg.util;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List; public class HxlsRead extends HxlsAbstract{ //数据处理解析数据的接口
private HxlsOptRowsInterface hxlsOptRowsInterface;
//处理数据总数
private int optRows_sum = 0;
//处理数据成功数量
private int optRows_success = 0;
//处理数据失败数量
private int optRows_failure = 0;
//excel表格每列标题
private List<String> rowtitle ;
//失败数据
private List<List<String>> failrows;
//失败原因
private List<String> failmsgs ; //要处理数据所在的sheet索引,sheet索引从0开始
private int sheetIndex;
/**
* 导入文件的名称
* @param filename 导入文件的物理路径
* @param sheetIndex 要读取数据所在sheet序号
* @param hxlsOptRowsInterface 处理读取每一行数据的接口
* @throws IOException
* @throws FileNotFoundException
* @throws SQLException
*/
public HxlsRead(String filename,int sheetIndex,HxlsOptRowsInterface hxlsOptRowsInterface) throws IOException,
FileNotFoundException, SQLException {
super(filename);
this.sheetIndex = sheetIndex;
this.hxlsOptRowsInterface = hxlsOptRowsInterface;
this.rowtitle = new ArrayList<String>();
this.failrows = new ArrayList<List<String>>();
this.failmsgs = new ArrayList<String>();
} /**
* 对读取到一行数据进行解析
*/
@Override
public void optRows(int sheetIndex,int curRow, List<String> rowlist) throws Exception {
/*for (int i = 0 ;i< rowlist.size();i++){
System.out.print("'"+rowlist.get(i)+"',");
}
System.out.println();*/
//将rowlist的长度补齐和标题一致
int k=rowtitle.size()-rowlist.size();
for(int i=0;i<k;i++){
rowlist.add(null);
}
if(sheetIndex == this.sheetIndex){
optRows_sum++; if(curRow == 0){//记录标题
rowtitle.addAll(rowlist);
}else{
//接口返回的结果是导入数据的结果，有成功，有失败
String result = hxlsOptRowsInterface.optRows(sheetIndex, curRow, rowlist);
if(result!=null && !result.equals(hxlsOptRowsInterface.SUCCESS)){
optRows_failure++;//失败统计数加1
//失败数据列表
failrows.add(new ArrayList<String>(rowlist));
failmsgs.add(result);
}else{
optRows_success++;
}
} } } public long getOptRows_sum() {
return optRows_sum;
} public void setOptRows_sum(int optRows_sum) {
this.optRows_sum = optRows_sum;
} public long getOptRows_success() {
return optRows_success;
} public void setOptRows_success(int optRows_success) {
this.optRows_success = optRows_success;
} public long getOptRows_failure() {
return optRows_failure;
} public void setOptRows_failure(int optRows_failure) {
this.optRows_failure = optRows_failure;
} public List<String> getRowtitle() {
return rowtitle;
} public List<List<String>> getFailrows() {
return failrows;
} public List<String> getFailmsgs() {
return failmsgs;
} public void setFailmsgs(List<String> failmsgs) {
this.failmsgs = failmsgs;
} public static void main(String[] args){
HxlsRead xls2csv;
try {
//第一个参数就是导入的文件
//第二个参数就是导入文件中哪个sheet
//第三个参数导入接口的实现类对象
xls2csv = new HxlsRead("d:/test11.xls",0,new HxlsOptRowsInterfaceImpl());
xls2csv.process();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} }
}
第二个抽象类：
package yycg.util;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.PrintStream;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List; import org.apache.poi.hssf.eventusermodel.EventWorkbookBuilder.SheetRecordCollectingListener;
import org.apache.poi.hssf.eventusermodel.FormatTrackingHSSFListener;
import org.apache.poi.hssf.eventusermodel.HSSFEventFactory;
import org.apache.poi.hssf.eventusermodel.HSSFListener;
import org.apache.poi.hssf.eventusermodel.HSSFRequest;
import org.apache.poi.hssf.eventusermodel.MissingRecordAwareHSSFListener;
import org.apache.poi.hssf.eventusermodel.dummyrecord.LastCellOfRowDummyRecord;
import org.apache.poi.hssf.eventusermodel.dummyrecord.MissingCellDummyRecord;
import org.apache.poi.hssf.model.HSSFFormulaParser;
import org.apache.poi.hssf.record.BOFRecord;
import org.apache.poi.hssf.record.BlankRecord;
import org.apache.poi.hssf.record.BoolErrRecord;
import org.apache.poi.hssf.record.BoundSheetRecord;
import org.apache.poi.hssf.record.FormulaRecord;
import org.apache.poi.hssf.record.LabelRecord;
import org.apache.poi.hssf.record.LabelSSTRecord;
