将BIRT整合到自己的Java项目中(二)

关于编写viewer，关键在于使用ReportEngine API，这个在birt官方文档上有很详细的描述。 这里将几个主要环节总结一下：

启动ReportEngine
这里需要注意启动ReportEngine的开销问题和图片链的协议的问题。使用IReportEngineFactory比每次new一个出来性能方面要好很多。使用HTMLEmitterConfig可以使得生成的HTML报表中的图片的src指向一个web资源而非file资源。




public IReportEngine getEngine() ...{




try ...{




if(platformContext == null) ...{


platformContext = new PlatformServletContext(servletContext);


}


engineConfig = new EngineConfig();


engineConfig.setEngineHome(


servletContext.getRealPath("/WEB-INF/platform/"));


// 要求ENGINE HOME 位于WEB-INF/Platform


engineConfig.setPlatformContext(platformContext);


//This call sets the Log directory name and level


engineConfig.setLogConfig(getLogDir(), Level.FINE);




//设置Emitter，渲染HTML的时候，image的地址是HTTP协议而不是File协议


HTMLEmitterConfig emitterConfig = new HTMLEmitterConfig( );


emitterConfig.setActionHandler(new HTMLActionHandler());


HTMLServerImageHandler imageHandler = new HTMLServerImageHandler();


emitterConfig.setImageHandler(imageHandler);


engineConfig.getEmitterConfigs().put("html", emitterConfig);




//设置日志level


engineConfig.setLogConfig(getLogDir(), Level.WARNING);


//启动Platform，创建ReportEngine


Platform.startup(engineConfig);


IReportEngineFactory factory = (IReportEngineFactory) Platform


.createFactoryObject(IReportEngineFactory.EXTENSION_REPORT_ENGINE_FACTORY);


engine = factory.createReportEngine(engineConfig);


engine.changeLogLevel(Level.WARNING);




log.debug("A new engine startup.");




} catch (BirtException e) ...{


e.printStackTrace();


}




return engine;


}

运行报表
我理解为编译报表文件。BIRT在渲染报表之前，要将报表编译为.rptdocument，再根据这个文件将报表渲染为HTML格式或PDF格式。编译报表使用IRunTask：




protected void run(String rptDesign) ...{


assert (context != null);




IReportEngine engine = context.getEngine();


// Open a report design


IReportRunnable design = null;




try ...{


design = engine.openReportDesign(context


.getFullRptDesignFilename(rptDesign));


// Create task to run the report - use the task to


// execute the report and save to disk.


IRunTask task = engine.createRunTask(design);


String doc = context.getFullRptDocumentFilename(rptDesign);


// run the report and destroy the engine


task.run(doc);




log.debug("save rpt design to " + doc);


task.close();




} catch (EngineException e) ...{


e.printStackTrace();


}


}

渲染报表
BIRT支持HTML格式和PDF格式，这两种报表生成的过程相同，只是设置不同的RenderContext和RenderOptions。我们把相同的部分提取为父类的公共方法，不同的部分留给子类实现：


IReportDocument iReportDocument = engine.openReportDocument(docFilename);


//Create Render Task


IRenderTask task = engine.createRenderTask(iReportDocument);


task.addScriptableJavaObject("jsBirtObject",


getScriptableObject(scriptObj));




if(params != null && !params.isEmpty()) ...{


task.setParameterValues(params);


}


setRenderContext(task); //设置Render Context，具体由子类实现


setRenderOptions(task, out); //设置Render Options，具体由子类实现


task.render();


task.close();




} catch (EngineException e) ...{


e.printStackTrace();




} finally ...{


engine.shutdown();


}

渲染PDF和HTML报表

PDF




/** *//**


* @see AbstractBirtReportParser#setRenderContext(IRenderTask)


*/


@Override




protected void setRenderContext(IRenderTask task) ...{


PDFRenderContext renderContext = new PDFRenderContext();


renderContext.setEmbededFont(true);


HashMap contextMap = new HashMap();


contextMap.put( EngineConstants.APPCONTEXT_PDF_RENDER_CONTEXT, renderContext);


task.setAppContext( contextMap );


}






/** *//**


* @see AbstractBirtReportParser#setRenderOptions(IRenderTask, OutputStream)


*/


@Override




protected void setRenderOptions(IRenderTask task, OutputStream out) ...{


RenderOptionBase options = new RenderOptionBase();


options.setOutputStream(out);


options.setOutputFormat(RenderOptionBase.OUTPUT_FORMAT_PDF);


task.setRenderOption(options);


}

HTML
我们要生成一个HTML的一部分，而非包含<html/>标记的完整的HTML文档




/** *//**


* @see AbstractBirtReportParser#setRenderContext(IRenderTask)


*/


@Override




protected void setRenderContext(IRenderTask task) ...{


HTMLRenderContext renderContext = new HTMLRenderContext();


renderContext.setBaseURL(context.getBaseURL());


//You must define HTMLServerImageHandler to use a URL


renderContext.setBaseImageURL(context.getBaseImageURL());


//renderContext.setImageDirectory("myimages");


renderContext.setImageDirectory(context.getImageDirectory());


renderContext.setSupportedImageFormats("JPG;PNG");


HashMap contextMap = new HashMap();


contextMap.put( EngineConstants.APPCONTEXT_HTML_RENDER_CONTEXT, renderContext);


task.setAppContext( contextMap );


}






/** *//**


* @see AbstractBirtReportParser#setRenderOptions(oIRenderTask, OutputStream)


*/


@Override




protected void setRenderOptions(IRenderTask task, OutputStream out) ...{


HTMLRenderOption options = new HTMLRenderOption();


options.setOutputStream(out);


options.setEmbeddable(true);


task.setRenderOption(options);


}