activiti源码剖析之使用图片生成器设置流程图高亮显示

在一个流程流转的过程中，可能已经经过多个节点，或者正在停留在某个任务节点。那么我们如何直观的显示当前流程已经完成了哪些节点，或者此时当前流程流转到了哪里？那么这里就用到了activiti提供的图片生成器ProcessDiagramGenerator。使用它可以对流程中的节点或者连线等进行高亮标识（也就是用显著的颜色圈起来)后生成图片的输入流，当然也可以对流程图中各个节点的图标，字体之类进行设置。

一、使用ProcessDiagramGenerator对流程运转到的节点进行高亮显示

        ProcessEngine defaultProcessEngine = ProcessEngines.getDefaultProcessEngine();

        ProcessEngineConfigurationImpl processEngineConfiguration = (ProcessEngineConfigurationImpl) defaultProcessEngine.getProcessEngineConfiguration();

        //获取默认图片生成器
        ProcessDiagramGenerator processDiagramGenerator = processEngineConfiguration.getProcessDiagramGenerator();
        //获取要生成的流程图的BpmnModel
        BpmnModel bpmnModel = defaultProcessEngine.getRepositoryService().getBpmnModel("delegateTest:1:4");
        //设置需要标注高亮的节点
        List<String> hightLightElements = new ArrayList<>();
        hightLightElements.add("usertask1");
        InputStream inputStream = processDiagramGenerator.generateDiagram(bpmnModel, "PNG", hightLightElements);

• 大致的步骤就是：

1. 获取流程引擎
2. 获取流程引擎配置实现类
3. 通过流程引擎配置实现类获取图片默认生成器ProcessDiagramGenerator
4. 获取流程模型BpmnModel
5. 创建需要高亮展示的节点的集合，元素为节点ID值
6. 调用ProcessDiagramGenerator的generateDiagram获取生成图片的输入流
7. 客户端展示

流程运转图.png

二、通过扩展源码实现设置自定义高亮图颜色，字体等绘制属性

如果默认的图片生成器满足不了我们的业务需求，比如我要求用户任务被标注高亮的时候颜色使用蓝色或者其他颜色，我想要图片中显示的字体是黑体、楷体？那么如果是这样应该怎么实现呢?

• 场景：使用蓝色标注流程图已经走过的连线。
• 实战
  1、扩展DefaultProcessDiagramCanvas

自定义类继承DefaultProcessDiagramCanvas，这里业务需求是连线标注为蓝色所以需要重写drawConnection方法，只需要修改当highLighted为true时，调用this.g.setPaint(）参数为连线的颜色。

public class CFProcessDiagramCanvasExt extends DefaultProcessDiagramCanvas {

    //定义连线颜色为蓝色
    protected static Color HIGHLIGHT_SequenceFlow_COLOR = Color.BLUE;

    public CFProcessDiagramCanvasExt(int width, int height, int minX, int minY, String imageType, String activityFontName, String labelFontName, String annotationFontName, ClassLoader customClassLoader) {
        super(width, height, minX, minY, imageType, activityFontName, labelFontName, annotationFontName, customClassLoader);
    }

    /**
     * 重写绘制连线的方式,设置绘制颜色
     */
    @Override
    public void drawConnection(int[] xPoints, int[] yPoints, boolean conditional, boolean isDefault, String connectionType, AssociationDirection associationDirection, boolean highLighted, double scaleFactor) {
        Paint originalPaint = this.g.getPaint();
        Stroke originalStroke = this.g.getStroke();
        this.g.setPaint(CONNECTION_COLOR);
        if (connectionType.equals("association")) {
            this.g.setStroke(ASSOCIATION_STROKE);
        } else if (highLighted) {
            this.g.setPaint(HIGHLIGHT_SequenceFlow_COLOR);
            this.g.setStroke(HIGHLIGHT_FLOW_STROKE);
        }

        for(int i = 1; i < xPoints.length; ++i) {
            Integer sourceX = xPoints[i - 1];
            Integer sourceY = yPoints[i - 1];
            Integer targetX = xPoints[i];
            Integer targetY = yPoints[i];
            java.awt.geom.Line2D.Double line = new java.awt.geom.Line2D.Double((double)sourceX, (double)sourceY, (double)targetX, (double)targetY);
            this.g.draw(line);
        }

