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package org.example.app.components;
import org.apache.tapestry5.annotations.AfterRender;
import org.apache.tapestry5.annotations.Parameter;
import org.apache.tapestry5.annotations.SetupRender;
public class Count
{
@Parameter
private int start = 1;
@Parameter(required = true)
private int end;
@Parameter
private int value;
private boolean increment;
@SetupRender
void initializeValue()
{
value = start;
increment = start < end;
}
@AfterRender
boolean next()
{
if (increment)
{
int newValue = value + 1;
if (newValue <= end)
{
value = newValue;
return false;
}
}
else
{
int newValue = value - 1;
if (newValue >= end)
{
value = newValue;
return false;
}
}
return true;
}
}
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The name of the parameter is derived from the field name (by stripping leading "_" and "$" characters). Here, the parameter names are "start", "end" and "value".
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<t:layout xmlns:t="http://tapestry.apache.org/schema/tapestry_5_1_0.xsd">
<p> Countdown:
<t:count start="5" end="1" value="index">
${index} ...
</t:count>
</p>
</t:layout>
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...
Inherited bindings are useful for complex components; they are often used when an inner component has a default value for a parameter, and the outer component wants to make it possible to override that default.
More examples on this coming soon.
Parameter Binding Defaults
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<html xmlns:t="http://tapestry.apache.org/schema/tapestry_5_1_0.xsd">
<body>
<div t:type="layout" t:menuTitle="literal:The Title">
...
</div>
</body>
</html>
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<t:container xmlns:t="http://tapestry.apache.org/schema/tapestry_5_1_0.xsd">
<div t:type="title" t:title="inherit:menuTitle"></div>
<t:body />
</t:container>
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package org.example.app.components;
import org.apache.tapestry5.annotations.Parameter;
public class Title {
@Parameter
private String title;
}
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Parameter Binding Defaults
The @Parameter annotation's value() attribute can be used to specify a binding expression that will be the default binding for the parameter is otherwise left unbound. Typically, this is the name of a The @Parameter annotation's value() attribute can be used to specify a binding expression that will be the default binding for the parameter is otherwise left unbound. Typically, this is the name of a property that that will compute the value on the fly.
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@Parameter("defaultMessage")
private String message;
@Parameter(required=true)
private int maxLength;
public String getDefaultMessage()
{
return String.format("Maximum field length is %d.", _maxLength);
}
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@Parameter
private String message;
@Parameter(required=true)
private int maxLength;
@Inject
private ComponentResources resources;
@Inject
private BindingSource bindingSource;
Binding defaultMessage()
{
return bindingSource.newBinding("default value", resources, "basicMessage");
}
public String getBasicMessage()
{
return String.format("Maximum field length is %d.", maxLength);
}
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@Parameter
private String message;
@Parameter(required=true)
private int maxLength;
@Inject
private ComponentResources resources;
String defaultMessage()
{
return String.format("Maximum field length is %d.", maxLength);
}
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This form is more like using the "literal:" binding prefix, except that the literal value is computed by the defaultMessage() method.
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public class MyComponent
{
@Parameter
private int myParam;
@Inject
private ComponentResources resources;
@BeginRender
void setup()
{
if (resources.isBound("myParam"))
{
. . .
}
}
}
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...