We sometimes need to target a FacesMessage instance to a specific component. For example, suppose we have p:growl and p:messages/p:message tags on the same page and need to display some messages as p:growl and some as p:message. PrimeFaces has a grouping feature for messages to associate a notification component to specific command components so that messages created as a result of an action will be displayed in the associated messages or the growl tags.
In this recipe, we will develop samples for targetable messages. Furthermore, we will discuss the severity attribute. By means of severity, we can display messages depending on their severities.
Let's use one p:messages tag and two p:growl tags, as shown in the following code snippet:
<h:panelGroup id="msg1">
<p:messages for="save" showDetail="true"/>
<p:growl for="change" showDetail="true"/>
<p:growl globalOnly="true" showDetail="true"/>
</h:panelGroup>
<p:commandButton value="Save" update="msg1"
action="#{targetableMessagesBean.addSaveMessage}"/>
<p:commandButton value="Change" update="@form"
action="#{targetableMessagesBean.addChangeMessage}"/>
<p:commandButton value="Delete" update="@form"
action="#{targetableMessagesBean.addDeleteMessage}"/>Three command buttons create FacesMessage instances. The first button creates two messages that are displayed only by the p:messages tag. The second command button creates one message that is displayed only by the first p:growl tag with the for attribute set to change. The message created by the third command button is displayed only by the second p:growl tag with globalOnly set to true. The action methods look as follows:
public String addSaveMessage() {
addMessage("save", FacesMessage.SEVERITY_INFO,
"Sample info message",
"First data was successfully saved");
addMessage("save", FacesMessage.SEVERITY_INFO,
"Sample info message",
"Second data was successfully saved");
return null;
}
public String addChangeMessage() {
addMessage("change", FacesMessage.SEVERITY_INFO,
"Sample info message",
"Data was successfully changed");
return null;
}
public String addDeleteMessage() {
addMessage(null, FacesMessage.SEVERITY_INFO,
"Sample info message",
"Data was successfully deleted");
return null;
}
private void addMessage(String key,
FacesMessage.Severity severity,
String message, String detail) {
FacesMessage msg = new FacesMessage(severity, message, detail);
FacesContext.getCurrentInstance().addMessage(key, msg);
}Let's now use the p:messages and p:growl tags without the for attribute but with a severity attribute:
<h:panelGroup id="msg2">
<p:messages severity="error" showDetail="true"/>
<p:growl severity="info, warn" showDetail="true"/>
<p:growl showDetail="true"/>
</h:panelGroup>
<p:commandButton value="Generate error message" update="msg2"
action="#{targetableMessagesBean.addErrorMessage}"/>The command button should create an error message with the severity error:
public String addErrorMessage() {
addMessage(null, FacesMessage.SEVERITY_ERROR,
"Sample error message",
"Operation failed");
return null;
}The message created is only displayed by the p:messages tag with severity="error" and by the second p:growl tag without a severity attribute.
The key of an added FacesMessage instance should match the for attribute of the p:growl, p:messages, or p:message components to be displayed. If the for attribute is missing, all added FacesMessage instances will be accepted. If a notification component has set the globalOnly flag (globalOnly="true"), only the FacesMessage instances without a defined key (key is null) will be displayed.
The severity attribute of a notification component defines exactly which severities can be displayed by this component. It accepts a comma-separated list. The possible values are info, warn, error, and fatal. They match the Java constants, FacesMessage.SEVERITY_INFO, FacesMessage.SEVERITY_WARN, FacesMessage.SEVERITY_ERROR, and FacesMessage.SEVERITY_FATAL, respectively. If the severity attribute is missing, messages with any severity will be displayed.
This recipe is available in the demo web application on GitHub (https://github.com/ova2/primefaces-cookbook/tree/second-edition). Clone the project if you have not done it yet, explore the project structure, and build and deploy the WAR file on application servers compatible with Servlet 3.x, such as JBoss WildFly and Apache TomEE.
The showcase for the recipe is available at http://localhost:8080/pf-cookbook/views/chapter11/targetableMessages.jsf.