视图渲染

视图渲染

接上一节，获取到了ModelAndView对象，ModelAndView包含有view对象和Model对象，而视图渲染最为关键的就是这部分。

	@Override
	public void render(Map<String, ?> model, HttpServletRequest request, HttpServletResponse response) throws Exception {
		if (logger.isTraceEnabled()) {
			logger.trace("Rendering view with name '" + this.beanName + "' with model " + model +
				" and static attributes " + this.staticAttributes);
		}
		Map<String, Object> mergedModel = createMergedOutputModel(model, request, response);
		prepareResponse(request, response);
		renderMergedOutputModel(mergedModel, getRequestToExpose(request), response);
	}

	protected abstract void renderMergedOutputModel(
			Map<String, Object> model, HttpServletRequest request, HttpServletResponse response) throws Exception;

在进行视图渲染时，会获取到上一节构造的view和model对象作为参数传递给renderMergedOutputModel,不同view的子类，做具体的渲染操作。如InternalResourceView就是进行redirect或者forword操作，这属于servlet的范畴。不做详细解释。

下载Excel视图的例子

在这使用继承AbstractXlsxView来实现，并实现抽象方法buildExcelDocument。

public class RecordSetExportView extends AbstractXlsxView {
    private String title = UUID.randomUUID().toString();
    public RecordSetExportView(){
    }
    public RecordSetExportView(String title){
        this.title = title;
    }
    @Override
    protected void buildExcelDocument(Map<String, Object> model,Workbook workbook,HttpServletRequest request,HttpServletResponse response) throws Exception {
        RecordSet rs = (RecordSet) model.get("rs");
        Font font1 = workbook.createFont();
        font1.setFontName("黑体");
        font1.setFontHeightInPoints((short) 16);//设置字体大小
        font1.setBold(true);
        Font font2 = workbook.createFont();
        font2.setFontName("仿宋_GB2312");
        font2.setFontHeightInPoints((short) 12);
        CellStyle cellStyleTitle = workbook.createCellStyle();
        cellStyleTitle.setFont(font1);
        cellStyleTitle.setFillBackgroundColor((short) 13);
        CellStyle cellStyleLabel = workbook.createCellStyle();
        cellStyleLabel.setFont(font2);
        if(rs!= null && !rs.getData().isEmpty()){
            fileterColumnIfNeed(rs);
            Sheet sheet = null ;
            int rownum = 0;
            if(!rs.getColumns().isEmpty()){
                sheet = workbook.createSheet();
                Row row = sheet.createRow(rownum++);
                for(int i = 0;i < rs.getColumns().size();i++){
                    Cell cell = row.createCell(i);
                    cell.setCellType(CellType.STRING);
                    cell.setCellValue(rs.getColumns().get(i).get("desc"));
                    cell.setCellStyle(cellStyleTitle);
                    sheet.autoSizeColumn(i);
                }
                if(!rs.getData().isEmpty()){
                    for(Map<String,String> data:rs.getData()) {
                        Row row2 = sheet.createRow(rownum++);
                        for (int i = 0; i < rs.getColumns().size(); i++) {
                            String value = data.get(rs.getColumns().get(i).get("name"));
                            Cell cell = row2.createCell(i);
                            cell.setCellType(CellType.STRING);
                            cell.setCellValue(value);
                            cell.setCellStyle(cellStyleLabel);
                        }
                    }
                }
            }
        }
    }
    private void fileterColumnIfNeed(RecordSet rs){
        Iterator<Map<String,String>> iterator = rs.getColumns().iterator();
        while(iterator.hasNext()){
            Map<String,String> map = iterator.next();
            if("1".equals(map.get("hidden"))){
                iterator.remove();
            }
        }
    }
    }