type conversions

[tony lee]

hi,
what's the type conversion in jsp?
i read from spec that there're two kinds of conversions: Conversions from String values & Conversions from request-time expressions. i just don't know why we use them
thanks,

[Peter den Haan]

Say you have a JavaBean with an int property:

public void setMyProperty(int myProperty);

and you set it inside a JSP:

< jsp:setProperty name="myBean" property="myProperty" value="101" />

Now the value is really just a string in the JSP source. What the spec says is that this string will be converted to an int with the value 101.
Now consider

< jsp:setProperty name="myBean" property="myProperty" value="<%= "101" %>" />

This time round, the value is a scriptlet evaluated at request time. Even though the result is still a String, the JSP container will not perform any of the automatic conversions and so this code won't work at all (I'd expect it to fail during the java compilation phase).
- Peter

[tony lee]

Thanks peter,
But from spec,Table JSP.4-2, we see:
"This (value) attribute can accept a request-time attribute expression as a value."
1) Why the last code segment you gave is wrong?
2) I now supposed you were right, how can we convert the value "101" manually in the scenario?

[Goan Balchao]

You will have to declare the property as a String type, I suppose , so that you can use the expressions in your value attribute.