import org.apache.poi.hssf.record.NoteRecord;
import org.apache.poi.hssf.record.NumberRecord;
import org.apache.poi.hssf.record.RKRecord;
import org.apache.poi.hssf.record.Record;
import org.apache.poi.hssf.record.SSTRecord;
import org.apache.poi.hssf.record.StringRecord;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.poifs.filesystem.POIFSFileSystem; public abstract class HxlsAbstract implements HSSFListener {
private int minColumns;
private POIFSFileSystem fs;
private PrintStream output; private int lastRowNumber;
private int lastColumnNumber; /** Should we output the formula, or the value it has? */
private boolean outputFormulaValues = true; /** For parsing Formulas */
private SheetRecordCollectingListener workbookBuildingListener;
private HSSFWorkbook stubWorkbook; // Records we pick up as we process
private SSTRecord sstRecord;
private FormatTrackingHSSFListener formatListener; /** So we known which sheet we're on */
private int sheetIndex = -1;
private BoundSheetRecord[] orderedBSRs;
@SuppressWarnings("unchecked")
private ArrayList boundSheetRecords = new ArrayList(); // For handling formulas with string results
private int nextRow;
private int nextColumn;
private boolean outputNextStringRecord; private int curRow;
private List<String> rowlist;
@SuppressWarnings( "unused")
private String sheetName; public HxlsAbstract(POIFSFileSystem fs)
throws SQLException {
this.fs = fs;
this.output = System.out;
this.minColumns = -1;
this.curRow = 0;
this.rowlist = new ArrayList<String>();
} public HxlsAbstract(String filename) throws IOException,
FileNotFoundException, SQLException {
this(new POIFSFileSystem(new FileInputStream(filename)));
} //excel记录行操作方法，以行索引和行元素列表为参数，对一行元素进行操作，元素为String类型
// public abstract void optRows(int curRow, List<String> rowlist) throws SQLException ; //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,rowlist存储了行数据
public abstract void optRows(int sheetIndex,int curRow, List<String> rowlist) throws Exception; /**
* 遍历 excel 文件
*/
public void process() throws IOException {
MissingRecordAwareHSSFListener listener = new MissingRecordAwareHSSFListener(
this);
formatListener = new FormatTrackingHSSFListener(listener); HSSFEventFactory factory = new HSSFEventFactory();
HSSFRequest request = new HSSFRequest(); if (outputFormulaValues) {
request.addListenerForAllRecords(formatListener);
} else {
workbookBuildingListener = new SheetRecordCollectingListener(
formatListener);
request.addListenerForAllRecords(workbookBuildingListener);
} factory.processWorkbookEvents(request, fs);
} /**
* HSSFListener 监听方法，处理 Record
*/
@SuppressWarnings("unchecked")
public void processRecord(Record record) {
int thisRow = -1;
int thisColumn = -1;
String thisStr = null;
String value = null; switch (record.getSid()) {
case BoundSheetRecord.sid:
boundSheetRecords.add(record);
break;
case BOFRecord.sid:
BOFRecord br = (BOFRecord) record;
if (br.getType() == BOFRecord.TYPE_WORKSHEET) {
// Create sub workbook if required
if (workbookBuildingListener != null && stubWorkbook == null) {
stubWorkbook = workbookBuildingListener
.getStubHSSFWorkbook();
} // Works by ordering the BSRs by the location of
// their BOFRecords, and then knowing that we
// process BOFRecords in byte offset order
sheetIndex++;
if (orderedBSRs == null) {
orderedBSRs = BoundSheetRecord
.orderByBofPosition(boundSheetRecords);
}
sheetName = orderedBSRs[sheetIndex].getSheetname();
}
break; case SSTRecord.sid:
sstRecord = (SSTRecord) record;
break; case BlankRecord.sid:
BlankRecord brec = (BlankRecord) record; thisRow = brec.getRow();
thisColumn = brec.getColumn();
thisStr = "";
break;
case BoolErrRecord.sid:
BoolErrRecord berec = (BoolErrRecord) record; thisRow = berec.getRow();
thisColumn = berec.getColumn();
thisStr = "";
break; case FormulaRecord.sid:
FormulaRecord frec = (FormulaRecord) record; thisRow = frec.getRow();
thisColumn = frec.getColumn(); if (outputFormulaValues) {
