有的时候，我们需要Excel中的数据，通过一个图画，可视化的表现出来。 那么这个时候，应该如何做呢？现在就借花献佛，以Apache POI自己提供的一个例子为例，给大家演示一下POI的API 如何画图的。下面是一个最终的效果图。然后分别给大家解释每段代码的作用和意义。
代码如下，
- import java.io.FileOutputStream;
- import org.apache.poi.ss.usermodel.*;
- import org.apache.poi.ss.util.*;
- import org.apache.poi.ss.usermodel.charts.*;
- import org.apache.poi.xssf.usermodel.XSSFWorkbook;
- /**
- * Illustrates how to create a simple scatter chart.
- *
- * @author Roman Kashitsyn
- */
- public class ScatterChart {
- public static void main(String[] args) throws Exception {
- Workbook wb = new XSSFWorkbook();
- Sheet sheet = wb.createSheet("Sheet 1");
- final int NUM_OF_ROWS = 3;
- final int NUM_OF_COLUMNS = 10;
- // Create a row and put some cells in it. Rows are 0 based.
- Row row;
- Cell cell;
- for (int rowIndex = 0; rowIndex < NUM_OF_ROWS; rowIndex++) {
- row = sheet.createRow((short) rowIndex);
- for (int colIndex = 0; colIndex < NUM_OF_COLUMNS; colIndex++) {
- cell = row.createCell((short) colIndex);
- cell.setCellValue(colIndex * (rowIndex + 1));
- }
- }
- Drawing drawing = sheet.createDrawingPatriarch();
- ClientAnchor anchor = drawing.createAnchor(0, 0, 0, 0, 0, 5, 10, 15);
- Chart chart = drawing.createChart(anchor);
- ChartLegend legend = chart.getOrCreateLegend();
- legend.setPosition(LegendPosition.TOP_RIGHT);
- ScatterChartData data = chart.getChartDataFactory().createScatterChartData();
- ValueAxis bottomAxis = chart.getChartAxisFactory().createValueAxis(AxisPosition.BOTTOM);
- ValueAxis leftAxis = chart.getChartAxisFactory().createValueAxis(AxisPosition.LEFT);
- leftAxis.setCrosses(AxisCrosses.AUTO_ZERO);
- ChartDataSource<Number> xs = DataSources.fromNumericCellRange(sheet, new CellRangeAddress(0, 0, 0, NUM_OF_COLUMNS - 1));
- ChartDataSource<Number> ys1 = DataSources.fromNumericCellRange(sheet, new CellRangeAddress(1, 1, 0, NUM_OF_COLUMNS - 1));
- ChartDataSource<Number> ys2 = DataSources.fromNumericCellRange(sheet, new CellRangeAddress(2, 2, 0, NUM_OF_COLUMNS - 1));
- data.addSerie(xs, ys1);
- data.addSerie(xs, ys2);
- chart.plot(data, bottomAxis, leftAxis);
- // Write the output to a file
- FileOutputStream fileOut = new FileOutputStream("ooxml-scatter-chart.xlsx");
- wb.write(fileOut);
- fileOut.close();
- }
- }
下面逐一来分解：
1.下面的代码新建一个工作簿和工作表单的对象
- Workbook wb = new XSSFWorkbook();
- Sheet sheet = wb.createSheet("Sheet 1");
2.下面这段代码是用生成初始化数据的，总共的数据有3行10列。
- final int NUM_OF_ROWS = 3;
- final int NUM_OF_COLUMNS = 10;
- // Create a row and put some cells in it. Rows are 0 based.
- Row row;
- Cell cell;
- for (int rowIndex = 0; rowIndex < NUM_OF_ROWS; rowIndex++) {
- row = sheet.createRow((short) rowIndex);
- for (int colIndex = 0; colIndex < NUM_OF_COLUMNS; colIndex++) {
- cell = row.createCell((short) colIndex);
- cell.setCellValue(colIndex * (rowIndex + 1));
- }
- }
3. 下面这段代码设置了画图的区域：从第5行开始，到15行结束；总共占用10列
- Drawing drawing = sheet.createDrawingPatriarch();
- ClientAnchor anchor = drawing.createAnchor(0, 0, 0, 0, 0, 5, 10, 15);
4.创建一个离散图的坐标系
- Chart chart = drawing.createChart(anchor);
- ChartLegend legend = chart.getOrCreateLegend();
- legend.setPosition(LegendPosition.TOP_RIGHT);
- ScatterChartData data = chart.getChartDataFactory().createScatterChartData();
- ValueAxis bottomAxis = chart.getChartAxisFactory().createValueAxis(AxisPosition.BOTTOM);
- ValueAxis leftAxis = chart.getChartAxisFactory().createValueAxis(AxisPosition.LEFT);
- leftAxis.setCrosses(AxisCrosses.AUTO_ZERO);
5.往离散图上填充数据
- ChartDataSource<Number> xs = DataSources.fromNumericCellRange(sheet, new CellRangeAddress(0, 0, 0, NUM_OF_COLUMNS - 1));
- ChartDataSource<Number> ys1 = DataSources.fromNumericCellRange(sheet, new CellRangeAddress(1, 1, 0, NUM_OF_COLUMNS - 1));
- ChartDataSource<Number> ys2 = DataSources.fromNumericCellRange(sheet, new CellRangeAddress(2, 2, 0, NUM_OF_COLUMNS - 1));
- data.addSerie(xs, ys1);
- data.addSerie(xs, ys2);
其中，下面的方法定义
- DataSources.fromNumericCellRange(sheet, new CellRangeAddress(0, 0, 0, NUM_OF_COLUMNS - 1));
如下，
- public static ChartDataSource<Number> fromNumericCellRange(Sheet sheet, CellRangeAddress cellRangeAddress)
从上面可以看出，其实填充数据的关键方法是，
- <pre name="code" class="java">new CellRangeAddress(0, 0, 0, NUM_OF_COLUMNS - 1)
那么这个方式是如何定义的呢？
- public CellRangeAddress(int firstRow, int lastRow, int firstCol, int lastCol)
从上面可以看出，其让我们制定数据是从那一行开始的，那一行结束的，那一列开始的，那一列结束。
在上面的代码的5句话中，分别把第1行的1到10列做为基准，然后把第2行的1到10列做一个比较，画出曲线系列1
把第1行的1到10列做为基准，然后把第3行的1到10列做一个比较，画出曲线系列2
6. 开始画图
- chart.plot(data, bottomAxis, leftAxis);
7. 保存成一个Excel文件
- FileOutputStream fileOut = new FileOutputStream("ooxml-scatter-chart.xlsx");
- wb.write(fileOut);
- fileOut.close();