空指針異常，而自動裝配

嗨，我收到空指針異常，而我嘗試從我的導出Excel類自動裝配到後臺辦公室控制器，但其他方式正在工作。請幫助我，我需要從我的後臺控制器獲取數據.... 下面是我的代碼片段空指針異常，而自動裝配

這是我ExportExcelView

import java.util.ArrayList; 
import java.util.List; 
import java.util.Map; 

import javax.annotation.Resource; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 

import org.apache.log4j.Logger; 
import org.apache.poi.hssf.usermodel.HSSFRow; 
import org.apache.poi.hssf.usermodel.HSSFSheet; 
import org.apache.poi.hssf.usermodel.HSSFWorkbook; 
import org.springframework.beans.factory.annotation.Autowired; 
import org.springframework.beans.factory.annotation.Qualifier; 
import org.springframework.context.annotation.Configuration; 
import org.springframework.stereotype.Component; 
import org.springframework.stereotype.Repository; 
import org.springframework.stereotype.Service; 
import org.springframework.transaction.annotation.Transactional; 
import org.springframework.web.servlet.view.document.AbstractExcelView; 

import com.rectrix.exide.controller.BackOfficeController; 
import com.rectrix.exide.form.model.QuestionBankDetails; 
import com.rectrix.exide.service.ModuleService; 
@Configuration 
@Component 
@Repository 
@Service 
@Transactional 
public class ExportExcelView extends AbstractExcelView { 

    private BackOfficeController backOfficeController; 


    public BackOfficeController getBackOfficeController() { 
     return backOfficeController; 
    } 

    @Resource(name="backOfficeController") 
    public void setBackOfficeController(BackOfficeController backOfficeController) { 
     this.backOfficeController = backOfficeController; 
    } 

    private static final Logger logger = Logger.getLogger(ExportExcelView.class); 
    @Override 
    protected void buildExcelDocument(Map<String, Object> model, 
      HSSFWorkbook workbook, HttpServletRequest request, 
      HttpServletResponse response) throws Exception { 
     String value=(String) model.get("excel"); 


     if(value.equalsIgnoreCase("questionbankupload")){ 
         /* List<QuestionBankDetails> list=(List<QuestionBankDetails>)model.get("transactiondata");*/ 
         HSSFSheet excelSheet = workbook.createSheet("Question Bank Excel"); 
         setExcelForQuestionBankUpload(excelSheet/*,list*/);        
           } 

     } 
     public void setExcelForQuestionBankUpload(HSSFSheet excelSheet/*, List<QuestionBankDetails> list*/) { 


     HSSFRow excelHeader = excelSheet.createRow(0); 
     excelHeader.createCell(0).setCellValue("QUESTION"); 
     excelHeader.createCell(1).setCellValue("OPT1"); 
     excelHeader.createCell(2).setCellValue("OPT2"); 
     excelHeader.createCell(3).setCellValue("OPT3"); 
     excelHeader.createCell(4).setCellValue("OPT4"); 
     excelHeader.createCell(5).setCellValue("OPT5"); 
     excelHeader.createCell(6).setCellValue("CORRECT_ANSWER_OPTION"); 
     excelHeader.createCell(7).setCellValue("QUESTION_TYPE"); 
     excelHeader.createCell(8).setCellValue("SECTION_ID"); 
     excelHeader.createCell(9).setCellValue("LEVEL"); 

     // just for try 
     List<QuestionBankDetails> list = new ArrayList<QuestionBankDetails>(); 

     try { 
      list=backOfficeController.toGet(); // from this part my code is not going to controller 
        int i=1; 
      for(QuestionBankDetails qd : list) { 

       excelHeader = excelSheet.createRow(i++); 
        excelHeader.createCell(0).setCellValue(qd.getQuestion()); 
        excelHeader.createCell(1).setCellValue(qd.getOpt1()); 
        excelHeader.createCell(2).setCellValue(qd.getOpt2()); 
        excelHeader.createCell(3).setCellValue(qd.getOpt3()); 
        excelHeader.createCell(4).setCellValue(qd.getOpt4()); 
        excelHeader.createCell(5).setCellValue(qd.getOpt5()); 
        excelHeader.createCell(6).setCellValue(qd.getCorrectAnswer()); 
        excelHeader.createCell(7).setCellValue(qd.getQuestionType()); 
        excelHeader.createCell(8).setCellValue(qd.getSectionId()); 
        excelHeader.createCell(9).setCellValue(qd.getLevel()); 
       } 

     } catch (Exception e) { 
      e.printStackTrace(); 
      e.getMessage(); 
     } 
} 

