原文：http://blog.csdn.net/z69183787/article/details/50737709
参考资料：http://bbs.51cto.com/thread-1074293-1-1.html
目前Java框架中能够生成excel文件的的确不少，但是，能够生成大数据量的excel框架，我倒是没发现，一般数据量大了都会出现内存溢出，所以，生成大数据量的excel文件要返璞归真，用java的基础技术,IO流来实现。
如果想用IO流来生成excel文件，必须要知道excel的文件格式内容，相当于生成html文件一样，用字符串拼接html标签保存到文本文件就可以生成一个html文件了。同理，excel文件也是可以的。怎么知道excel的文件格式呢？其实很简单，随便新建一个excel文件，双击打开，然后点击“文件”-》“另存为”，保存的类型为“xml表格”，保存之后用文本格式打开，就可以看到excel的字符串格式一览无遗了。
把下面的xml字符串复制到文本文件，然后保存为xls格式，就是一个excel文件。
<?xml version="1.0"?>
<?mso-application progid="Excel.Sheet"?>
<Workbook xmlns="urn:schemas-microsoft-com:office:spreadsheet"
xmlns:o="urn:schemas-microsoft-com:office:office"
xmlns:x="urn:schemas-microsoft-com:office:excel"
xmlns:ss="urn:schemas-microsoft-com:office:spreadsheet"
xmlns:html="http://www.w3.org/TR/REC-html40">
<DocumentProperties xmlns="urn:schemas-microsoft-com:office:office">
<Created>1996-12-17T01:32:42Z</Created>
<LastSaved>2000-11-18T06:53:49Z</LastSaved>
<Version>11.9999</Version>
</DocumentProperties>
<OfficeDocumentSettings xmlns="urn:schemas-microsoft-com:office:office">
<RemovePersonalInformation/>
</OfficeDocumentSettings>
<ExcelWorkbook xmlns="urn:schemas-microsoft-com:office:excel">
<WindowHeight>4530</WindowHeight>
<WindowWidth>8505</WindowWidth>
<WindowTopX>480</WindowTopX>
<WindowTopY>120</WindowTopY>
<AcceptLabelsInFormulas/>
<ProtectStructure>False</ProtectStructure>
<ProtectWindows>False</ProtectWindows>
</ExcelWorkbook>
<Styles>
<Style ss:ID="Default" ss:Name="Normal">
<Alignment ss:Vertical="Bottom"/>
<Borders/>
<Font ss:FontName="宋体" x:CharSet="134" ss:Size="12"/>
<Interior/>
<NumberFormat/>
<Protection/>
</Style>
</Styles>
<Worksheet ss:Name="Sheet1">
<Table ss:ExpandedColumnCount="2" ss:ExpandedRowCount="2" x:FullColumns="1"
x:FullRows="1" ss:DefaultColumnWidth="54" ss:DefaultRowHeight="14.25">
<Column ss:AutoFitWidth="0" ss:Width="73.5"/>
<Row>
<Cell><Data ss:Type="String">zhangzehao</Data></Cell>
<Cell><Data ss:Type="String">zhangzehao</Data></Cell>
</Row>
<Row>
<Cell><Data ss:Type="String">zhangzehao</Data></Cell>
</Row>
</Table>
<WorksheetOptions xmlns="urn:schemas-microsoft-com:office:excel">
<Selected/>
<Panes>
<Pane>
<Number>3</Number>
<ActiveRow>5</ActiveRow>
<ActiveCol>3</ActiveCol>
</Pane>
</Panes>
<ProtectObjects>False</ProtectObjects>
<ProtectScenarios>False</ProtectScenarios>
</WorksheetOptions>
</Worksheet>
<Worksheet ss:Name="Sheet2">
<Table ss:ExpandedColumnCount="0" ss:ExpandedRowCount="0" x:FullColumns="1"
x:FullRows="1" ss:DefaultColumnWidth="54" ss:DefaultRowHeight="14.25"/>
<WorksheetOptions xmlns="urn:schemas-microsoft-com:office:excel">
<ProtectObjects>False</ProtectObjects>
<ProtectScenarios>False</ProtectScenarios>
</WorksheetOptions>
</Worksheet>
<Worksheet ss:Name="Sheet3">
<Table ss:ExpandedColumnCount="0" ss:ExpandedRowCount="0" x:FullColumns="1"
x:FullRows="1" ss:DefaultColumnWidth="54" ss:DefaultRowHeight="14.25"/>
<WorksheetOptions xmlns="urn:schemas-microsoft-com:office:excel">
<ProtectObjects>False</ProtectObjects>
<ProtectScenarios>False</ProtectScenarios>
</WorksheetOptions>
</Worksheet>
</Workbook>
