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OSGi™ Service Platform Release 2 |
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An RFC 1960-based Filter.
Filter objects can be created by calling
BundleContext.createFilter(java.lang.String)
with the chosen filter string.
A Filter object can be used numerous times to determine if the match argument matches the filter string that was used to create the Filter object.
The syntax of a filter string is the string representation of LDAP search filters as defined in RFC 1960: A String Representation of LDAP Search Filters (available at http://www.ietf.org/rfc/rfc1960.txt). It should be noted that RFC 2254: A String Representation of LDAP Search Filters (available at http://www.ietf.org/rfc/rfc2254.txt) supercedes RFC 1960 but only adds extensible matching and is not applicable for this OSGi Framework API.
The string representation of an LDAP search filter uses a prefix format, and is defined with the following grammar.
<filter> ::= '(' <filtercomp> ')' <filtercomp> ::= <and> | <or> | <not> | <item> <and> ::= '&' <filterlist> <or> ::= '|' <filterlist> <not> ::= '!' <filter> <filterlist> ::= <filter> | <filter> <filterlist> <item> ::= <simple> | <present> | <substring> <simple> ::= <attr> <filtertype> <value> <filtertype> ::= <equal> | <approx> | <greater> | <less> <equal> ::= '=' <approx> ::= '~=' <greater> ::= '>=' <less> ::= '<=' <present> ::= <attr> '=*' <substring> ::= <attr> '=' <initial> <any> <final> <initial> ::= NULL | <value> <any> ::= '*' <starval> <starval> ::= NULL | <value> '*' <starval> <final> ::= NULL | <value>
<attr> is a string representing an attribute, or key, in the properties objects of the services registered in the Framework. Attribute names are not case sensitive; that is, cn and CN both refer to the same attribute. <attr> should contain no spaces though white space is allowed between the initial parenthesis "(" and the start of the key, and between the end of the key and the equal sign "=". <value> is a string representing the value, or part of one, of a key in the properties objects of the registered services. If a <value> must contain one of the characters '*' or '(' or ')', these characters should be escaped by preceding them with the backslash '\' character. Spaces are significant in <value>. Space charactes are defined by java.lang.Character.isWhiteSpace(). Note that although both the <substring> and <present> productions can produce the 'attr=*' construct; this construct is used only to denote a presence filter.
Examples of LDAP filters are:
"(cn=Babs Jensen)" "(!(cn=Tim Howes))" "(&(" + Constants.OBJECTCLASS + "=Person)(|(sn=Jensen)(cn=Babs J*)))" "(o=univ*of*mich*)"
The approximate match (~=) is implementation specific but should at least ignore case and white space differences. Optional are codes like soundex or other smart "closeness" comparisons.
Comparison of values is not straightforward. Strings are compared differently than numbers and it is possible for a key to have multiple values. Note that keys in the match argument must always be strings. The comparison is defined by the object type of the key's value. The following rules apply for comparison:
Property Value Type Comparison Type String String comparison Integer, Long, Float, Double, Byte, Short, BigInteger,BigDecimal Numerical comparison Character Character comparison Boolean Equality comparisons only [ ] (array) Recursively applied to values Vector Recursively applied to elementsArrays of primitives are also supported. A filter matches a key that has multiple values if it matches at least one of those values. For example,
Dictionary d = new Hashtable(); d.put( "cn", new String[] { "a", "b", "c" } );d will match (cn=a) and also (cn=b)
A filter component that references a key having an unrecognizable data type will evaluate to false.
Method Summary | |
boolean |
equals(java.lang.Object obj)
Compares this Filter object to another object. |
int |
hashCode()
Returns the hashCode for this Filter object. |
boolean |
match(java.util.Dictionary dictionary)
Filter using a Dictionary object. |
boolean |
match(ServiceReference reference)
Filter using a service's properties. |
java.lang.String |
toString()
Returns this Filter object's filter string. |
Method Detail |
public boolean match(ServiceReference reference)
The filter is executed using properties of the referenced service.
reference
- The reference to the service whose properties are used in the match.
public boolean match(java.util.Dictionary dictionary)
dictionary
- The Dictionary object whose keys are used in the match.
java.lang.IllegalArgumentException
- If dictionary contains case
variants of the same key name.public java.lang.String toString()
The filter string is normalized by removing whitespace which does not affect the meaning of the filter.
public boolean equals(java.lang.Object obj)
obj
- The object to compare against this Filter object.
public int hashCode()
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OSGi™ Service Platform Release 2 |
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