Communicating between portlets using Public Render Parameters

Create two portlets, each in a separate portlet application, one to search for stocks and the other to show a list of stocks in a watchlist. When a stock is retrieved in the first portlet it will provide the option to watch that stock, and if clicked the stock will be visible within the watchlist by passing that stock through Public Render Parameters.

Note

A portlet application equates to a single web archive, and there is no restriction on how many portlets can be within a single portlet application.

Getting ready

The following are required for this recipe:

  • Apache Maven
  • An IDE of your choice
  • GateIn-3.2.0.Final

How to do it...

To create the portlet that will search for stocks, do the following:

  1. Create a new Maven project within your IDE, specifying Group ID: gatein.cookbook, Artifact ID: chapter6-prp, and Packaging: war.
  2. Inside the project's pom.xml, add the following dependency:
         <dependency>
        <groupId>javax.portlet</groupId>
        <artifactId>portlet-api</artifactId>
        <version>2.0</version>
        <scope>provided</scope>
     </dependency>
  3. Create a class named StockSearchPortlet that extends javax.portlet.GenericPortlet within a package named gatein.cookbook.chapter6.
  4. Add a private variable to StockSearchPortlet named availableStocks of type String[] and set it to null.
  5. Create a method named init within StockSearchPortlet with the following content:
      @Override
  public void init(PortletConfig config) throws PortletException {
    super.init(config);
    initStockList();
  }
  6. Create a method named initStockList within StockSearchPortlet with the following content:
      private void initStockList() {
    availableStocks = new String[5];
        
    availableStocks[0] = "IBM:International Business Machines Corp.";
    availableStocks[1] = "IBN:Icici Bank Limited";
    availableStocks[2] = "REV:Revlon";
    availableStocks[3] = "RHI:Robert Half International Inc.";
    availableStocks[4] = "RHT:Red Hat";
  }
  7. Create a method named display within StockSearchPortlet as follows:
      @RenderMode(name = "view")
  public void display(RenderRequest request, RenderResponse response) throws PortletException, IOException {
    request.setAttribute("stockList", filterStocks(request));
    getPortletContext().getRequestDispatcher("/stockSearch.jsp").include(request, response);
  }
  8. Create a method named filterStocks within StockSearchPortlet with the following content:
      private String[] filterStocks(RenderRequest request) {
    String filter = request.getParameter("ticker");
    if (null != filter && filter.trim().length() > 0) {
      filter = filter.trim().toLowerCase();
      StringBuffer filterStocks = new StringBuffer(60);
      boolean found = false;
      for (String stock : availableStocks) {
        if (stock.toLowerCase().startsWith(filter)) {
          if (found) {
            filterStocks.append(";");
          }
          filterStocks.append(stock);
          found = true;
        }
      }
      return found == true ? filterStocks.toString().split(";") : null;
    }
    return availableStocks;
  }
  9. Create a method named searchStocks within StockSearchPortlet with the following content:
      @ProcessAction(name = "searchStocks")
  public void searchStocks(ActionRequest request, ActionResponse response) throws PortletException {
    response.setRenderParameter("ticker", request.getParameter("ticker"));
  }
  10. Create a method named addWatch within StockSearchPortlet with the following content:
      @ProcessAction(name = "watch")
  public void addWatch(ActionRequest request, ActionResponse response) throws PortletException {
    String stock = request.getParameter("stock");
    response.setRenderParameter("watch_stock", stock);
  }
  11. Create stockSearch.jsp in the src/main/webapp folder of the project.
  12. Add the following content into stockSearch.jsp:
    <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://java.sun.com/portlet_2_0" prefix="portlet" %>

