Download does not start - spring

Question

I want to generate an excel file :
...
Export
...
// inside controller :
#RequestMapping(value = "/exportExcel", method = RequestMethod.GET)
public ModelAndView exportExcel(HttpServletRequest request) {
return new ModelAndView("excelExport");
}
servlet-context.xml :
<?xml version="1.0" encoding="UTF-8"?>
<beans:beans xmlns="http://www.springframework.org/schema/mvc"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:beans="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
<!-- DispatcherServlet Context: defines this servlet's request-processing infrastructure -->
<!-- Enables the Spring MVC #Controller programming model -->
<annotation-driven />
<!-- Handles HTTP GET requests for /resources/** by efficiently serving up static resources in the ${webappRoot}/resources directory -->
<resources mapping="/resources/**" location="/resources/" />
<beans:bean id="viewResolver1" class="org.springframework.web.servlet.view.XmlViewResolver">
<beans:property name="order" value="1"/>
<beans:property name="location" value="/WEB-INF/views.xml"/>
</beans:bean>
<!-- Resolves views selected for rendering by #Controllers to .jsp resources in the /WEB-INF/views directory -->
<beans:bean id="viewResolver2"
class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<beans:property name="order" value="2"/>
<beans:property name="prefix" value="/WEB-INF/views/" />
<beans:property name="suffix" value=".jsp" />
</beans:bean>
<beans:bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
<beans:property name="maxUploadSize" value="300000000"/>
</beans:bean>
<context:component-scan base-package="com.ambre.pta" />
</beans:beans>
views.xml :
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
<bean id="excelExport" class="com.ambre.pta.view.ExcelExportView" />
</beans>
the ExcelExportView class :
public class ExcelExportView extends AbstractXlsxView {
#Autowired
private ExportationDAO exportationDao;
#Override
protected void buildExcelDocument(Map<String, Object> model, Workbook workbook, HttpServletRequest request, HttpServletResponse response) throws Exception {
response.setHeader("Content-Disposition", "attachment; filename=\"export.xlsx\"");
for(Object[] param : exportationDao.getAllParams()) {
Sheet sheet = workbook.createSheet(String.valueOf(param[1]));
Row header = sheet.createRow(0);
List<DetailsParamExport> entetes = exportationDao.getAllDetailsParams(Integer.parseInt(String.valueOf(param[0])));
int enteteIdx = 0;
for (DetailsParamExport detail : entetes) {
header.createCell(enteteIdx).setCellValue(detail.getEntete());
enteteIdx++;
}
List<Object[]> rows = exportationDao.getSqlResults(String.valueOf(param[3]));
int rowIdx = 1;
for (Object[] row : rows) {
Row excelRow = sheet.createRow(rowIdx++);
for (int p=0; p<enteteIdx; p++) {
excelRow.createCell(p).setCellValue("cccccccc");
}
}
}
}
}
At runtime when clicking the link "Export" then I get blank page and the download box does not appear. So what is wrong ?

Answer 1

You are injecting a Spring bean
#Autowired
private ExportationDAO exportationDao;
inside a non-managed from Spring class, ExcelExportView. So you probably get a null-pointer exception when you call exportationDao.getAllParams(). Have you checked your logs?
You can pass the params array from the controller to the view and do not use the exportationDao at all in your ExcelExportView
Your Controller:
#Autowired
private ExportationDAO exportationDao;
#RequestMapping(value = "/exportExcel", method = RequestMethod.GET)
public ModelAndView exportExcel(HttpServletRequest request) {
ModelAndView mv = new ModelAndView("excelExport");
modelAndView.addObject("params", exportationDao.getAllParams());
return mv;
}
Your ExcelExportView:
// suppose the exportationDao.getAllParams() returns a Collection of Object arrays, if different replace it as required.
Collection<Object[]>params = (Collection<Object[]>) query.get("params");
for(Object[] param : params) {
....