SpringMVC: PropertyPlaceHolder

Another interesting support feature provided by Spring is using properties in your code through PropertyPlaceholderConfigurer. It helps load application properties from either a file or database table. The XML for using both,which will go into your spring context file,is 

<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">

    <property name="properties">

        <bean class="org.apache.commons.configuration.ConfigurationConverter"

             factory-method="getProperties">

                 <constructor-arg>

                   <bean class="org.apache.commons.configuration.DatabaseConfiguration">

                          <constructor-arg ref="<database bean>" />

                          <constructor-arg value="<database property table>" />

                          <constructor-arg value="<tablecolumn for placeholdernames>" />

                          <constructor-arg value="<tablecolumn for placeholdervalues>" />

                   </bean>

                </constructor-arg>

        </bean>

     </property>

     <property name="locations">

         <list>

            <value>file:src/main/webapp/WEB-INF/application.properties</value>

         </list>

     </property>

</bean>

<constructor-arg value="datasource" /> refers to a database bean defined in the spring context xml.

<constructor-arg value="app_config" /> refers to a database table APP_CONFIG.

<constructor-arg value="config_key" /> refers to column 'CONFIG_KEY' in APP_CONFIG that will contain the property you want to use in your code.

<constructor-arg value="config_value" />  refers to column 'CONFIG_VALUE' in APP_CONFIG that will contain the corresponding value of the property.

The below example shows how to then use the pre-loaded properties in your Spring code.

@Controller

public class DocumentController{

     @Value("${doc_Base}")

      String docBase="";

      @Value("${app_Env}")
      String appEnv=null;
      @Value("${doc_Path}")
      String docPath="";

      @Autowired
      private DocumentDAO documentDao;

      @Autowired
      private UserDAO userDao;

      @RequestMapping(value="/upload")
      public String uploadDocument(@RequestParam("docName)String documentName,
                                  @RequestParam("docFile")MultipartFile file)
      {
         <upload logic>

     }

       

}

The members docBase,appEnv & docPath will be initialized when the Controller instance gets created. Here doc_Base,app_Env & doc_Path are property names defined in CONFIG_KEY & their corresponding values in CONFIG_VALUE will be used for initialization

CONFIG_KEY       CONFIG_VALUE
doc_Base              test
app_Env               Dev
doc_Path              /dev/reviews



References

http://forum.spring.io/forum/spring-projects/container/82142-propertyplaceholderconfigurer-problems

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