Class SetNestedPropertiesRule
Rule implementation that sets properties on the object at the top of the stack, based on child elements with names matching properties on that object.
Example input that can be processed by this rule:
[widget] [height]7[/height] [width]8[/width] [label]Hello, world[/label] [/widget]
For each child element of [widget], a corresponding setter method is located on the object on the top of the digester stack, the body text of the child element is converted to the type specified for the (sole) parameter to the setter method, then the setter method is invoked.
This rule supports custom mapping of xml element names to property names. The default mapping for particular elements
can be overridden by using SetNestedPropertiesRule(String[] elementNames, String[] propertyNames)
. This
allows child elements to be mapped to properties with different names. Certain elements can also be marked to be
ignored.
A very similar effect can be achieved using a combination of the BeanPropertySetterRule
and the
ExtendedBaseRules
rules manager; this Rule
, however, works fine with the default
RulesBase
rules manager.
Note that this rule is designed to be used to set only "primitive" bean properties, eg String, int, boolean. If some of the child xml elements match ObjectCreateRule rules (ie cause objects to be created) then you must use one of the more complex constructors to this rule to explicitly skip processing of that xml element, and define a SetNextRule (or equivalent) to handle assigning the child object to the appropriate property instead.
Implementation Notes
This class works by creating its own simple Rules implementation. When begin is invoked on this rule, the digester's current rules object is replaced by a custom one. When end is invoked for this rule, the original rules object is restored. The digester rules objects therefore behave in a stack-like manner.
For each child element encountered, the custom Rules implementation ensures that a special AnyChildRule instance is included in the matches returned to the digester, and it is this rule instance that is responsible for setting the appropriate property on the target object (if such a property exists). The effect is therefore like a "trailing wildcard pattern". The custom Rules implementation also returns the matches provided by the underlying Rules implementation for the same pattern, so other rules are not "disabled" during processing of a SetNestedPropertiesRule.
TODO: Optimise this class. Currently, each time begin is called, new AnyChildRules and AnyChildRule objects are created. It should be possible to cache these in normal use (though watch out for when a rule instance is invoked re-entrantly!).
- Since:
- 1.6
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionprivate class
private class
Private Rules implementation -
Field Summary
FieldsModifier and TypeFieldDescriptionprivate boolean
private org.apache.commons.logging.Log
private boolean
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Constructor Summary
ConstructorsConstructorDescriptionBase constructor, which maps every child element into a bean property with the same name as the xml element.SetNestedPropertiesRule
(String[] elementNames, String[] propertyNames) Constructor which allows element->property mapping to be overridden.SetNestedPropertiesRule
(String elementName, String propertyName) Convenience constructor which overrides the default mappings for just one property.SetNestedPropertiesRule
(Map<String, String> elementNames) Constructor which allows element->property mapping to be overridden. -
Method Summary
Modifier and TypeMethodDescriptionvoid
Add an additional custom xml-element -> property mapping.void
begin
(String namespace, String name, Attributes attributes) This method is called when the beginning of a matching XML element is encountered.void
This method is called when the body of a matching XML element is encountered.boolean
Return the flag to ignore any child element for which there is no corresponding object propertyboolean
Return the flag to have leading and trailing whitespace removed.void
setAllowUnknownChildElements
(boolean allowUnknownChildElements) Determines whether an error is reported when a nested element is encountered for which there is no corresponding property-setter method.void
setDigester
(Digester digester) Set theDigester
with which thisRule
is associated.void
setTrimData
(boolean trimData) When set to true, any text within child elements will have leading and trailing whitespace removed before assignment to the target object.toString()
Methods inherited from class org.apache.commons.digester3.Rule
end, finish, getDigester, getNamespaceURI, setNamespaceURI
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Field Details
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log
private org.apache.commons.logging.Log log -
trimData
private boolean trimData -
allowUnknownChildElements
private boolean allowUnknownChildElements -
elementNames
-
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Constructor Details
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SetNestedPropertiesRule
public SetNestedPropertiesRule()Base constructor, which maps every child element into a bean property with the same name as the xml element.It is an error if a child xml element exists but the target java bean has no such property (unless
setAllowUnknownChildElements(boolean)
has been set to true). -
SetNestedPropertiesRule
Convenience constructor which overrides the default mappings for just one property.
