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13.3 Setting Bean Properties

303

Associating All Properties with Input Parameters

Associating a property with an input parameter saves you the bother of per 

forming conversions for many of the simple built in types. JSP lets you take

the process one step further by associating all properties with identically

named input parameters. All you have to do is to supply 

"*"

 for the 

prop 

erty

 parameter. So, for example, all three of the 

jsp:setProperty

 state 

ments of Listing 13.5 can be replaced by the following simple line. Listing

13.6 shows the complete page.

Although this approach is simple, four small warnings are in order. First, as

with individually associated properties, no action is taken when an input

parameter is missing. In particular, the system does not supply 

null

 as the

property value. Second, the JSWDK and the Java Web Server both fail for

conversions to properties that expect 

double

 values. Third, automatic type

conversion does not guard against illegal values as effectively as does manual

type conversion. So you might consider error pages (see Sections 11.9 and

11.10) when using automatic type conversion. Fourth, since both property

names and input parameters are case sensitive, the property name and input

parameter must match exactly. 

Core Warning

In order for all properties to be associated with input parameters, the 

property names must match the parameter names exactly, including case.

Listing 13.6 SaleEntry3.jsp