public class SetNestedPropertiesRule extends Rule
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!).
| Constructor and Description |
|---|
SetNestedPropertiesRule()
Base constructor, which maps every child element into a bean property with the same name as the xml element.
|
SetNestedPropertiesRule(Map<String,String> elementNames)
Constructor which allows element->property mapping to be overridden.
|
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.
|
| Modifier and Type | Method and Description |
|---|---|
void |
addAlias(String elementName,
String propertyName)
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 |
body(String namespace,
String name,
String text)
This method is called when the body of a matching XML element is encountered.
|
boolean |
getAllowUnknownChildElements()
Return the flag to ignore any child element for which there is no corresponding object property
|
boolean |
getTrimData()
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 the
Digester with which this Rule 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.
|
String |
toString() |
end, finish, getDigester, getNamespaceURI, setNamespaceURIpublic SetNestedPropertiesRule()
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).
public SetNestedPropertiesRule(String elementName, String propertyName)
Convenience constructor which overrides the default mappings for just one property.
For details about how this works, see
SetNestedPropertiesRule(String[] elementNames, String[] propertyNames).
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.public SetNestedPropertiesRule(String[] elementNames, String[] propertyNames)
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.
The following constructs a rule that maps the alt-city element to the city property and
the alt-state to the state property. All other child elements are mapped as usual using
exact name matching.
SetNestedPropertiesRule(
new String[] {"alt-city", "alt-state"},
new String[] {"city", "state"});
The following constructs a rule that maps the class xml element to the className
property. The xml element ignore-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"});
elementNames - names of elements to mappropertyNames - names of properties mapped topublic SetNestedPropertiesRule(Map<String,String> elementNames)
elementNames - names of elements->properties to mappublic void setDigester(Digester digester)
Digester with which this Rule is associated.setDigester in class Ruledigester - the Digester with which this Rule is associatedpublic void setTrimData(boolean trimData)
trimData - flag to have leading and trailing whitespace removedpublic boolean getTrimData()
setTrimData(boolean)public void setAllowUnknownChildElements(boolean allowUnknownChildElements)
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).
allowUnknownChildElements - flag to ignore any child element for which there is no corresponding
object propertypublic boolean getAllowUnknownChildElements()
setAllowUnknownChildElements(boolean)public void begin(String namespace, String name, Attributes attributes) throws Exception
begin in class Rulenamespace - 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 elementException - if any error occurspublic void body(String namespace, String name, String text) throws Exception
body in class Rulenamespace - 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 elementException - if any error occurspublic void addAlias(String elementName, String propertyName)
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.
elementName - the xml-element has to be mappedpropertyName - the property name targetCopyright © 2001-2013 The Apache Software Foundation. All Rights Reserved.