createValueExpression

javax.el 
Class ExpressionFactory

java.lang.Object
  javax.el.ExpressionFactory

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public abstract class ExpressionFactory
   
    extends 
    Object
   

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Constructor Summary
ExpressionFactory()

 

Method Summary
abstract  Object	coerceToType(Object obj, Class<?> targetType)            Coerces an object to a specific type according to the EL type conversion rules.
abstract  MethodExpression	createMethodExpression(ELContext context, String expression, Class<?> expectedReturnType, Class<?>[] expectedParamTypes)            Parses an expression into a MethodExpression for later evaluation.
abstract  ValueExpression	createValueExpression(ELContext context, String expression, Class<?> expectedType)            Parses an expression into a ValueExpression for later evaluation.
abstract  ValueExpression	createValueExpression(Object instance, Class<?> expectedType)            Creates a ValueExpression that wraps an object instance.
static ExpressionFactory	newInstance()            Creates a new instance of a ExpressionFactory.
static ExpressionFactory	newInstance(Properties properties)            Create a new instance of a ExpressionFactory, with optional properties.

 

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

 

Constructor Detail

ExpressionFactory

public ExpressionFactory()

Method Detail

newInstance

public static ExpressionFactory newInstance()

Creates a new instance of a  ExpressionFactory. This method uses the following ordered lookup procedure to determine the  ExpressionFactoryimplementation class to load:

• Use the Services API (as detailed in the JAR specification). If a resource with the name of META-INF/services/javax.el.ExpressionFactoryexists, then its first line, if present, is used as the UTF-8 encoded name of the implementation class.
• Use the properties file "lib/el.properties" in the JRE directory. If this file exists and it is readable by thejava.util.Properties.load(InputStream) method, and it contains an entry whose key is "javax.el.ExpressionFactory", then the value of that entry is used as the name of the implementation class.
• Use the javax.el.ExpressionFactory system property. If a system property with this name is defined, then its value is used as the name of the implementation class.
• Use a platform default implementation.

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newInstance

public static ExpressionFactory newInstance(Properties properties)

Create a new instance of a ExpressionFactory, with optional properties. This method uses the same lookup procedure as the one used innewInstance().

If the argument properties is not null, and if the implementation contains a constructor with a single parameter of type java.util.Properties, then the constructor is used to create the instance.

Properties are optional and can be ignored by an implementation.

The name of a property should start with "javax.el."

The following are some suggested names for properties.

• javax.el.cacheSize

Parameters:

properties - Properties passed to the implementation. If null, then no properties.

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createValueExpression

public abstract ValueExpression createValueExpression(ELContext context,
                                                      String expression,
                                                      Class<?> expectedType)

Parses an expression into a  ValueExpression for later evaluation. Use this method for expressions that refer to values.

This method should perform syntactic validation of the expression. If in doing so it detects errors, it should raise an ELException.

Parameters:

context - The EL context used to parse the expression. The  FunctionMapper and  VariableMapper stored in the ELContext are used to resolve functions and variables found in the expression. They can be  null, in which case functions or variables are not supported for this expression. The object returned must invoke the same functions and access the same variable mappings regardless of whether the mappings in the provided  FunctionMapper and  VariableMapper instances change between calling  ExpressionFactory.createValueExpression() and any method on  ValueExpression.

Note that within the EL, the ${} and #{} syntaxes are treated identically. This includes the use of VariableMapper and FunctionMapper at expression creation time. Each is invoked if not null, independent of whether the #{} or ${} syntax is used for the expression.

expression - The expression to parse

expectedType - The type the result of the expression will be coerced to after evaluation.

Returns:

The parsed expression

Throws:

NullPointerException - Thrown if expectedType is null.

ELException - Thrown if there are syntactical errors in the provided expression.