Empty form input fields bound to bean String type are received as empty strings ("") when the expected value is NULL.
This is an old problem that seems to get recreated with each version of Oracle EL or Apache EL or Tomcat.
@BalusC has addressed it many times. Empty String Madness, Tomcat 8 (and 9) coerce behaviour, null strings are incorrectly set as empty strings are a couple of examples.
I have tried all previous workarounds without success.
someform.xhtml
<h:form>
<h:outputText value="Some Input: " />
<p:inputText value="#{someBean.stringVariable}" />
<p:commandButton id="search-button"
value="Search"
actionListener="#{someBean.doSearch}" />
</form>
SomeBean.java
private String stringVariable;
// Setter & Getter
public void doSearch()
{
if(stringVariable == null)
{
System.out.println("Input is NULL");
}
else if(stringVariable.equals(""))
{
System.out.println("Input is EMPTY STRING");
}
}
faces-config.xml
<?xml version="1.0" encoding="UTF-8"?>
<faces-config
xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-facesconfig_2_3.xsd"
version="2.3">
<application>
<el-resolver>com.example.EmptyToNullStringELResolver</el-resolver>
</application>
<application>
<resource-handler>org.jepsar.primefaces.theme.jepsar.FontAwesomeResourceHandler</resource-handler>
<resource-handler>org.omnifaces.resourcehandler.UnmappedResourceHandler</resource-handler>
</application>
<application>
<el-resolver>
org.primefaces.application.exceptionhandler.PrimeExceptionHandlerELResolver
</el-resolver>
</application>
<factory>
<exception-handler-factory>
org.primefaces.application.exceptionhandler.PrimeExceptionHandlerFactory
</exception-handler-factory>
</factory>
</faces-config>
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
<context-param>
<param-name>javax.faces.INTERPRET_EMPTY_STRING_SUBMITTED_VALUES_AS_NULL</param-name>
<param-value>true</param-value>
</context-param>
<context-param>
<param-name>org.apache.myfaces.EXPRESSION_FACTORY</param-name>
<param-value>com.sun.el.ExpressionFactoryImpl</param-value>
</context-param>
</web-app>
When I use the custom EmptyToNullStringELResolver method, a NPE is thrown.
java.lang.NullPointerException
at org.apache.myfaces.shared.resource.ValueExpressionFilterInputStream.read(ValueExpressionFilterInputStream.java:130)
at java.io.InputStream.read(InputStream.java:179)
at java.nio.channels.Channels$ReadableByteChannelImpl.read(Channels.java:385)
at org.omnifaces.util.Utils.stream(Utils.java:397)
at org.omnifaces.resourcehandler.UnmappedResourceHandler.handleResourceRequest(UnmappedResourceHandler.java:176)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:196)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at ...
Dropping the most recent EL jar from Oracle into WEB/lib seems to have no effect. (javax.el-3.0.1-b11.jar)
Thank you, Ted S