They are doing it by IPC. First they define the public render parameter in portlet-custom.xml
<public-render-parameter>
<identifier>tag</identifier>
<qname xmlns:x="http://www.liferay.com/public-render-parameters">x:tag</qname>
</public-render-parameter>
Then they tell which portlets support that public render parmeter. In our case Tag clouds and blogs. Check the same in portlet-custom.xml
<portlet>
<portlet-name>33</portlet-name>
<display-name>Blogs</display-name>
....
<supported-public-render-parameter>tag</supported-public-render-parameter>
</portlet>
<portlet>
<portlet-name>148</portlet-name>
<display-name>Asset Tags Cloud</display-name>
...
<supported-public-render-parameter>tag</supported-public-render-parameter>
</portlet>
Then whenever someone clicks on tag from tag cloud they make sure that they set tag parameter. See page.jsp of asset_tags_navigation
portletURL.setParameter("tag", tag.getName());
Finally when someone clicks the tag as you know, render for all portlets gets called, so if blogs portlet is in the page then it will get rendered again. While rendering it will see if url consists parameter tag, if yes then it will query db to get all the content based on the particular tag and show the result. See view.jsp of blogs portlet
String tagName = ParamUtil.getString(request, "tag");
if ((categoryId != 0) || Validator.isNotNull(tagName)) {
AssetEntryQuery assetEntryQuery = new AssetEntryQuery(BlogsEntry.class.getName(), searchContainer);
assetEntryQuery.setExcludeZeroViewCount(false);
if (BlogsPermission.contains(permissionChecker, scopeGroupId, ActionKeys.ADD_ENTRY)) {
assetEntryQuery.setVisible(Boolean.TRUE);
}
total = AssetEntryServiceUtil.getEntriesCount(assetEntryQuery);
results = AssetEntryServiceUtil.getEntries(assetEntryQuery);
}
Regards,
Sandeep
You wanted communication between two separate portlets like Tag Clouds and blogs