如果要生成千万级别以上的excel，除了这个关键点之外，还要控制IO流，如果有1000万记录，要迭代1000万次组装xml字符串，这样肯定占用相当大的内存，肯定内存溢出，所以，必须把组装的xml字符串分批用IO流刷新到硬盘里，如果是在web应用中，可以刷新到response中，web应用会自动把临时流保存到客户端的临时文件中，然后再一次性复制到你保存的路径。言归正传，分批刷新的话，可以迭代一批数据就flush进硬盘，同时把list，大对象赋值为空，显式调用垃圾回收器，表明要回收内存。这样的话，不管生成多大的数据量都不会出现内存溢出的，我曾经试过导出1亿的excel文件，都不会出现内存溢出，只是用了35分钟。
当然，如果要把实现做的优雅一些，在组装xml字符串的时候，可以结合模板技术来实现，我个人喜好stringtemplate这个轻量级的框架，我给出的DEMO也是采用了模板技术生成的，当然velocity和freemarker都是可以，stringbuilder也行，呵呵。
我为人比较懒，本意不是为了写个帖子的，只是想多赚点下载豆:lol1 ，这和赚钱一样谁不想？谁知道就写了那么多。同时鄙人知识寡陋，希望可以抛砖引玉。
综上：使用技术为 stringTemplate
pom.xml：
<dependency>
<groupId>antlr</groupId>
<artifactId>antlr</artifactId>
<version>2.7.7</version>
</dependency>
<dependency>
<groupId>org.antlr</groupId>
<artifactId>stringtemplate</artifactId>
<version>3.2.1</version>
</dependency>
template对象：
class Row{
private List<String> result;
public List<String> getResult() {
return result;
}
public void setResult(List<String> result) {
this.result = result;
}
}
class Worksheet{
private String sheet;
private int columnNum;
private int rowNum;
private List<String> title;
private List<Row> rows;
public String getSheet() {
return sheet;
}
public void setSheet(String sheet) {
this.sheet = sheet;
}
public List<Row> getRows() {
return rows;
}
public void setRows(List<Row> rows) {
this.rows = rows;
}
public int getColumnNum() {
return columnNum;
}
public void setColumnNum(int columnNum) {
this.columnNum = columnNum;
}
public int getRowNum() {
return rowNum;
}
public void setRowNum(int rowNum) {
this.rowNum = rowNum;
}
public List<String> getTitle() {
return title;
}
public void setTitle(List<String> title) {
this.title = title;
}
}
模版文件（通用）：
excel 头模板
<?xml version="1.0"?>
<?mso-application progid="Excel.Sheet"?>
<Workbook xmlns="urn:schemas-microsoft-com:office:spreadsheet"
xmlns:o="urn:schemas-microsoft-com:office:office"
xmlns:x="urn:schemas-microsoft-com:office:excel"
xmlns:ss="urn:schemas-microsoft-com:office:spreadsheet"
xmlns:html="http://www.w3.org/TR/REC-html40">
<DocumentProperties xmlns="urn:schemas-microsoft-com:office:office">
<Created>1996-12-17T01:32:42Z</Created>
<LastSaved>2013-08-02T09:21:24Z</LastSaved>
<Version>11.9999</Version>
</DocumentProperties>
<OfficeDocumentSettings xmlns="urn:schemas-microsoft-com:office:office">
<RemovePersonalInformation/>
</OfficeDocumentSettings>
<ExcelWorkbook xmlns="urn:schemas-microsoft-com:office:excel">
<WindowHeight>4530</WindowHeight>
<WindowWidth>8505</WindowWidth>
<WindowTopX>480</WindowTopX>
<WindowTopY>120</WindowTopY>
<AcceptLabelsInFormulas/>
<ProtectStructure>False</ProtectStructure>
<ProtectWindows>False</ProtectWindows>
</ExcelWorkbook>
<Styles>
<Style ss:ID="Default" ss:Name="Normal">
<Alignment ss:Vertical="Bottom"/>
<Borders/>
<Font ss:FontName="宋体" x:CharSet="134" ss:Size="12"/>
<Interior/>
<NumberFormat/>
<Protection/>
</Style>
</Styles>
body模板：
$worksheet:{
<Worksheet ss:Name="$it.sheet$">
<Table ss:ExpandedColumnCount="$it.columnNum$" ss:ExpandedRowCount="$it.rowNum$" x:FullColumns="1"
x:FullRows="1" ss:DefaultColumnWidth="54" ss:DefaultRowHeight="14.25">
<Row>
$it.title:{
<Cell><Data ss:Type="String">$it$</Data></Cell>
