Spring MVC: PagedListHolder

Spring 3 MVC framework provides supporting classes/annotations that can prove to be real "gems" during development of your web application. I'll be covering a few of them, the first being "PagedListHolder".

PagedListHolder

Spring Framework comes with a bean called org.springframework.bean.support. PagedListHolder. As per documentation, PagedListHolder is a simple state holder bean for handling lists of objects, separating them into pages. It has setter methods to indicate page size, page number.

For e.g in your specific Controller class you can add the following code snippet to create paginated data that can be accessed in a JSP or any other View.

String srchkey= request.getParameter("srchkey"); if (srchkey!= null) { PagedListHolder<Product> productList = new PagedListHolder<Product>(getProductList(srchkey)); productList.setPage(0);         productList.setPageSize(4);        request.getSession().setAttribute("productList", productList);         return new ModelAndView("ListProducts", "productList", productList);    } else {         String page = request.getParameter("page");         PagedListHolder productList = (PagedListHolder)request.getSession().getAttribute("productList");         if ("next".equals(page))             productList.nextPage();         else if ("previous".equals(page))             productList.previousPage();                return new ModelAndView("ListProducts", "productList", productList);    }

References

http://stackoverflow.com/questions/2245035/how-to-implement-pagination-in-spring-mvc-3

Use AJAX to access JSON from a Struts2 Action class

If there is a use-case wherein a HTTPRequest invokes a Struts2 Action class to perform an action & its output is then to be received by an AJAX function on the target webpage, for e.g.population of data rows in an HTML table, then this is one approach to do it

1. Send the output of the Struts2 Action class as a JSON object. 

 Let's say we have an Action class 'JSONResponseAction.java' that is required to send a Java bean 'ResponseVO.java' ( it has 2 String fields- a status & a message) as a JSON object to client e.g a browser. 

public class JSONResponseAction extends BaseActionSupport
{

public ResponseVO responsVO;

public String load() throws IOException, ServletException

{

   

responseVO=new ResponseVO();

responseVO.setStatus("success");

responsVO.setMessage("Process completed");

}

public ResponseVO  getResponseVO() 

{

    return responseVO;

}

public void setResponseVO(ResponseVO responseVO) 

{

    this.responseVO= responseVO;

}

}

It is mandatory that setter & getter methods be present for 'ResponseVo' bean in the Action class for corresponding JSON object to be created & sent across the n/w. We can also use the default 'execute()' method of Struts2 Action class for this. In that case,We will not have to explicitly mention the method-name in the request URL in pt.3

2. In the struts.xml, we define an action 'JSONResponseAction.action' as follows

  <action name="JSONResponseAction"  class=JSONResponseAction>
  <result name="success" type="json">
     <param name="root">
             responseVO
  </param>
  <result name="failure">/error.jsp</result>
  <interceptor-ref name="defaultStack"/>
 </action>


3. On the client side, we can have JQuery code, something similar to what I have written below, to access 'ResponseVO'.

$.getJSON( "${pageContext.request.contextPath}/JSONResponseAction.action?method:load",

{<requestparamName>:<requestParamvalue>},

function(responseVO) {

     //Jquery or Javascript code to use 'ResponseVO'

});

4. We can also send an array of 'ResponsVO' beans in a similar fashion

public class JSONResponseAction extends BaseActionSupport
{

public ResponseVO[] responseVO;

public String load() throws IOException, ServletException
{
  //populate the array

}

public ResponseVO[]  getResponseVO() 

{

    return responseVO;

}

public void setResponseVO(ResponseVO[] responseVO) 

{

    this.responseVO= responseVO;

}

}