Class MethodExpressionImpl
- All Implemented Interfaces:
Externalizable,Serializable
Expression that refers to a method on an object.
The ExpressionFactory.createMethodExpression(javax.el.ELContext, java.lang.String, java.lang.Class<?>, java.lang.Class<?>[]) method can be used to parse an expression string and
return a concrete instance of MethodExpression that encapsulates the parsed expression. The
FunctionMapper is used at parse time, not evaluation time, so one is not needed to evaluate an expression
using this class. However, the ELContext is needed at evaluation time.
The getMethodInfo(javax.el.ELContext) and invoke(javax.el.ELContext, java.lang.Object[]) methods will evaluate the expression each time they are called. The
ELResolver in the ELContext is used to resolve the top-level variables and to determine
the behavior of the . and [] operators. For any of the two methods, the
ELResolver.getValue(javax.el.ELContext, java.lang.Object, java.lang.Object) method is used to resolve all properties up to but excluding the last one. This
provides the base object on which the method appears. If the base object is null, a
NullPointerException must be thrown. At the last resolution, the final property is then
coerced to a String, which provides the name of the method to be found. A method matching the name and
expected parameters provided at parse time is found, and it is either queried or invoked (depending on the method
called on this MethodExpression).
See the notes about comparison, serialization and immutability in the Expression javadocs.
- Author:
- Jacob Hookom [jacob@hookom.net]
- See Also:
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Constructor Summary
ConstructorsConstructorDescriptionMethodExpressionImpl(String expr, org.apache.el.parser.Node node, FunctionMapper fnMapper, VariableMapper varMapper, Class<?> expectedType, Class<?>[] paramTypes) -
Method Summary
Modifier and TypeMethodDescriptionbooleanDetermines whether the specified object is equal to thisExpression.Returns the original String used to create thisExpression, unmodified.getMethodInfo(ELContext context) Evaluates the expression relative to the provided context, and returns information about the actual referenced method.inthashCode()Returns the hash code for thisExpression.Evaluates the expression relative to the provided context, invokes the method that was found using the supplied parameters, and returns the result of the method invocation.booleanbooleanbooleanvoidvoid
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Constructor Details
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MethodExpressionImpl
public MethodExpressionImpl() -
MethodExpressionImpl
public MethodExpressionImpl(String expr, org.apache.el.parser.Node node, FunctionMapper fnMapper, VariableMapper varMapper, Class<?> expectedType, Class<?>[] paramTypes)
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Method Details
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equals
Determines whether the specified object is equal to thisExpression.The result is
trueif and only if the argument is notnull, is anExpressionobject that is the of the same type (ValueExpressionorMethodExpression), and has an identical parsed representation.Note that two expressions can be equal if their expression Strings are different. For example,
${fn1:foo()}and${fn2:foo()}are equal if their correspondingFunctionMappers mappedfn1:fooandfn2:footo the same method.- Specified by:
equalsin classExpression- Parameters:
obj- theObjectto test for equality.- Returns:
trueifobjequals thisExpression;falseotherwise.- See Also:
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getExpressionString
Returns the original String used to create thisExpression, unmodified.This is used for debugging purposes but also for the purposes of comparison (e.g. to ensure the expression in a configuration file has not changed).
This method does not provide sufficient information to re-create an expression. Two different expressions can have exactly the same expression string but different function mappings. Serialization should be used to save and restore the state of an
Expression.- Specified by:
getExpressionStringin classExpression- Returns:
- The original expression String.
- See Also:
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getMethodInfo
public MethodInfo getMethodInfo(ELContext context) throws PropertyNotFoundException, MethodNotFoundException, ELException Evaluates the expression relative to the provided context, and returns information about the actual referenced method.- Specified by:
getMethodInfoin classMethodExpression- Parameters:
context- The context of this evaluation- Returns:
- an instance of
MethodInfocontaining information about the method the expression evaluated to. - Throws:
NullPointerException- if context isnullor the base object isnullon the last resolution.PropertyNotFoundException- if one of the property resolutions failed because a specified variable or property does not exist or is not readable.MethodNotFoundException- if no suitable method can be found.ELException- if an exception was thrown while performing property or variable resolution. The thrown exception must be included as the cause property of this exception, if available.- See Also:
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hashCode
public int hashCode()Returns the hash code for thisExpression.See the note in the
equals(java.lang.Object)method on how two expressions can be equal if their expression Strings are different. Recall that if two objects are equal according to theequals(Object)method, then calling thehashCodemethod on each of the two objects must produce the same integer result. Implementations must take special note and implementhashCodecorrectly.- Specified by:
hashCodein classExpression- Returns:
- The hash code for this
Expression. - See Also:
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invoke
public Object invoke(ELContext context, Object[] params) throws PropertyNotFoundException, MethodNotFoundException, ELException Evaluates the expression relative to the provided context, invokes the method that was found using the supplied parameters, and returns the result of the method invocation.- Specified by:
invokein classMethodExpression- Parameters:
context- The context of this evaluation.params- The parameters to pass to the method, ornullif no parameters.- Returns:
- the result of the method invocation (
nullif the method has avoidreturn type). - Throws:
NullPointerException- if context isnullor the base object isnullon the last resolution.PropertyNotFoundException- if one of the property resolutions failed because a specified variable or property does not exist or is not readable.MethodNotFoundException- if no suitable method can be found.ELException- if an exception was thrown while performing property or variable resolution. The thrown exception must be included as the cause property of this exception, if available. If the exception thrown is anInvocationTargetException, extract itscauseand pass it to theELExceptionconstructor.- See Also:
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readExternal
- Specified by:
readExternalin interfaceExternalizable- Throws:
IOExceptionClassNotFoundException
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writeExternal
- Specified by:
writeExternalin interfaceExternalizable- Throws:
IOException
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isLiteralText
public boolean isLiteralText()- Specified by:
isLiteralTextin classExpression
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isParametersProvided
public boolean isParametersProvided()- Overrides:
isParametersProvidedin classMethodExpression- Returns:
- This default implementation always returns
false
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isParmetersProvided
public boolean isParmetersProvided()- Overrides:
isParmetersProvidedin classMethodExpression- Returns:
- Always
false - Since:
- EL 2.2 Note: The spelling mistake is deliberate. isParmetersProvided() - Specification definition isParametersProvided() - Corrected spelling
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