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Archive for the ‘YUI Integration’ Category

Ajax file upload in Struts2 - Using Ajax File Upload Plugin

Saturday, January 19th, 2008

One of the advanced features of Struts2 is its plugin support. By using a standard interface API, you can seamlessly extend Struts2 capability.

Plugins are packaged as jar files along with any dependency jars. To use a plugin, you need to add it to the classpath. Struts automatically configures a plugin by using struts-plugin.xml packaged as part of the plugin jar.

When you use external plugins (plugins which are not part of standard Struts2 distribution) you must be aware of the risks. The plugin may not be fully tested and there could be other hidden issues. So always evaluate an external plugin before using it in a production server.

In this post, I will look at a very useful external Struts2 plugin - Monitored Ajax File Upload. Here is are the steps required for a sample demo.

1. Download Ajax File Upload plugin - You can download this from here.

2. Extract the zip and then copy the jars to WEB-INF/lib of your Web application. The jars are json-lib-2.0, commons-io-1.3.1, commons-fileupload-1.2 and AjaxFileUpload-0.03

3. Now create a FileUploadDemoAction action class extending from com.davidjc.ajaxfileupload.action.FileUpload. This is given below.

4. Configure struts.xml with the action and along with an additional interceptor as given below.

5. Create a JSP which contains file upload control. You need to use the ajaxfileuploadform custom tag. In this example, this jsp is ajaxupload.jsp.

<%@ taglib uri="http://www.davidjc.com/taglibs" prefix="afile"%>
<%@ taglib prefix="s" uri="/struts-tags" %>
<head>
<script src="http://yui.yahooapis.com/2.4.1/build/yahoo/yahoo-min.js"></script>  
<script src="http://yui.yahooapis.com/2.4.1/build/event/event-min.js"></script>  
<script src="http://yui.yahooapis.com/2.4.1/build/connection/connection-min.js"></script>

<afile:head />

</head>
<style>
body {font-family:"Tahoma";}
.file_container {width:480px;font-size:11px;border: 1px solid black;margin:0px;border-collapse:collapse;}
.filelist {font-size:11px;width:100%;margin:0px;border-collapse:collapse;}
#ajaxFileUploadForm .label {font-size:11px;}
#ajaxFileUploadForm input {font-size:11px;}
.filelist tr.odd {background-color:#eef;}
.filelist tr.even {	background-color:#dde;}
.filelist tr td {padding:4px;}
</style>

<body>
	<table class="file_container">
		<tr><td>This demonstrates the use of Struts2 Ajax upload plugin and YUI Ajax connect library.
		For more details see <a href="">here</a>.
		</td></tr>
		<tr>
			<td><afile:ajaxfileuploadform action="FileUploadDemoAction" dobefore="" doafter="show_list" /></td>
		</tr>
		<tr>
			<td><div id='did'></div></td>
		</tr>
	</table> 
</body>

6. This added files are displayed below the upload control using Ajax. For this YUI component connect is used for the GET request. The request is made to FileUploadDetailsAction and the results are returned using uploadlist.jsp. This content is added to the div tag (with id “did”) in the main page. Note how the ajax call is done from show_list method. This method is given as doafter parameter which is a JavaScript function executed immediately after file upload.

The above code also illustrates usage OGNL expressions and the use of status attribute on iterator tag for handling even/odd rows.

7. Configure the server location of the uploaded temporary file by setting struts.multipart.saveDir property. This can be done in struts.properties or web.xml. In this sample, it is set to c:/temp (windows machine) in web.xml. Make sure that the directory exists on the filesystem. In this example I have also set the maximum upload file size to 1MB using struts.multipart.maxSize property.

Complete details of the uploaded file is available in the FileUploadDemoAction. The temporary file created during upload is deleted after sometime. So you can use the File object to save the content to a separate folder or to a database.

To test this sample, use the JSP URL directly : http://localhost:8080/struts2demo/ajaxupload.jsp

Important: Ensure that you have Log4J jar in your application server’s lib folder.Also I am aware that this example gives errors and is not properly showing progress bar. I am still investigating these problems.

Got any questions? Don’t hesitate to contact me. Greetings to Dave Casserly for this excellent plugin.

Posted in Ajax, Howto, Struts2 Plugins, YUI Integration | 5 Comments »

Creating a cascading application menu using Struts2 and YUI

Saturday, January 19th, 2008

Download Source | View Demo

Yahoo User Interface (YUI) library is a set of Javascript based client side components for building highly interactive Web applications. All the YUI components work on the client side data. It also has built in Ajax support.

By integrating YUI to your Struts2 application, you can create cutting edge Web 2.0 rich client applications. In this post, I will show you how the YUI Menu component can be used along with Struts2 to create a cascading application menu.

Following are the components used in this sample project.

1. struts.xml - Struts2 action mappings.