}$
</Row>
$it.rows:{
<Row>
$it.result:{
<Cell><Data ss:Type="String">$it$</Data></Cell>
}$
</Row>
}$
</Table>
</Worksheet>
}$
实际处理类：传入list对象，利用反射获取对象属性名及属性值
long startTimne = System.currentTimeMillis();
StringTemplateGroup stGroup = new StringTemplateGroup("stringTemplate");
//写入excel文件头部信息
StringTemplate head = stGroup.getInstanceOf("head");
File file = new File("D:/output2.xls");
PrintWriter writer = new PrintWriter(new BufferedOutputStream(new FileOutputStream(file)));
writer.print(head.toString());
writer.flush();
int totalRowNum = listWinningRecordDTOList.size();
int maxRowNum = 60000;
int sheets = totalRowNum % 60000 == 0 ? (totalRowNum/maxRowNum) : (totalRowNum/maxRowNum +1);
//excel单表最大行数是65535
List record = listWinningRecordDTOList;
List<String> title = new ArrayList<String>();
List<Method> getMethods = new ArrayList<Method>();
Class<?> clazz = record.get(0).getClass();
Field[] fields = clazz.getDeclaredFields();
if(fields != null && fields.length > 0){
for(Field field : fields){
if(!"serialVersionUID".equals(field.getName())) {
title.add(field.getName());
getMethods.add(clazz.getDeclaredMethod("get" + field.getName().substring(0, 1).toUpperCase() + field.getName().substring(1)));
}
}
}
// BeanInfo beanInfo=Introspector.getBeanInfo(clazz,Object.class);
// PropertyDescriptor[] proDescrtptors=beanInfo.getPropertyDescriptors();
// for(PropertyDescriptor propertyDescriptor : proDescrtptors){
// title.add(propertyDescriptor.getName());
// getMethods.add(propertyDescriptor.getReadMethod());
// }
int columnLength = title.size();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
//写入excel文件数据信息
for(int i=0;i<sheets;i++){
StringTemplate body = stGroup.getInstanceOf("body");
Worksheet worksheet = new Worksheet();
worksheet.setTitle(title);
worksheet.setSheet(" "+(i+1)+" ");
worksheet.setColumnNum(columnLength);
worksheet.setRowNum(maxRowNum+1);
List<Row> rows = new ArrayList<Row>();
int startIndex = i*maxRowNum;
int endIndex = Math.min((i+1)*maxRowNum -1,totalRowNum-1);
for(int j=startIndex;j<=endIndex;j++){
Row row = new Row();
List<String> result = new ArrayList<String>(columnLength);
for(int n=0;n<columnLength;n++){
Object value = getMethods.get(n).invoke(record.get(j));
if(value == null){
result.add("");
}else{
if(value instanceof Date){
result.add(sdf.format((Date)value));
}else{
result.add(value.toString());
}
}
}
row.setResult(result);
rows.add(row);
}
worksheet.setRows(rows);
body.setAttribute("worksheet", worksheet);
writer.print(body.toString());
writer.flush();
rows.clear();
rows = null;
worksheet = null;
body = null;
Runtime.getRuntime().gc();
System.out.println("正在生成excel文件的 sheet"+(i+1));
}
//写入excel文件尾部
writer.print("</Workbook>");
writer.flush();
writer.close();
System.out.println("生成excel文件完成");
long endTime = System.currentTimeMillis();
System.out.println("用时="+((endTime-startTimne)/1000)+"秒");
整理后的公用类：
import org.antlr.stringtemplate.StringTemplate;
import org.antlr.stringtemplate.StringTemplateGroup;
import java.io.*;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
/**
* Created by Administrator on 2016/2/25.