For details about how this works, see
SetNestedPropertiesRule(String[] elementNames, String[] propertyNames)
.- Parameters:
elementName
- is the child xml element to matchpropertyName
- is the java bean property to be assigned the value of the specified xml element. This may be null, in which case the specified xml element will be ignored.
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SetNestedPropertiesRule
Constructor which allows element->property mapping to be overridden.
Two arrays are passed in. One contains xml element names and the other java bean property names. The element name / property name pairs are matched by position; in order words, the first string in the element name array corresponds to the first string in the property name array and so on.
If a property name is null or the xml element name has no matching property name due to the arrays being of different lengths then this indicates that the xml element should be ignored.
Example One
The following constructs a rule that maps the
alt-city
element to thecity
property and thealt-state
to thestate
property. All other child elements are mapped as usual using exact name matching.SetNestedPropertiesRule( new String[] {"alt-city", "alt-state"}, new String[] {"city", "state"});
Example Two
The following constructs a rule that maps the
class
xml element to theclassName
property. The xml elementignore-me
is not mapped, ie is ignored. All other elements are mapped as usual using exact name matching.SetPropertiesRule( new String[] {"class", "ignore-me"}, new String[] {"className"});
- Parameters:
elementNames
- names of elements to mappropertyNames
- names of properties mapped to
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SetNestedPropertiesRule
Constructor which allows element->property mapping to be overridden.- Parameters:
elementNames
- names of elements->properties to map- Since:
- 3.0
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Method Details
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setDigester
Set theDigester
with which thisRule
is associated.- Overrides:
setDigester
in classRule
- Parameters:
digester
- theDigester
with which thisRule
is associated
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setTrimData
public void setTrimData(boolean trimData) When set to true, any text within child elements will have leading and trailing whitespace removed before assignment to the target object. The default value for this attribute is true.- Parameters:
trimData
- flag to have leading and trailing whitespace removed
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getTrimData
public boolean getTrimData()Return the flag to have leading and trailing whitespace removed.- Returns:
- flag to have leading and trailing whitespace removed
- See Also:
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setAllowUnknownChildElements
public void setAllowUnknownChildElements(boolean allowUnknownChildElements) Determines whether an error is reported when a nested element is encountered for which there is no corresponding property-setter method.When set to false, any child element for which there is no corresponding object property will cause an error to be reported.
When set to true, any child element for which there is no corresponding object property will simply be ignored.
The default value of this attribute is false (unknown child elements are not allowed).
- Parameters:
allowUnknownChildElements
- flag to ignore any child element for which there is no corresponding object property
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getAllowUnknownChildElements
public boolean getAllowUnknownChildElements()Return the flag to ignore any child element for which there is no corresponding object property- Returns:
- flag to ignore any child element for which there is no corresponding object property
- See Also:
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begin
This method is called when the beginning of a matching XML element is encountered.- Overrides:
begin
in classRule
- Parameters:
namespace
- the namespace URI of the matching element, or an empty string if the parser is not namespace aware or the element has no namespacename
- the local name if the parser is namespace aware, or just the element name otherwiseattributes
- The attribute list of this element- Throws:
Exception
- if any error occurs
-
body
This method is called when the body of a matching XML element is encountered. If the element has no body, this method is called with an empty string as the body text.- Overrides:
body
in classRule
- Parameters:
namespace
- the namespace URI of the matching element, or an empty string if the parser is not namespace aware or the element has no namespacename
- the local name if the parser is namespace aware, or just the element name otherwisetext
- The text of the body of this element- Throws:
Exception
- if any error occurs
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addAlias
Add an additional custom xml-element -> property mapping.This is primarily intended to be used from the xml rules module (as it is not possible there to pass the necessary parameters to the constructor for this class). However it is valid to use this method directly if desired.
- Parameters:
elementName
- the xml-element has to be mappedpropertyName
- the property name target
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toString
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