if (Double.isNaN(frec.getValue())) {
// Formula result is a string
// This is stored in the next record
outputNextStringRecord = true;
nextRow = frec.getRow();
nextColumn = frec.getColumn();
} else {
thisStr = formatListener.formatNumberDateCell(frec);
}
} else {
thisStr = '"' + HSSFFormulaParser.toFormulaString(stubWorkbook,
frec.getParsedExpression()) + '"';
}
break;
case StringRecord.sid:
if (outputNextStringRecord) {
// String for formula
StringRecord srec = (StringRecord) record;
thisStr = srec.getString();
thisRow = nextRow;
thisColumn = nextColumn;
outputNextStringRecord = false;
}
break; case LabelRecord.sid:
LabelRecord lrec = (LabelRecord) record; curRow = thisRow = lrec.getRow();
thisColumn = lrec.getColumn();
value = lrec.getValue().trim();
value = value.equals("")?" ":value;
this.rowlist.add(thisColumn, value);
break;
case LabelSSTRecord.sid:
LabelSSTRecord lsrec = (LabelSSTRecord) record; curRow = thisRow = lsrec.getRow();
thisColumn = lsrec.getColumn();
if (sstRecord == null) {
rowlist.add(thisColumn, " ");
} else {
value = sstRecord
.getString(lsrec.getSSTIndex()).toString().trim();
value = value.equals("")?" ":value;
rowlist.add(thisColumn,value);
}
break;
case NoteRecord.sid:
NoteRecord nrec = (NoteRecord) record; thisRow = nrec.getRow();
thisColumn = nrec.getColumn();
// TODO: Find object to match nrec.getShapeId()
thisStr = '"' + "(TODO)" + '"';
break;
case NumberRecord.sid:
NumberRecord numrec = (NumberRecord) record; curRow = thisRow = numrec.getRow();
thisColumn = numrec.getColumn();
value = formatListener.formatNumberDateCell(numrec).trim();
value = value.equals("")?" ":value;
// Format
rowlist.add(thisColumn, value);
break;
case RKRecord.sid:
RKRecord rkrec = (RKRecord) record; thisRow = rkrec.getRow();
thisColumn = rkrec.getColumn();
thisStr = '"' + "(TODO)" + '"';
break;
default:
break;
} // 遇到新行的操作
if (thisRow != -1 && thisRow != lastRowNumber) {
lastColumnNumber = -1;
} // 空值的操作
if (record instanceof MissingCellDummyRecord) {
MissingCellDummyRecord mc = (MissingCellDummyRecord) record;
curRow = thisRow = mc.getRow();
thisColumn = mc.getColumn();
rowlist.add(thisColumn," ");
} // 如果遇到能打印的东西，在这里打印
if (thisStr != null) {
if (thisColumn > 0) {
output.print(',');
}
output.print(thisStr);
} // 更新行和列的值
if (thisRow > -1)
lastRowNumber = thisRow;
if (thisColumn > -1)
lastColumnNumber = thisColumn; // 行结束时的操作
if (record instanceof LastCellOfRowDummyRecord) {
if (minColumns > 0) {
// 列值重新置空
if (lastColumnNumber == -1) {
lastColumnNumber = 0;
}
}
// 行结束时， 调用 optRows() 方法，就是解析完每一行数据后，调用optRows进行这一行数据的处理，
lastColumnNumber = -1;
try {
optRows(sheetIndex,curRow, rowlist);
} catch (Exception e) {
e.printStackTrace();
}
rowlist.clear();
}
}
}
一个接口：把excel中数据的导出处理，就要实现这个接口
package yycg.util;
import java.util.List;
public interface HxlsOptRowsInterface {
public static final String SUCCESS="success";
/**
* 处理excel文件每行数据方法
* @param sheetIndex 为sheet的序号
* @param curRow 为行号
* @param rowlist 行数据
* @return success：成功，否则为失败原因
* @throws Exception
*/
public String optRows(int sheetIndex,int curRow, List<String> rowlist) throws Exception;
}
总结结构如下：
我们直接看HxlsRead里面的main函数里面是怎么用的（主要看注释）：
public static void main(String[] args){
HxlsRead xls2csv;
try {
//第一个参数就是导入的文件
//第二个参数就是导入文件中哪个sheet
//第三个参数导入接口的实现类对象
/**
* 这里的HxlsOptRowsInterfaceImpl()是HxlsOptRowsInterface接口的实现类。主要是 处理excel文件每行数据方法
* 就是说我们后续要把每一行数据存入到数据库的话，只要实现这个接口，然后在实现方法里面
* 实现吧数据插入到数据库就可以了。这是一个接口，当我想做别的应用的话，就可以实现这个接口，做相应的功能。
* 其他的任何结构都不用修改
*
*/
xls2csv = new HxlsRead("d:/test11.xls",0,new HxlsOptRowsInterfaceImpl());
/*
* 我们的xls2csv就是HxlsRead的类型，而HxlsRead继承了HxlsAbstract这个抽象类
* process是HxlsAbstract这个抽象类中的具体方法。这里的xls2csv.process();实际上调用的是父类
* 的process方法，我们看下父类的process方法，看到里面要调用optRows(sheetIndex,curRow, rowlist);这个抽象方法
* 在子类（本类中）已经实现了这个方法，由于多态的原因，调用的就是子类的这个方法。
*
*/
xls2csv.process();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
}
这样这个类的封装就好了。