Class ValueExpressionImpl

java.lang.Object
javax.el.Expression
javax.el.ValueExpression
com.sun.el.ValueExpressionImpl
All Implemented Interfaces:
Externalizable, Serializable
public final class ValueExpressionImpl extends javax.el.ValueExpression implements Externalizable
An Expression that can get or set a value.

In previous incarnations of this API, expressions could only be read. ValueExpression objects can now be used both to retrieve a value and to set a value. Expressions that can have a value set on them are referred to as l-value expressions. Those that cannot are referred to as r-value expressions. Not all r-value expressions can be used as l-value expressions (e.g. "${1+1}" or "${firstName} ${lastName}"). See the EL Specification for details. Expressions that cannot be used as l-values must always return true from isReadOnly().

The ExpressionFactory.createValueExpression(ELContext, String, Class) method can be used to parse an expression string and return a concrete instance of ValueExpression 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 getValue(ELContext), setValue(ELContext, Object), isReadOnly(ELContext) and getType(ELContext) 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 four methods, the ELResolver.getValue(ELContext, Object, Object) method is used to resolve all properties up to but excluding the last one. This provides the base object. At the last resolution, the ValueExpression will call the corresponding ELResolver.getValue(ELContext, Object, Object), ELResolver.setValue(ELContext, Object, Object, Object), ELResolver.isReadOnly(ELContext, Object, Object) or ELResolver.getType(ELContext, Object, Object) method, depending on which was called on the ValueExpression.

See the notes about comparison, serialization and immutability in the Expression javadocs.

Version:
$Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: dochez $
Author:
Jacob Hookom [jacob@hookom.net]
See Also:

  • Constructor Details

    • ValueExpressionImpl

      public ValueExpressionImpl()

    • ValueExpressionImpl

      public ValueExpressionImpl(String expr, Node node, javax.el.FunctionMapper fnMapper, javax.el.VariableMapper varMapper, Class expectedType)

  • Method Details

    • equals

      public boolean equals(Object obj)
      Specified by:
      equals in class javax.el.Expression

    • getExpectedType

      public Class getExpectedType()
      Specified by:
      getExpectedType in class javax.el.ValueExpression

    • getExpressionString

      public String getExpressionString()
      Returns the type the result of the expression will be coerced to after evaluation.
      Specified by:
      getExpressionString in class javax.el.Expression
      Returns:
      the expectedType passed to the ExpressionFactory.createValueExpression method that created this ValueExpression.
      See Also:
      • Expression.getExpressionString()

    • getType

      public Class getType(javax.el.ELContext context) throws javax.el.PropertyNotFoundException, javax.el.ELException
      Specified by:
      getType in class javax.el.ValueExpression
      Throws:
      javax.el.PropertyNotFoundException
      javax.el.ELException

    • getValueReference

      public javax.el.ValueReference getValueReference(javax.el.ELContext context) throws javax.el.PropertyNotFoundException, javax.el.ELException
      Overrides:
      getValueReference in class javax.el.ValueExpression
      Throws:
      javax.el.PropertyNotFoundException
      javax.el.ELException

    • getValue

      public Object getValue(javax.el.ELContext context) throws javax.el.PropertyNotFoundException, javax.el.ELException
      Specified by:
      getValue in class javax.el.ValueExpression
      Throws:
      javax.el.PropertyNotFoundException
      javax.el.ELException

    • hashCode

      public int hashCode()
      Specified by:
      hashCode in class javax.el.Expression

    • isLiteralText

      public boolean isLiteralText()
      Specified by:
      isLiteralText in class javax.el.Expression

    • isReadOnly

      public boolean isReadOnly(javax.el.ELContext context) throws javax.el.PropertyNotFoundException, javax.el.ELException
      Specified by:
      isReadOnly in class javax.el.ValueExpression
      Throws:
      javax.el.PropertyNotFoundException
      javax.el.ELException

    • readExternal

      public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException
      Specified by:
      readExternal in interface Externalizable
      Throws:
      IOException
      ClassNotFoundException

    • setValue

      public void setValue(javax.el.ELContext context, Object value) throws javax.el.PropertyNotFoundException, javax.el.PropertyNotWritableException, javax.el.ELException
      Specified by:
      setValue in class javax.el.ValueExpression
      Throws:
      javax.el.PropertyNotFoundException
      javax.el.PropertyNotWritableException
      javax.el.ELException

    • writeExternal

      public void writeExternal(ObjectOutput out) throws IOException
      Specified by:
      writeExternal in interface Externalizable
      Throws:
      IOException

    • toString

      public String toString()
      Overrides:
      toString in class Object