Question

In the documentation, the “name” inside a <bean:write> tag is mentioned to be the name of the bean whose property has to be printed. If the property isn’t mentioned, the value of the bean itself is printed.

But if I set an attribute in the Action class like :

setAttribute("dda","hello");

and in the JSP say :

<bean:write name="dda"/>

I get “hello” even though “dda” is not the name of any bean.

Why does that happen? And what is meant by “bean itself is printed”? Is its object’s hashcode rendered?

Answer 1

The documentation says the following about the name attribute:

Specifies the attribute name of the bean whose property is accessed to retrieve the value specified by property (if specified). If property is not specified, the value of this bean itself will be rendered.

Pay close attention to this wording: the attribute name of the bean.

Let’s lose the naming “bean” for a moment and talk about objects (since a bean is just a special kind of object).

You can create an object and place it as attribute in a scope (request.setAttribute(...), session.setAttribute(...) etc). And you place it with an attribute name. This is like a map if you will, the attribute name is the key and the object is the value.

What <bean:write> does is lookup an object with the name attribute you give it (by means of jspContext.findAttribute(...)). Now it has an object to work with!

If you also specify a property attribute for the tag, the tag will try to call a getter with the property name on that object. Now we are talking about beans because by definition a bean has getters/setters for its properties.

But in your example you have set a string "hello" with a named attribute "dda" and you specified no property attribute for <bean:write>. A string is not a bean by definition because it has no getters/setters, it is just a plain object. In this case, the tag falls-back to printing the object itself; as the documentations again specifies: the usual toString() conversions will be applied. "hello".toString() is still "hello" so that gets printed.

Instead of "hello" just place a new Object() in your code and you will see the Object.toString() method being called and you get something like java.lang.Object@123456 printed out.

Place instead a bean with a getBla getter and a <bean:write name="dda" property="bla" /> will trigger the call to the dda bean for the bla’s property getter.