<portlet:defineObjects/>

<div class="portlet-section-header">Search Stocks</div>
<br/>
<div class="portlet-section-body">
  <form action='<portlet:actionURL name="searchStocks"/>' method="post">
    <span class="portlet-form-label">Ticker:</span>
    <input class="portlet-form-input-field" type="text" name="ticker"/>
    <input class="portlet-form-button" type="Submit" value="Search"/>
  </form>
  <br/>
<%
  String ticker = (String)renderRequest.getParameter("ticker");
  String[] results = (String[])renderRequest.getAttribute("stockList");
%>
  <c:choose>
    <c:when test="<%= results != null && results.length > 0 %>">
        <table border="1">
          <thead class="portlet-table-header">
            <tr>
              <th>Ticker</th>
              <th>Company</th>
              <th></th>
            </tr>
          </thead>
          <tbody class="portlet-table-body">
          <%
            for (String stock: results) {
              if (null != stock) {
                String[] split = stock.split(":");
          %>
                <tr>
                  <td align="center" class="portlet-table-text"><%= split[0] %></td>
                  <td align="center" class="portlet-table-text"><%= split[1] %></td>
                  <td align="center" class="portlet-table-text"><a class="portlet-font-dim" href="<portlet:actionURL name='watch'><portlet:param name='stock' value='<%= split[0] %>' /></portlet:actionURL>">Watch!</a></td>
                </tr>
          <%
              }
            }
          %>
          </tbody>
        </table>
    </c:when>
    <c:otherwise>
      <c:if test="<%= ticker != null && ticker.trim().length() > 0 %>">
        <span>No results found for ticker: <%= ticker %></span>
      </c:if>
    </c:otherwise>
  </c:choose>
</div>
<br/>
  13. Create portlet.xml in the src/main/webapp/WEB-INF folder of the project.
  14. Add the following content to portlet.xml:
    <?xml version="1.0" encoding="UTF-8"?>
<portlet-app xmlns="http://java.sun.com/xml/ns/portlet/portlet-app_2_0.xsd"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/portlet/portlet-app_2_0.xsd http://java.sun.com/xml/ns/portlet/portlet-app_2_0.xsd"
    version="2.0">
  <portlet>
    <portlet-name>StockSearch-PRP</portlet-name>
    <portlet-class>gatein.cookbook.chapter6.StockSearchPortlet</portlet-class>
    <supports>
      <mime-type>text/html</mime-type>
      <portlet-mode>view</portlet-mode>
    </supports>
    <portlet-info>
      <title>Stock Search - PRP portlet</title>
    </portlet-info>
    <supported-public-render-parameter>watch_stock</supported-public-render-parameter>
  </portlet>
  <public-render-parameter>
    <identifier>watch_stock</identifier>
    <qname xmlns:gi="http://www.gatein.org/xml/ns/cookbook">gi:watch_stock</qname>
  </public-render-parameter>
</portlet-app>
  15. Create web.xml in the src/main/webapp/WEB-INF folder of the project.
  16. Add the following to web.xml:
    <?xml version="1.0"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_5.xsd"
        version="2.5">
</web-app>

    To create the portlet that will maintain a watch list of stocks, do the following:

  17. Create a new Maven project within your IDE, specifying Group ID: gatein.cookbook, Artifact ID: chapter6-prp-receiver, and Packaging: war.
  18. Create a class named WatchlistPortlet that extends javax.portlet.GenericPortlet within a package named gatein.cookbook.chapter6.
  19. Add a private variable to WatchlistPortlet named watchedStocks of type String[] and set it to new String[5].
  20. Add a private variable to WatchlistPortlet named watchedCount of type int and set it to 0.
  21. Create a method named displayWatchList within WatchlistPortlet as follows:
      @RenderMode(name = "view")
  public void displayWatchList(RenderRequest request, RenderResponse response) throws PortletException, IOException {
    String watchStock = (String)request.getParameter("watch_stock");

    if (null != watchStock && watchStock.trim().length() > 0) {
      if (watchCount > 0) {
        boolean found = false;
        for (String stock : watchedStocks) {
          if (null != stock && stock.equals(watchStock)) {
            found = true;
            break;
          }
        }
        if (!found) {
          watchedStocks[watchCount++] = watchStock;
        }
      } else {
        watchedStocks[watchCount++] = watchStock;
      }
    }
    request.setAttribute("watchlist", watchedStocks);
    request.setAttribute("watchCount", watchCount);
    getPortletContext().getRequestDispatcher("/watchlist.jsp").include(request, response);
  }
  22. Create watchlist.jsp in the src/main/webapp folder of the project.
  23. Add the following content into watchlist.jsp:
    <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://java.sun.com/portlet_2_0" prefix="portlet" %>

