Problem Statement and Source Files

Theory without examples can be hard to grasp and less useful. So just making a small problem and corresponding files. Lets see
Problem statement: Given an online reporting application. There is a form that posts certain parameters and displays reports accordingly. Let us say that there are two basic parameters: report type and date range. Report type may be word, pdf, text. Date range consists of a from and a to time. Further user has an option to specify current time as the to time. Our form bean would look something like this:

package myPackage;

public class MyFormBean{
 private String reportType;
 //date in format dd/MM/yyyy HH:mm
 privateDate fromDate;
 private Date toDate;
 private boolean useCurrentTime=true;

 //.......
 //public getters and setters for fields
 //.......
}   

Reports are denoted by a simple interface:

package myPackage;

public interface Report{
 String getFileUrl();
 String getType();
 Date getCreationTime();
}

Reports are fetched using this interface:

package myPackage;

public interface DataBaseUtil{
  List<Report> getReports(MyFormBean myFormBean);
}        

which may have some implementation like:

package myPackage;

public class DataBaseUtilImpl{
  private static DataBaseUtilImpl singleInst = new DataBaseUtilImpl();
  private DataBaseUtilImpl(){}

  public static DataBaseUtilImpl getInstance(){ return singleInst ; }

  public List<Report> getReports(MyFormBean myFormBean){
            //process command object to get a list of reports
 }
}
         

The controller will be injected something like this in the config file:

 <bean id="reportFormController" class="myPackage.ReportFormController">
     <property name "dataBaseUtil" ref="DataBaseUtilBean"/>
     <property name="formView" value="reportInput"/>
     <property name="bindOnNewForm" value="true"/>
     <property name="successView" value="reportOutput"/>
     <property name="validator" ref="myValidator"/>
     <property name="commandName" value="reportFormBean"/>
     <property name="commandClass" value="myPackage.MyFormBean"/>
</bean>
     

The actual form controller will look something like:

package myPackage;

import org.springframework.web.servlet.mvc.SimpleFormController;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.bind.ServletRequestDataBinder;
import org.springframework.beans.propertyeditors.CustomDateEditor;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.*;
import java.text.*;

public class ReportFormController extends SimpleFormController {
 private DataBaseUtil dataBaseUtil;

 public void setDataBaseUtil(DataBaseUtil dbUtil){
     this.dataBaseUtil = dbUtil;
 }

 public DataBaseUtil getDataBaseUtil(){
     return this.dataBaseUtil;
 }

 /*Override so as string inputs in the form bind directly to date in command object*/
  @Override
 protected void initBinder(HttpServletRequest request, ServletRequestDataBinder dataBinder) throws Exception{
     DateFormat df = new SimpleDateFormat("dd/MM/yyyy HH:mm");
     df.setLenient(false);
     dataBinder.registerCustomEditor(Date.class,new CustomDateEditor(df,false));
     super.initBinder(request,dataBinder);
 }


 @Override
 protected ModelAndView onSubmit(HttpServletRequest request, HttpServletResponse response,Object command, BindException bindException)throws Exception{
     //handle submit request
     ReportFormBean repFormBean = (ReportFormBean ) command;

     List<Report> reps ;

     if(dataBaseUtil != null)
         reps = dataBaseUtil.getReports(repFormBean);
     else
         reps = new ArrayList<Report>();

     ModelAndView mv = showForm(request, response, bindException);

     mvmodel.put("REPORTS", reps);

     return mv;
 }
}
         

From next post we will start exploring some practical problems using these files as our base.