J2EE项目中如何设计一个比较通用的Excel模板功能

在最近的项目开发中，发现，每个查询页面，都需要要去下载生成一个Excel文件的功能，并且，这个需求还是比较常见的，以前呢？就是单独为每个下载Excel，去定制写好下载功能了。。但是，渐渐发现，这种方式是不可取的，因为每个下载都要去设计一个下载功能，这样就无形中做了很多的重复劳动。。能不能写个通用的生成Excel模块呢？实际上就是要把重复处理的代码单独封装出来了！当然，这里参考了原来同事的写法后，在上面作了一些改进，代码量就大大减少了，如是就有了今天这遍“写个一个比较通用的Excel生成模板的方法”的文章来产生了，也希望的这遍文章，能对其它网友有所帮助！这里主要是用到了java反射方面的知识！

当然，要把的如下这种做法，想移植到自己的项目中去的话，稍作修改就可以了！

如下图

红色框中，有九个链接，都有对应的查询页面，每个查询页面得到的最终结果页面上，都会有一个“下载”的功能

根据下载的实际需求，生成模板的基本格式大致如下所示

对于上面的九个链接，也有如下九个模板文件

(每个模板文件的字段都各不相同的，相同的是“第一行是显示列名，第二行开始是以EL ${属性名}来表示的)

点击前面页面的“下载”功能后，显示结果页面效果大致如下所示

“下载”链接基本形式如下所示

<a href="DownDataPortalExcel?flag=dp_receiptjoborder" title="点击下载吧">下载</a>

也就是说用同一个Serverlet　DownDataPortalExcel来响应，根据flag标识的值来区分是下载的哪个模块

DownDataPortalExcel.java 文件中主要代码如下

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

HttpSession session=request.getSession();

//新生成的Excel文件名

String filename="";

List<Object> list=null;

String flag=request.getParameter("flag");

//在途

if(flag.equals("dp_transit"))

{

filename="transit";

// List<TransitBean> list=null;

list=(ArrayList<Object>)session.getAttribute("transitbeanlist");

}

//进货

if(flag.equals("dp_receipt"))

{

filename="receipt";

//List<ReceiptBean> list=null;

list=(ArrayList<Object>)session.getAttribute("receiptbeanlist");

}

//出货

if(flag.equals("dp_issue"))

{

filename="issue";

//List<IssueBean> list=null;

list=(ArrayList<Object>)session.getAttribute("issuebeanlist");

}

//库存

if(flag.equals("dp_inventory"))

{

filename="inventory";

// List<InventoryBean> list=null;

list=(ArrayList<Object>)session.getAttribute("inventorybeanlist");

}

//sku control

if(flag.equals("dp_skucontrol"))

{

filename="skucontrol";

// List<SkuControlBean> list=null;

list=(ArrayList<Object>)session.getAttribute("skucontrolbeanlist");

}

//aging report

if(flag.equals("dp_agingreport"))

{

filename="agingreport";

// List<AgingReportBean> list=null;

list=(ArrayList<Object>)session.getAttribute("agingreportbeanlist");

}

//active skus

if(flag.equals("dp_activeskus"))

{

filename="activesku";

// List<ActiveSKUSBean> list=null;

list=(ArrayList<Object>)session.getAttribute("activeskusbeanlist");

}

//log search

if(flag.equals("dp_logsearch"))

{

filename="logsearch";

// List<LogSearchBean> list=null;

list=(ArrayList<Object>)session.getAttribute("logsearchbeanlist");

}

//receipt joborder 进货工作单

if(flag.equals("dp_receiptjoborder"))

{

filename="receiptjoborder";

// List<ReceiptJobOrderBean> list=null;

list=(ArrayList<Object>)session.getAttribute("receiptjoborderbeanlist");

}

//封装项目名 从web.xml中来取值

ServletContext globlctx=request.getSession().getServletContext();

String projectname=globlctx.getInitParameter("projectname"); //得到ishprojects

OutputStream os = response.getOutputStream();

response.reset(); // 清空输出流

response.setHeader("Content-disposition", "attachment; filename="+filename+".xls");// 设定输出文件头

response.setContentType("application/msexcel");//

WriteExcel we = new WriteExcel();

we.WriteDPDataToExcel(list, projectname, filename,os);

os.close();

}

WriteExcel.java 文件　中调用方法如下

//处理 在途 进货 出货 库存 skucontrol activesku agingreport logsearch receiptjoborder

public void WriteDPDataToExcel(List list,String projectname,String filename,OutputStream os)

{

try

{

String root = System.getProperty("user.dir");

String src = root.substring(0, root.lastIndexOf("\"))+ "\\webapps\"+projectname+"\\excelstemplate\"+filename+".xls";

String dst = root.substring(0, root.lastIndexOf("\"))+ "\\webapps\"+projectname+"\\excelstemplate\"+filename+"_temp.xls";

File srcfile=new File(src);

File dstfile=new File(dst);

JWriterExcelTemplet jwe = new JWriterExcelTemplet(srcfile,dstfile);

//向目标文件写入内容

if(list!=null)

{

//从第二行开始

int fromrow=1;

jwe.setValues(fromrow,list);