}

這是我的控制器（內勤控制器）

import java.text.ParseException; 
import java.text.SimpleDateFormat; 
import java.util.ArrayList; 
import java.util.Calendar; 
import java.util.Collection; 
import java.util.Collections; 
import java.util.Date; 
import java.util.HashMap; 
import java.util.HashSet; 
import java.util.Iterator; 
import java.util.List; 
import java.util.Map; 
import java.util.Set; 
import java.util.regex.Pattern; 

import javax.mail.Multipart; 
import javax.management.relation.Role; 
import javax.resource.spi.AdministeredObject; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
import javax.servlet.http.HttpSession; 

import org.apache.log4j.Logger; 
import org.apache.poi.hssf.usermodel.HSSFRow; 
import org.apache.poi.hssf.usermodel.HSSFSheet; 
import org.apache.poi.hssf.usermodel.HSSFWorkbook; 
import org.apache.poi.ss.usermodel.Cell; 
import org.apache.poi.ss.usermodel.Row; 
import org.apache.poi.ss.usermodel.Sheet; 
import org.apache.poi.ss.usermodel.Workbook; 
import org.apache.poi.ss.usermodel.WorkbookFactory; 
import org.apache.poi.xssf.usermodel.XSSFSheet; 
import org.apache.poi.xssf.usermodel.XSSFWorkbook; 
import org.apache.xmlbeans.impl.xb.xsdschema.Public; 
import org.hibernate.engine.jdbc.batch.spi.Batch; 
import org.springframework.beans.factory.annotation.Autowired; 
import org.springframework.context.annotation.ComponentScan; 
import org.springframework.messaging.support.ErrorMessage; 
import org.springframework.security.authentication.AnonymousAuthenticationToken; 
import org.springframework.security.core.Authentication; 
import org.springframework.security.core.GrantedAuthority; 
import org.springframework.security.core.context.SecurityContextHolder; 
import org.springframework.security.core.userdetails.UserDetails; 
import org.springframework.security.web.authentication.logout.SecurityContextLogoutHandler; 
import org.springframework.stereotype.Component; 
import org.springframework.stereotype.Controller; 
import org.springframework.web.bind.annotation.RequestBody; 
import org.springframework.web.bind.annotation.RequestMapping; 
import org.springframework.web.bind.annotation.RequestMethod; 
import org.springframework.web.bind.annotation.RequestParam; 
import org.springframework.web.bind.annotation.ResponseBody; 
import org.springframework.web.multipart.MultipartFile; 
import org.springframework.web.multipart.MultipartHttpServletRequest; 
import org.springframework.web.servlet.ModelAndView; 

import sun.security.jca.GetInstance; 

import com.rectrix.exide.dao.LanguageDetailsDao; 
import com.rectrix.exide.dao.RoleDetailsDao; 
import com.rectrix.exide.dao.SlotDao; 
import com.rectrix.exide.exception.BatchNotFound; 
import com.rectrix.exide.exception.DuplicateFound; 
import com.rectrix.exide.exception.EmployeeIdNotFound; 
import com.rectrix.exide.exception.GroupNotFound; 
import com.rectrix.exide.exception.LanguageNotFound; 
import com.rectrix.exide.exception.ModuleNotFound; 
import com.rectrix.exide.exception.RoleNotFound; 
import com.rectrix.exide.exception.TopicNotFound; 
import com.rectrix.exide.form.model.AddConfigDetails; 
import com.rectrix.exide.form.model.AddToModuleDetails; 
import com.rectrix.exide.form.model.AddVariable; 
import com.rectrix.exide.form.model.AttendanceDetailsForm; 
import com.rectrix.exide.form.model.CreateBatchDetails; 
import com.rectrix.exide.form.model.CreateModuleDetails; 
import com.rectrix.exide.form.model.DummyModel; 
import com.rectrix.exide.form.model.EditModuleAdminDetails; 
import com.rectrix.exide.form.model.EmployeeDetails; 
import com.rectrix.exide.form.model.EmployeeFormDetails; 
import com.rectrix.exide.form.model.ExternalUploadDetails; 
import com.rectrix.exide.form.model.InternalUploadDetails; 
import com.rectrix.exide.form.model.LangDetailsForm; 
import com.rectrix.exide.form.model.ListAdminDetails; 
import com.rectrix.exide.form.model.ListModuleDetails; 
import com.rectrix.exide.form.model.QuestionBankDetails; 
import com.rectrix.exide.form.model.RoleModuleDetails; 
import com.rectrix.exide.form.model.SectionDetailsForm; 
import com.rectrix.exide.form.model.SessionStoreDetails; 
import com.rectrix.exide.form.model.SlotForm; 
import com.rectrix.exide.form.model.TopicDetailsForm; 
import com.rectrix.exide.form.model.TopicSectionCountDetails; 
import com.rectrix.exide.hris.model.EmployeeMasterLookUp; 
import com.rectrix.exide.model.BatchDetails; 
import com.rectrix.exide.model.GroupMaster; 
import com.rectrix.exide.model.LanguageDetails; 
import com.rectrix.exide.model.LoginUserDetail; 
import com.rectrix.exide.model.ModuleConfigDetails; 
import com.rectrix.exide.model.RoleDetails; 
import com.rectrix.exide.model.Slot; 
import com.rectrix.exide.model.StudentDetails; 
import com.rectrix.exide.model.ModuleDetails; 
import com.rectrix.exide.service.AttendanceService; 
import com.rectrix.exide.service.BatchService; 
import com.rectrix.exide.service.ModuleService; 
import com.sun.java.swing.plaf.motif.resources.motif; 
import com.sun.org.apache.bcel.internal.generic.RETURN; 
import com.sun.org.apache.regexp.internal.recompile; 
import com.sun.org.apache.xml.internal.serializer.EmptySerializer; 

