1.背景
Excel在打印的时候需要附带水印打出，水印需要在下载Excel文件时就设置好
需要在打印的时候打印出水印，使用添加背景添加的水印在打印的时候不会出现，只有设置页眉，并将页眉设置为一长与打印纸张一样大小的图片，才可以在每一页中打印出水印
2.出现的问题
需要在打印的时候打印出水印，使用添加背景添加的水印在打印的时候不会出现，所以只有设置页眉，并将页眉设置为一长与打印纸张一样大小的图片，才可以在每一页中打印出水印，因为poi默认只支持字符串页眉设置，具体原因可以看下面参考文章。最终找到下面两种实现方法
参考：
poi源码详解默认只支持字符串页眉原因
3.实现方法
1 使用poi修改xlsx里面的xml文件来实现我们自己的页眉
2 使用Spire.XLS为Excel添加图片到页眉
有两种实现方法,推荐第一种，因为第一种是基于poi的另外扩展实现图片页眉，只要能拿到XSSFSheet就可以无缝切换到这种方式，能实现平滑迁移。
第二种方式jar包本身比较大，只用一个设置页眉的功能，依赖比较重。而且第二种只能在Excel处理完成后使用本地读取或者使用流读取在重新设置页眉，需要大幅修改原来代码输入输出流方式，整体调整会比较大。
4.使用poi修改xlsx里面的xml文件来实现我们自己的页眉
4.1 原理说明：
Excel本质上来说是一种xml描述文件，可以反向找到页眉设置的位置，然后改动xlsx里面的xml文件添加vmlDrawing1.vml页眉文件实现我们自己的页眉。
4.2 重写POIXMLDocumentPart 中的commit方法，写入我们自定义的vml文件
导入依赖
<!--poi导入导出组件-->
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>ooxml-schemas</artifactId>
<version>1.0</version>
</dependency>
```java
import org.apache.poi.POIXMLDocumentPart;
import org.apache.poi.openxml4j.opc.PackagePart;
import org.apache.xmlbeans.XmlObject;
import static org.apache.poi.POIXMLTypeLoader.DEFAULT_XML_OPTIONS;
import java.io.IOException;
import java.io.OutputStream;
public class VmlDrawing extends POIXMLDocumentPart {
String rIdPic = "";
String pictureTitle = "";
java.awt.Dimension imageDimension = null;
String headerPos = "";
VmlDrawing(PackagePart part) {
super(part);
}
void setRIdPic(String rIdPic) {
this.rIdPic = rIdPic;
}
void setPictureTitle(String pictureTitle) {
this.pictureTitle = pictureTitle;
}
void setHeaderPos(String headerPos) {
this.headerPos = headerPos;
}
void setImageDimension(java.awt.Dimension imageDimension) {
this.imageDimension = imageDimension;
}
@Override
protected void commit() throws IOException {
PackagePart part = getPackagePart();
OutputStream out = part.getOutputStream();
try {
// WPS测试通过版本
XmlObject doc = XmlObject.Factory.parse(
"<xml xmlns:v=\"urn:schemas-microsoft-com:vml\""
+ " xmlns:o=\"urn:schemas-microsoft-com:office:office\""
+ " xmlns:x=\"urn:schemas-microsoft-com:office:excel\">"
+ " <o:shapelayout v:ext=\"edit\">"
+ " <o:idmap v:ext=\"edit\" data=\"1\"/>"
+ " </o:shapelayout><v:shapetype id=\"_x0000_t75\" coordsize=\"21600,21600\" o:spt=\"75\""
+ " o:preferrelative=\"t\" path=\"m@4@5l@4@11@9@11@9@5xe\" filled=\"f\" stroked=\"f\">"
+ " <v:stroke joinstyle=\"miter\"/>"
+ " <v:formulas>"
+ " <v:f eqn=\"if lineDrawn pixelLineWidth 0\"/>"
+ " <v:f eqn=\"sum @0 1 0\"/>"
+ " <v:f eqn=\"sum 0 0 @1\"/>"
+ " <v:f eqn=\"prod @2 1 2\"/>"
+ " <v:f eqn=\"prod @3 21600 pixelWidth\"/>"
+ " <v:f eqn=\"prod @3 21600 pixelHeight\"/>"
+ " <v:f eqn=\"sum @0 0 1\"/>"
+ " <v:f eqn=\"prod @6 1 2\"/>"
+ " <v:f eqn=\"prod @7 21600 pixelWidth\"/>"
+ " <v:f eqn=\"sum @8 21600 0\"/>"
+ " <v:f eqn=\"prod @7 21600 pixelHeight\"/>"
+ " <v:f eqn=\"sum @10 21600 0\"/>"
+ " </v:formulas>"
+ " <v:path o:extrusionok=\"f\" gradientshapeok=\"t\" o:connecttype=\"rect\"/>"