<portlet:defineObjects/>

<div class="portlet-section-header">Stock Watchlist</div>
<br/>
<div class="portlet-section-body">
<%
  String[] stocks = (String[])renderRequest.getAttribute("watchList");
  Integer watchCount = (Integer)renderRequest.getAttribute("watchCount");
%>
  <c:choose>
    <c:when test="<%= watchCount > 0 %>">
        <table border="1">
          <thead class="portlet-table-header">
            <tr>
              <th>Ticker</th>
            </tr>
          </thead>
          <tbody class="portlet-table-body">
          <%
            for (String stock: stocks) {
              if (null != stock) {
          %>
                <tr>
                  <td align="center" class="portlet-table-text"><%= stock %></td>
                </tr>
          <%
              }
            }
          %>
          </tbody>
        </table>
    </c:when>
    <c:otherwise>
      <span>No stocks being watched at the moment.</span>
    </c:otherwise>
  </c:choose>
</div>
<br/>
  24. Create portlet.xml in the src/main/webapp/WEB-INF folder of the project.
  25. Add the following content to portlet.xml:
    <?xml version="1.0" encoding="UTF-8"?>
<portlet-app xmlns="http://java.sun.com/xml/ns/portlet/portlet-app_2_0.xsd"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/portlet/portlet-app_2_0.xsd http://java.sun.com/xml/ns/portlet/portlet-app_2_0.xsd"
    version="2.0">
  <portlet>
    <portlet-name>WatchList-PRP</portlet-name>
    <portlet-class>gatein.cookbook.chapter6.WatchlistPortlet</portlet-class>
    <supports>
      <mime-type>text/html</mime-type>
      <portlet-mode>view</portlet-mode>
    </supports>
    <portlet-info>
      <title>WatchList - PRP portlet</title>
    </portlet-info>
    <supported-public-render-parameter>watch_stock</supported-public-render-parameter>
  </portlet>
  <public-render-parameter>
    <identifier>watch_stock</identifier>
    <qname xmlns:gi="http://www.gatein.org/xml/ns/cookbook">gi:watch_stock</qname>
  </public-render-parameter>
</portlet-app>
  26. Run the following in the root of the project directory to build the web archive:
    >mvn clean package
  27. Copy the generated web archive, chapter6-prp-1.0.0.SNAPSHOT.war, from the target folder into the deployment folder where you unpacked the GateIn installation.
  28. Start the server and log in as an administrator.
  29. Access the Application Registry, as seen in Chapter 2, Managing Portal Contents Using the GUI, and click on Import Applications to make our portlet available.
  30. Create a new page for the StockSearch-Prp and WatchList-Prp portlets as seen in Chapter 2, Managing Portal Contents Using the GUI.
  31. The portlet page should like the following screenshot:
    How to do it...
  32. Click on Watch! in the row for Revlon stock, and the portal page should look like the following screenshot:
    How to do it...

How it works...

Steps 4, 5, and 6 create a String array to hold a list of stocks that are available to search for, and initialize that list during the init of the portlet. The initStockList method could retrieve the stocks from a database or any external source, but in this case it is purely hard-coded for convenience.

Step 7 sets the list of stocks that will be displayed onto the RenderRequest, before redirecting to the stockSearch.jsp page. The list of stocks set on the RenderRequest is generated in the filterStocks method in Step 8. It uses the value of ticker, set in Step 9, to reduce the number of stocks returned if there are partial matches.

Step 10 sets the stock we want to watch as a render parameter of the ActionResponse within the portlet. By default, this is only available to StockSearchPortlet, but by adding the <public-render-parameter> section to portlet.xml in Step 14 the render parameter is exposed publicly under the namespace and name specified.

Step 21 retrieves the parameter value from the request, which is available because the portlet definition specifies that it supports the Public Render Parameter details configured in Step 25.

A major restriction with using Public Render Parameters is that they are only suitable for passing string parameters between portlets.

See also

  • The Creating a portlet with the Portlet 2.0 Specification recipe
  • The Communicating between portlets using events recipe
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