//将新生成的文件作为输入源，放到输出流中去输出来就可完成下载的过程了

File srfile=new File(dst);

FileInputStream fi=new FileInputStream(srfile);

byte[] buf = new byte[2048];

int hasRead=0;

while((hasRead=fi.read(buf))>0)

{

os.write(buf, 0, hasRead);

}

os.close();

dstfile.deleteOnExit();

}

}

catch(Exception e)

{

e.printStackTrace();

}

}

通用的处理Excel文件模板类JWriterExcelTemplet代码如下

public class JWriterExcelTemplet {

private Workbook srcWorkbook = null;

private WritableWorkbook destWorkbook = null;

private WritableSheet sheet = null;

private OutputStream os = null;

public JWriterExcelTemplet() {

}

public JWriterExcelTemplet(File src, File dest) {

try {

srcWorkbook = Workbook.getWorkbook(src);

destWorkbook = Workbook.createWorkbook(dest, srcWorkbook);

sheet = destWorkbook.getSheet(0);

} catch (IOException e) {

e.printStackTrace();

} catch (BiffException e) {

e.printStackTrace();

}

}

public JWriterExcelTemplet(File src,OutputStream os) {

try {

this.os = os;

srcWorkbook = Workbook.getWorkbook(src);

destWorkbook = Workbook.createWorkbook(os, srcWorkbook);

sheet = destWorkbook.getSheet(0);

} catch (IOException e) {

e.printStackTrace();

} catch (BiffException e) {

e.printStackTrace();

}

}

public OutputStream getOs() {

return os;

}

public void setOs(OutputStream os) {

this.os = os;

}

public void setValues(int fromrow,List list) {

try {

//记录从Excel文件第几行开始搜索EL ${}的名字

int row = fromrow;

int col=30;

for (int j = 0; j < col; j++)

{

//设置可以写的单元格

WritableCell cell = sheet.getWritableCell(j,row);

if (cell.getType() == CellType.LABEL)

{

Label label = (Label) cell;

//当单元格中没有出现以$开头的字符时，不执行后面的语句，继续开始循环

if (!label.getString().startsWith("${"))

{

continue;

}

//下面这句就得到了${}中{和}之间的内容了

String vs = getField(label.getString());

//将List中相应的所有数据全部插入到Excel文件中的某一列中

insertCells(vs,row,j,list);

}

}

destWorkbook.write();

destWorkbook.close();

srcWorkbook.close();

} catch (WriteException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}

}

public String getField(String arg) {

if (arg.startsWith("${") && arg.endsWith("}"))

{

return arg.substring(arg.indexOf("{") + 1, arg.indexOf("}"));

}

return "";

}

public void insertCells(String fieldRef,int row,int col,List list) {

try {

Object object = null;

//只取list的第一个元素的值

object = (Object)list.get(0);

Class classType = object.getClass();

//getDeclaredFields() 包括公共、保护、默认（包）访问和私有字段

Field[] fields = classType.getDeclaredFields();

for (int i = 0; i < fields.length; i++)

{

Field f = fields[i];

String fValue = f.getName();

if (fValue.equalsIgnoreCase(fieldRef))

{

String firstLetter = fValue.substring(0, 1).toUpperCase();

String methodName = "get" + firstLetter+ fValue.substring(1);

//这里的classType实际上就是上面的类名

Method method = classType.getMethod(methodName, new Class[] {});

if (list.size() == 1)

{

Object obj = method.invoke(object, new Object[]{});

addCell(row,col,obj == null ? "":obj.toString()); //加入值

}

else

{

//这里要作一个判断，因为记录行，超过了Excel 2003 sheet文件最大行数65535行数后，会报错

//如超过，就只取65530行记录生成到Excel文件中了

int size=list.size();

if(size>=65535)

{

size=65530;

}

for (int k = 0; k < size; k++)

{

Object obj = method.invoke((Object)list.get(k), new Object[]{});

addCell(row,col,obj == null ? "":obj.toString()); //加入值

row ++;

}

}

}

else

{

continue;

}

}

} catch (NoSuchMethodException e) {

e.printStackTrace();

} catch (IllegalArgumentException e) {

e.printStackTrace();

} catch (IllegalAccessException e) {

e.printStackTrace();

} catch (InvocationTargetException e) {

e.printStackTrace();

}

}

public void addCell(int row,int col,String value) {

try {

Label label = new Label(col,row,value);

sheet.addCell(label);

} catch (Exception e) {

e.printStackTrace();

}

}

public static void main(String[] args) {

@SuppressWarnings("unused")

JWriterExcelTemplet jwe = new JWriterExcelTemplet(new File("D:\\aa.xls"), new File("D:\\xy.xls"));

}

public WritableWorkbook getDestWorkbook() {

return destWorkbook;

}

public void setDestWorkbook(WritableWorkbook destWorkbook) {

this.destWorkbook = destWorkbook;

}

public WritableSheet getSheet() {

return sheet;

}

public void setSheet(WritableSheet sheet) {

this.sheet = sheet;

}

public Workbook getSrcWorkbook() {

return srcWorkbook;

}

public void setSrcWorkbook(Workbook srcWorkbook) {

this.srcWorkbook = srcWorkbook;

}

}