*/
public class ExcelStUtil {
public static void export(OutputStream outputStream,List target) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
long startTime = System.currentTimeMillis();
StringTemplateGroup stGroup = new StringTemplateGroup("stringTemplate");
//解决可能发生的中文乱码
stGroup.setFileCharEncoding("UTF-8");
//写入excel文件头部信息
StringTemplate head = stGroup.getInstanceOf("st/head");
PrintWriter writer = new PrintWriter(new BufferedOutputStream(outputStream));
writer.print(head.toString());
writer.flush();
int totalRowNum = target.size();
int maxRowNum = 60000;
int sheets = totalRowNum % 60000 == 0 ? (totalRowNum/maxRowNum) : (totalRowNum/maxRowNum +1);
//excel单表最大行数是65535
List record = target;
List<String> title = new ArrayList<String>();
List<Method> getMethods = new ArrayList<Method>();
Class<?> clazz = record.get(0).getClass();
Field[] fields = clazz.getDeclaredFields();
if(fields != null && fields.length > 0){
for(Field field : fields){
if(!"serialVersionUID".equals(field.getName())) {
title.add(field.getName());
getMethods.add(clazz.getDeclaredMethod("get" + field.getName().substring(0, 1).toUpperCase() + field.getName().substring(1)));
}
}
}
// BeanInfo beanInfo=Introspector.getBeanInfo(clazz,Object.class);
// PropertyDescriptor[] proDescrtptors=beanInfo.getPropertyDescriptors();
// for(PropertyDescriptor propertyDescriptor : proDescrtptors){
// title.add(propertyDescriptor.getName());
// getMethods.add(propertyDescriptor.getReadMethod());
// }
int columnLength = title.size();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
//写入excel文件数据信息
for(int i=0;i<sheets;i++){
StringTemplate body = stGroup.getInstanceOf("st/body");
Worksheet worksheet = new Worksheet();
worksheet.setTitle(title);
worksheet.setSheet(" "+(i+1)+" ");
worksheet.setColumnNum(columnLength);
worksheet.setRowNum(maxRowNum+1);
List<Row> rows = new ArrayList<Row>();
int startIndex = i*maxRowNum;
int endIndex = Math.min((i+1)*maxRowNum -1,totalRowNum-1);
for(int j=startIndex;j<=endIndex;j++){
Row row = new Row();
List<String> result = new ArrayList<String>(columnLength);
for(int n=0;n<columnLength;n++){
Object value = getMethods.get(n).invoke(record.get(j));
if(value == null){
result.add("");
}else{
if(value instanceof Date){
result.add(sdf.format((Date)value));
}else{
result.add(value.toString());
}
}
}
row.setResult(result);
rows.add(row);
}
worksheet.setRows(rows);
body.setAttribute("worksheet", worksheet);
writer.print(body.toString());
writer.flush();
rows.clear();
rows = null;
worksheet = null;
body = null;
Runtime.getRuntime().gc();
System.out.println("正在生成excel文件的 sheet"+(i+1));
}
//写入excel文件尾部
writer.print("</Workbook>");
writer.flush();
writer.close();
System.out.println("生成excel文件完成");
long endTime = System.currentTimeMillis();
System.out.println("用时="+((endTime-startTime)/1000)+"秒");
}
public static void main(String[] args) throws IOException, NoSuchMethodException, IllegalAccessException, InvocationTargetException {
System.out.println(Thread.currentThread().getContextClassLoader().getResource("").getPath());
System.out.println(ExcelStUtil.class.getResource("").getPath());
System.out.println(ExcelStUtil.class.getClassLoader().getResource("").getPath());
List<Sample> result = new ArrayList<Sample>();
for(int i=0;i<100;i++){
result.add(new Sample("放大双方的"+String.valueOf(i),String.valueOf(i)));
}
//OutputStream outputStream = new FileOutputStream("D:/output2.xls");
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
ExcelStUtil.export(byteArrayOutputStream,result);
//ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(byteArrayOutputStream.toByteArray());
//解决可能发生的中文乱码
ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(byteArrayOutputStream.toString().getBytes("UTF-8"));
File file = new File("D:/output2.xls");
OutputStream output = new FileOutputStream(file);
BufferedOutputStream bufferedOutput = new BufferedOutputStream(output);
//bufferedOutput.write(byteArrayOutputStream.toByteArray());
bufferedOutput.write(byteArrayOutputStream.toString().getBytes("UTF-8"));
bufferedOutput.flush();
bufferedOutput.close();
}
}
