Daniel Matthews-Grout created WW-3822:
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Summary: Struts 2 and Generic Class - Null Pointer Exception
Key: WW-3822
URL: https://issues.apache.org/jira/browse/WW-3822
Project: Struts 2
Issue Type: Bug
Components: Core Actions
Affects Versions: 2.3.1.1
Environment: Windows 7 - Java 6 - Tomcat 7
Reporter: Daniel Matthews-Grout
Priority: Minor
I have a class that extends a generic abstract class and types that generic -
e.g.
class MyClass extends AbstractClass<Integer> ..
class AbstractClass<ID extends Serializable> {
public abstract ID getId();
}
JSP:
<s:property value="myClass.id"/>
The abstract class defined an abstract getter that I implemented in the
concrete class. I then referenced this getter in the JSP of a Struts 2 action
and got the following:
java.lang.NullPointerException
at
com.opensymphony.xwork2.conversion.impl.DefaultObjectTypeDeterminer.getClass(DefaultObjectTypeDeterminer.java:314)
at
com.opensymphony.xwork2.conversion.impl.DefaultObjectTypeDeterminer.getKeyClass(DefaultObjectTypeDeterminer.java:93)
at
com.opensymphony.xwork2.ognl.accessor.XWorkMapPropertyAccessor.getProperty(XWorkMapPropertyAccessor.java:93)
at ognl.OgnlRuntime.getProperty(OgnlRuntime.java:2303)
at ognl.ASTProperty.getValueBody(ASTProperty.java:114)
at ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212)
at ognl.SimpleNode.getValue(SimpleNode.java:258)
at ognl.ASTChain.getValueBody(ASTChain.java:141)
at ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212)
at ognl.SimpleNode.getValue(SimpleNode.java:258)
at ognl.Ognl.getValue(Ognl.java:494)
at ognl.Ognl.getValue(Ognl.java:458)
....
So what I had to do was to add a another get/set pair in the concrete class
that updated/read from the same field. This stopped the error.
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