How to Access Files in Portlets

 

Introduction

When developing a portlet, there will be many times in which you need to read or write information to a file. However, you cannot use the File or FileReader/Writer classes in your portlet code because these constructors require the exact location of the file you are opening, which you do not know at the time of developing your portlet. This tip describes how files can be accessed in your portlet code.

 

Steps

1. In your par file, package the files you want to access similar to the following directory structure:

eg

images

   |-img1.gif

   |-img2.gif

html

   |-static.html

PORTLET-INF

   |-portlet.xml

   |-classes

         |- class files….

   |-resources

         |-news

               |-html

                     |- news.html

                     |-ja

|-news.html

                        |-zh

                              |-news.html

                  |-wml

                  ……

         |-xsl

               |-news.xsl

 

      Note: images and html folder names are arbitary, PORTLET-INF is required.

 

2. When the par file is installed, WPS will expand the images and html folders to the <wps_root>\app\web\portlets\yourparfilename directory. It will expand the PORTLET-INF folder to the <wps_root>\app\web\WEB-INF\portletapps\yourparfilename directory.
3. The difference between the images/html folder and the PORTLET-INF folder is that the files in images/html folders can be accessed directly by the client browser, but not those in PORTLET-INF. On the other hand, files in the PORTLET-INF folder can be accessed by your portlet’s java code, but not those in images/html folder. Note also the folder structure for multimarkup and multilanguage support.
4. So, the implication of this is that you should placed files that you want to access from your java code in the PORTLET-INF folder, and those files that you want the client browsers to access via the JSPs in the images/html folders.
5. To access the files (in the PORTLET-INF folder) from your java code, use the getResourceAsStream() method of the PortletContext class:

eg

InputStream stylesheetIOS =

               getPortletConfig().getContext().getResourceAsStream(“/PORTLET-INF/resources/xsl/news.xsl”);

 

for multi-language support:

eg

InputStream newsIOS =

               getPortletConfig().getContext().getResourceAsStream(“/PORTLET-INF/resources/news/news.html”,htmlClient,chineseLocale);

 

            See the javadocs of the PortletContext class for details of these two methods.

 

Note that you need to specify the “/PORTLET-INF” root in the resource path.

What happens if you don’t?

If you specify something like this:

                getPortletConfig().getContext().getResourceAsStream(“/resources/xsl/news.xsl”);

The portal engine will look for the news.xsl file in the following directory:

<wps_root>\web\app\WEB-INF\portlets\resources\xsl\news.xsl for your file.

The problem with this is that there is no way for you to create your par file such that WPS will expand your xsl file to this directory. You will need the WPS administrator to create the directory manually after he installs your par file.

6. To let the browser access the files in the images/html folder, you need to call the encodeURI() method of the implicit portlet response object to create the URL.

eg

<TD><IMG src="<%=response.encodeURI("images/img1.gif")%>"></TD>

or

<TD><IMG src="<%=response.encodeURI("/images/img1.gif")%>"></TD

 

Both the paths will map to <wps_root>\app\web\portlets\yourparfilename\images\img1.gif.