displaytag的Excel導出實踐

本文轉自 http://lingceng.iteye.com/blog/1820081/

Displaytag官網有1.0, 1.1, 1.2等，注意找到對應的版本。源碼和API可以在Maven庫中找到。 
  常規的使用不是問題，這里說說關於Excel導出的問題，中文亂碼，使用POI等。我使用的是Displaytag1.1。 

基本導出功能 
  這種情況只需引入displaytag-1.1.jar。 
  設置column屬性media="html"將不會導出，media="excel"不會頁面顯示，默認既顯示又導出。 
  setProperty也可以寫在displaytag.properties中應用於所有表格。 

<display:table name="test" export="true" id="currentRowObject">  
  <display:column property="id" title="ID" />  
  <display:column property="email" />  
  <display:column property="status" />  
  <display:column media="html" property="date" />  
  <display:setProperty name="export.excel" value="true" />  
  <display:setProperty name="export.excel.filename" value="export.xls" />  
</display:table>  

 這時候導出的excel打開的時候office會報警，但是能夠打開，因為這不是正真的excel，只是csv改了后綴的純文本格式。可能出現中文亂碼，通過重載ExcelView來解決。 

Class SimpleChineseExcelView extends ExcelView {  
  public String getMimeType(){  
    //原代碼是return "application/vnd.ms-excel";  
    return "application/vnd.ms-excel;charset=gbk";   
  }  
}  

修改displaytag.properties中對應條目： 
  export.excel.class=yourpackage.SimpleChineseExcelView 
  
  這樣就勉強能用了，只要能夠忍受每次都需要另存為excel來避免報警，不用中文文件名，不在bodycontent中使用中文。這樣的實現只能是差強人意。中文問題解決 

使用POI 
  需要引入額外的displaytag-export-excel-1.1.jar，使用Maven解決依賴。 
  修改displaytag.properties中對應條目： 
  export.excel.class=org.displaytag.export.excel.ExcelHssfView 
  配置export filter： 

<!--Configure the Filter in your web.xml:-->  
  <filter>  
    <filter-name>ResponseOverrideFilter</filter-name>  
    <filter-class>org.displaytag.filter.ResponseOverrideFilter</filter-class>  
  </filter>  
<!--And add mappings for urls the filter will intercept, for example:-->  
  <filter-mapping>  
    <filter-name>ResponseOverrideFilter</filter-name>  
    <url-pattern>*.do</url-pattern>  
  </filter-mapping>  
  <filter-mapping>  
    <filter-name>ResponseOverrideFilter</filter-name>  
    <url-pattern>*.jsp</url-pattern>  
  </filter-mapping>  

 filter-mapping加在struts之前，acegi之后（如果有），放struts之后會出問題。 
  很好地解決各種中文問題，也是真正的excel。 

  實踐Hack： 
  項目中已經有了poi3.6，而displaytag-export-excel-1.1依賴的是poi3.0，版本太高，需要重新寫一個ExcelHssfView。其實很簡單，找到ExcelHssfView的源碼，刪除其中的所有的setEncoding方法，setEncoding方法在poi3.6中沒有。修改后的代碼如下，當然記得修改export.excel.class： 

package com.lingceng;  
  
import java.io.OutputStream;  
import java.util.Calendar;  
import java.util.Date;  
import java.util.Iterator;  
  
import javax.servlet.jsp.JspException;  
  
import org.apache.commons.lang.ObjectUtils;  
import org.apache.commons.lang.StringEscapeUtils;  
import org.apache.commons.lang.StringUtils;  
import org.apache.poi.hssf.usermodel.HSSFCell;  
import org.apache.poi.hssf.usermodel.HSSFCellStyle;  
import org.apache.poi.hssf.usermodel.HSSFFont;  
import org.apache.poi.hssf.usermodel.HSSFRow;  
import org.apache.poi.hssf.usermodel.HSSFSheet;  
import org.apache.poi.hssf.usermodel.HSSFWorkbook;  
import org.apache.poi.hssf.util.HSSFColor;  
import org.displaytag.Messages;  
import org.displaytag.exception.BaseNestableJspTagException;  
import org.displaytag.exception.SeverityEnum;  
import org.displaytag.export.BinaryExportView;  
import org.displaytag.model.Column;  
import org.displaytag.model.ColumnIterator;  
import org.displaytag.model.HeaderCell;  
import org.displaytag.model.Row;  
import org.displaytag.model.RowIterator;  
import org.displaytag.model.TableModel;  
  
  
/** 
 * Excel exporter using POI HSSF. 
 * @author Fabrizio Giustina 
 * @author rapruitt 
 * @version $Revision: 1.2 $ ($Author: fgiust $) 
 */  
public class MyExcelHssfView implements BinaryExportView  
{  
  
    /** 
     * TableModel to render. 
     */  
    private TableModel model;  
  
    /** 
     * export full list? 
     */  
    private boolean exportFull;  
  
    /** 
     * include header in export? 
     */  
    private boolean header;  
  
    /** 
     * decorate export? 
     */  
    private boolean decorated;  
  
    /** 
     * Generated sheet. 
     */  
    private HSSFSheet sheet;  
  
    /** 
     * @see org.displaytag.export.ExportView#setParameters(TableModel, boolean, boolean, boolean) 
     */  
    public void setParameters(TableModel tableModel, boolean exportFullList, boolean includeHeader,  
        boolean decorateValues)  
    {  
        this.model = tableModel;  
        this.exportFull = exportFullList;  
        this.header = includeHeader;  
        this.decorated = decorateValues;  
    }  
  