+ " <o:lock v:ext=\"edit\" aspectratio=\"t\"/>"
+ " </v:shapetype><v:shape id=\"" + headerPos + "\" o:spid=\"_x0000_s1025\" type=\"#_x0000_t75\""
+ " style='position:absolute;margin-left:0;margin-top:0;"
+ "width:" + (int) imageDimension.getWidth() + "px;height:" + (int) imageDimension.getHeight() + "px;"
+ "z-index:1'>"
+ " <v:imagedata o:relid=\"" + rIdPic + "\" o:title=\"" + pictureTitle + "\"/>"
+ " <o:lock v:ext=\"edit\" rotation=\"t\"/>"
+ " </v:shape></xml>"
);
doc.save(out, DEFAULT_XML_OPTIONS);
out.close();
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
4.3 使用PackagePartName将图片打包进xml，然后使用重写的VmlDrawing写入vml页眉到对应文件目录位置
import org.apache.poi.openxml4j.opc.OPCPackage;
import org.apache.poi.openxml4j.opc.PackagePart;
import org.apache.poi.openxml4j.opc.PackagePartName;
import org.apache.poi.openxml4j.opc.PackagingURIHelper;
import org.apache.poi.ss.usermodel.Header;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.ss.util.ImageUtils;
import org.apache.poi.util.IOUtils;
import org.apache.poi.xssf.usermodel.*;
/**
* 为Excel设置图片页眉,大体思路为改动xlsx里面的xml文件来实现我们自己的页眉
* @param sheet
* @param waterRemarkPath
* @param position
* @throws Exception
*/
public static void putWaterRemarkToExcel(XSSFSheet sheet, String waterRemarkPath, String position)throws Exception {
InputStream inputStream = WaterMarkHandler.class.getResourceAsStream("/jpg/平台水印.png");
byte[] byteData = FileUtil.readInputStream(inputStream);
int pictureIdx = sheet.getWorkbook().addPicture(byteData, Workbook.PICTURE_TYPE_PNG);
OPCPackage opcpackage = ((XSSFWorkbook)sheet.getWorkbook()).getPackage();
PackagePartName partname = PackagingURIHelper.createPartName("/xl/drawings/vmlDrawing" + pictureIdx + ".vml");
PackagePart part = opcpackage.createPart(partname, "application/vnd.openxmlformats-officedocument.vmlDrawing");
VmlDrawing vmldrawing = new VmlDrawing(part); //创建页眉,位置LEFT,下面headerPos填写对应的
Header header = sheet.getHeader();
switch (position) {
case "LEFT":
header.setLeft("&G");
vmldrawing.setHeaderPos("LH");
break;
case "CENTER":
header.setCenter("&G");
vmldrawing.setHeaderPos("CH");
break;
case "RIGHT":
header.setRight("&G");
vmldrawing.setHeaderPos("RH");
break;
default:
throw new IllegalArgumentException("输入的position参数不合法");
}
XSSFPictureData picData = (XSSFPictureData)sheet.getWorkbook().getAllPictures().get(pictureIdx);
String rIdPic = vmldrawing.addRelation(null, XSSFRelation.IMAGES, picData).getRelationship().getId();
ByteArrayInputStream is = new ByteArrayInputStream(picData.getData());
java.awt.Dimension imageDimension = ImageUtils.getImageDimension(is, picData.getPictureType());
IOUtils.closeQuietly(is);
vmldrawing.setRIdPic(rIdPic);
vmldrawing.setPictureTitle(waterRemarkPath);
vmldrawing.setImageDimension(imageDimension);
String rIdExtLink = ((XSSFSheet)sheet).addRelation(null, XSSFRelation.VML_DRAWINGS, vmldrawing).getRelationship().getId();