@Controller 
@RequestMapping(value="/admin/") 
@Component 
@ComponentScan 

public class BackOfficeController { 

    private static final Logger logger = Logger.getLogger(BackOfficeController.class); 



    public BackOfficeController() { 
     // TODO Auto-generated constructor stub 
    } 



    @Autowired 
    private ModuleService moduleService; 



    @RequestMapping(value="questionuploadtemplate", method=RequestMethod.GET) 
    public ModelAndView getQuestionUploadTemplate(){ 
     return new ModelAndView("ExportExcel","excel","questionbankupload"); 
    } 



@RequestMapping(value="listquestions",method={RequestMethod.POST,RequestMethod.GET}) 
    public @ResponseBody List<QuestionBankDetails> getQuestionListByTopicId(@RequestParam String topicId, @RequestParam String langId, @RequestParam Long moduleId){ 
     List<QuestionBankDetails>list = new ArrayList<QuestionBankDetails>(); 
     try { 

      /*String topicId = "1"; 
         String langId = "l1"; 
         Long moduleId = (long)1;*/ 
      list = moduleService.getQuestionListByTopicId(topicId, langId, new Long(moduleId)); 
      return list; 

     }catch (Exception e) { 
      logger.error("error in fetching the questions from the topic id", e); 
     } 
     return list; 

    } 





public List<QuestionBankDetails> toGet(){ 

     List<QuestionBankDetails> list = new ArrayList<QuestionBankDetails>(); 
     try { 
      String topicId ="1"; 
      String langId ="l1"; 
      Long moduleId =(long)1; 
      list=getQuestionListByTopicId(topicId, langId, new Long(moduleId)); 
      return list; 

     }catch(Exception e) { 
      e.printStackTrace(); 
      e.getMessage(); 
     } 
     return new ArrayList<QuestionBankDetails>(); 
    } 

    }

這是我的豆

<beans xmlns="http://www.springframework.org/schema/beans" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns:context="http://www.springframework.org/schema/context" 
    xmlns:mvc="http://www.springframework.org/schema/mvc" 
    xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.1.xsd 
     http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.1.xsd 
     http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.1.xsd"> 
    <context:component-scan base-package="com.rectrix.exide.controller"></context:component-scan> 

    <mvc:annotation-driven /> 

    <bean 
     class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"> 
     <property name="locations" value="classpath:system.properties" /> 
    </bean> 



    <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver"> 
     <property name="prefix" value="${spring.view.prefix}" /> <property name="suffix" 
     value="${spring.view.suffix}" /> </bean> 



    <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"/> 

    <bean class="org.springframework.web.servlet.view.XmlViewResolver"> 
    <property name="location"> 
     <value>classpath:/META-INF/spring/spring-excel-views.xml</value> 
    </property> 
    <property name="order" value="0" /> 
    </bean> 
    <bean id="excelExport" class="com.rectrix.exide.excel.ExportExcelView"> 
    <property name="backOfficeController" ref="backOfficeController"/> 
    </bean> 

    <bean id="backOfficeController" class="com.rectrix.exide.controller.BackOfficeController"/> 



    <mvc:default-servlet-handler /> 



</beans>

來源

2015-04-03 Nitesh kumar

你不應該注入任何東西到你的看法。數據應該在模型中。該模型應該由控制器準備好。該觀點的任務是使用模型來表現自己。它不應該承擔任何其他的負擔。除此之外，你的配置和類是一團糟，你真的需要清理的東西。 – 2015-04-03 11:20:33

你的配置很混亂。首先修復你的課程..

public class ExportExcelView extends AbstractExcelView { ... }

刪除所有這些註釋。

@Controller 
@RequestMapping(value="/admin/") 
public class BackOfficeController { ... }