    /** 
     * @return "application/vnd.ms-excel" 
     * @see org.displaytag.export.BaseExportView#getMimeType() 
     */  
    public String getMimeType()  
    {  
        return "application/vnd.ms-excel"; //$NON-NLS-1$  
    }  
  
    /** 
     * @see org.displaytag.export.BinaryExportView#doExport(OutputStream) 
     */  
    public void doExport(OutputStream out) throws JspException  
    {  
        try  
        {  
            HSSFWorkbook wb = new HSSFWorkbook();  
            sheet = wb.createSheet("-");  
  
            int rowNum = 0;  
            int colNum = 0;  
  
            if (this.header)  
            {  
                // Create an header row  
                HSSFRow xlsRow = sheet.createRow(rowNum++);  
  
                HSSFCellStyle headerStyle = wb.createCellStyle();  
                headerStyle.setFillPattern(HSSFCellStyle.FINE_DOTS);  
                headerStyle.setFillBackgroundColor(HSSFColor.BLUE_GREY.index);  
                HSSFFont bold = wb.createFont();  
                bold.setBoldweight(HSSFFont.BOLDWEIGHT_BOLD);  
                bold.setColor(HSSFColor.WHITE.index);  
                headerStyle.setFont(bold);  
  
                Iterator iterator = this.model.getHeaderCellList().iterator();  
  
                while (iterator.hasNext())  
                {  
                    HeaderCell headerCell = (HeaderCell) iterator.next();  
  
                    String columnHeader = headerCell.getTitle();  
  
                    if (columnHeader == null)  
                    {  
                        columnHeader = StringUtils.capitalize(headerCell.getBeanPropertyName());  
                    }  
  
                    HSSFCell cell = xlsRow.createCell((short) colNum++);  
                    cell.setCellValue(columnHeader);  
                    cell.setCellStyle(headerStyle);  
                    //cell.setEncoding(HSSFCell.ENCODING_UTF_16);  
                }  
            }  
  
            // get the correct iterator (full or partial list according to the exportFull field)  
            RowIterator rowIterator = this.model.getRowIterator(this.exportFull);  
            // iterator on rows  
  
            while (rowIterator.hasNext())  
            {  
                Row row = rowIterator.next();  
                HSSFRow xlsRow = sheet.createRow(rowNum++);  
                colNum = 0;  
  
                // iterator on columns  
                ColumnIterator columnIterator = row.getColumnIterator(this.model.getHeaderCellList());  
  
                while (columnIterator.hasNext())  
                {  
                    Column column = columnIterator.nextColumn();  
  
                    // Get the value to be displayed for the column  
                    Object value = column.getValue(this.decorated);  
  
                    HSSFCell cell = xlsRow.createCell((short) colNum++);  
                    //cell.setEncoding(HSSFCell.ENCODING_UTF_16);  
  
                    if (value instanceof Number)  
                    {  
                        Number num = (Number) value;  
                        cell.setCellValue(num.doubleValue());  
                    }  
                    else if (value instanceof Date)  
                    {  
                        cell.setCellValue((Date) value);  
                    }  
                    else if (value instanceof Calendar)  
                    {  
                        cell.setCellValue((Calendar) value);  
                    }  
                    else  
                    {  
                        cell.setCellValue(escapeColumnValue(value));  
                    }  
  
                }  
            }  
            wb.write(out);  
        }  
        catch (Exception e)  
        {  
            throw new ExcelGenerationException(e);  
        }  
    }  
  
    // patch from Karsten Voges  
    /** 
     * Escape certain values that are not permitted in excel cells. 
     * @param rawValue the object value 
     * @return the escaped value 
     */  
    protected String escapeColumnValue(Object rawValue)  
    {  
        if (rawValue == null)  
        {  
            return null;  
        }  
        String returnString = ObjectUtils.toString(rawValue);  
        // escape the String to get the tabs, returns, newline explicit as \t \r \n  
        returnString = StringEscapeUtils.escapeJava(StringUtils.trimToEmpty(returnString));  
        // remove tabs, insert four whitespaces instead  
        returnString = StringUtils.replace(StringUtils.trim(returnString), "\\t", "    ");  
        // remove the return, only newline valid in excel  
        returnString = StringUtils.replace(StringUtils.trim(returnString), "\\r", " ");  
        // unescape so that \n gets back to newline  
        returnString = StringEscapeUtils.unescapeJava(returnString);  
        return returnString;  
    }  
  
    /** 
     * Wraps IText-generated exceptions. 
     * @author Fabrizio Giustina 
     * @version $Revision: 1.2 $ ($Author: fgiust $) 
     */  
    static class ExcelGenerationException extends BaseNestableJspTagException  
    {  
  
        /** 
         * D1597A17A6. 
         */  
        private static final long serialVersionUID = 899149338534L;  
  
        /** 
         * Instantiate a new PdfGenerationException with a fixed message and the given cause. 
         * @param cause Previous exception 
         */  
        public ExcelGenerationException(Throwable cause)  
        {  
            super(ExcelHssfView.class, Messages.getString("ExcelView.errorexporting"), cause); //$NON-NLS-1$  
        }  
  
        /** 
         * @see org.displaytag.exception.BaseNestableJspTagException#getSeverity() 
         */  
        public SeverityEnum getSeverity()  
        {  
            return SeverityEnum.ERROR;  
        }  
    }  
  
}