2. web.xml - Configuration file for the sample web application

3. Menu.java - This encapsulates a Menu object. Can contain sub menus.

4. MenuDemoAction.java - Controller class for Menu demo. Contains code to populate sample Menu data. In real projects, you will populate this from database.

package yuimenudemo.action;

import java.util.ArrayList;
import java.util.List;
import javax.servlet.http.HttpServletRequest;
import org.apache.struts2.interceptor.ServletRequestAware;
import yuimenudemo.dto.Menu;
import com.opensymphony.xwork2.ActionSupport;

public class MenuDemoAction extends ActionSupport implements ServletRequestAware{
	HttpServletRequest request;
	public void setServletRequest(HttpServletRequest req) {
		request = req;
	}
	public String execute() throws Exception {
		
		List<Menu> menuList = createAppMenu();
		request.setAttribute("menu", menuList);
		return SUCCESS;
    }
	
	List<Menu> createAppMenu() {
		Menu m = new Menu();
		m.setId("1");
		m.setLabel("Search Engines");
		m.setUrl("");
		
		Menu n = new Menu();
		n.setId("2");
		n.setLabel("Internet Mail");
		n.setUrl("");	
		
		Menu m1 = new Menu();
		m1.setId("3");
		m1.setLabel("Google");
		m1.setUrl("http://www.google.com");
		
		Menu m2 = new Menu();
		m2.setId("4");
		m2.setLabel("Yahoo");
		m2.setUrl("http://www.yahoo.com");
		
		Menu n1 = new Menu();
		n1.setId("5");
		n1.setLabel("Gmail");
		n1.setUrl("http://gmail.com");	
		
		m.addMenu(m1);
		m.addMenu(m2);
		n.addMenu(n1);
		
		List<Menu> l = new ArrayList<Menu>();
		l.add(m);
		l.add(n);
		return l;
		
	}
	
}

5. menudemo.jsp - This is a sample application screen with application menu at the top.

6. AppMenuTag.java - This is a custom tag library which renders a YUI based Menu bar.

package yuimenudemo.tag;

import java.util.List;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.TagSupport;

import yuimenudemo.dto.Menu;

public class AppMenuTag extends TagSupport {

public int doEndTag() throws JspException {
		List<Menu> l = (List<Menu>) pageContext.getRequest().getAttribute(
				"menu");
       JspWriter out = pageContext.getOut();
        try {
            out.println("<script>");
            out.println("var str_jSon= '"+getMenuDataScript(l)+"';");
            out.println(getMenuCodeScript());
            out.println("</script>");
        }catch(Exception ex) {
            ex.printStackTrace();
        }
		return (EVAL_PAGE);
	}

private String getMenuDataScript(List<Menu> l) {
		StringBuffer jSon = new StringBuffer();
		jSon.append("[");
		menuToJSon(l, jSon);
		jSon.append("]");
		return jSon.toString();
	}
	
	private String getMenuCodeScript() {
	       return " YAHOO.util.Event.onDOMReady(function () { "
           + " var jSon = YAHOO.lang.JSON.parse(str_jSon); "
           + " var menuBar = new YAHOO.widget.MenuBar('sample_menubar',{ autosubmenudisplay: true }); "
           + " YAHOO.util.Dom.addClass(menuBar.element, 'yuimenubarnav');  "
           + " menuBar.addItems(jSon); "
           + " menuBar.render('menu_div'); "
           + "}); "; 
	}

public void menuToJSon(List<Menu> l, StringBuffer jSon) {
		for (int i = 0; i < l.size(); i++) {
			Menu menu = (Menu) l.get(i);
			String s1 = menu.getLabel();
			jSon.append("{\"text\":");
			jSon.append("\"" + s1 + "\"");

if (menu.getUrl() != null
					&& !menu.getUrl().equals("")) {
				jSon.append(",\"url\":");
				jSon.append("\"" + menu.getUrl() + "\"");
			}

if (menu.getSubmenus() != null
					&& menu.getSubmenus().size() > 0) {
				jSon.append(",\"submenu\":{\"id\":\"" + menu.getId() + "\", \"itemdata\":[");
				menuToJSon(menu.getSubmenus(), jSon);
				jSon.append("]}");
			}

jSon.append("}");
			if (i != (l.size() - 1)) {
				jSon.append(",");
			}
		}
	}

}

7. menu.tld - The tag library configuration file inside WEB-INF folder.

In addition, this example uses the following css and JavaScript files provided as part of YUI. In real projects, these also must be part of your project.

8. http://yui.yahooapis.com/2.4.1/build/menu/assets/skins/sam/menu.css

9. http://yui.yahooapis.com/2.4.1/build/yahoo-dom-event/yahoo-dom-event.js
10. http://yui.yahooapis.com/2.4.1/build/container/container_core-min.js
11. http://yui.yahooapis.com/2.4.1/build/menu/menu-min.js
12. http://yui.yahooapis.com/2.4.1/build/json/json-beta-min.js

Now let us see how the code works.

When user accesses http://localhost:8080/struts2demo/MenuDemoAction.action, MenuDemoAction’s execute is invoked. This prepares the Menu data. A list of Menu objects is created. Each of this in turn can contain sub menus. After this control is passed to menudemo.jsp. In real applications, this will be fed from an XML file or from database tables.

menudemo.jsp contains AppMenuTag and it is invoked during JSP rendering. This converts the Menu object structure to a JSON structure using a YUI library. This JSON structure is given as input to the YUI menu control which renders the CSS based menu on the screen! Can it be any simpler? This whole project took me about 20 minutes to implement and test.

Now using similar techniques you can implement a wide range of controls available in YUI. These include tree, grid etc. which are frequently required in Web applications. YUI also contains utility functions such as a JSON library and methods for AJax interaction (YUI Connect).

Posted in Ajax, Howto, Struts2 Tips, YUI Integration | No Comments »

Archive for the ‘YUI Integration’ Category

Ajax file upload in Struts2 - Using Ajax File Upload Plugin

Creating a cascading application menu using Struts2 and YUI

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