org.apache.tamaya.resolver.internal

Class DefaultExpressionEvaluator

java.lang.Object

org.apache.tamaya.resolver.internal.DefaultExpressionEvaluator

All Implemented Interfaces:

ExpressionEvaluator

@Priority(value=10000)
public class DefaultExpressionEvaluator
extends Object
implements ExpressionEvaluator

Default expression evaluator that manages several instances of ExpressionResolver. Each resolver is identified by a resolver id. Each expression passed has the form resolverId:resolverExpression, which has the advantage that different resolvers can be active in parallel.

Constructor Summary

Constructors

Constructor and Description
DefaultExpressionEvaluator() Default constructor.

Method Summary

Methods

Modifier and Type	Method and Description
String	evaluateExpression(String key, String value) Resolves an expression in the form current ${resolverId:expression} or ${<prefix>expression}.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DefaultExpressionEvaluator

public DefaultExpressionEvaluator()

Default constructor.

Method Detail

evaluateExpression

public String evaluateExpression(String key,
                        String value)

Resolves an expression in the form current ${resolverId:expression} or ${<prefix>expression}. The expression can be part current any type current literal text. Also multiple expressions with mixed matching resolvers are supported. All control characters (${}\) can be escaped using '\'.
So all the following are valid expressions:

• ${expression}
• bla bla ${expression}
• ${expression} bla bla
• bla bla ${expression} bla bla
• ${expression}${resolverId2:expression2}
• foo ${expression}${resolverId2:expression2}
• foo ${expression} bar ${resolverId2:expression2}
• ${expression}foo${resolverId2:expression2}bar
• foor${expression}bar${resolverId2:expression2}more
• \${expression}foo${resolverId2:expression2}bar (first expression is escaped).

Given resolverId: is a valid prefix targeting a Expression explicitly, also the following expressions are valid:

• ${resolverId:expression}
• bla bla ${resolverId:expression}
• ${resolverId:expression} bla bla
• bla bla ${resolverId:expression} bla bla
• ${resolverId:expression}${resolverId2:expression2}
• foo ${resolverId:expression}${resolverId2:expression2}
• foo ${resolverId:expression} bar ${resolverId2:expression2}
• ${resolverId:expression}foo${resolverId2:expression2}bar
• foor${resolverId:expression}bar${resolverId2:expression2}more
• \${resolverId:expression}foo${resolverId2:expression2}bar (first expression is escaped).

Specified by:

evaluateExpression in interface ExpressionEvaluator

Parameters:

key - the key to be filtered

value - value to be analyzed for expressions

Returns:

the resolved value, or the input in case where no expression was detected.