        java.awt.geom.Line2D.Double line;
        if (isDefault) {
            line = new java.awt.geom.Line2D.Double((double)xPoints[0], (double)yPoints[0], (double)xPoints[1], (double)yPoints[1]);
            this.drawDefaultSequenceFlowIndicator(line, scaleFactor);
        }

        if (conditional) {
            line = new java.awt.geom.Line2D.Double((double)xPoints[0], (double)yPoints[0], (double)xPoints[1], (double)yPoints[1]);
            this.drawConditionalSequenceFlowIndicator(line, scaleFactor);
        }

        if (associationDirection.equals(AssociationDirection.ONE) || associationDirection.equals(AssociationDirection.BOTH)) {
            line = new java.awt.geom.Line2D.Double((double)xPoints[xPoints.length - 2], (double)yPoints[xPoints.length - 2], (double)xPoints[xPoints.length - 1], (double)yPoints[xPoints.length - 1]);
            this.drawArrowHead(line, scaleFactor);
        }

        if (associationDirection.equals(AssociationDirection.BOTH)) {
            line = new java.awt.geom.Line2D.Double((double)xPoints[1], (double)yPoints[1], (double)xPoints[0], (double)yPoints[0]);
            this.drawArrowHead(line, scaleFactor);
        }

        this.g.setPaint(originalPaint);
        this.g.setStroke(originalStroke);
    }


}

2. 扩展DefaultProcessDiagramGenerator，当initProcessDiagramCanvas时候，使用自定义的ProcessDiagramCanvas,只需要修改initProcessDiagramCanvas方法中最后一行为创建我们自定义的initProcessDiagramCanvas

注意：这里必须同时定义generateProcessDiagram方法，实现与DefaultProcessDiagramGenerator中的实现相同。如果不定义，程序依然会调用DefaultProcessDiagramGenerator中的generateProcessDiagram方法生成默认的DefaultProcessDiagramCanvas

public class ProcessDiagramGenarateExt extends DefaultProcessDiagramGenerator {

    @Override
    protected DefaultProcessDiagramCanvas generateProcessDiagram(BpmnModel bpmnModel, String imageType, List<String> highLightedActivities, List<String> highLightedFlows, String activityFontName, String labelFontName, String annotationFontName, ClassLoader customClassLoader, double scaleFactor) {
        this.prepareBpmnModel(bpmnModel);
        DefaultProcessDiagramCanvas processDiagramCanvas = initProcessDiagramCanvas(bpmnModel, imageType, activityFontName, labelFontName, annotationFontName, customClassLoader);
        ....
      实现同父类实现一模一样
    }

    protected static DefaultProcessDiagramCanvas initProcessDiagramCanvas(BpmnModel bpmnModel, String imageType, String activityFontName, String labelFontName, String annotationFontName, ClassLoader customClassLoader) {
       。。。。这里与父类代码一模一样
      
        //设置返回自定义ProcessDiagramCanvas
        return new CFProcessDiagramCanvasExt((int)maxX + 10, (int)maxY + 10, (int)minX, (int)minY, imageType, activityFontName, labelFontName, annotationFontName, customClassLoader);
    }

}

3. 使用自定义图片生成器进行流程运转图的生成

        ProcessEngine defaultProcessEngine = ProcessEngines.getDefaultProcessEngine();

        ProcessEngineConfigurationImpl processEngineConfiguration = (ProcessEngineConfigurationImpl) defaultProcessEngine.getProcessEngineConfiguration();

        //获取自定义图片生成器
        ProcessDiagramGenerator processDiagramGenerator = new ProcessDiagramGenarateExt();

        //获取要生成的流程图的BpmnModel
        BpmnModel bpmnModel = defaultProcessEngine.getRepositoryService().getBpmnModel("delegateTest:1:4");
        //设置需要标注高亮的节点
        List<String> hightLightElements = new ArrayList<>();
        hightLightElements.add("usertask1");
        //设置需要标注高亮的连线
        List<String> hightLightFlows = new ArrayList<>();
        hightLightFlows.add("flow1");
        InputStream inputStream = processDiagramGenerator.generateDiagram(bpmnModel, "PNG", hightLightElements,hightLightFlows);

- 生成结果

自定义生成结果.png