((XSSFSheet)sheet).getCTWorksheet().addNewLegacyDrawingHF().setId(rIdExtLink);
}
参考：
poi 版本_poi的excel图片水印生成
easypoi代码git地址
5.使用Spire.XLS为Excel添加图片到页眉
5.1 下载jar包后放入工程/resources/lib本地，pom引入
<dependency>
<groupId>e-iceblue</groupId>
<artifactId>spire.xls.free</artifactId>
<version>5.1.0</version>
<scope>system</scope>
<systemPath>${project.basedir}/src/main/resources/lib/spire.xls.free-5.1.0.jar</systemPath>
</dependency>
<!--includeSystemScope 修改pom打包,将本地libjar打入-->
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>2.1.4.RELEASE</version>
<configuration>
<includeSystemScope>true</includeSystemScope>
</configuration>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
5.2 设置页眉为图片示例代码
public class ImageHeader {
public static void main(String[] args) throws IOException {
String imageFile = "C:\\Users\\Test1\\Desktop\\Image.png";
//加载Excel示例文档
Workbook workbook = new Workbook();
workbook.loadFromFile("C:\\Users\\Test1\\Desktop\\Sample.xlsx");
//获取第一个工作表
Worksheet worksheet = workbook.getWorksheets().get(0);
//加载图片
BufferedImage image = ImageIO.read( new File(imageFile));
//设置图片页眉
worksheet.getPageSetup().setLeftHeaderImage(image);
worksheet.getPageSetup().setLeftHeader("&G");
//设置显示样式
worksheet.setViewMode(ViewMode.Layout);
//保存文档
workbook.saveToFile("output/ImageHeader.xlsx", ExcelVersion.Version2010);
}
}
参考：
使用Spire.XLS为Excel添加图片到页眉
6.扩展，EsayExcel设置图片页眉
6.1 实现SheetWriteHandler的afterSheetCreate方法，调用putWaterRemarkToExcel为页眉添加图片水印
import com.alibaba.excel.write.handler.SheetWriteHandler;
/**
* excel添加水印，只支持XSSFWorkbook，其余类别：SXSSFWorkbook、SXSSFWorkbook请另寻他法
* easyExcel使用时需要设置inMemory(true)，否者默认使用的是SXSSFWorkbook，会报错！
*/
@Slf4j
@RequiredArgsConstructor
public class WaterMarkHandler implements SheetWriteHandler {
private final String WATER_MARK;
@Override
public void beforeSheetCreate(WriteWorkbookHolder writeWorkbookHolder, WriteSheetHolder writeSheetHolder) {
}
@Override
public void afterSheetCreate(WriteWorkbookHolder writeWorkbookHolder, WriteSheetHolder writeSheetHolder) {
// 获取sheet表
XSSFSheet sheet = (XSSFSheet) writeSheetHolder.getSheet();
try {
putWaterRemarkToExcel(sheet, WATER_MARK, "LEFT");
} catch (Exception e) {
log.info("添加水印失败, Message : {}", e.getMessage(), e);
}
}
}
6.2 导出示例，inMemory一定要配置
@GetMapping("/export")
public void export(HttpServletResponse response) throws IOException {
response.setContentType("application/vnd.ms-excel");
response.setCharacterEncoding("utf-8");
// 这里URLEncoder.encode可以防止中文乱码 当然和easyexcel没有关系
String fileName = URLEncoder.encode("导出测试", "UTF-8");
response.setHeader("Content-disposition", "attachment;filename=" + fileName + ".xlsx");
EasyExcel.write(response.getOutputStream(), DemoData.class)
.inMemory(true) // 注意，此项配置不能少
.registerWriteHandler(new WaterMarkHandler("我是水印"))
.sheet("模板")
.doWrite(data());
}
参考：
EasyExcel导出添加水印(设置背景，非插入图片的方式)