@Component和@ComponentScan沒有意義在這裏。

清理你的xml。

<beans xmlns="http://www.springframework.org/schema/beans" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns:context="http://www.springframework.org/schema/context" 
    xmlns:mvc="http://www.springframework.org/schema/mvc" 
    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"> 


    <context:component-scan base-package="com.rectrix.exide.controller" /> 
    <context:property-placeholder location="classpath:system.properties" /> 

    <mvc:annotation-driven /> 
    <mvc:default-servlet-handler /> 

    <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver"> 
     <property name="prefix" value="${spring.view.prefix}" /> 
     <property name="suffix" value="${spring.view.suffix}" /> 
    </bean> 

    <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"/> 

    <bean class="org.springframework.web.servlet.view.XmlViewResolver"> 
     <property name="location" value="classpath:/META-INF/spring/spring-excel-views.xml" /> 
     <property name="order" value="0" /> 
    </bean> 

</beans>

注：我假設你的基於Excel視圖在spring-excel-views.xml還定義！

然而，真正的問題是爲什麼你在視圖中注入控制器？視圖應該只使用模型來呈現它自己。它不應該做任何事情。不要將控制器注入視圖中，而應正確地準備模型。

您的看法應該是這樣的。

public class ExportExcelView extends AbstractExcelView { 

    private static final Logger logger = Logger.getLogger(ExportExcelView.class); 

    @Override 
    protected void buildExcelDocument(Map<String, Object> model, 
      HSSFWorkbook workbook, HttpServletRequest request, 
      HttpServletResponse response) throws Exception { 

     String value=(String) model.get("excel"); 

     if(value.equalsIgnoreCase("questionbankupload")){ 
      /* List<QuestionBankDetails> list=(List<QuestionBankDetails>)model.get("transactiondata");*/ 
      HSSFSheet excelSheet = workbook.createSheet("Question Bank Excel"); 
      setExcelForQuestionBankUpload(excelSheet, model);        
     }   
    } 

    public void setExcelForQuestionBankUpload(HSSFSheet excelSheet, model) { 

     HSSFRow excelHeader = excelSheet.createRow(0); 
     excelHeader.createCell(0).setCellValue("QUESTION"); 
     excelHeader.createCell(1).setCellValue("OPT1"); 
     excelHeader.createCell(2).setCellValue("OPT2"); 
     excelHeader.createCell(3).setCellValue("OPT3"); 
     excelHeader.createCell(4).setCellValue("OPT4"); 
     excelHeader.createCell(5).setCellValue("OPT5"); 
     excelHeader.createCell(6).setCellValue("CORRECT_ANSWER_OPTION"); 
     excelHeader.createCell(7).setCellValue("QUESTION_TYPE"); 
     excelHeader.createCell(8).setCellValue("SECTION_ID"); 
     excelHeader.createCell(9).setCellValue("LEVEL"); 

     // just for try 
     List<QuestionBankDetails> list = model.get("details"); 

     try { 
      int i=1; 
      for(QuestionBankDetails qd : list) { 
       excelHeader = excelSheet.createRow(i++); 
       excelHeader.createCell(0).setCellValue(qd.getQuestion()); 
       excelHeader.createCell(1).setCellValue(qd.getOpt1()); 
       excelHeader.createCell(2).setCellValue(qd.getOpt2()); 
       excelHeader.createCell(3).setCellValue(qd.getOpt3()); 
       excelHeader.createCell(4).setCellValue(qd.getOpt4()); 
       excelHeader.createCell(5).setCellValue(qd.getOpt5()); 
       excelHeader.createCell(6).setCellValue(qd.getCorrectAnswer()); 
       excelHeader.createCell(7).setCellValue(qd.getQuestionType()); 
       excelHeader.createCell(8).setCellValue(qd.getSectionId()); 
       excelHeader.createCell(9).setCellValue(qd.getLevel()); 
      } 

     } catch (Exception e) { 
      e.printStackTrace(); 
      e.getMessage(); 
     } 
    } 
}

和你的控制器應該準備模型。

@RequestMapping(value="questionuploadtemplate", method=RequestMethod.GET) 
public ModelAndView getQuestionUploadTemplate(){ 
    ModelAndView mav = new ModelAndView("ExportExcel"); 
    mav.addObject("excel", "questionbankupload"); 
    mav.addObject("details", doGet()); 
    return mav; 
}

來源

2015-04-03 11:28:19

非常感謝，先生，我是新來的泉水。你的解決方案在我的項目中運行你能告訴我，什麼是學習彈簧和MVC的最佳方式。我一天比一天困惑。我正在一個項目中工作，他們給我當天的任務，並且非常困難，我在谷歌搜索並在我的項目中實施它...請幫助我，並告訴我快速學習技術的最佳方式.... 。再一次感謝你 – 2015-04-03 11:52:32

空指針異常，而自動裝配

回答

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