当预期值为 NULL 时,绑定到 bean String 类型的空表单输入字段作为空字符串 ("") 接收。
这是一个老问题,似乎每个版本的 Oracle EL 或 Apache EL 或 Tomcat 都会重新创建。
@BalusC 已多次解决此问题。空字符串疯狂,Tomcat 8(和 9)强制行为,空字符串被错误地设置为空字符串是几个例子。
我已经尝试了所有以前的解决方法,但都没有成功。
某种形式的.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");
}
}
面孔-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>
当我使用自定义 EmptyToNullStringELResolver 方法时,会抛出 NPE。
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 ...
将最新的 EL jar 从 Oracle 放入 WEB/lib 似乎没有任何效果。(javax.el-3.0.1-b11.jar)
谢谢你,泰德小号